Single-zinc vacancy unlocks high-rate H₂O₂ electrosynthesis from mixed dioxygen beyond Le Chatelier principle.

Abstract

Le Chatelier's principle is a basic rule in textbook defining the correlations of reaction activities and specific system parameters (like concentrations), serving as the guideline for regulating chemical/catalytic systems. Here we report a model system breaking this constraint in O₂ electroreduction in mixed dioxygen. We unravel the central role of creating single-zinc vacancies in a crystal structure that leads to enzyme-like binding of the catalyst with enhanced selectivity to O₂, shifting the reaction pathway from Langmuir-Hinshelwood to an upgraded triple-phase Eley-Rideal mechanism. The model system shows minute activity alteration of H₂O₂ yields (25.89~24.99 mol g_cat^-1 h^-1) and Faradaic efficiencies (92.5%~89.3%) in the O₂ levels of 100%~21% at the current density of 50~300 mA cm^-2, which apparently violate macroscopic Le Chatelier's reaction kinetics. A standalone prototype device is built for high-rate H₂O₂ production from atmospheric air, achieving the highest Faradaic efficiencies of 87.8% at 320 mA cm^-2, overtaking the state-of-the-art catalysts and approaching the theoretical limit for direct air electrolysis (~345.8 mA cm^-2). Further techno-economics analyses display the use of atmospheric air feedstock affording 21.7% better economics as comparison to high-purity O₂, achieving the lowest H₂O₂ capital cost of 0.3 $ Kg^-1. Given the recent surge of demonstrations on tailoring chemical/catalytic systems based on the Le Chatelier's principle, the present finding would have general implications, allowing for leveraging systems "beyond" this classical rule.