Highly-Efficient Capillary Photoelectrochemical Water Splitting Using Cellulose Nanofiber-Templated TiO2 Photoanodes
Among all nanostructured three-dimensional (3D) morphologies, natural cellulose-based nanomaterials such as cellulose nanofibers (CNFs) have been attracting the most attention in nanomanufacturing because of their great abundance, low cost, degradability and biocompatibility. CNFs are composed of elementary cellulose fibrils that are extracted directly from natural plant resources. CNFs also demonstrate great adsorbability in both hydrophilic and hydrophobic materials. Thus, CNFs are considered an excellent template for creating functional, fibrous 3D nanostructures that possess extremely large porosity, such as silver fiber networks, nanotubular indium tin oxide sheets, and porous TiO2, ZnO, and alumina nanostructures. These CNF-templated nanostructures are very promising for the development of energy harvesting and storage devices. CNF-supported polyaniline nanocomposites showed an improved mass-speci?c capacitance in supercapacitor applications. In the Forest Service study, 3D fibrous TiO2 nanotube architecture was synthesized by atomic layer deposition of titania films over CNF templates. Because of the excellent hydrophilic properties of CNF films, a capillary PEC setup was developed to perform water splitting reactions outside of the electrolyte body, where electrolyte was supplied through nano- and micro-channels in the CNF film driven by capillary force. Enhanced reaction kinetics and higher efficiency were observed from the capillary photoelectricalchemical process.
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