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 H 2 O 2 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 ‐C 2 O 4 ) through the self‐dissociation of nickel oxalate in an alkaline medium, leading to a notable enhancement in H 2 O 2 yield at elevated current densities. Remarkably, Ni(OH) 2 ‐C 2 O 4 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 ‐C 2 O 4 catalyst demonstrates stable operation for 50 h at 200 mA cm −2 , with a Faradaic efficiency surpassing 90% and a peak H 2 O 2 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 H 2 O 2 production.