Copper doping strategy for the protection and dynamic regulation of in-situ grown heterogeneous structures on iron substrates to achieve overall water splitting in electrocatalysis

Designing and preparing bifunctional fully hydrated electrocatalysts through interface engineering and valence state modulation is an effective method to reduce the catalytic energy barriers for the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). However, developing and constructing efficient, low-cost non-precious metal mixed catalysts pose significant challenges, especially in terms of metal electronic configuration and structural control. In this study, we prepared a nanoflower heterostructure array of copper iron sulfide and cobalt iron layered double hydroxide by copper doping and in-situ sulfurization of dynamically protected iron substrates. The construction of this heterostructure exposes more catalytic active sites and optimizes the electron arrangement of the catalyst, significantly enhancing the superhydrophilicity/superaerophobicity of the electrocatalyst and improving its catalytic activity and stability during the OER and HER processes. Density functional theory (DFT) calculations indicate that the synergistic regulation of cobalt and copper, along with the optimization of the sulfide, reduces the free energy required for OER intermediate adsorption, adjusts the surface electronic structure of the material, promotes electron transfer between the heterostructures, and accelerates the kinetics of the catalytic reaction. As a result, the prepared catalytic material exhibits excellent electrocatalytic performance for both OER and HER, requiring overpotentials of 285 mV and 72 mV, respectively, to achieve a current density of 10 mA cm −2 in an alkaline electrolyte (1 M KOH solution). The assembled electrocatalytic water splitting cell operates at a low voltage of only 1.53 V. This study provides an attractive approach for the future design of efficient water splitting electrocatalysts.