Co-regulation of anion-cation in transition metal high entropy oxide for outstanding OER electrocatalytic performance

Transition metal oxides (TMO) are promising non-noble-metal electrocatalysts for OER due to their high activities and abundant crustal reserves. Introducing multiple cations and anions simultaneously into TMO is an effective route to ameliorate the catalytic property. Herein, a series of S-doped high entropy oxide (HEO) electrocatalysts consisting of five transition metals (including Cr, Mn, Fe, Co, and Ni) have been synthesized by microwave-assisted hydrothermal method. Compare with the low-component counterparts and the HEO without anion-doping, MS0.3 with the optimized S content exhibits superior performance, in terms of a low overpotential of 243 mV at a current density of 10 mA cm−2 and excellent stability. The synergistic effect of multiple cations and anion doping not only regulates the morphology and crystallinity of the catalyst significantly, but also effectively adjusts the electronic structure of the catalyst, improves conductivity, and provides suitable covalent bonds. In addition, the quasi-amorphous structure derived from the low-temperature microwave-hydrothermal effects and S doping introduces more defects and increases the active sites. The intrinsic entropy stabilization mechanism of HEO improves the durability of the catalyst. This work provides a guide for the design of electrocatalyst with controllable morphology, composition, and structure to achieve remarkable catalytic performance.