Catalytic Effect of Gray Gallium Nitride for Hydrogen Peroxide Generation: Insights into Mechanical Stimuli-Driven Semiconductor–Liquid Interface Alteration

Mechanical stimuli have been shown to dynamically alter solid-liquid interfaces and induce electron transfer, enabling catalytic reactions, most notably contact-electro-catalysis (CEC). However, the underlying mechanism of charge transfer at solid-liquid interfaces under mechanical stimulation remains unclear, particularly at semiconductor-liquid interfaces. To date, rare studies have reported on the catalytic activity of semiconductor-liquid interfaces under mechanical stimulation. In this work, we discovered that hydrogen-treated gallium nitride (GaN), which appears gray in optical images, exhibits catalytic activity for hydrogen peroxide generation, whereas conventional yellow GaN shows no catalytic effect under the same conditions. Through material characterization, mechanistic analysis, and density functional theory (DFT) simulations, we unveil the charge transfer dynamics and catalytic mechanism at semiconductor-liquid interface. We found that the nonuniform structure formed during hydrogen treatment, which contributes to the gray color, also plays a crucial role in the catalytic process. Under mechanical stimuli-induced oxygen concentration fluctuations, this interface becomes polarized, creating conditions conducive to electron transfer and sustaining the full hydrogen peroxide reaction cycle. This work provides fundamental insights into mechanically driven semiconductor-based catalysis at semiconductor-liquid interface and contributes to the development of strategies for sustainable energy conversion.