Spinel MnFeCoNiCuO high-entropy oxides synthesized via aerosol-assisted spray pyrolysis with different temperatures: impacts on oxygen evolution reaction

It remains unclear how various temperatures used in spray pyrolysis to synthesize high-entropy oxides (HEOs) could affect the HEOs’ electrochemical performance for oxygen evolution reaction (OER). To answer this question, a series of MnFeCoNiCuO HEOs were synthesized from 600 to 1100 °C via spray pyrolysis. Detailed characterization confirmed the single-phase spinel structures, and increasing temperature can improve the crystallinity of the products along with increased lattice strain. When utilized as electrocatalysts for OER, MnFeCoNiCuO HEOs synthesized from 700 °C exhibit better catalytic performance compared to those synthesized at higher temperatures (e.g., 900 °C and 1100 °C), as evidenced by the lower overpotentials and smaller Tafel slopes. The variations in the OER performance of HEOs are attributable to the dependence of the electrochemically active surface area and charge-transfer resistance on the synthesis temperatures. In the meantime, density functional theory calculations suggested that the temperature-induced lattice strain can also impact the catalyst-intermediate interactions, thus influencing the OER performance. Overall, this work contributes to the improved understanding of the structure–property-performance of HEOs synthesized from spray pyrolysis for optimized OER performance.