Synergetic modulation of a hierarchical nanoflower-like NiMoO4/Ni(OH)2 composite toward efficient alkaline water oxidation

Abstract

Electrocatalysts with densely exposed sites and high intrinsic activity are desired for high-efficiency oxygen evolution reaction (OER). In this paper, we report the microwave assisted solvothermal growth of NiMoO4 nanoflowers on electrodeposited Ni(OH)2 nanosheets, forming a high specific surface area (132.5 m2g-1) nanoflower-like NiMoO4/Ni(OH)2 configuration supported on a conductive nickel foam (NF) substrate. The as-prepared NiMoO4/Ni(OH)2/NF behaved efficiently as a self-supported 3D catalyst electrode for alkaline OER, compared with commercial RuO2 (298 mV overpotential at 10 mA cm−2 and Tafel slope of 88.6 mV dec−1), needing a low overpotential of 292 mV to attain 10 mA cm−2, with a small Tafel slope of 85.0 mV dec−1 and good stability for 100 h running at 10 mA cm−2 in 1.0 M KOH. Aside from enlarged surface area for more exposed edge sites for catalysis, the modulated synergy between Ni and Mo atoms probably contributes to enhanced intrinsic activity. A more electronegative Mo increases the electron density of Ni, thus accelerating the deprotonation of intermediates and driving the transition from Ni to NiOOH, leading to modulated thermodynamics and kinetics for OER catalysis.