A P-GaInP2 Photoelectrode for Water Reduction Stabilized with TiO2 and MoS2 Catalyst

To achieve an efficient, low cost system for the conversion and storage of solar energy, stable light absorber and robust electrocatalyst need to be coupled into one setup. Noble metals like platinum are usually used because of their high efficiency. Identifying earth-abundant material alternatives to replace precious metal catalyst is highly desired. One of the most efficient PEC systems demonstrated to date is the III-V PEC/PV tandem concept pioneered at NREL however it suffers from inert instability under aqueous solution. Here, we report studies of a p-GaInP₂ photocathode protected via an atomic layer deposition of TiO₂. With an appropriate TiO₂ layer thickness as well as HER catalyst (MoS₂) electrodeposited to the TiO₂ surface, the resulting photoelectrode mediates photo-driven H₂ production with a current density of ~10 mA∙cm^-2 at a potential of 0 V vs. RHE under 1 sun illumination either at neutral or acidic solution. The MoS₂ modified GaInP₂ also showed comparable performance as GaInP₂-Pt control whereas the bare surface demonstrate only half or less photocurrent density at the same condition.