Electrochemical Evaluation for Multiple Functions of Pt-loaded TiO2 Nanoparticles Deposited on a Photocathode

Pt-loaded TiO2 nanoparticles (Pt/TiO2) were deposited on a near-infrared responsive photocathode as a reaction field for the photoelectrochemical (PEC) hydrogen evolution from water. The multiple functions of the Pt/TiO2 layer for improving the PEC performances were evaluated by electrochemical methods. Considering the electrochemically active surface area (ECSA) of Pt, the Pt/TiO2 surface modification was revealed to increase the number of active sites (Pt), resulting in a decreased current density per active site. Consequently, the potential of the Pt/TiO2-modified photocathode surface during the PEC reaction was expected to be located around 38-46 mV vs. a reversible hydrogen electrode (mV(RHE)), while that of the unmodified one was negatively shifted to around 13 mV(RHE). In addition, the TiO2 layer also functioned to block the migration of holes to the photocathode-electrolyte interface due to its deep valence band position, as well as to improve the wettability of the photocathode surface during light irradiation. These combined effects of the TiO2, as a transparent and conductive support, enhanced the photocurrent, and stability of the photocathode.