Enhanced solar hydrogen production via reconfigured semi-polar facet/cocatalyst heterointerfaces in GaN/Si photocathodes

The development of an efficient and durable photoelectrode is critical for achieving large-scale applications in photoelectrochemical water splitting. Here, we report a unique photoelectrode composed of reconfigured gallium nitride nanowire-on-silicon wafer loaded with Au nanoparticles as cocatalyst that achieved an impressive applied bias photon-to-current efficiency of 10.36% under AM 1.5G one sun illumination while exhibiting stable PEC hydrogen evolution over 800 h at a high current density. Specifically, by tailoring the GaN nanowires via a simple alkaline-etching step to expose the inner (10 $\overline{1}\overline{1}$ ) facets, we achieve a highly coupled semiconductor nanowire-cocatalyst heterointerface with strong electron interaction. The strongly coupled reconfigured GaN nanowire/Au heterointerface not only optimizes the electronic structure of Au nanoparticles to form abundant highly active interfacial regions, eventually realizing superior hydrogen evolution activity but also enables GaN nanowires to provide a stronger anchoring effect for Au nanoparticles, preventing the detachment of Au nanoparticles during the intense hydrogen evolution process. The proposed photoelectrode offers a feasible structure for overcoming the efficiency-reliability bottleneck of PEC devices for producing clean hydrogen fuel.