Amorphous FeOOH Decorated CoSe₂ Nanorod Heterostructured Arrays for Efficient Water Oxidation

In meeting the energy demand of green resources, the fabrication of effective yet cheap electrocatalytic active catalysts for the rate-limiting half reaction, oxygen evolution reaction (OER), of electrochemical water splitting is highly desired. In this study, it is presented that a deliberately deposited amorphous FeOOH layer can drastically promote the electrocatalytic OER activity of CoSe₂. Unlike the pristine CoSe₂ which is consumed gradually, the amorphous FeOOH layer facilitates the capture and fixation of dissolved Co²⁺ ions, which is confirmed by the stable element contents during OER process. As a result, a low overpotential of 253 mV (@ j = 40 mA cm⁻²) is displayed by CoSe₂@FeOOH nanorod arrays (NAs) on carbon cloth (CC) with a small Tafel slope of 69 mV dec⁻¹, which are comparable or even lower than the state-of-the-art OER electrocatalysts. In addition, the long-time durability test indicates the remarkable stability of this material over 20 h. These outcomes provide new perception in design and large scale fabrication of cheap yet effective heterostructured OER catalysts.