HER activity of MxNi1-x (M = Cr, Mo and W; x ≈ 0.2) alloy in acid and alkaline media

Abstract

Reported are the synthesis and HER activity of MxNi1-x (M = Cr, Mo and W; x ≈ 0.2) alloy in acid and alkaline media. It was realized that doping group ⅥB element (Cr, Mo, W) in Ni metal matrix can greatly improve corresponding HER activity in both acid and alkaline electrolyte. MoxNi1-x exhibits the highest HER activity among all samples in 1.0 M H2SO4 electrolyte, which it requires only 64 mV to reach current density of 10 mA/cm2. Calculated free-energy of ΔGH∗ for MxNi1-x (M = Cr, Mo and W) well explained their HER activity trend in acid and it follows the order of MoxNi1-x > WxNi1-x > CrxNi1-x. In alkaline condition, their HER activities all deteriorate except CrxNi1-x. HER activity of CrxNi1-x in 1.0 M KOH (η10(base) = 106 mV) surpasses that in 1.0 M H2SO4 (η10(acid) = 160 mV) is quite unexpected. The DFT calculation suggesting the adsorbed OH holds the key and will alter the adsorption energy (ΔGH∗) of neighboring H atom on the surface in alkaline condition. This case study offers a good opportunity to investigate the factor to influence HER behavior of electrocatalyst in acid and alkaline media.