A novel ligand with –NH2 and –COOH-decorated Co/Fe-based oxide for an efficient overall water splitting: dual modulation roles of active sites and local electronic structure

Abstract

Excellent electrochemical water splitting with remarkable durability can provide a solution to satisfy the increasing global energy demand in which the electrode materials play an important role. Herein, Co/Fe-based metal–organic frameworks (MOFs) were designed and fabricated by a two-step hydrothermal method using CoFe₂O₄ as the precursor. The Co/Fe-based MOFs are organic–inorganic hybrid materials with adjustable structures bearing –NH₂, –COOH and benzene as the coordinated donor, acceptor, and π-crosslinker units, respectively, and strands of metal and ligand associated via bonds located in the channels are predestined to possess superior catalytic performance. Electrochemical studies showed that the catalyst required an overpotential of only 1.468 V to reach 10 mA cm⁻² with good stability for 100 h, which is superior to the transition metal oxides and noble metals. In the process of electrocatalysis, the Co–N and Fe–N bonds formed between the Co/Fe metal and amino functional group serve as the center of the hydrogen evolution reaction, and the formation of a catalytic intermediate via –NH₂ and –COOH activation of π-electrons to π*-electrons is helpful for intermolecular interactions. This work demonstrates that MOFs prepared by Co and Fe-based precursors are promising to be employed for the overall water splitting and have huge potential for practical utilization.