High-nuclearity cobalt(II)-containing polyoxometalate anchored on nickel foam as electrocatalyst for electrochemical water oxidation studies

Abstract

Polyoxometalates (POMs) are known for their unique structural properties and have attracted widespread attention in the field of storage devices, energy conversion materials, catalysis, electronics and molecular sensing. This article focuses on the anchoring of high nuclearity 16-cobalt(II)-containing POM that is, Na30.5K1.5[{Co4(OH)3PO4}4(A-α-GeW9O34)4]٠116H2O (Co16-GeW9) using 3-aminopropyl triethoxysilane (APTS) as chemical linker over nickel foam (NiF) and is tested as electrocatalyst for water oxidation studies. The fabricated POM-based electrode (Co16-GeW9@NiF) has been characterized by UV–visible spectroscopy, Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and energy-dispersive X-ray (EDX) analysis. Co16-GeW9 @NiF has been tested for its electrocatalytic water oxidation activity in 1 M KOH (pH 14) and sodium phosphate buffer (pH 7) with NaNO3 as a supporting electrolyte. The catalyst exhibited excellent electrocatalytic oxygen evolution reaction (OER) activity with overpotential of 370 mV at 10 mA/cm2 and a Tafel slope of 84 mV/dec in 1 M KOH, while overpotential of 530 mV at 10 mA/cm2 and a Tafel slope of 153 mV/dec in sodium phosphate buffer. The immobilization of POM over NiF could generate a way for developing efficient electrocatalysts for water oxidation in both neutral and basic pH.