Highly Efficient Acidic Electrosynthesis of Hydrogen Peroxide at Industrial-Level Current Densities Promoted by Alkali Metal Cations.

Acidic HO synthesis through electrocatalytic 2e oxygen reduction presents a sustainable alternative to the energy-intensive anthraquinone oxidation technology. Nevertheless, acidic HO electrosynthesis suffers from low HO Faradaic efficiencies primarily due to the competing reactions of 4e oxygen reduction to HO and hydrogen evolution in environments with high H concentrations. Here, we demonstrate the significant effect of alkali metal cations, acting as competing ions with H, in promoting acidic HO electrosynthesis at industrial-level currents, resulting in an effective current densities of 50-421 mA cm with 84-100 % Faradaic efficiency and a production rate of 856-7842 μmol cm h that far exceeds the performance observed in pure acidic electrolytes or low-current electrolysis. Finite-element simulations indicate that high interfacial pH near the electrode surface formed at high currents is crucial for activating the promotional effect of K. In situ attenuated total reflection Fourier transform infrared spectroscopy and ab initio molecular dynamics simulations reveal the central role of alkali metal cations in stabilizing the key *OOH intermediate to suppress 4e oxygen reduction through interacting with coordinated HO.