Heterostructure of polyoxometalate/zinc-iron-oxide nanoplates as an outstanding bifunctional electrocatalyst for the hydrogen and oxygen evolution reaction

Electrocatalysts play an important role to increase the energy conversion efficiency of electrolysis processes. In this study, a heterostructure of zinc iron oxide (ZnFe2O4) and polyoxometalate (POM) nanoplates (POM-ZnFe2O4) was fabricated for the first time by a hydrothermal process. The hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) analysis of POM-ZnFe2O4 furnished low overpotentials of 268 and 356 mV, and 220 and 290 mV to achieve current densities of 20 and 50 mA cm-2, respectively. In addition, an electrolytic cell composed of a POM-ZnFe2O4 cathode and anode required an operating voltage of 1.53 V to deliver a current of 10 mA cm-2. The improved electrochemical performance of POM-ZnFe2O4 compared to commercial and recently reported catalysts is attributed to the high electrocatalytically active surface area, modulation in the electronic and chemical properties and the formation of heterojunction of ZnFe2O4 and POM, which are vital for accelerating HER and OER activity.