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

NiCl2 center dot 6H(2)O ([Ni(H2O)(6)](2)Cl-2) 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 K-2[Ni(H2O)(6)](2)[V10O28]center dot 4H(2)O (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.