Modulating local pH environment in ZnO–Cex catalysts for efficient neutral H2O2 electrosynthesis

Abstract

The electrochemical synthesis of hydrogen peroxide (H₂O₂) in neutral media is highly desirable for practical applications but suffers from sluggish kinetics due to insufficient proton availability. Here, we report a strategy to overcome this limitation by engineering the local reaction microenvironment of ZnO catalysts. We construct tuneable Lewis acidic sites by grafting CeO₂ nanoparticles onto ZnO nanorods, creating a ZnO–Ce_x composite. This Ce-derived interface polarizes water molecules, functioning as an efficient hydroxyl pump to establish a localized alkaline microenvironment that facilitates the two-electron oxygen reduction pathway. In situ spectroscopic tracking of reaction intermediates reveals that optimal Ce modification significantly accelerates the protonation of *OOH to *HOOH. The ZnO–Ce_0.2 catalyst achieves a faradaic efficiency of approximately 97% and a high H₂O₂ production rate of 54.29 mol g_cat⁻¹ h⁻¹ at 0.6 A cm⁻² in a neutral electrolyte with pure O₂. Notably, this performance is successfully extended to operation under ambient air, where the catalyst maintains exceptional activity and selectivity. This work demonstrates that tailoring interfacial Lewis acidity to modulate the local pH is a potent strategy for advancing sustainable H₂O₂ electrosynthesis.