Modified p-GaN Microwells with Vertically Aligned 2D-MoS2 for Enhanced Photoelectrochemical Water Splitting.

Photoelectrochemical (PEC) water splitting has been considered as the future technology for storing solar energy in the chemical bonds. However, due to the search of ideal heterostructured materials for photoanode/cathode, the full potential of this technology has not been realized yet. Herein we present, the nanotextured hexagonal microwell of p-GaN [p-GaN(Et)] synthesized via wet chemical etching route as a photocathode (PC) for PEC water splitting. The p-GaN(Et) was further modified by interconnected nanowall network of two-dimensional (2D) transition metal dichalcogenide (MoS2) [2D-MoS2/p-GaN(Et)]. Both PCs were characterized for their morphology, structures, and optical and electronic properties. The overall PEC performance was validated through photocurrent values followed by the amount of hydrogen and oxygen evolution. This combination of 2D-MoS2/p-GaN(Et) outplayed pristine p-GaN(Et) by several orders of magnitude in overall PEC performance. The extraordinary stability under a continuous operating condition with 1 sun illumination (100 mW/cm2) provides the much-needed flavor of an efficient photocathode. The optimized photocathode [2D-MoS2/p-GaN(Et)] shows the highest applied bias photon-to-current conversion efficiency of ∼3.18% with hydrogen evolution rate of 89.56 μmol/h at -0.3 V vs RHE. This wafer-level cost-effective synthesis of 2D-MoS2/GaN heterostructure based PCs opens a new way for large-scale solar-fuel conversion.