Sunlight-Driven Oxidation of Cellulose in Solution Using Stabilized WO ₃ Photoanodes

Sunlight-driven direct oxidation of cellulose dissolved in a strong alkaline aqueous solution is first demonstrated by using particulate WO3 photoanodes coated with an appropriate protective layer. Because WO3 is easily corroded in a strong alkaline environment, a bare WO3 photoanode is almost incapable of generating a photocurrent derived from cellulose oxidation. A thin protective layer (such as NiFeOx or RuO2) can densely cover the surface of particulate WO3 photoanodes and thus successfully stabilize the photoanodes under such harsh conditions. The stabilized WO3 photoanodes in the cellulose solution exhibit more negative onset potentials and larger anodic photocurrents originating from cellulose oxidation compared to those observed during water oxidation. These more negative potentials and greater photocurrents are attributed to the cellulose oxidation being electrochemically preferred over water oxidation. The present protection strategy provides new insights into the photoinduced direct reforming of biomass to H2 or electricity.