Phase Reconstruction‐Directed Synthesis of Oxalate‐Functionalized Nickel Hydroxide Electrocatalyst for High‐Yield H₂O₂ Generation at Industrial Currents

Abstract The electrochemical oxygen reduction reaction (2e⁻ ORR) offers a promising approach for H₂O₂ production, yet developing highly active, selective, and stable electrocatalysts remains a challenge. In this work, a phase reconstruction strategy is presented to synthesize an oxalate‐adsorbed nickel hydroxide electrocatalyst (Ni(OH)₂‐C₂O₄) through the self‐dissociation of nickel oxalate in an alkaline medium, leading to a notable enhancement in H₂O₂ yield at elevated current densities. Remarkably, Ni(OH)₂‐C₂O₄ exhibits a 2e⁻ selectivity exceeding 93% across a broad voltage range (0.0 to 0.5 V vs RHE) in 0.1 M KOH, outperforming pristine Ni(OH)₂. When deployed as a gas diffusion electrode in a flow cell, the Ni(OH)₂‐C₂O₄ catalyst demonstrates stable operation for 50 h at 200 mA cm⁻², with a Faradaic efficiency surpassing 90% and a peak H₂O₂ yield of 6.2 mol g⁻¹_cat h⁻¹. Comprehensive advanced characterizations, including in situ Raman spectroscopy, transient photovoltage spectra, and transient potential scanning spectra, coupled with post‐ORR analyses, reveal that surface‐adsorbed oxalate groups on Ni(OH)₂ enhance the interfacial reaction kinetics between active Ni sites and reactants by inducing a charge trapping effect and forming a hydrogen‐bonded network, facilitating robust and high‐yield H₂O₂ production.