Hydrothermally/electrochemically decorated FeSe on Ni-foam electrode: An efficient bifunctional electrocatalysts for overall water splitting in an alkaline medium

A new hybrid catalyst based on Ni foam (NF) and FeSe was prepared by a facial hydrothermal method, in which Se-decorated NF was subsequently electrochemically doped by Fe. Binder-free catalyst containing electrodes were directly tested for the hydrogen and oxygen evolution reaction (HER/OER). The FeSe/NF electrode displayed an OER current density of 100 mA cm−2 at potential of 1.42 V, and a relatively small Tafel slope of 109 mV dec−1 in a 1 M KOH solution. Also, FeSe/NF electrode exhibited reasonable HER overpotential of 200 mV at 10 mAcm−2 current density with Tafel slope of 145 mV dec−1. The XRD and TEM studies revealed that the formation of heterogeneous interfaces of NiSe2 and FeSe2,generated more active sites that can promote better ions and electron transport in the electrode/electrolyte interfaces. Furthermore, HRTEM analysis indicates that FeSe2 rich in Se vacancy defects can be created with suitable M − O and M − H bond for better OER and HER performance, respectively. In a-two electrode alkaline water electrolyzer, current densities of 10 mA cm−2 and 50 mA cm−2 were obtained at cell voltages of 1.52 V and 1.85 V, respectively, using pure FeSe–NF as both the cathode and anode.