Rhodium-enhanced reducibility and coke resistance in low-loading Ni and Co/Al2O3 catalysts for CO2 methanation

Rhodium-enhanced reducibility and coke resistance in low-loading Ni and Co/Al2O3 catalysts for CO2 methanation | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Rhodium-enhanced reducibility and coke resistance in low-loading Ni and Co/Al 2 O 3 catalysts for CO 2 methanation Robinson L. Manfro, Julia F. P. Nascimento, Mariana M.V.M. Souza, and 1 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-9520506/v1 This work is licensed under a CC BY 4.0 License Status: Under Revision Version 1 posted 10 You are reading this latest preprint version Abstract Low-loading Ni (2.9 wt%) and Co (2.8 wt%) catalysts supported on γ-Al 2 O 3 were promoted with small amounts of Rh (0.8–1.9 wt%) and evaluated for CO 2 methanation under high space velocity (60,000 mL g cat −1 h − 1 ). A monometallic Rh/Al 2 O 3 catalyst was used as a reference. Rhodium significantly enhances the reducibility of Ni 2+ and Co 3+ /Co 2+ species, lowering reduction temperatures to ~ 240°C (Ni) and below 570°C (Co), achieving near-complete reduction (~ 100%) for both bimetallic systems. Despite lower dispersion in the bimetallic catalysts (~ 14–15%) compared to RhAlO (~ 55%), competitive catalytic performance is achieved at elevated temperatures. CO 2 -TPD reveals only weak basic sites for all catalysts, and the significantly lower CO 2 uptake observed for NiRhAlO does not compromise activity, suggesting that the metallic phase primarily governs CO 2 activation. Catalytic tests show that while RhAlO is more active at low temperatures (28% conversion at 250°C), NiRhAlO and CoRhAlO reach comparable conversions (> 80%) at 450°C, with CH 4 selectivity above 90% up to 350°C. All catalysts exhibit high stability over 30 h at 450°C, with no clear evidence of sintering or carbon deposition, as confirmed by XRD, TGA, and Raman analyses. These results suggest that Rh promotion enables low-loading Ni and Co catalysts to achieve high activity, enhanced reducibility, and high stability under demanding methanation conditions, offering a cost-effective alternative to high-loading or noble-metal-based systems. CO2 methanation rhodium promotion low-loading nickel catalyst low-loading cobalt catalyst coke resistance hydrogen spillover Full Text Additional Declarations No competing interests reported. Supplementary Files SupportingInformation.docx Cite Share Download PDF Status: Under Revision Version 1 posted Editorial decision: Revision requested 13 May, 2026 Reviews received at journal 13 May, 2026 Reviewers agreed at journal 07 May, 2026 Reviews received at journal 05 May, 2026 Reviewers agreed at journal 30 Apr, 2026 Reviewers agreed at journal 29 Apr, 2026 Reviewers invited by journal 28 Apr, 2026 Editor assigned by journal 28 Apr, 2026 Submission checks completed at journal 28 Apr, 2026 First submitted to journal 24 Apr, 2026 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. 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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-9520506","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":635006351,"identity":"5c4b85db-cb72-4ce6-b2f7-04d5da2c1411","order_by":0,"name":"Robinson L. Manfro","email":"","orcid":"","institution":"Federal University of Rio de Janeiro","correspondingAuthor":false,"prefix":"","firstName":"Robinson","middleName":"L.","lastName":"Manfro","suffix":""},{"id":635006352,"identity":"57edc5fa-d7b5-4425-a7bd-92644e36ea24","order_by":1,"name":"Julia F. P. Nascimento","email":"","orcid":"","institution":"Federal University of Rio de Janeiro","correspondingAuthor":false,"prefix":"","firstName":"Julia","middleName":"F. P.","lastName":"Nascimento","suffix":""},{"id":635006353,"identity":"cb1f7849-3c8b-4e24-bbd7-735e07a070ce","order_by":2,"name":"Mariana M.V.M. Souza","email":"","orcid":"","institution":"Federal University of Rio de Janeiro","correspondingAuthor":false,"prefix":"","firstName":"Mariana","middleName":"M.V.M.","lastName":"Souza","suffix":""},{"id":635006354,"identity":"013d0d67-ddff-4daa-b30d-cddc1bbcf766","order_by":3,"name":"Carlos Alberto Chagas","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAy0lEQVRIiWNgGAWjYHACxgMMDDZg1gcGHoYEovQAtaSB9c4gRcthqBYGIrTwt599cODDn/NyfAd4DJsrZBjyzBsIaJE4k25wcGbbbWNJoJbGMzwMxTIHCGgxAHrjMG/D7cQNB3jMHzbwMCTOIOQwA/5nDId5/pyr3wCyhTgtEkBbeNgOJBgQrUXixjMGoF+SDWceZisEapEoliCkhb8/jfHBhz928nzHmzc2NvbY5BHUggCgqGHsIUEDOEIZGH6QomMUjIJRMApGCgAAHntAwJM65g0AAAAASUVORK5CYII=","orcid":"","institution":"Federal University of Rio de Janeiro","correspondingAuthor":true,"prefix":"","firstName":"Carlos","middleName":"Alberto","lastName":"Chagas","suffix":""}],"badges":[],"createdAt":"2026-04-24 20:08:31","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-9520506/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-9520506/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":108804985,"identity":"9e5a207e-e7dc-4993-a479-2c769d930cd4","added_by":"auto","created_at":"2026-05-08 15:24:26","extension":"pdf","order_by":1,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":432144,"visible":true,"origin":"","legend":"","description":"","filename":"Manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-9520506/v1_covered_1a4010cd-161f-4165-8ef5-260e2d0be320.pdf"},{"id":108571226,"identity":"54ac02eb-a594-482a-babb-c32ae83b63b0","added_by":"auto","created_at":"2026-05-06 06:20:32","extension":"docx","order_by":0,"title":"","display":"","copyAsset":false,"role":"supplement","size":746072,"visible":true,"origin":"","legend":"","description":"","filename":"SupportingInformation.docx","url":"https://assets-eu.researchsquare.com/files/rs-9520506/v1/009f6d27349bb8b736b3b335.docx"}],"financialInterests":"No competing interests reported.","formattedTitle":"\u003cp\u003eRhodium-enhanced reducibility and coke resistance in low-loading Ni and Co/Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e catalysts for CO\u003csub\u003e2\u003c/sub\u003e methanation\u003c/p\u003e","fulltext":[],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":false,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":true,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":true,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"catalysis-letters","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"","sideBox":"Learn more about [Catalysis Letters](https://link.springer.com/journal/10562)","snPcode":"10562","submissionUrl":"https://submission.springernature.com/new-submission/10562/3","title":"Catalysis Letters","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"CO2 methanation, rhodium promotion, low-loading nickel catalyst, low-loading cobalt catalyst, coke resistance, hydrogen spillover","lastPublishedDoi":"10.21203/rs.3.rs-9520506/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-9520506/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eLow-loading Ni (2.9 wt%) and Co (2.8 wt%) catalysts supported on γ-Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e were promoted with small amounts of Rh (0.8\u0026ndash;1.9 wt%) and evaluated for CO\u003csub\u003e2\u003c/sub\u003e methanation under high space velocity (60,000 mL g\u003csub\u003ecat\u003c/sub\u003e\u003csup\u003e\u0026minus;1\u003c/sup\u003e h\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e). A monometallic Rh/Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e catalyst was used as a reference. Rhodium significantly enhances the reducibility of Ni\u003csup\u003e2+\u003c/sup\u003e and Co\u003csup\u003e3+\u003c/sup\u003e/Co\u003csup\u003e2+\u003c/sup\u003e species, lowering reduction temperatures to ~\u0026thinsp;240\u0026deg;C (Ni) and below 570\u0026deg;C (Co), achieving near-complete reduction (~\u0026thinsp;100%) for both bimetallic systems. Despite lower dispersion in the bimetallic catalysts (~\u0026thinsp;14\u0026ndash;15%) compared to RhAlO (~\u0026thinsp;55%), competitive catalytic performance is achieved at elevated temperatures. CO\u003csub\u003e2\u003c/sub\u003e-TPD reveals only weak basic sites for all catalysts, and the significantly lower CO\u003csub\u003e2\u003c/sub\u003e uptake observed for NiRhAlO does not compromise activity, suggesting that the metallic phase primarily governs CO\u003csub\u003e2\u003c/sub\u003e activation. Catalytic tests show that while RhAlO is more active at low temperatures (28% conversion at 250\u0026deg;C), NiRhAlO and CoRhAlO reach comparable conversions (\u0026gt;\u0026thinsp;80%) at 450\u0026deg;C, with CH\u003csub\u003e4\u003c/sub\u003e selectivity above 90% up to 350\u0026deg;C. All catalysts exhibit high stability over 30 h at 450\u0026deg;C, with no clear evidence of sintering or carbon deposition, as confirmed by XRD, TGA, and Raman analyses. These results suggest that Rh promotion enables low-loading Ni and Co catalysts to achieve high activity, enhanced reducibility, and high stability under demanding methanation conditions, offering a cost-effective alternative to high-loading or noble-metal-based systems.\u003c/p\u003e","manuscriptTitle":"Rhodium-enhanced reducibility and coke resistance in low-loading Ni and Co/Al2O3 catalysts for CO2 methanation","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-05-06 06:20:22","doi":"10.21203/rs.3.rs-9520506/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2026-05-13T14:13:38+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-05-13T08:46:58+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"153762774862465271610262709988888037518","date":"2026-05-07T06:59:15+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-05-05T18:42:13+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"66076060779663923432890959614660283264","date":"2026-04-30T15:36:04+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"243775769707235801986236836614715631397","date":"2026-04-29T08:17:44+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2026-04-28T12:48:00+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2026-04-28T11:55:31+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2026-04-28T11:55:16+00:00","index":"","fulltext":""},{"type":"submitted","content":"Catalysis Letters","date":"2026-04-24T19:53:57+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"catalysis-letters","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"","sideBox":"Learn more about [Catalysis Letters](https://link.springer.com/journal/10562)","snPcode":"10562","submissionUrl":"https://submission.springernature.com/new-submission/10562/3","title":"Catalysis Letters","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"7659793b-3f3e-45af-b4ed-30d6f27c21c2","owner":[],"postedDate":"May 6th, 2026","published":true,"recentEditorialEvents":[{"type":"decision","content":"Revision requested","date":"2026-05-13T14:13:38+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-05-13T08:46:58+00:00","index":37,"fulltext":""},{"type":"reviewerAgreed","content":"153762774862465271610262709988888037518","date":"2026-05-07T06:59:15+00:00","index":36,"fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-05-05T18:42:13+00:00","index":35,"fulltext":""},{"type":"reviewerAgreed","content":"66076060779663923432890959614660283264","date":"2026-04-30T15:36:04+00:00","index":34,"fulltext":""},{"type":"reviewerAgreed","content":"243775769707235801986236836614715631397","date":"2026-04-29T08:17:44+00:00","index":31,"fulltext":""}],"rejectedJournal":[],"revision":"","amendment":"","status":"in-revision","subjectAreas":[],"tags":[],"updatedAt":"2026-05-13T15:10:47+00:00","versionOfRecord":[],"versionCreatedAt":"2026-05-06 06:20:22","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-9520506","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-9520506","identity":"rs-9520506","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}