Ultrathin NiFe-Based Nanosheet Electrocatalysts for Efficient Water Oxidation

Abstract

Exploiting highly active, low cost, and stable electrocatalysts for overall water splitting is the central issue for conquering the energy crises and environmental pollution. Herein, an element-incorporation strategy is proposed to synthesize NiFe-based (oxy)hydroxide and selenide nanosheets anchored on a stainless steel mesh (SSM). The (Ni,Fe)OOH/SSM (D-Ni2Fe1/SSM) obtained via sputtering, alloying, and dealloying strategies and (Ni,Fe)Se2 (S–Ni2Fe1/SSM-450) sintering at 450 °C based on the D-Ni2Fe1/SSM exhibit outstanding hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) activities in 1 M KOH, respectively. The preparation of precursor bimetallic hybrid films via sputtering is vital for the subsequent regulation of electronic structures near the active sites between Ni and Fe atoms. D-Ni2Fe1/SSM requires 176 mV to reach 10 mA cm–2 for the HER, whereas 194 mV is needed for S–Ni2Fe1/SSM-450 to reach 10 mA cm–2 for the OER. Additionally, these two electrodes are assembled into an alkaline electrolyzer for overall water splitting with a cell voltage of 1.64 V at 10 mA cm–2 and exhibit outstanding stability. The unique roughened nanosheet morphology, large electrochemical surface area, and optimized electronic structures are responsible for the outstanding HER/OER performances.