Cobalt borophosphate on nickel foam as an electrocatalyst for water splitting

Abstract

One of the most critical steps in the transition to carbon-free energy systems is sustainable hydrogen evolution from water. In this research, a cobalt borophosphate crystalline compound consisting of phosphate and borate anions was synthesized with a solid-state reaction. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and X-ray Photoelectron (XPS) was employed to investigate the structure, composition, and morphology of Co3BPO7. Electrocatalytic performances of the catalyst towards oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) have been investigated on nickel foam (NF) electrode in 1.0 M KOH (pH 13.6) by linear sweep voltammetry, chronopotentiometry, cyclic voltammetry, and electrochemical impedance spectroscopy. For OER, the catalyst exhibits an overpotential of 230 mV at 10 mA cm−2 with a Tafel slope of 130 mV dec−1, which is comparable to that of the benchmark RuO2 electrocatalyst, and 220 mV overpotential for a current density of 10 mA cm−2 with a Tafel slope of 147 mV dec−1 for HER process. Long-term chronoamperometry and multiple cyclic voltammetric experiments indicate the catalyst is stable throughout both HER and OER processes. Electrochemical experiments and characterization studies performed on the pristine and post-catalytic electrode indicate that the catalyst is robust under alkaline electrocatalytic conditions (pH 13.6).