A hybrid of MIL-53(Fe) rhombus and conductive CoNi2S4 nanosheets as a synergistic electrocatalyst for the oxygen evolution reaction

Abstract

Hydrogen energy is considered to be a zero-carbon chemical energy alternative to traditional fossil energy, and electrolysis of water, as one of the most effective methods of producing hydrogen, can produce high-purity hydrogen under the premise of zero pollution. The oxygen evolution reaction (OER) is a slow and energy-intensive four-electron process that limits the rate of decomposition of electrolyzed water and is considered as the bottleneck for overall water splitting. In this paper, CoNi₂S₄ nanosheets were assembled on blank nickel foam with a conventional two-step hydrothermal method, which then was continued with a hydrothermal method to load the diamond-block structure of MIL-53(Fe) on top of CoNi₂S₄ nanosheets, denoted as MIL-53(Fe)@CoNi₂S₄/NF. The MIL-53(Fe)@CoNi₂S₄/NF catalyst exhibited excellent electrochemical performance in 1 M KOH aqueous solution, which required an overpotential of only 201 mV when the current density reached 20 mA cm⁻². In addition, after long-term stability testing, the MIL-53(Fe)@CoNi₂S₄/NF catalyst maintained its favourable OER activity due to the lattice structure of the rhombic blocks which enhanced both the stability of the catalyst structure and the internal ion transport channels.