III-V’s via Hydride Vapor Phase Epitaxy for Photoelectrochemical Water Splitting

Photoelectrochemical (PEC) water splitting is a potentially promising route to direct solar-driven hydrogen production. III-V multijunction, or tandem, semiconductor absorbers have demonstrated the highest solar-to-hydrogen (STH) efficiencies to date. To achieve the U.S. DOE’s hydrogen production target of $2/kg, in addition to high STH efficiency, the semiconductor absorber synthesis cost must come down 1-2 orders of magnitude from the current metal organic vapor phase epitaxial route. Hydride vapor phase epitaxy (HVPE) is a technique that has the potential to lower tandem III-V synthesis costs. Here we report the PEC performance of HVPE-grown GaInP/GaAs tandem photoelectrodes with 1.85/1.38 eV bandgaps. We sputtered a PtRu nanoparticulate hydrogen evolution cocatalyst on the III-V photocathode surface and used an IrOx anode for water oxidation. Upon illumination, the HVPE-grown structures were able to drive water electrolysis spontaneously (e.g., without an external bias) at STH efficiencies up to 10%. The durability of III-V photoelectrodes remains and unresolved challenge for cost effective hydrogen production via photoelectrolysis.