Low-temperature synthesis of nano-porous high entropy spinel oxides with high grain boundary density for oxygen evolution reaction

Recently, high entropy spinel oxides have become a hotspot for oxygen evolution electrocatalysts. However, high temperature preparation method offers limited control over their morphology and size, leading to unsatisfactory OER catalytic activity. It is worth noting that low temperature can prevent grain coarsening and increase the grain boundary density of catalysts, effectively promoting the OER catalytic activity. However, low temperature preparation of nano-porous high-entropy spinel oxides catalysts has rarely been reported. In this paper, a nano-porous high-entropy oxide catalyst with high grain boundary density (Fe0.2Co0.2Ni0.2Cr0.2Mn0.2)3O4 was first prepared by low temperature solution combustion method. Benefiting from the nano-porous morphology and high grain boundary density, it shows the enhanced OER activity with the overpotential of 275 mV at a current density of 10 mA cm−2, and the Tafel slope is 50.27 mVdec−1. Importantly, it also presents an outstanding long-term stability due to its high structural stability caused by high entropy, and its overpotential has almost no obvious attenuation at a current density of 10 mA cm−2 for 60 h and at a current density of 250 mA cm−2 for 40 h. This work provides a novel strategy to prepare high-performance nanostructured high entropy spinel oxides catalysts.