Nickel-Constructing Interfaces of Multiheterostructure on Self-Supporting Electrode for Efficient Overall Urea-Water Splitting

Abstract

Water splitting is an environmentally friendly strategy for producing hydrogen, it is constrained by the high theoretical potential of oxygen evolution reaction (OER) at the anode. It is possible to save energy by substituting OER with urea oxidation reaction (UOR) with low theoretical potential. Particularly, developing bi-functional catalysts (hydrogen evolution reactions (HER)/UOR) and exploring their catalytic mechanisms and active sites are highly desirable with the rapid development of the hydrogen economy. Herein, combining electrodeposition and immersion method are reported to grow well-aligned MOF on Graphene-like material (Mxene). Specifically, Ni3S2 species were formed on the hexahedral structure of cobalt-based MOF (CoMOF) by electrodeposition. The resultant M/CM/Ni3S2/NF demonstrates good electrocatalytic capabilities towards HER and UOR, with overpotential and potential of 0.174 and 1.392 V required to arrive at 100 mA cm-2, respectively. DFT results establish that the coupling of Mxene, CoMOF, and Ni3S2 can maximize the free energy of hydrogen adsorption on the catalyst surface. Furthermore, in-suit XRD reveal the (020) crystal plane of Ni3S2 may be the active site of  M/CM/Ni3S2/NF and has good stability. This work will innovate a novel route for designing high-activity bifunctional catalysts for various electrochemical energy applications.

Keywords: Bifunctional, UOR, HER, CoMOF, Mxene (Ti3C2Tx), Ni3S2