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

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