High-Entropy Oxides as Next-Generation Catalysts for Clean Energy Conversion

Abstract

The transition toward carbon-neutral energy technologies requires catalysts that combine high efficiency, durability, and economic viability. High-entropy oxides (HEOs), comprising five or more metal cations in a single-phase lattice, have recently emerged as a transformative class of catalytic materials due to their entropy-driven structural stability, tunable electronic configurations, and abundance of active sites. This study systematically investigates the synthesis, structural design, and catalytic performance of HEOs, with a focus on their application in key clean energy conversion reactions, including the oxygen evolution reaction (OER), oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER). Multicomponent HEO catalysts were synthesized via Sol–gel assisted combustion method followed by controlled thermal treatment to ensure uniform elemental dispersion and lattice stabilization. The crystallographic and morphological features were examined using X-ray diffraction (XRD), while surface composition and oxidation states were characterized through X-ray photoelectron spectroscopy (XPS). Electrochemical performance was evaluated in alkaline and acidic media using cyclic and linear sweep voltammetry, electrochemical impedance spectroscopy, and durability tests under extended chronoamperometric conditions. The synthesized HEOs exhibited stable single-phase crystalline frameworks with homogeneous elemental distribution, confirming entropy-induced stabilization. A representative (Co, Ni, Fe, Mn, Cu) O catalyst demonstrated remarkable OER activity, delivering an overpotential as low as 280 mV at 10 mA cm⁻², surpassing the benchmark RuO₂. The HEOs also exhibited enhanced HER and ORR activities, attributable to synergistic multi-cation interactions that optimized charge transfer and modulated adsorption energetics. Durability tests revealed outstanding structural and electrochemical stability, with negligible degradation after 100 hours of continuous operation. This study underscores the potential of high-entropy oxides as multifunctional and durable catalysts for next-generation energy conversion technologies. Their entropy-stabilized lattice enables tunable catalytic activity and resilience under harsh electrochemical environments, making them cost-effective alternatives to precious metal catalysts. These findings pave the way for rational design strategies that couple entropy engineering with computational screening and scalable synthesis, thereby accelerating the integration of HEOs into sustainable energy systems such as water electrolyzers, fuel cells, and metal–air batteries.