A novel high-entropy sulfide (ZnCoMnFeAlMg)9S8 as a low potential and long life electrocatalyst for overall water splitting in experiments and DFT analysis

Abstract

Sulfide compounds offer promising alternatives for electrocatalysts in water splitting, thanks to their diverse nature, intrinsic activities, affordability, and abundance in the Earth's crust. However, the limited active sites, hindered substance transport, larger particle size, and structural collapse restrict their performance in the electrolysis of water. In order to achieve a dual-functional catalyst with multiple catalytic sites, it is often necessary to construct heterogeneous or composite structures. However, this typically leads to an increase in catalyst resistance and also affects its operational stability. In response, we successfully prepared a high-entropy sulfide (ZnCoMnFeAlMg)₉S₈ through a low-temperature solvothermal method. This approach resulted in a reduction in grain size and a doubling of the specific surface area. The high entropy not only maintains the stability of the structure but also induces electron interactions within the catalyst through the interactions of multiple metals. This exposure of more active sites enables the realization of a dual-functional catalyst with multiple catalytic sites within a single structure. In addition, the increased presence of high-valence Fe and Ni ions promotes the chemisorption of intermediates, facilitating electron transfer during the reaction process. Benefiting from this multi-scale regulation strategy, the (ZnCoMnFeAlMg)₉S₈ displays an ultralow overpotential of 1.39 V at 10 mA cm⁻² and a small Tafel slope of 35.3 mV dec⁻¹. Density functional theory calculations indicate that high entropy can significantly modulate the local charge distribution and electronic properties of sulfides, thereby achieving optimal adsorption energy and reducing the potential energy barrier for hydrolysis. This study introduces a fresh approach to the functionalization of high entropy nanomaterials, while simultaneously enhancing the performance of water splitting catalysts.