Electron enriched ternary NiMoB electrocatalyst for improved overall water splitting: Better performance as compared to the Pt/C || RuO2 at high current density

Abstract

The high energy density and zero carbon emission makes the hydrogen energy most suitable for the next-generation alternative to reduce the greenhouse gas emissions and prevent the climate changes. In this work, the ternary nickel-molybdenum-boron (NiMoB) electrocatalyst is systematically studied and the best optimized NiMoB electrode demonstrates better electrochemical water splitting performance over the benchmark electrodes of Pt/C || RuO2 at high current density. Along with the systematic fabrication parameter optimization, the ternary NiMoB electrocatalyst with the multi-sphere morphology demonstrates significantly high active surface area, low impedance, and low reaction energy barriers with the improved crystallinity of electrodes and absorption and desorption of intermediates. The incorporation of boron in the transition metal matrix of Ni-Mo significantly boosts up the water splitting capability by lowering the kinetic barriers with the electron enriched metallic sites and improved stability of electrodes. Specifically, the turnover overpotential of 1.61 V is achieved at 50 mA/cm2 in 1 M KOH with the improved hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) kinetics in a 2-electrode system. More importantly, the NiMoB electrocatalyst demonstrates better performances at high current range above 1250 mA/cm2 in 1 M KOH and 1100 mA/cm2 in seawater (SW) + 1 M KOH. The NiMoB || NiMoB also demonstrates an equivalent water splitting performance in the real SW + 1 M KOH solution. In addition, a very stable chronoamperometry (CA) operation over 12 h at 500 mA/cm2 and 1,000-time repetition of linear sweep voltammetry (LSV) over 8 h in 6 M KOH at 60 °C confirm that the optimized electrode can demonstrate stable and repetitive operations in an industrial electrochemical water splitting condition.