Solution combustion synthesis of high-entropy metal spinel oxide as oxygen evolution reaction catalyst

High-entropy metal spinel oxide (HEO) is proved to be a promising oxygen evolution reaction (OER) catalyst with high catalytic performance and stability. A short routine synthesis process based on solution combustion synthesis was proposed to prepare (Co0.25Ni0.25Mn0.25Zn0.25)Fe2O4 spinel HEO in this work. During the process, the products were rapidly synthesized and melted due to the high-temperature reaction, and then quickly crystallized on the surface of nickel foam to form a nano-structure coating. With the aid of nano-scale spinel structure, the overpotential of non-activation HEO electrode reaches 276 mV at the current density of 10 mA·cm−2, and after 100 h i-t test, it can be further reduced to 230 mV, which proves the high activity of OER catalysis. The promotion of OER catalytic performance can be attributed to the surface reconstruction caused by the selective element leaching and the boost of oxygen vacancy, leading to the formation of nano-scale flocculation around spinel core after the long-term OER process. This work indicates a special casting process for functional materials and explores the application of rapid crystallization.