Structure-Induced Catalytic Activity of Nickel- and Cobalt-Substituted Layered MoB2toward Hydrogen Evolution

Abstract

Production of high-quality green hydrogen gas as a potential alternative to fossil fuels has been of vital importance in recent years. Among many functional materials, layered metal diborides (MDbs) have attracted great attention from the scientific community due to their outstanding catalytic activity toward hydrogen evolution. This study is dedicated to examine the water electrolysis of a series of metal-substituted MoB2 electrocatalysts (Mo(1-x)TMxB2; TM = Ni and Co; x = 0, 0.05, 0.1, 0.2, 0.3, 0.4, and 0.5) synthesized by a facile molten salt technique. The electrocatalysis of materials was assessed in 1.0 M KOH by measuring the hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and overall water splitting. Interestingly, as the substitution content of TM increases, α-MoB2, with graphene-like boron layers, transforms into β-MoB2 comprising both flat and puckered boron layers, where α-MoB2 has demonstrated enhanced electrocatalytic performance. Mo0.9Ni0.1B2 afforded 10 mA cm-2 at a low overpotential of 222 mV toward HER (located very close to the commercial Pt/C). The assembled Mo0.9Ni0.1B2 (cathode)∥Mo0.8Co0.2B2 (anode) couple demanded 1.75 V to produce 10 mA cm-2, which is near the potential of state-of-the-art Pt/C∥RuO2 pair. The Faradaic efficiency of generated H2 was determined to be approximately 80%.