Cr-enhanced selective dealloying and sequential electrochemical reconstruction to tailor NiFe-based integrated catalysts for industrial-level water oxidation

Abstract

In-situ reconstruction of multi-element alloy into oxyhydroxides is a promising path to efficient, durable oxygen evolution reaction (OER) electrocatalysts. However, uncontrolled elemental dissolution during reconstruction disrupts target compositions, compromising long-term stability under industrial conditions. Here, we present a controllable multi-step electrochemical etching strategy for precise surface composition and structure regulation. Through sequential Cr-reinforced acid and basic etching under high current densities, we fabricate an integrated NiFe-OOH@Ni/Fe-Cr2O3@NiFeCr catalyst (NiFeCr-aee/bee). Acid electrochemical etching drives competitive dealloying and surface oxidation, generating a mixed Ni/Fe-doped Cr2O3 and NiFe-OOH nanostructure (Ni/Fe-Cr2O3). Subsequent basic electrochemical etching induces surface Cr leaching and enhances surface Ni/Fe hydroxylation, forming a more refined NiFe-OOH@Ni/Fe-Cr2O3 core-shell nanoparticles with abundant active sites. This process rearranges energy levels, greatly enhancing charge transfer and OER kinetics. NiFeCr-aee/bee requires only 292 mV overpotential at 1000  mA  cm−2 and a Tafel slope of 27.3  mV dec−1. After over 1000  h continuous operation at 500  mA  cm−2, the overpotential decreases by 12 mV, indicating ongoing surface activation. Coupled with a Ni4Mo/MoO2/Ni cathode in full-cell electrolysis, only 1.63  V is needed for 500  mA  cm−2 with stability exceeding 1100  h. This work introduces a novel approach for customizing high-performance electrocatalysts by precisely controlling the selective dealloying and self-reconstruction of multi-element alloys through multi-step electrochemical etching.