A Series of Polyoxometalate-Based Metal–Bis(pyridyl-tetrazole) Complexes with High Electrocatalytic Activity for Hydrogen Evolution Reaction in Alkaline and Acid Media

In this work, a succession of Keggin-type polyoxometalate (POM)-based metal–bis­(pyridyl-tetrazole) complexes, {Cu2(3-bptzp)3(H2O)4[SiW12O40]}·H2O (1), {Cu2(3-bptzpe)2(H2O)8[SiW12O40]}·4H2O (2), and {Cu2(3-bptzh)3(H2O)6[SiW12O40]} (3) (3-bptzp = 1,4-bis­(5-(3-pyridyl)­tetrazolyl)-butane; 3-bptzpe = 1,4-bis­(5-(3-pyridyl)­tetrazolyl)-pentane; 3-bptzh = 1,4-bis­(5-(3-pyridyl)­tetrazolyl)-hexane), were prepared and structurally characterized, which exhibited different architectures. The title complexes were used directly as electrocatalysts for hydrogen evolution reaction in alkaline and acidic media. The electrocatalytic activity for generating hydrogen was reinforced by the introduction of POMs. Complex 1 possesses the highest electrocatalytic activity for hydrogen evolution reaction with a low overpotential of 59.4 mV, achieving the current density of 10 mA·cm–2 in 0.1 M KOH. The different structures of the title complexes showed effects on the hydrogen evolution performance. For 1, the insertion of POMs between the ordered 2D metal–organic layers induced the enhancement of electrocatalytic activity.