Engineering Amorphous/Crystalline Ni/NiO Electrocatalysts for Highly Efficient Hydrogen Peroxide Production.

Abstract

Enhanced O₂ adsorption and favorable oxygen-intermediate desorption are essential for efficient electrochemical hydrogen peroxide production (EHPP) via the two-electron oxygen reduction reaction (2e^- ORR). Here, we report an amorphous/crystalline Ni-NiO electrocatalyst synthesized via a partial reduction strategy. By engineering the amorphous/crystalline interfacial strain through varying the reduction time, the optimized Ni/NiO catalyst achieves a hydrogen peroxide selectivity of 91.78% with a Faradaic efficiency of 97.47%. It maintains a high H₂O₂ yield of 949.5 mM/g^-1_cat h^-1 across three electrode systems, outperforming most Ni-based benchmarks. Density functional theory calculations and in situ characterizations reveal that strain at unsaturated Ni sites promotes electron redistribution and Ni-O bond lengthening, thereby shifting the d-p band center difference to favor O₂ adsorption while weakening *OOH binding. The enhanced O₂ adsorption and accelerated *OOH desorption direct the ORR pathway toward the two-electron route for H₂O₂ generation. Furthermore, the in situ generated H₂O₂ effectively degrades organic pollutants, indicating its practical utility in water remediation. This work presents the strain engineering approach in amorphous/crystalline Ni/NiO heterostructures for high-performance EHPP and selective two-electron ORR.