Unique activity of a Keggin POM for efficient heterogeneous electrocatalytic OER

Highlights•Keggin POM was entrapped for the first time in a sol-gel matrix•The Co-POM-TMOS electrode could be reused for OER for more than 90 days•The sol-gel matrix stabilizes Co-POM under electrochemical conditions at pH 2SummaryPolyoxometalates (POMs) have been well studied and explored in electro/photochemical water oxidation catalysis for over a decade. The high solubility of POMs in water has limited its use in homogeneous conditions. Over the last decade, different approaches have been used for the heterogenization of POMs to exploit their catalytic properties. This study focused on a Keggin POM, K6[CoW12O40], which was entrapped in a sol-gel matrix for heterogeneous electrochemical water oxidation. Its entrapment in the sol-gel matrix enables it to catalyze the oxygen evolution reaction at acidic pH, pH 2.0. Heterogenization of POMs using the sol-gel method aids in POM's recyclability and structural stability under electrochemical conditions. The prepared sol-gel electrode is robust and stable. It achieved electrochemical water oxidation at a current density of 2 mA/cm2 at a low overpotential of 300 mV with a high turnover frequency (TOF) of 1.76 [mol O2 (mol Co)−1s−1]. A plausible mechanism of the electrocatalytic process is presented.Graphical abstract