Anderson polyoxometalate supported Cu(H < inf > 2 < /inf > O)(phen) complex as an electrocatalyst for hydrogen evolution reaction in neutral medium

Abstract

Two structurally analogous Anderson polyoxometalate (POM) supported copper complexes found to be an efficient catalyst for hydrogen production from neutral aqueous medium. These compounds, [Cr(OH)6Mo6O18{Cu(phen)(H2O)2}2][Cr(OH)6Mo6O18{Cu(phen)(H2O)Cl}2].5H2O (1) and [Al(OH)6Mo6O18{Cu(phen)(H2O)2}2][Al(OH)6Mo6O18{Cu(phen)(H2O)Cl}2].5H2O (2), catalyze electrochemical hydrogen evolution reaction (HER) from water (phosphate buffer, pH 7) with relatively low overpotentials of 300 mV and 644 mV at current density of 1 mA/cm2 respectively. Compounds 1 and 2 show remarkable Faradic efficiencies of 95.7% and 89.4% respectively. In terms of overpotential and Faradic efficiency, compound 1 turns out to be a better electrocatalyst for HER from water than compound 2. In this report, we have evidently proved that the active site of this electrochemical HER is the water coordinated Cu(II) center, supported onto POM cluster anion; the polyoxometalate, onto which these aqua-Cu(phen)-complexes are supported, plays an important role in making the overall system heterogeneous, for designing a better electrocatalyst for direct reduction of neutral water.