Hierarchical Selenium-Doped Nickel–Cobalt Hybrids on Carbon Paper for the Overall Water-Splitting Electrocatalytic System
Anh Ngoc Nguyen, Anisa Fitriani Rosyadi, Dahae Kim, Hyojong Yoo
Abstract
Designing and constructing hierarchically structured materials with heterogeneous compositions is the key to developing an effective catalyst for overall water-splitting applications. Herein, we report the fabrication of hollow-structured selenium-doped nickel–cobalt hybrids on carbon paper as a self-supported electrode (denoted as Se–Ni|Co/CP, where Ni|Co hybrids consist of nickel–cobalt alloy-incorporated nickel–cobalt oxide). The procedure involves direct growth of zeolitic imidazolate framework-67 (ZIF-67) on bimetal-based nickel–cobalt hydroxide (NiCoOH) electrodeposited on CP, followed by selenous etching and pyrolysis to obtain the final Se–Ni|Co/CP electrocatalytic system. The optimized Se–Ni|Co/CP [Se–Ni 1 |Co 9 /CP(0.3)] exhibits remarkable performance in the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), displaying a current density of 10 mA cm –2 at small overpotentials of 105 mV for HER and 235 mV for OER. Furthermore, it allows an alkali electrolyzer to achieve a current density of 10 mA cm –2 at a cell voltage of only 1.51 V. The outstanding catalytic activity of Se–Ni|Co/CP is ascribed to the high intrinsic activity of the bimetallic catalyst, efficient interfaces, and charge transport facilitated by the heterogeneous component, the hollow structure inherited from the metal–organic frameworks (MOF)-derived material providing ample porosity and active sites, and structural robustness achieved through self-supported construction.