Enhanced Hydrogen Evolution Reaction on Heterostructured GaN Nanowire/Carbon Nanotube Photocathodes

Abstract Photoelectrochemical water splitting is a promising strategy for sustainable hydrogen production, yet its efficiency is largely limited by sluggish interfacial charge transfer and severe carrier recombination in semiconductor photocathodes. In this work, a gallium nitride/carbon nanotube (GaN/CNT) nanowire heterostructure photocathode is constructed via a facile and controllable dip-coating method. The unique one-dimensional nanowire architecture provides a large surface area and efficient light harvesting. The introduced CNT network forms an interconnected conductive pathway that facilitates rapid electron transport. Thanks to the optimized heterostructure, the GaN/CNT nanowire photocathode delivers an impressive saturated photocurrent density of −10.3 mA·cm−2 at −1.9 V, representing a remarkable 35.5% enhancement compared to that of the pristine GaN nanowire photocathode. One of the key reasons is attributed to the reduced charge-transfer resistance and improved carrier separation in the heterostructure photocathode. Furthermore, the CNT modification can improve the surface wettability, with the water contact angle dropping sharply from 121.8° to 73.7°. It achieves operational stability in an acidic electrolyte with an exceptionally low degradation rate of 0.065 mA·cm−2·h−1 over 5 h, significantly outperforming the bare GaN counterpart. The interconnected CNT network serves as an efficient conductive bridge that accelerates electron extraction from GaN. Overall, this work demonstrates that rational carbon-based interfacial engineering is an effective approach to enhance the efficiency and stability of photocathodes for solar-driven hydrogen generation.