Ultrathin NiFe-Based\nNanosheet Electrocatalysts for\nEfficient Water Oxidation

Abstract

Exploiting highly active, low cost, and stable electrocatalysts\nfor overall water splitting is the central issue for conquering the\nenergy crises and environmental pollution. Herein, an element-incorporation\nstrategy is proposed to synthesize NiFe-based (oxy)hydroxide and selenide\nnanosheets anchored on a stainless steel mesh (SSM). The (Ni,Fe)OOH/SSM\n(D-Ni₂Fe₁/SSM) obtained via sputtering, alloying,\nand dealloying strategies and (Ni,Fe)Se₂ (S–Ni₂Fe₁/SSM-450) sintering at 450 °C based on\nthe D-Ni₂Fe₁/SSM exhibit outstanding hydrogen\nevolution reaction (HER) and oxygen evolution reaction (OER) activities\nin 1 M KOH, respectively. The preparation of precursor bimetallic\nhybrid films via sputtering is vital for the subsequent regulation\nof electronic structures near the active sites between Ni and Fe atoms.\nD-Ni₂Fe₁/SSM requires 176 mV to reach 10 mA\ncm^–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\nan alkaline electrolyzer for overall water splitting with a cell voltage\nof 1.64 V at 10 mA cm^–2 and exhibit outstanding\nstability. The unique roughened nanosheet morphology, large electrochemical\nsurface area, and optimized electronic structures are responsible\nfor the outstanding HER/OER performances.