One-step synthesis of heterostructured cobalt-iron selenide as bifunctional catalyst for overall water splitting

Abstract

Transition metal selenide catalysts have been identified as suitable materials for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) as a result of their high electrical conductivity, large surface area, and tunable electronic structure to generate clean hydrogen through electrocatalytic water splitting. In this work, we report the fabrication of cobalt-iron selenide nanoparticles to form a heterostructured Co-Fe Selenide catalyst through a one-step hydrothermal process. The fabricated Co-Fe Selenide shows an improved performance toward HER in both acidic and alkaline electrolyte as compared to individual CoSe2 and FeSe2 catalysts. The HER activity of Co-Fe Selenide, at a current density of 10 mA cm−2, generates an overpotential of 129 and 142 mV, a Tafel slope of 47 and 46 mV dec−1 in both acidic and alkaline electrolytes, respectively. Furthermore, the catalyst exhibits an OER activity with an overpotential of 270 mV at a current density of 10 mA cm−2 with a small Tafel slope (78 mV dec−1) in alkaline electrolyte. Moreover, a symmetric water electrolysis cell assembled using Co-Fe Selenide on carbon cloth as both anode and cathode in alkaline electrolyte achieves a cell voltage of 1.68 V at a current density of 10 mA cm−2 with strong stability for 9 h. This outcome renders Co-Fe Selenide as a low-cost material for efficient HER and OER activity and as a potential replacement to noble metal catalysts for overall water splitting devices.