Protection of GaInP2 Photocathodes by Direct Photoelectrodeposition of MoSx Thin Films

Catalytic MoS_x thin films have been directly photoelectrodeposited on GaInP₂ photocathodes for stable photoelectrochemical hydrogen generation. Specifically, the MoS_x deposition conditions were controlled to obtain 8-10 nm films directly on p-GaInP₂ substrates without ancillary protective layers. The films were nominally composed of MoS₂, with additional MoO_xS_y and MoO₃ species detected and showed no long-range crystalline order. The as-deposited material showed excellent catalytic activity toward the hydrogen evolution reaction relative to bare p-GaInP₂. Notably, no appreciable photocurrent reduction was incurred by the addition of the photoelectrodeposited MoS_x catalyst to the GaInP₂ photocathode under light-limited operating conditions, highlighting the advantageous optical properties of the film. The MoS_x catalyst also imparted enhanced durability toward photoelectrochemical hydrogen evolution in acidic conditions, maintaining nearly 85% of the initial photocurrent after 50 h of electrolysis. In total, this work demonstrates a simple method for producing dual-function catalyst/protective layers directly on high-performance, planar III-V photoelectrodes for photoelectrochemical energy conversion.