Microwave synthesis of rock-salt type high entropy oxides immobilized on graphene oxide nanosheets as an efficient catalyst for oxygen evolution reaction

High-entropy oxides (HEOs) have emerged as a promising class of materials for advanced energy storage and conversion technologies, owing to their unique configurational disorder, tunable electronic structures, and compositional flexibility. In this work, we developed a novel heterostructure catalyst by immobilizing HEO nanoparticles on graphene oxide (GO) nanosheets, demonstrating exceptional electrocatalytic performance and durability for the oxygen evolution reaction (OER). Comprehensive physicochemical characterization confirmed the formation of a crystalline HEO phase with uniform elemental distribution and strong interfacial bonding with the GO support. The excellent electrochemical response is attributed to the self-regulating electronic structure of HEOs, high concentration of oxygen vacancies and fine structure exposed to electrolytes. Among all prepared electrocatalysts, the optimum composition (HEO@GO-50) demonstrated outstanding OER activity with low overpotential (?) ~303 mV, small Tafel slope 44.4 mVdec- 1, high exchange current density (Jo) 14.16 mAcm-2, high double layer capacitance (Cdl) 21.35 mFcm-2, large electrochemical surface area (ECSA) 355.83 2, low charge transfer resistance (Rct) 28.64 O, high turnover frequency (TOF) 1.033 s-1 and current retention of 92 % over 10 h of chronoamperometric analysis. These parameters are very competitive with other transition metal oxide based electrocatalysts and noble metal oxides. Our findings suggest that HEO-GO hybrids could represent a promising approach for designing high-performance, noble-metal-free electrocatalysts for sustainable energy applications. 2025 Published by Elsevier Ltd.