Engineering GaN photoanodes for high-efficiency solar-driven hydrogen production: Bridging longevity and performance in photoelectrochemical energy systems

The quest for renewable energy sources has propelled solar-driven hydrogen production via water splitting to the forefront of research. Amongst various materials explored for photoanodes, Gallium Nitride (GaN) stands out due to its direct and wide bandgap, robust chemical stability, and superior electronic properties. This review critically assesses the latest advancements in the engineering of GaN photoanodes for photoelectrochemical (PEC) water splitting, focusing on high-efficiency hydrogen production. We provide an in-depth analysis of the state-ofthe-art strategies in doping, surface passivation, and the integration of novel electrocatalysts with GaN substrates to enhance photoelectrochemical activity and stability. These strategies effectively improve charge carrier dynamics, minimize electron-hole recombination, and optimize surface reaction kinetics, thereby elevating the photocatalytic water splitting efficiency. The review also addresses the pivotal challenge of GaN photoanode degradation, discussing advanced protective strategies and nano-engineering approaches that safeguard against photocorrosion while maintaining high PEC performance. A critical evaluation of the interplay between GaN's nanostructure and its photoelectrochemical behavior is presented, shedding light on the optimization of photoanode design for maximum hydrogen yield. The article concludes by identifying key research gaps and potential innovative approaches in GaN photoanode development, underlining their significant potential in advancing the field of photoelectrochemical energy conversion. This comprehensive review aims to catalyze further research into GaN-based photoanodes, ultimately contributing to developing more efficient, durable, and sustainable solar hydrogen production systems.