Graphene oxide-driven passivation of GaN nanorods for enhanced charge separation and durable seawater PEC hydrogen evolution

Solar-powered photoelectrochemical water splitting (PEC-WS) offers a sustainable pathway for clean hydrogen production, particularly when applied in seawater-based systems. In this work, we introduce a novel heterostructured photoanode composed of GaN nanorods (NRs) coated with monolayer graphene oxide (GO), forming a type-II band-aligned interface. The measured band offsets (ΔEV = 1.25 eV, ΔEC = 0.63 eV) enable efficient charge separation and reduced recombination. Critically, this study represents the first successful integration of GO onto N-polar GaN nanorod arrays, addressing longstanding challenges in surface passivation and chemical instability inherent to III-nitride systems. The GO shell functions dually as a co-catalyst and a passivation layer, mitigating photocorrosion and enhancing interfacial charge dynamics. As a result, the GO/GaN photoanode exhibits a dramatic ~110-fold increase in photocurrent compared to unmodified photoelectrodes, demonstrating the high potential of this configuration under seawater conditions. Structural and spectroscopic analyses (SEM, TEM, XPS) confirm the uniformity and chemical integrity of the heterostructure. This innovative approach paves the way for next-generation PEC devices by combining the robustness of wide-bandgap nitrides with the versatility of 2D materials, offering a powerful design strategy for efficient, durable, and scalable hydrogen production technologies.