Structure and electrocatalytical properties of electrodeposited M-Ir (M=Co, Ni) bimetallic alloy catalysts with low Ir loading obtained on copper foams for hydrogen evolution reaction

Abstract M-iridium (M = cobalt (Co), nickel (Ni)) bimetallic alloy catalysts with low iridium (Ir) loading of 0.3 ~ 2.0 mg·cm− 2 were prepared on copper foam (CF) supports by electrodeposition. The top surface of as-deposited M-Ir catalysts was mainly composed of metallic state and oxides states, such as metallic Ir, Ni(OH)2 or Co(OH)2, Co(Ir) and Ni(Ir) solid solution, Ir oxides. M-Ir catalysts with low Ir loading exhibited excellent catalytic performance. Ni67.4Ir32.6/CF catalyst with low Ir loading of 2.0 mg·cm− 2 achieved a current density of 10 mA·cm2 at an overpotential of 52 mV and a Tafel slope of 36 mV·dec− 1. Co64.2Ir35.8/CF catalyst with low Ir loading of 0.7 mg·cm− 2 was uniformly scattered with small ellipsoidal particles, looking like fine fluff, requiring an overpotential of 51 mV for hydrogen evolution reaction to reach a current density of 10 mA·cm− 2, having a Tafel slope of 38 mV·dec− 1. After long-term hydrogen evolution testing, M-Ir/CF catalysts exhibited excellent electrocatalytic stability for water splitting in alkaline solution.