Efficient homogeneous electrocatalytic hydrogen evolution using a Ni-containing polyoxometalate catalyst

Abstract

NiCl₂·6H₂O ([Ni(H₂O)₆]₂Cl₂) per se does not show electrocatalytic hydrogen evolution reaction activity (HER) in an acidic aqueous medium as well as in neutral water. Interestingly, when [Ni(H₂O)₆]²⁺ is present in a polyoxovanadate matrix, for example, in the compound K₂[Ni(H₂O)₆]₂[V₁₀O₂₈]·4H₂O (1), it exhibits homogeneous electrocatalytic HER activity in an acidic aqueous solution with a turn over frequency of 2.1 s⁻¹ and an effective low overpotential of 127 mV at pH 2.3. Compound 1 is the first nickel-containing polyoxometalate catalyst for hydrogen production via homogeneous electrocatalytic proton reduction without its decomposition under electrochemical conditions of HER.