Long-term stability of GaN-based photocatalyst nanostructures through dynamic oxide protection

Abstract

Solar photocatalytic reactions are a very promising approach to clean energy production. Even though significant efficiency improvement has been made in photocatalytic devices, simultaneously achieving their long-term stability has remained a formidable challenge. As such, to date, there have been very few demonstrations of semiconductor photocatalysts showing stable and long-term operation under concentrated solar irradiation, crucial for practical applications. Herein, we design a unique photocatalyst protection architecture comprising an Al₂O₃ capping layer on the cocatalyst-decorated light-absorbing GaN-based nanostructures to mitigate two of the most dominant bottlenecks in long-term stability: photocatalytic corrosion and cocatalyst nanoparticle displacement. Thereby, we demonstrate the stable operation of this oxide-protected photocatalyst nanostructure for ∼1500 hours without significant performance degradation under concentrated sunlight, which is significantly longer than the stability of the photocatalyst without any protection. Detailed investigation reveals the dynamic characteristic of the capping layer, where Al atoms diffuse from the nanowire c-plane toward the m-plane during the reaction and subsequently get oxidized to form an Al₂O₃ layer. As such, this protection architecture stabilizes the cocatalyst nanoparticles on the sidewall m-plane and prevents the photocatalyst top c-plane corrosion at the same time. Our study overcomes the critical challenge of simultaneously achieving high efficiency and stability in clean fuel generation, offering a crucial means for practical applications of photocatalytic devices for sustainable green energy.