High-performance electrocatalyst of vanadium-iron bimetal organic framework arrays on nickel foam for overall water splitting

Abstract

The development of active, low-cost and durable bifunctional electrocatalysts toward both oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) are important for overall water splitting. Here, well-defined arrays of vanadium-iron bimetal organic frameworks (VFe-MOF) with controllable stoichiometry have been successfully prepared on nickel foam (NF). The as-fabricated VFe-MOF@NF electrode exhibits excellent electrocatalytic activity and durability for OER and HER in alkaline medium. The material’s overpotentials of 10 mA/cm2 are 246 mV for OER and 147 mV for HER, respectively. The electrolyzer made from the VFe-MOF@NF electrodes as both the cathode and anode in 1 mol/L KOH needs only a voltage of 1.61 V to reach a current density of 10 mA/cm2. The superior performance of VFe-MOF@NF can be attributed to the morphological control and electronic regulation of the bimetals, that is, 1) the exposure of the active sites at electrocatalyst/electrolyte interfaces due to the array structure; 2) the synergistic effect of vanadium and iron metals on electro-catalyzing the overall water splitting.