Characterization of a Photoelectrochemical Cell Using Porous TiO₂ and Its Application to a Z-Scheme System for Water Splitting in Combination with a P-Type InP Photocathode

Specific surface area is one of the most important factors for improving the photoelectrochemical properties of photoelectrodes. We have investigated the interface resistance between TiO₂ and an electrolyte solution on increasing the specific surface area through the impedance analysis. A change in morphology was found to produce an increase in the photocurrent associated with proton production, thus promoting H₂ evolution in the photocathode. A Z-scheme system with no need of an external electrical bias was employed using a porous TiO₂ photoanode, a P-type InP photocathode, and platinum as electrocatalyst. A conversion efficiency of 0.35% was achieved for solar water splitting in a neutral electrolyte solution, as determined by quantifying the amount of hydrogen evolved.