Designing Photoelectrodes for Photocatalytic Fuel Cells and Elucidating the Effects of Organic Substrates

Photocatalytic fuel cells (PFCs) are constructed from anodized photoanodes with the aim of effectively converting organic materials into solar electricity. The syntheses of the photoanodes (TiO₂, WO₃, and Nb₂O₅) were optimized using the statistical 2^k factorial design. A systematic study was carried out to catalog the influence of eleven types of organic substrate on the photocurrent responses of the photoanodes, showing dependence on the adsorption of the organic substrates and on the associated photocatalytic degradation mechanisms. Strong adsorbates, such as carboxylic acids, generated high photocurrent enhancements. Simple and short-chained molecules, such as formic acid and methanol, are the most efficient in the corresponding carboxylic acid and alcohol groups as a result of their fast degradation kinetics. The TiO₂-based PFC yielded the highest photocurrent and obtainable power, whereas the Nb₂O₅-based PFC achieved the highest open-circuit voltage, which is consistent with its most negative Fermi level.