Abstract
Gallium nitride (GaN), with its wide bandgap and high chemical stability, is an attractive photoanode material for photoelectrochemical (PEC) water splitting. GaN thin films are commonly fabricated by metal organic chemical vapor deposition (MOCVD), yet the high cost and environmental burden of this process motivate hightemperature radio-frequency sputtering as a promising alternative. In this work, MOCVD- and sputtered-GaN photoanodes are prepared with two film thicknesses and further configured with an anti-reflection layer and interdigitated electrodes to systematically evaluate the effects of deposition technique and structural engineering on PEC hydrogen evolution. Both MOCVD- and sputtered-GaN photoanodes exhibit hydrogen evolution, with the former exhibiting superior PEC performance. Structural engineering further boosts the applied bias photon-tocurrent efficiency, increasing it by up to 15 times for MOCVD-GaN and 3.9 times for sputtered-GaN relative to the respective bare photoanodes.