Influence of calcination temperature on sol-gel surfactant derived micro-mesoporous cobalt silica

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Diniz da Costa This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6251509/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract This work investigates the effect of calcination temperature on the sol-gel structural properties of surfactant (hexyl trimethyl ammonium bromide (HTAB)) derived cobalt silica xerogels. Experimental results revealed that no significant changes were detected on the structure and cobalt state beyond 400 °C for samples with low surfactant/Co loads ( x ≤1). Pore structure and Co 3 O 4 phase showed almost similar values for calcination temperature from 400 to 600 °C. In contrast, the incorporation of an excess amount of surfactant ( x =2 and 3) induced a delayed evolution of both properties beyond 400 °C, strongly suggesting an influence of the additional interactions between Co-Br complexes and surfactant. The additional metal-surfactant interaction induces a dual influence on the evolution of material properties throughout the heat treatment, partially inhibiting the oxidation of cobalt and significantly altering the mesoporous structure due to surfactant removal at temperatures in excess of 400 °C. Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Highlights • Calcination temperature effect on xerogels derived from surfactant and cobalt silica. • No structure and cobalt state effect for low surfactant/Co ( ≤ 1) samples. • Excess surfactant ( = 2 and 3) induced a delayed evolution of both properties beyond 400°C. • Suggesting an influence of the additional interactions between Co-Br complexes and surfactant. • Metal-surfactant interaction induces a partial inhibition of the oxidation of cobalt . Though significantly altering the mesoporous structure due to surfactant removal above 400°C. 1. Introduction With the advent of nanotechnology, surfactants have been extensively reported in literature as pore forming agent in silica sol gel. By allowing surfactants to group as micelles, MCM-41 silicates form hexagonal structures showing consistent cylindrical pores of 5Å [ 1 – 2 ]. An array of surfactants has been used to prepare ordered MCM materials based on cationic (tetraalkylammonium salts (C n H 2n+1 )(CH 3 ) 3 NX)) and anionic (sulfates (C n H 2n+1 OSO 3 )) surfactants as examples [ 3 ]. The ability to precisely control the pore size of MCMs [ 4 ] in tandem with surface properties conferred this material with selective adsorptive properties for gas [ 5 ] and organic solvents [ 6 ] separation. By the same token, amorphous silica templated with surfactant resulted in micro and mesoporous structures upon calcination in air at high temperatures. In this case, the surfactant was burnt off leaving a cavity of similar dimensions and the molecular size of the surfactant or template [ 7 ]. In another approach, calcination was carried out under non-oxidise atmosphere as surfactants were pyrolyzed within the silica matrix [ 8 , 9 ] and formed carbon silica matrices with improved hydrostability of silica materials. This new functionalisation was attributed to carbon embedded in the pores of micropore silica that impeded the mobility of silica silanols under hydrolytic attack [ 10 ]. Organosilicas have also been used successfully delivering good pore size tailorability [ 11 – 13 ]. Organosilicas are derived from organoalkoxysilanes where the alkoxy groups in the precursor are usually ethoxy –OCH 2 CH 3 and methoxy –OCH 3 in a few cases [ 14 ]. The incorporation of metal oxides within the silica structure via sol-gel synthesis became very attractive as a novel approach for the precise control of pores [ 15 ], particularly at micropore and/or molecular sieve dimensions. A wide range of metal oxide dopants were embedded into silica matrices such as cobalt oxide [ 16 – 17 ], nickel oxide [ 18 – 19 ], niobia [ 20 ], zinc [ 21 ], palladium [ 22 – 23 ], and binary metal oxide mixtures containing cobalt plus palladium [ 24 ], lanthanum [ 25 ], iron [ 26 ] and zirconia coupled with silver nanoparticles [ 27 ]. Conversely, the properties of aerogels containing cobalt oxide silica were studied to understand their pore size formation under supercritical drying conditions [ 28 ]. Of all cobalt oxide has been the most explored metal oxide used in silicas for membranes for gas separation particularly due to improved hydostability of silica structures [ 29 – 30 ]. In addition, cobalt oxide incorporation into silica is also desirable in a number of applications such as catalysis [ 31 – 32 ], magnetic properties [ 33 , 34 ] for extraction applications [ 35 ], optical gas sensors [ 36 ], dieletric materials [ 37 ] and bioactive glasses [ 38 , 39 ]. Reports of incorporation of either surfactant or cobalt oxide into silica have been focused separately in literature. Despite the achievements of these two functionalisation pathways, studies of the dual effect of their combination within silica matrices have been limited. The incorporation of both cationic surfactant and cobalt within microporous silica unveiled a novel tailoring effect on cobalt oxidation and porous structure [ 40 ]. The simultaneous evolution of metal oxidation, surfactant removal and silica condensation may be influenced by mutual synergistic effects. For instance, Cu 2+ lowered the decomposition temperature of methyl groups within siloxane structures [ 41 ]. This became of interest when considering the crucial role of heat treatment, given the desired material functionality for further applications [ 42 ]. The tailorability of surfactants on porous structures is highly dependent on surfactant removal throughout the heat treatment, in addition to the size of the precursor surfactant. Further, the cobalt oxidation degree is basically controlled by adjusting some treatment parameters such as atmosphere and temperature [ 43 ]. Thus, the understanding about the mutual influence between porous structure evolution and the oxidation of cobalt becomes relevant in influencing the final functionalised material. Herein we report a novel interconnected evolution of both porous structures and cobalt state as a function of the calcination process for cobalt silica surfactant loads. A series of surfactant to cobalt silica ( x = 0 to 3) were prepared via a one-step sol-gel process and thermally treated at three different calcination temperatures (400, 500 and 600°C). The calcined samples were characterised using thermogravimetric analysis and differential thermal analysis to determine thermal evolution; X-ray photoelectron spectroscopy to determine elemental compositions; nitrogen sorption isotherms to determine pore volumes and pore size distribution determined by density functional theory. A mechanistic idealised model is proposed to explain the properties and pore volume evolution of samples based on thermal evolution during calcination. 2. Experimental Cobalt silica (CoSi) samples were synthesised via a sol-gel synthesis method. Briefly, cobalt nitrate hexahydrate (Co(NO 3 ) 2 .6H 2 O) was dissolved in 30%vol hydrogen peroxide (H 2 O 2 ) in order to keep the pH stable at around 3.0 and then diluted in an excess of ethanol. Subsequently, the solution was cooled to 0°C, followed by a slow drop-wise addition of tetraethyl orthosilicate (TEOS). The final molar ratios are TEOS:H 2 O:H 2 O 2 :EtOH:Co(NO 3 ) 2 .6H 2 O = 4:45.5:9:256:1. Lastly, the solution was moderately stirred in an ice-bath at 0°C for three hours. The preparation of surfactant cobalt silica samples follows this same procedure, except for the addition of hexyl trimethyl ammonium bromide (HTAB) after the ice-bath treatment. The surfactant/cobalt molar ratio (x) was varied from 0 to 3. The solubility of surfactant was guaranteed by keeping the concentration below the critical micelle concentration (CMC) point. After preparation, all sol-gel solutions were dried in air atmosphere using an electric oven for 96 hours at 60°C. The dried gels (xerogels) were then ground to a fine powder and stored in sealed containers. Subsequently, each sample was calcined at three different temperatures (400, 500 and 600°C) in an electric furnace under air atmosphere, at a ramp rate of 1°C min − 1 and a dwell time of 150 min. Calcined xerogels were degassed under vacuum at 200°C for at least four hours and characterised by nitrogen gas adsorption using a Micromeritics TriStar 3000 instrument. Pore size distribution (PSD) was calculated using density functional theory from the Micromeritics 3020 v1.04 software. Surface elemental compositions were obtained on a Kratos Axis ULTRA X-ray Photoelectron Spectrometer (XPS) using Al Kα X-rays (1486.6 eV) at 150W (15 kV, 10 mA). High-resolution XPS spectra were charge-corrected using the C 1s peak at 284.6 eV. Thermal gravimetric analysis was monitored from room temperature to 600°C on a Shimadzu TGA-50 with a 1°C min − 1 ramping rate, dwell time of 150 min, and an air flux of 80–90 cm 3 min − 1 . Differential Thermal Analysis was undertaken with a Mettler Toledo TGA/DSC Thermogravimetric Analyzer with GC200 Gas controller. 3. Results and discussion The evolution of mass loss and energy flux throughout the calcination process is depicted in Fig. 1 . It is observed on Fig. 1 a that a major fraction of mass reduction takes place below 400°C for low surfactant samples ( x ≤ 1) whilst samples with higher loads of surfactant ( x = 2 and 3) exhibited significant mass losses above 400°C. The mass loss patterns for the samples loaded with surfactant differs from that of the blank sample ( x = 0). The latter has a 30% constant mass loss up to 250°C associated with the silica condensation reaction followed by insignificant mass loss related to the strengthening of the cobalt silica structure. In the case of surfactant loaded samples, there was a mass loss delayed step for temperatures below 200°C. Further, the mass loss delayed step increased as a function of the surfactant load. These results suggest that the thermal evolution of the SiCo is affected by the surfactant load. The energy flux of the same samples (See Fig. 1 b) displays characteristic surfactant decomposition within silica materials. In the case of low surfactant load ( x ≤ 1), an initial endothermic profile shows a water desorption related peak below 100°C followed by a smaller peak related with nitrate decomposition [ 44 ]. The noticeable shift of the latter peak to lower temperatures might correspond to NO 3 − ions due to the presence of Co-Br coordination within the matrix when surfactant is incorporated. At higher temperatures, exothermic steps take place between 200 and 300°C mainly due to the combustion of aliphatic groups from the surfactant decomposition [ 45 – 46 ]. The main exothermic peak is enlarged and slightly shifted to higher temperatures as the surfactant load is increased. This adequately concurs with a major combustion activity due to the increment on surfactant load. The absence of distinct peaks above 400°C indicates that no relevant thermal process takes place at higher temperatures. The continuous decrease in the DTA curve plus the small variation of mass suggests that a faint condensation reaction (endothermic) continues above 400°C. Thus, it is inferred that the reactive activity is complete within the silica matrix at calcination temperature of 400°C in any sample with low surfactant load ( x ≤ 1). In contrast, Fig. 1 b shows that samples with higher surfactant loads ( x = 2 and 3) energy flux patterns differ from those samples with lower surfactant load ( x ≤ 1). The differences are attributed to the ongoing mass losses above 400°C (See Fig. 1 a). Indeed, the energy flux in Fig. 1 b confirms a significant activity level beyond 400°C. Moreover, a major deviation from the characteristic profile for surfactant-silica materials is observed as compared to work published elsewhere [ 45 ]. The reduction of exothermic peaks as compared to low surfactant samples is associated with enhanced endothermic stages, likely triggered by pyrolysis of aliphatic groups. Further, the overall shift of this peak to higher temperatures of 500°C, or even greater temperatures, relates with a late release of surfactant head groups [ 40 ]. This clear alteration of surfactant decomposition within the silica matrix has been attributed to metal-surfactant interactions [ 47 – 48 ]. These results concur that the interaction between Co-Br complexes and excess surfactant heads simultaneously alters the surfactant decomposition and inhibits the oxidation of cobalt. A representative XPS spectra in Fig. 2 a shows the evolution of Co 3 O 4 phase as a function of calcination temperatures. The XPS spectra for these samples were deconvoluted and results are displayed in Fig. 2 b. The blank sample ( x = 0) depicts a slight decrease in oxide fraction above 400°C, whereas a trend to gradually increase the oxidation is observed for the surfactant loaded samples. It is observed that samples with low surfactant load ( x ≤ 1) reach an almost stable amount of tetroxide at 400°C, with further variations in the oxide phase (0 to 15%) are possibly within experimental error as function of the calcination temperature. In the case of excess amount of surfactant ( x = 2 and 3), these loads inhibit the growth of the Co 3 O 4 phase. A stable value is reached only at 500°C, showing a steep increment from values around 40 to 60% (~ 35% increase in average) with calcination temperatures beyond 400°C. The representative nitrogen sorption isotherms are shown in Fig. 3 . The functionalised SCoSi samples with x ≤ 1 resulted mainly in type I isotherms, characteristic of microporous materials. By increasing the surfactant load to x = 2 and 3, the isotherms changed in shape to type IV, characteristic of mesoporous materials. Although the latter isotherms show saturation at p/p 0 ~ 0.45, there is no significant hysteresis, suggesting the formation of small mesopores. There are two further interesting trends in Fig. 1 . First, the total pore volume increases from 400 to 500°C, and then reduces from 500 to 600°C for samples x = 0 and 0.25. Second, the total pore volume is almost similar for the x = 1 sample independently of the applied calcination temperature. In the case of samples with surfactant loads of x = 2 and 3, a significant total pore volume increase occurred as the calcination temperatures were raised from 400 or 500°C, and then from 500 or 600°C. This trend is attributed to surfactant mass losses at higher temperatures determined from TGA analysis (see Fig. 1 ). Figure 4 shows the pore size distribution (PSD) calculated from the density functional theory from the Micromeritics software. It is clearly observed that for samples with low surfactant load ( x ≤ 1), the structure is mainly dominated by microporosity ( d p < 2 nm). The sharp tri-modal peak below 2 nm is commonly observed in microporoussilica simulated by DFT mode [ 49 ]. As the surfactant load increases towards x = 1, or as the calcination temperature increases from 400 to 600°C, there is an increase in the PSD towards mesoporosity (2 < d p <50 nm). Contrary to this trend, as high surfactant loads (x = 2 and 3) are used, the PSD is dominated by mesoporous structures, where pores become much broader to sizes as large as 5 nm. It is interesting to note that the PSD for x ≤ 1samples mimic each other as a function of the temperature. These results suggest that the silica structure pore formation was not affected by the surfactant load. The opposite trend is for x = 2 and 3 samples as the PSD differs considerably as a function of the calcination temperature. In this case, the surfactant load played a significant role in the pore formation, although the surfactant load in this work is below the MCM point. In addition, the surfactant mass loss at higher temperatures for x = 2 and 3 samples (Fig. 1 ) clearly indicates that varying interactions between surfactant, porous silica and the cobalt oxide particles, leading to structural pore formation. To understand further the thermal effect during calcination, Fig. 5 plots the increments of mesopore volume and mass loss after calcination from 400 to 600°C as function of Co 3 O 4 increment in a similar temperature range. This figure clearly shows the trends between low and high surfactant load, where changes or increments in mesopore volume and mass losses are simultaneously displayed as a function of the changes or increments in Co 3 O 4 phase fraction. Of particular interest, these results clearly indicate that there are two different regimes occurring in tandem, with small variations for the low surfactant loads ( x ≤ 1), and large variations for high surfactant load ( x = 2 and 3). Thus, a degree of interconnection between the evolution of porous structure and cobalt oxidation can be suggested for these materials. These results suggest that a fraction of the embedded cobalt and alkyl heads remain attached within the silica framework until high calcination temperatures, thus deterring further oxidation. This is verified from the DTA analyses which show an endothermic peak at 535°C attributed to the combustion of surfactants. Hence, this high temperature release of surfactant groups may also contribute with a high temperature tailoring effect of the silica matrix, thus corroborating with the PSD of the resultant samples (see Fig. 4 ). Actually, it can be inferred from the TGA analysis (Fig. 1 ) that a considerable fraction of surfactant has not been removed after calcination at 400°C for samples x = 2 and 3. Subtracting the contribution of early processes such as nitrate decomposition (T < 200°C) [ 50 ] and solvent desorption (T < 100°C), around 30% of the total surfactant remains incorporated in the xerogel matrix. This remaining template agent is basically formed by head groups which are attached to the silica framework due to the interaction with cobalt. Thus, the larger size of HTAB head group in relation with the whole monomer (Table 1) can explain the tailoring effect of the silica matrix at 400°C. The subsequent increase in mesopore volume at higher calcination temperatures concurs with a further detachment of head groups, thereby confirming the importance of the template effect of these groups. Table 4.1: Surfactant monomer characteristic sizes and contact area. (*) Estimated value considering bond length difference between methyl and ethyl groups . The evidence of reduced metal oxidation at lower calcination temperature for the samples with high surfactant loads ( x = 2 and 3) is also interesting (See Fig. 2 ). This suggests that the proposed inhibition of cobalt oxidation is not only influenced by the surfactant load, but that the calcination temperature also plays an important role. The proposed CoBr-surfactant interaction may be strong enough to retain a fraction of cobalt at lower oxidation state even at temperatures around 400°C. Subsequently, the release of attached head groups beyond 400°C may promote extra metal oxidation as some CoBr–surfactant interactions gradually vanish. Nevertheless, the non-favourable conditions for cobalt bromide oxidation at high temperature may reduce the likelihood of tetroxide formation. Indeed, the ideal conversion of CoBr 2 oxidation (3CoBr 2 + 2O 2 →Co 3 O 4 + 3Br 2 ) is inhibited as the reaction temperature shifts into higher values. Therefore, a fraction of the embedded metal is finally not oxidised at temperatures above 400°C, despite the complete removal of alkyl groups from the silica. The evolution of the tailoring process and cobalt oxidation throughout calcination is schematically represented in Fig. 6 and Fig. 7 for an additional step for samples ( x = 2 and 3). In the case of low surfactant load ( x ≤ 1), after the synthesis the CoBr species independently adsorb within the silica interface (Figs. 6 a) and surfactant monomers (Fig. 6 b). The tetra-coordinated Co 2+ ions are likely to be surrounded within the silica/surfactant matrix. At around 400°C, an almost complete tailoring process is attained due to the total removal of surfactant (Fig. 6 c-d). At this stage, the PSD results show similar structural patterns as evidenced in Fig. 4 as a function of the calcination temperature, suggesting the surfactant effect is minimal. This is supported by the TGA and structural nitrogen sorption isotherm results. At the same time, a maximum oxidation of cobalt is simultaneously reached (Fig. c). In contrast, high surfactant load samples ( x = 2 and 3) have an additional step as depicted in Fig. 7 . In this case, additional interactions emerge between a fraction of monomers and CoBr species due to surface saturation (Fig. 7 a). This configuration may introduce a steric effect during early stages of air calcination, thereby hindering the access of oxygen molecules. As a result, there is only a partial release of alkyl compounds mainly from surfactant tail groups, providing a low template effect (Fig. 7 b). Although the decomposition of part of the surfactant occurs, head groups may remain attached to the Co complexes and keep inducing a steric effect on metal oxidation. For calcination temperatures beyond 400°C, the TGA results show a significant increase in mass loss accompanied by a significant increase in total pore volume, particularly mesopore volumes (Fig. 5 a). These results suggest that release of attached head groups within high surfactant load samples provides a secondary template effect which substantially increases the mesoporosity (Fig. 7 c). Despite the enhanced freedom of CoBr species after surfactant detachment, the high temperature induces less favourable conditions for an extended oxidation. Consequently, a fraction of the cobalt remains as ionic Co 2+ or low valence oxide within the silica matrix. 4. Conclusion Sol-gel derived cobalt silica was prepared including different concentrations of a small cationic surfactant (HTAB). The evolution of porous structure and cobalt oxidation through air calcination was then investigated. In general, final values of all the analysed properties can be reached after calcination at 400°C in low surfactant samples (x ≤ 1), whereas high surfactant load ( x = 2 and 3) requires higher temperatures. The formation of mesoporous structure and cobalt oxidation was delayed in the case of high surfactant load samples, showing partial development at low calcination temperatures. This simultaneous evolution is attributed to the emerging interactions between Co-Br complexes and surfactant. The high temperature release of the surfactant’s attached head groups explains the evolution of the template effect on porous structure. In addition, the same interactions inhibit the oxidation of cobalt according to the postulated model. Declarations Author Contribution G.O. carried out all experimental work, data analysis and paper writing. 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Goworek J, Kierys A, Gac W, Borowka A, Kusak R (2009) Thermal degradation of CTAB in as-synthesized MCM-41. J Therm Anal Calorim 96:375-82. de Souza LKC, Pardauil JJR, Zamian JR, da Rocha GN, da Costa CEF (2011) Influence of the incorporated metal on template removal from MCM-41 type mesoporous materials. J Therm Anal Calorim 106:355-61. Wang S, Wang DK, Smart S, Diniz da Costa JC (2017) Improved stability of ethyl silicate interlayer-free membranes by the rapid thermal processing (RTP) for desalination. Desalination 402:25-32. Yuvaraj S, Lin FY, Chang TH, Yeh CT (2013) Thermal decomposition of metal nitrates in air and hydrogen environments. J Phys Chem B 107:1044-7. Rosen MJ, Kunjappu JT (2012) Micelle formation by surfactants: surfactants and interfacial phenomena. Wiley, New York. Lee YS (2008) Self-assembly and nanotechnology: a force balance approach 1 st edn. Wiley, New York. Additional Declarations No competing interests reported. Supplementary Files Graphicalabstract.jpg Graphical abstrac Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-6251509","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":433297471,"identity":"0626ae2a-8b61-4cc8-9069-78a9e47ce4ab","order_by":0,"name":"Gianni Olguin","email":"","orcid":"","institution":"Pontificia Universidad Católica de Valparaíso, Escuela de Ingeniería Química","correspondingAuthor":false,"prefix":"","firstName":"Gianni","middleName":"","lastName":"Olguin","suffix":""},{"id":433297472,"identity":"d82939c2-b2e5-49d7-9f3f-85c800a8219c","order_by":1,"name":"Christelle Yacou","email":"","orcid":"","institution":"Université des Antilles","correspondingAuthor":false,"prefix":"","firstName":"Christelle","middleName":"","lastName":"Yacou","suffix":""},{"id":433297473,"identity":"51489586-ac06-4ee8-adea-d8a594f84fa8","order_by":2,"name":"Simon Smart","email":"","orcid":"","institution":"University of Queensland","correspondingAuthor":false,"prefix":"","firstName":"Simon","middleName":"","lastName":"Smart","suffix":""},{"id":433297474,"identity":"39622825-b10e-42fb-ba2f-0a0c337f774d","order_by":3,"name":"Joao C. Diniz da Costa","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA2klEQVRIiWNgGAWjYBACxgYGAwiLvQFEMhOvRYKB5wCRWoAAqkUigUgtzA3MGz/8qKir45/5xvAGQ4V1YgP7GQMCDmMrluw5c1hC4naOsQXDmfTEBp4cQlp4DKQZ2w5IMNzOMZNgbDuc2MBAWIvxb8a2Ogn5m2eAWv4BtfC/IajFDGgLs4TBDR6glgagFglCtjSzlVkC/SK58UxasUXCsXTjNolnBXi1GLY3b74BDDF+ueOHN974UGMt28+fvAG/lmYkDjhq2PCqBwJ5ZI4EIdWjYBSMglEwMgEAZe1AsdHxn0sAAAAASUVORK5CYII=","orcid":"","institution":"University of Queensland","correspondingAuthor":true,"prefix":"","firstName":"Joao","middleName":"C. Diniz da","lastName":"Costa","suffix":""}],"badges":[],"createdAt":"2025-03-18 09:23:26","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6251509/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6251509/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":79567473,"identity":"20c18c21-b3a1-44e9-b6cd-e7f3ff4dc2e7","added_by":"auto","created_at":"2025-03-31 09:49:04","extension":"jpg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":47667,"visible":true,"origin":"","legend":"\u003cp\u003e(a) Mass loss evolution from TGA and (b) energy flux from DTA for C6-SCoSi xerogel samples.\u003c/p\u003e","description":"","filename":"1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-6251509/v1/613d784a7298cab79f3adcec.jpg"},{"id":79568677,"identity":"3b158e89-1251-44dc-b351-330515c7a9cd","added_by":"auto","created_at":"2025-03-31 09:57:04","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":51466,"visible":true,"origin":"","legend":"\u003cp\u003e(a) Representative XPS spectra of sample x = 1 showing the deconvoluted regions, and (b) Co\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e phase evolution as a function of calcination temperature for all samples. Cobalt speciation derived from Co 2p3/2 region at 778-792 eV on XPS spectrum.\u003c/p\u003e","description":"","filename":"2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-6251509/v1/3fd955e6dd951b5af7891ff0.jpg"},{"id":79567475,"identity":"afc499b2-172f-4040-8f40-0bb9c18b46d7","added_by":"auto","created_at":"2025-03-31 09:49:04","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":121007,"visible":true,"origin":"","legend":"\u003cp\u003eNitrogen adsorption isotherm of samples with varying surfactant (\u003cem\u003ex\u003c/em\u003e) loads of SCoSi-\u003cem\u003ex\u003c/em\u003e.\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-6251509/v1/2866cb0aa414822082069eea.png"},{"id":79568865,"identity":"a840de18-bc03-4a1e-af50-c58c181ba229","added_by":"auto","created_at":"2025-03-31 10:05:05","extension":"jpg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":163301,"visible":true,"origin":"","legend":"\u003cp\u003edV/dLog(D) graph of different C6 surfactant load SiCo samples and calcined at various temperatures.\u003c/p\u003e","description":"","filename":"4.jpg","url":"https://assets-eu.researchsquare.com/files/rs-6251509/v1/979c2a70460e121ac638beb6.jpg"},{"id":79568678,"identity":"0499ad7a-32dc-497b-9955-e656056c5a09","added_by":"auto","created_at":"2025-03-31 09:57:05","extension":"jpg","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":36183,"visible":true,"origin":"","legend":"\u003cp\u003eRelationship between the evolution of cobalt oxidation and material morphology. The increments in the oxidation state of cobalt from 400 to 600 °C calcination temperature correlated with (a) mesopore volume increments and (b) TGA mass loss increments.\u003c/p\u003e","description":"","filename":"5.jpg","url":"https://assets-eu.researchsquare.com/files/rs-6251509/v1/c3f2624807e541aa3434ba5a.jpg"},{"id":79567477,"identity":"7b9e8a5e-0d0e-4d26-aea8-19e030b3c803","added_by":"auto","created_at":"2025-03-31 09:49:05","extension":"jpg","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":61012,"visible":true,"origin":"","legend":"\u003cp\u003eIdealised schematic of the thermal evolution of SCoSi and surfactant loaded during calcination in air (adapted from [40]).\u003c/p\u003e","description":"","filename":"6.jpg","url":"https://assets-eu.researchsquare.com/files/rs-6251509/v1/34b2971059941b4428cb7657.jpg"},{"id":79567485,"identity":"8001101d-d143-4079-8196-d3ba7b3ef5b0","added_by":"auto","created_at":"2025-03-31 09:49:05","extension":"jpg","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":65265,"visible":true,"origin":"","legend":"\u003cp\u003eIdealized schematic representation of an additional step for SiCo samples load (\u003cem\u003ex\u003c/em\u003e=2 and 3) during calcination in air.\u003c/p\u003e","description":"","filename":"7.jpg","url":"https://assets-eu.researchsquare.com/files/rs-6251509/v1/502c28ec16742644c9ae3fdc.jpg"},{"id":82078739,"identity":"b75ff972-44ad-467c-893d-0aab2020ea1e","added_by":"auto","created_at":"2025-05-06 14:09:06","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1011439,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6251509/v1/c76be501-9342-449e-a305-62e6b5c51208.pdf"},{"id":79567474,"identity":"670e2a9c-4ebe-4f76-9d72-061713cbc37c","added_by":"auto","created_at":"2025-03-31 09:49:04","extension":"jpg","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":34969,"visible":true,"origin":"","legend":"\u003cp\u003eGraphical abstrac\u003c/p\u003e","description":"","filename":"Graphicalabstract.jpg","url":"https://assets-eu.researchsquare.com/files/rs-6251509/v1/fa6699a288a679e0e06ab84c.jpg"}],"financialInterests":"No competing interests reported.","formattedTitle":"Influence of calcination temperature on sol-gel surfactant derived micro-mesoporous cobalt silica","fulltext":[{"header":"Highlights","content":"\u003cp\u003e\u0026bull; Calcination temperature effect on xerogels derived from surfactant and cobalt silica.\u003c/p\u003e\u003cp\u003e\u0026bull; No structure and cobalt state effect for low surfactant/Co (\u0026thinsp;\u0026le;\u0026thinsp;1) samples.\u003c/p\u003e\u003cp\u003e\u0026bull; Excess surfactant (\u0026thinsp;=\u0026thinsp;2 and 3) induced a delayed evolution of both properties beyond 400\u0026deg;C.\u003c/p\u003e\u003cp\u003e\u0026bull; Suggesting an influence of the additional interactions between Co-Br complexes and surfactant.\u003c/p\u003e\u003cp\u003e\u0026bull; Metal-surfactant interaction induces a partial inhibition of the oxidation of cobalt .\u003c/p\u003e\u003cp\u003eThough significantly altering the mesoporous structure due to surfactant removal above 400\u0026deg;C.\u003c/p\u003e"},{"header":"1. Introduction","content":"\u003cp\u003eWith the advent of nanotechnology, surfactants have been extensively reported in literature as pore forming agent in silica sol gel. By allowing surfactants to group as micelles, MCM-41 silicates form hexagonal structures showing consistent cylindrical pores of 5\u0026Aring; [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. An array of surfactants has been used to prepare ordered MCM materials based on cationic (tetraalkylammonium salts (C\u003csub\u003en\u003c/sub\u003eH\u003csub\u003e2n+1\u003c/sub\u003e)(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e3\u003c/sub\u003eNX)) and anionic (sulfates (C\u003csub\u003en\u003c/sub\u003eH\u003csub\u003e2n+1\u003c/sub\u003eOSO\u003csub\u003e3\u003c/sub\u003e)) surfactants as examples [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. The ability to precisely control the pore size of MCMs [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e] in tandem with surface properties conferred this material with selective adsorptive properties for gas [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e] and organic solvents [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e] separation. By the same token, amorphous silica templated with surfactant resulted in micro and mesoporous structures upon calcination in air at high temperatures. In this case, the surfactant was burnt off leaving a cavity of similar dimensions and the molecular size of the surfactant or template [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. In another approach, calcination was carried out under non-oxidise atmosphere as surfactants were pyrolyzed within the silica matrix [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e] and formed carbon silica matrices with improved hydrostability of silica materials. This new functionalisation was attributed to carbon embedded in the pores of micropore silica that impeded the mobility of silica silanols under hydrolytic attack [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. Organosilicas have also been used successfully delivering good pore size tailorability [\u003cspan additionalcitationids=\"CR12\" citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]. Organosilicas are derived from organoalkoxysilanes where the alkoxy groups in the precursor are usually ethoxy \u0026ndash;OCH\u003csub\u003e2\u003c/sub\u003eCH\u003csub\u003e3\u003c/sub\u003e and methoxy \u0026ndash;OCH\u003csub\u003e3\u003c/sub\u003e in a few cases [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThe incorporation of metal oxides within the silica structure via sol-gel synthesis became very attractive as a novel approach for the precise control of pores [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e], particularly at micropore and/or molecular sieve dimensions. A wide range of metal oxide dopants were embedded into silica matrices such as cobalt oxide [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e], nickel oxide [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e], niobia [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e], zinc [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e], palladium [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e], and binary metal oxide mixtures containing cobalt plus palladium [\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e], lanthanum [\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e], iron [\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e] and zirconia coupled with silver nanoparticles [\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e]. Conversely, the properties of aerogels containing cobalt oxide silica were studied to understand their pore size formation under supercritical drying conditions [\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e]. Of all cobalt oxide has been the most explored metal oxide used in silicas for membranes for gas separation particularly due to improved hydostability of silica structures [\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e]. In addition, cobalt oxide incorporation into silica is also desirable in a number of applications such as catalysis [\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e], magnetic properties [\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e, \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e] for extraction applications [\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e], optical gas sensors [\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e], dieletric materials [\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e] and bioactive glasses [\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e, \u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eReports of incorporation of either surfactant or cobalt oxide into silica have been focused separately in literature. Despite the achievements of these two functionalisation pathways, studies of the dual effect of their combination within silica matrices have been limited. The incorporation of both cationic surfactant and cobalt within microporous silica unveiled a novel tailoring effect on cobalt oxidation and porous structure [\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e]. The simultaneous evolution of metal oxidation, surfactant removal and silica condensation may be influenced by mutual synergistic effects. For instance,\u003c/p\u003e \u003cp\u003eCu\u003csup\u003e2+\u003c/sup\u003e lowered the decomposition temperature of methyl groups within siloxane structures [\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e]. This became of interest when considering the crucial role of heat treatment, given the desired material functionality for further applications [\u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e]. The tailorability of surfactants on porous structures is highly dependent on surfactant removal throughout the heat treatment, in addition to the size of the precursor surfactant. Further, the cobalt oxidation degree is basically controlled by adjusting some treatment parameters such as atmosphere and temperature [\u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e43\u003c/span\u003e]. Thus, the understanding about the mutual influence between porous structure evolution and the oxidation of cobalt becomes relevant in influencing the final functionalised material.\u003c/p\u003e \u003cp\u003eHerein we report a novel interconnected evolution of both porous structures and cobalt state as a function of the calcination process for cobalt silica surfactant loads. A series of surfactant to cobalt silica (\u003cem\u003ex\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0 to 3) were prepared via a one-step sol-gel process and thermally treated at three different calcination temperatures (400, 500 and 600\u0026deg;C). The calcined samples were characterised using thermogravimetric analysis and differential thermal analysis to determine thermal evolution; X-ray photoelectron spectroscopy to determine elemental compositions; nitrogen sorption isotherms to determine pore volumes and pore size distribution determined by density functional theory. A mechanistic idealised model is proposed to explain the properties and pore volume evolution of samples based on thermal evolution during calcination.\u003c/p\u003e"},{"header":"2. Experimental","content":"\u003cp\u003eCobalt silica (CoSi) samples were synthesised via a sol-gel synthesis method. Briefly, cobalt nitrate hexahydrate (Co(NO\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e.6H\u003csub\u003e2\u003c/sub\u003eO) was dissolved in 30%vol hydrogen peroxide (H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e) in order to keep the pH stable at around 3.0 and then diluted in an excess of ethanol. Subsequently, the solution was cooled to 0\u0026deg;C, followed by a slow drop-wise addition of tetraethyl orthosilicate (TEOS). The final molar ratios are TEOS:H\u003csub\u003e2\u003c/sub\u003eO:H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e:EtOH:Co(NO\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e.6H\u003csub\u003e2\u003c/sub\u003eO\u0026thinsp;=\u0026thinsp;4:45.5:9:256:1. Lastly, the solution was moderately stirred in an ice-bath at 0\u0026deg;C for three hours. The preparation of surfactant cobalt silica samples follows this same procedure, except for the addition of hexyl trimethyl ammonium bromide (HTAB) after the ice-bath treatment. The surfactant/cobalt molar ratio (x) was varied from 0 to 3. The solubility of surfactant was guaranteed by keeping the concentration below the critical micelle concentration (CMC) point. After preparation, all sol-gel solutions were dried in air atmosphere using an electric oven for 96 hours at 60\u0026deg;C. The dried gels (xerogels) were then ground to a fine powder and stored in sealed containers. Subsequently, each sample was calcined at three different temperatures (400, 500 and 600\u0026deg;C) in an electric furnace under air atmosphere, at a ramp rate of 1\u0026deg;C min\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and a dwell time of 150 min.\u003c/p\u003e \u003cp\u003eCalcined xerogels were degassed under vacuum at 200\u0026deg;C for at least four hours and characterised by nitrogen gas adsorption using a Micromeritics TriStar 3000 instrument. Pore size distribution (PSD) was calculated using density functional theory from the Micromeritics 3020 v1.04 software. Surface elemental compositions were obtained on a Kratos Axis ULTRA X-ray Photoelectron Spectrometer (XPS) using Al Kα X-rays (1486.6 eV) at 150W (15 kV, 10 mA). High-resolution XPS spectra were charge-corrected using the C 1s peak at 284.6 eV. Thermal gravimetric analysis was monitored from room temperature to 600\u0026deg;C on a Shimadzu TGA-50 with a 1\u0026deg;C min\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e ramping rate, dwell time of 150 min, and an air flux of 80\u0026ndash;90 cm\u003csup\u003e3\u003c/sup\u003e min\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. Differential Thermal Analysis was undertaken with a Mettler Toledo TGA/DSC Thermogravimetric Analyzer with GC200 Gas controller.\u003c/p\u003e"},{"header":"3. Results and discussion","content":"\u003cp\u003eThe evolution of mass loss and energy flux throughout the calcination process is depicted in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. It is observed on Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ea that a major fraction of mass reduction takes place below 400\u0026deg;C for low surfactant samples (\u003cem\u003ex\u003c/em\u003e\u0026thinsp;\u0026le;\u0026thinsp;1) whilst samples with higher loads of surfactant (\u003cem\u003ex\u003c/em\u003e\u0026thinsp;=\u0026thinsp;2 and 3) exhibited significant mass losses above 400\u0026deg;C. The mass loss patterns for the samples loaded with surfactant differs from that of the blank sample (\u003cem\u003ex\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0). The latter has a 30% constant mass loss up to 250\u0026deg;C associated with the silica condensation reaction followed by insignificant mass loss related to the strengthening of the cobalt silica structure. In the case of surfactant loaded samples, there was a mass loss delayed step for temperatures below 200\u0026deg;C. Further, the mass loss delayed step increased as a function of the surfactant load. These results suggest that the thermal evolution of the SiCo is affected by the surfactant load.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe energy flux of the same samples (See Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eb) displays characteristic surfactant decomposition within silica materials. In the case of low surfactant load (\u003cem\u003ex\u003c/em\u003e\u0026thinsp;\u0026le;\u0026thinsp;1), an initial endothermic profile shows a water desorption related peak below 100\u0026deg;C followed by a smaller peak related with nitrate decomposition [\u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e44\u003c/span\u003e]. The noticeable shift of the latter peak to lower temperatures might correspond to NO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e\u0026minus;\u003c/sup\u003e ions due to the presence of Co-Br coordination within the matrix when surfactant is incorporated. At higher temperatures, exothermic steps take place between 200 and 300\u0026deg;C mainly due to the combustion of aliphatic groups from the surfactant decomposition [\u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e45\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e46\u003c/span\u003e]. The main exothermic peak is enlarged and slightly shifted to higher temperatures as the surfactant load is increased. This adequately concurs with a major combustion activity due to the increment on surfactant load. The absence of distinct peaks above 400\u0026deg;C indicates that no relevant thermal process takes place at higher temperatures. The continuous decrease in the DTA curve plus the small variation of mass suggests that a faint condensation reaction (endothermic) continues above 400\u0026deg;C. Thus, it is inferred that the reactive activity is complete within the silica matrix at calcination temperature of 400\u0026deg;C in any sample with low surfactant load (\u003cem\u003ex\u003c/em\u003e\u0026thinsp;\u0026le;\u0026thinsp;1).\u003c/p\u003e \u003cp\u003eIn contrast, Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eb shows that samples with higher surfactant loads (\u003cem\u003ex\u003c/em\u003e\u0026thinsp;=\u0026thinsp;2 and 3) energy flux patterns differ from those samples with lower surfactant load (\u003cem\u003ex\u003c/em\u003e\u0026thinsp;\u0026le;\u0026thinsp;1). The differences are attributed to the ongoing mass losses above 400\u0026deg;C (See Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ea). Indeed, the energy flux in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eb confirms a significant activity level beyond 400\u0026deg;C. Moreover, a major deviation from the characteristic profile for surfactant-silica materials is observed as compared to work published elsewhere [\u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e45\u003c/span\u003e]. The reduction of exothermic peaks as compared to low surfactant samples is associated with enhanced endothermic stages, likely triggered by pyrolysis of aliphatic groups. Further, the overall shift of this peak to higher temperatures of 500\u0026deg;C, or even greater temperatures, relates with a late release of surfactant head groups [\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e]. This clear alteration of surfactant decomposition within the silica matrix has been attributed to metal-surfactant interactions [\u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e47\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e48\u003c/span\u003e]. These results concur that the interaction between Co-Br complexes and excess surfactant heads simultaneously alters the surfactant decomposition and inhibits the oxidation of cobalt.\u003c/p\u003e \u003cp\u003eA representative XPS spectra in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ea shows the evolution of Co\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e phase as a function of calcination temperatures. The XPS spectra for these samples were deconvoluted and results are displayed in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eb. The blank sample (\u003cem\u003ex\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0) depicts a slight decrease in oxide fraction above 400\u0026deg;C, whereas a trend to gradually increase the oxidation is observed for the surfactant loaded samples. It is observed that samples with low surfactant load (\u003cem\u003ex\u003c/em\u003e\u0026thinsp;\u0026le;\u0026thinsp;1) reach an almost stable amount of tetroxide at 400\u0026deg;C, with further variations in the oxide phase (0 to 15%) are possibly within experimental error as function of the calcination temperature. In the case of excess amount of surfactant (\u003cem\u003ex\u003c/em\u003e\u0026thinsp;=\u0026thinsp;2 and 3), these loads inhibit the growth of the Co\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e phase. A stable value is reached only at 500\u0026deg;C, showing a steep increment from values around 40 to 60% (~\u0026thinsp;35% increase in average) with calcination temperatures beyond 400\u0026deg;C.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe representative nitrogen sorption isotherms are shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e. The functionalised SCoSi samples with \u003cem\u003ex\u003c/em\u003e\u0026thinsp;\u0026le;\u0026thinsp;1 resulted mainly in type I isotherms, characteristic of microporous materials. By increasing the surfactant load to \u003cem\u003ex\u003c/em\u003e\u0026thinsp;=\u0026thinsp;2 and 3, the isotherms changed in shape to type IV, characteristic of mesoporous materials. Although the latter isotherms show saturation at p/p\u003csub\u003e0\u003c/sub\u003e\u0026thinsp;~\u0026thinsp;0.45, there is no significant hysteresis, suggesting the formation of small mesopores. There are two further interesting trends in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. First, the total pore volume increases from 400 to 500\u0026deg;C, and then reduces from 500 to 600\u0026deg;C for samples \u003cem\u003ex\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0 and 0.25. Second, the total pore volume is almost similar for the \u003cem\u003ex\u003c/em\u003e\u0026thinsp;=\u0026thinsp;1 sample independently of the applied calcination temperature. In the case of samples with surfactant loads of \u003cem\u003ex\u003c/em\u003e\u0026thinsp;=\u0026thinsp;2 and 3, a significant total pore volume increase occurred as the calcination temperatures were raised from 400 or 500\u0026deg;C, and then from 500 or 600\u0026deg;C. This trend is attributed to surfactant mass losses at higher temperatures determined from TGA analysis (see Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e shows the pore size distribution (PSD) calculated from the density functional theory from the Micromeritics software. It is clearly observed that for samples with low surfactant load (\u003cem\u003ex\u003c/em\u003e\u0026thinsp;\u0026le;\u0026thinsp;1), the structure is mainly dominated by microporosity (\u003cem\u003ed\u003c/em\u003e\u003csub\u003e\u003cem\u003ep\u003c/em\u003e\u003c/sub\u003e \u0026lt; 2 nm). The sharp tri-modal peak below 2 nm is commonly observed in microporoussilica simulated by DFT mode [\u003cspan citationid=\"CR49\" class=\"CitationRef\"\u003e49\u003c/span\u003e]. As the surfactant load increases towards \u003cem\u003ex\u003c/em\u003e\u0026thinsp;=\u0026thinsp;1, or as the calcination temperature increases from 400 to 600\u0026deg;C, there is an increase in the PSD towards mesoporosity (2\u0026thinsp;\u0026lt;\u0026thinsp;\u003cem\u003ed\u003c/em\u003e\u003csub\u003e\u003cem\u003ep\u003c/em\u003e\u003c/sub\u003e\u0026lt;50 nm). Contrary to this trend, as high surfactant loads (x\u0026thinsp;=\u0026thinsp;2 and 3) are used, the PSD is dominated by mesoporous structures, where pores become much broader to sizes as large as 5 nm.\u003c/p\u003e \u003cp\u003eIt is interesting to note that the PSD for \u003cem\u003ex\u003c/em\u003e\u0026thinsp;\u0026le;\u0026thinsp;1samples mimic each other as a function of the temperature. These results suggest that the silica structure pore formation was not affected by the surfactant load. The opposite trend is for x\u0026thinsp;=\u0026thinsp;2 and 3 samples as the PSD differs considerably as a function of the calcination temperature. In this case, the surfactant load played a significant role in the pore formation, although the surfactant load in this work is below the MCM point. In addition, the surfactant mass loss at higher temperatures for x\u0026thinsp;=\u0026thinsp;2 and 3 samples (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e) clearly indicates that varying interactions between surfactant, porous silica and the cobalt oxide particles, leading to structural pore formation.\u003c/p\u003e \u003cp\u003eTo understand further the thermal effect during calcination, Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e plots the increments of mesopore volume and mass loss after calcination from 400 to 600\u0026deg;C as function of Co\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e increment in a similar temperature range. This figure clearly shows the trends between low and high surfactant load, where changes or increments in mesopore volume and mass losses are simultaneously displayed as a function of the changes or increments in Co\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e phase fraction. Of particular interest, these results clearly indicate that there are two different regimes occurring in tandem, with small variations for the low surfactant loads (\u003cem\u003ex\u003c/em\u003e\u0026thinsp;\u0026le;\u0026thinsp;1), and large variations for high surfactant load (\u003cem\u003ex\u003c/em\u003e\u0026thinsp;=\u0026thinsp;2 and 3). Thus, a degree of interconnection between the evolution of porous structure and cobalt oxidation can be suggested for these materials.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThese results suggest that a fraction of the embedded cobalt and alkyl heads remain attached within the silica framework until high calcination temperatures, thus deterring further oxidation. This is verified from the DTA analyses which show an endothermic peak at 535\u0026deg;C attributed to the combustion of surfactants. Hence, this high temperature release of surfactant groups may also contribute with a high temperature tailoring effect of the silica matrix, thus corroborating with the PSD of the resultant samples (see Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e). Actually, it can be inferred from the TGA analysis (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e) that a considerable fraction of surfactant has not been removed after calcination at 400\u0026deg;C for samples \u003cem\u003ex\u003c/em\u003e\u0026thinsp;=\u0026thinsp;2 and 3. Subtracting the contribution of early processes such as nitrate decomposition (T\u0026thinsp;\u0026lt;\u0026thinsp;200\u0026deg;C) [\u003cspan citationid=\"CR50\" class=\"CitationRef\"\u003e50\u003c/span\u003e] and solvent desorption (T\u0026thinsp;\u0026lt;\u0026thinsp;100\u0026deg;C), around 30% of the total surfactant remains incorporated in the xerogel matrix. This remaining template agent is basically formed by head groups which are attached to the silica framework due to the interaction with cobalt. Thus, the larger size of HTAB head group in relation with the whole monomer (Table\u0026nbsp;1) can explain the tailoring effect of the silica matrix at 400\u0026deg;C. The subsequent increase in mesopore volume at higher calcination temperatures concurs with a further detachment of head groups, thereby confirming the importance of the template effect of these groups.\u003c/p\u003e\n\u003cp\u003eTable 4.1: Surfactant monomer characteristic sizes and contact area.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cimg 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\" width=\"655\" height=\"274\"\u003e\u003c/p\u003e \u003cp\u003e(*) \u003cem\u003eEstimated value considering bond length difference between methyl and ethyl groups\u003c/em\u003e.\u003c/p\u003e \u003cp\u003eThe evidence of reduced metal oxidation at lower calcination temperature for the samples with high surfactant loads (\u003cem\u003ex\u003c/em\u003e\u0026thinsp;=\u0026thinsp;2 and 3) is also interesting (See Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). This suggests that the proposed inhibition of cobalt oxidation is not only influenced by the surfactant load, but that the calcination temperature also plays an important role. The proposed CoBr-surfactant interaction may be strong enough to retain a fraction of cobalt at lower oxidation state even at temperatures around 400\u0026deg;C. Subsequently, the release of attached head groups beyond 400\u0026deg;C may promote extra metal oxidation as some CoBr\u0026ndash;surfactant interactions gradually vanish. Nevertheless, the non-favourable conditions for cobalt bromide oxidation at high temperature may reduce the likelihood of tetroxide formation. Indeed, the ideal conversion of CoBr\u003csub\u003e2\u003c/sub\u003e oxidation (3CoBr\u003csub\u003e2\u003c/sub\u003e\u0026thinsp;+\u0026thinsp;2O\u003csub\u003e2\u003c/sub\u003e\u0026rarr;Co\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e\u0026thinsp;+\u0026thinsp;3Br\u003csub\u003e2\u003c/sub\u003e) is inhibited as the reaction temperature shifts into higher values. Therefore, a fraction of the embedded metal is finally not oxidised at temperatures above 400\u0026deg;C, despite the complete removal of alkyl groups from the silica.\u003c/p\u003e \u003cp\u003eThe evolution of the tailoring process and cobalt oxidation throughout calcination is schematically represented in Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e and Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e for an additional step for samples (\u003cem\u003ex\u003c/em\u003e\u0026thinsp;=\u0026thinsp;2 and 3). In the case of low surfactant load (\u003cem\u003ex\u003c/em\u003e\u0026thinsp;\u0026le;\u0026thinsp;1), after the synthesis the CoBr species independently adsorb within the silica interface (Figs.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003ea) and surfactant monomers (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003eb). The tetra-coordinated Co\u003csup\u003e2+\u003c/sup\u003e ions are likely to be surrounded within the silica/surfactant matrix. At around 400\u0026deg;C, an almost complete tailoring process is attained due to the total removal of surfactant (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003ec-d). At this stage, the PSD results show similar structural patterns as evidenced in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e as a function of the calcination temperature, suggesting the surfactant effect is minimal. This is supported by the TGA and structural nitrogen sorption isotherm results. At the same time, a maximum oxidation of cobalt is simultaneously reached (Fig. c).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eIn contrast, high surfactant load samples (\u003cem\u003ex\u003c/em\u003e\u0026thinsp;=\u0026thinsp;2 and 3) have an additional step as depicted in Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e. In this case, additional interactions emerge between a fraction of monomers and CoBr species due to surface saturation (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003ea). This configuration may introduce a steric effect during early stages of air calcination, thereby hindering the access of oxygen molecules. As a result, there is only a partial release of alkyl compounds mainly from surfactant tail groups, providing a low template effect (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003eb). Although the decomposition of part of the surfactant occurs, head groups may remain attached to the Co complexes and keep inducing a steric effect on metal oxidation. For calcination temperatures beyond 400\u0026deg;C, the TGA results show a significant increase in mass loss accompanied by a significant increase in total pore volume, particularly mesopore volumes (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ea). These results suggest that release of attached head groups within high surfactant load samples provides a secondary template effect which substantially increases the mesoporosity (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003ec). Despite the enhanced freedom of CoBr species after surfactant detachment, the high temperature induces less favourable conditions for an extended oxidation. Consequently, a fraction of the cobalt remains as ionic Co\u003csup\u003e2+\u003c/sup\u003e or low valence oxide within the silica matrix.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e"},{"header":"4. Conclusion","content":"\u003cp\u003eSol-gel derived cobalt silica was prepared including different concentrations of a small cationic surfactant (HTAB). The evolution of porous structure and cobalt oxidation through air calcination was then investigated. In general, final values of all the analysed properties can be reached after calcination at 400\u0026deg;C in low surfactant samples (x\u0026thinsp;\u0026le;\u0026thinsp;1), whereas high surfactant load (\u003cem\u003ex\u003c/em\u003e\u0026thinsp;=\u0026thinsp;2 and 3) requires higher temperatures. The formation of mesoporous structure and cobalt oxidation was delayed in the case of high surfactant load samples, showing partial development at low calcination temperatures. This simultaneous evolution is attributed to the emerging interactions between Co-Br complexes and surfactant. The high temperature release of the surfactant\u0026rsquo;s attached head groups explains the evolution of the template effect on porous structure. In addition, the same interactions inhibit the oxidation of cobalt according to the postulated model.\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eG.O. carried out all experimental work, data analysis and paper writing. C.Y. and S.S. assisted in experimental data analysis, paper editing and project co-supervision. J.C.d.D.C. supervised the project, data analysis and edited the paper.\u003c/p\u003e\u003ch2\u003eAcknowledgement\u003c/h2\u003e \u003cp\u003eGianni Olguin acknowledges funding support from the bicentenary scholarship program from the Chilean Government. The authors gratefully acknowledge the technical assistance of Dr Barry Wood of the Australian Microscopy \u0026amp; Microanalysis Research Facility at the Centre for Microscopy and Microanalysis, The University of Queensland.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eKresge CT, Vartuli JC, Roth WJ, Leonowicz ME (2004) The discovery of ExxonMobil\u0026apos;s M41S family of mesoporous molecular sieves. Studies Surf Sci Catal148:53-72.\u003c/li\u003e\n\u003cli\u003eCosta JAS, de Jesus RA, Santos DO, Mano JF, Rom\u0026atilde;o LPC, Paranhos CM (2020) Recent progresses in the adsorption of organic, inorganic, and gas compounds by MCM-41-based mesoporous materials. 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J Memb Sci 489:4220\u0026ndash;226.\u003c/li\u003e\n\u003cli\u003eDarmawan A, Motuzas J, Smart S, Julbe A, Diniz da Costa JC (2015) Temperature dependent transition point of purity versus flux for gas separation in Fe/Co-Silica Membranes. Sep Purif Technol 151:284\u0026ndash;291.\u003c/li\u003e\n\u003cli\u003eMei Y, Yang J, Zhang R, Li H, Guo Y. Enhanced antibacterial activity, dye rejection and anti-fouling performance of ZrO\u003csub\u003e2\u003c/sub\u003e-SiO\u003csub\u003e2\u003c/sub\u003e composite ceramic membranes embedded by silver nanoparticles. J Sol-Gel Sci Technol (2025). https://doi.org/10.1007/s10971-025-06697-6.\u003c/li\u003e\n\u003cli\u003eCasula M, Corrias A, Paschina G (2003) Iron-Cobalt-Silica Aerogel Nanocomposite Materials. J SolGel Sci Technol 26:667\u0026ndash;670.\u003c/li\u003e\n\u003cli\u003eUhlmann D, Smart S, Diniz da Costa JC (2010) High temperature steam investigation of cobalt oxide silica membranes for gas separation. 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Wiley, New York.\u003c/li\u003e\n\u003cli\u003eLee YS (2008) Self-assembly and nanotechnology: a force balance approach 1\u003csup\u003est\u003c/sup\u003e edn. Wiley, New York.\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"","lastPublishedDoi":"10.21203/rs.3.rs-6251509/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6251509/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThis work investigates the effect of calcination temperature on the sol-gel structural properties of surfactant (hexyl trimethyl ammonium bromide (HTAB)) derived cobalt silica xerogels. Experimental results revealed that no significant changes were detected on the structure and cobalt state beyond 400 °C for samples with low surfactant/Co loads (\u003cem\u003ex\u003c/em\u003e≤1). Pore structure and Co\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e phase showed almost similar values for calcination temperature from 400 to 600 °C. In contrast, the incorporation of an excess amount of surfactant (\u003cem\u003ex\u003c/em\u003e=2 and 3) induced a delayed evolution of both properties beyond 400 °C, strongly suggesting an influence of the additional interactions between Co-Br complexes and surfactant. The additional metal-surfactant interaction induces a dual influence on the evolution of material properties throughout the heat treatment, partially inhibiting the oxidation of cobalt and significantly altering the mesoporous structure due to surfactant removal at temperatures in excess of 400\u0026nbsp;°C.\u003c/p\u003e","manuscriptTitle":"Influence of calcination temperature on sol-gel surfactant derived micro-mesoporous cobalt silica","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-03-31 09:49:00","doi":"10.21203/rs.3.rs-6251509/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"f91415ca-8ef1-4808-9a2c-0059bb750727","owner":[],"postedDate":"March 31st, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2025-05-06T14:08:32+00:00","versionOfRecord":[],"versionCreatedAt":"2025-03-31 09:49:00","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-6251509","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6251509","identity":"rs-6251509","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}