High-entropy oxides (HEOs) have emerged as a transformative class of materials in heterogeneous catalysis due to their unique compositional complexity and synergistic effects. Recent studies on (CoCrFeMnNi)O have demonstrated exceptional oxygen evolution reaction (OER) activity, with an overpotential of 270 mV at 10 mA/cm² in alkaline media, outperforming traditional catalysts like IrO₂ (320 mV). This enhanced performance is attributed to the multi-elemental synergy, which optimizes the adsorption energies of reaction intermediates. DFT calculations reveal that the presence of Cr and Mn significantly lowers the energy barrier for *OOH formation, a rate-limiting step in OER. Furthermore, the high configurational entropy stabilizes the material under harsh electrochemical conditions, as evidenced by a negligible increase in overpotential (<5 mV) after 1000 cycles.
The tunable electronic structure of HEOs like (CoCrFeMnNi)O enables precise control over catalytic selectivity. In CO₂ reduction reactions, (CoCrFeMnNi)O achieves a Faradaic efficiency of 92% for CO production at -0.8 V vs. RHE, compared to 75% for single-metal oxides like Co₃O₄. This improvement is linked to the optimized d-band center position (-1.8 eV), which facilitates CO₂ activation while suppressing competing hydrogen evolution. In situ X-ray absorption spectroscopy (XAS) reveals dynamic changes in oxidation states during catalysis, with Cr³⁺/Cr⁶⁺ and Mn³⁺/Mn⁴⁺ redox couples playing pivotal roles in electron transfer. The material’s robustness is further highlighted by its stability over 50 hours of continuous operation with <3% activity loss.
HEOs also exhibit remarkable potential in thermal catalysis, particularly for methane combustion. (CoCrFeMnNi)O achieves complete methane conversion at 450°C, significantly lower than conventional catalysts like Pd/Al₂O₃ (550°C). The high entropy configuration enhances oxygen mobility, as confirmed by oxygen isotope exchange experiments showing a surface exchange coefficient (k*) of 2.5 × 10⁻⁷ cm/s at 400°C, an order of magnitude higher than CeO₂-based catalysts. This property is critical for maintaining active oxygen species on the surface, as demonstrated by operando Raman spectroscopy identifying O₂²⁻ as the dominant reactive species. Additionally, the material’s resistance to sintering and coke formation ensures long-term stability, with <1% activity loss after 100 hours at 500°C.
The synthesis scalability and cost-effectiveness of HEOs further bolster their industrial viability. A recent breakthrough in flame spray pyrolysis enables large-scale production of (CoCrFeMnNi)O nanoparticles with controlled size distribution (10-20 nm) and high phase purity (>99%). The production cost is estimated at $50/kg, significantly lower than noble metal-based catalysts ($500-$1000/kg). Life cycle analysis indicates a 40% reduction in environmental impact compared to traditional catalysts due to lower energy consumption and waste generation during synthesis. These advancements position HEOs as sustainable alternatives for large-scale catalytic applications.
Future research directions include leveraging machine learning to optimize HEO compositions for specific reactions and exploring their potential in photocatalysis and electrocatalysis beyond OER and CO₂ reduction.
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