Sulfur-Doping Tailors BiOI for High-Efficiency Cocatalyst-Free Piezocatalytic H₂ Evolution

Piezocatalytic water splitting has emerged as a promising method for green hydrogen production, yet its efficiency typically relies on costly noble metal cocatalysts. Here, we hypothesize that tailoring the defect chemistry of a piezoelectric material can optimize its piezoelectric polarization, carrier transport, and intrinsic catalytic activity without relying on noble metals. As a proof of concept, we successfully synthesized sulfur-substituted BiOI through a controlled anion exchange (O^2- → S^2-) method. The optimized 10% sulfur-substituted catalyst achieved a 2.8-fold increase in piezocatalytic H₂ evolution activity, rising from 1.40 to 3.97 mmol·g^-1·h^-1, matching or surpassing the performance of noble-metal-modified BiOI systems. Experimental and theoretical analyses confirm that this performance leap stems from enhanced piezoelectric polarization, a narrowed bandgap, accelerated charge migration, optimized H* adsorption Gibbs free energy, and enhanced water affinity. This structural engineering strategy offers an economical, noble-metal-free methodology for designing advanced micro/nanostructured piezocatalysts for sustainable energy conversion.