Noble-Metal-Free Cocatalysts Reinforcing Hole Consumption for Photocatalytic Hydrogen Evolution with Ultrahigh Apparent Quantum Efficiency

Abstract

Achieving efficient and sustainable hydrogen production through photocatalysis is highly promising yet remains a significant challenge, especially when replacing costly noble metals with more abundant alternatives. Conversion efficiency with noble-metal-free alternatives is frequently limited by high charge recombination rates, mainly due to the sluggish transfer and inefficient consumption of photo-generated holes. To address these challenges, a rational design of noble-metal-free cocatalysts as oxidative sites is reported to facilitate hole consumption, leading to markedly increased H₂ yield rates without relying on expensive noble metals. By integrating femtosecond transient absorption spectroscopy with in situ characterizations and theoretical calculations, the rapid hole consumption is compellingly confirmed, which in turn promotes the effective separation and migration of photo-generated carriers. The optimized catalyst delivers an impressive photocatalytic H₂ yield rate of 57.84 mmol g_cat⁻¹ h⁻¹, coupled with an ultrahigh apparent quantum efficiency reaching up to 65.8%. Additionally, a flow-type quartz microreactor is assembled using the optimal catalyst thin film, which achieves a notable H₂ yield efficiency of 0.102 mL min⁻¹ and maintains high stability over 1260 min of continuous operation. The strategy of reinforcing hole consumption through noble-metal-free cocatalysts establishes a promising pathway for scalable and economically viable solar H₂ production.