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

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, CoNiS 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 CoNiS nanosheets, denoted as MIL-53(Fe)@CoNiS/NF. The MIL-53(Fe)@CoNiS/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. In addition, after long-term stability testing, the MIL-53(Fe)@CoNiS/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.