Selective hydroxylation of carbon surfaces for long-lasting hydrophilicity by a green chemistry process

Abstract We report the selective hydroxylation of carbon surfaces that rendered initially hydrophobic carbon fiber paper hydrophilic for more than five months. This long time of sustained hydrophilicity is unprecedented. Carbon fiber paper is an inexpensive, electrically conductive, high surface area material that is additionally nontoxic, biocompatible, robust, and scalable. But its hydrophobicity prevents widespread use in aqueous applications. Inhibition of overoxidation of carbon beyond hydroxylation is especially challenging because the first oxidation step is thermodynamically most difficult and subsequent oxidations are much easier. We achieved selectivity for less oxidized hydroxyls over carboxyls by an environmentally friendly, solution-processable, acid-free carbon surface functionalization treatment that is rapid, amenable to large scale applications, and did not damage carbon fibers and their network architectures. The development of this mild, green chemistry carbon surface treatment that provides selectivity for surface hydroxyls transforms the utility of carbon materials.