Nanocrystalline (CrMnFeCoCu)₃O₄ High-Entropy Oxide for Efficient Oxygen Evolution Reaction

High-entropy materials have exhibited excellent catalytic performance due to the rich defects and active sites brought about by the random distribution of individual elements. In the paper, the spinel (CrMnFeCoCu) 3 O 4 high-entropy oxide (HEO) nanoparticles were synthesized by a coprecipitation method followed by calcination. The results showed that the (CrMnFeCoCu) 3 O 4 HEO exhibited high crystallinity with a spinel structure and nanoparticle sizes of 30–50 nm. Meanwhile, the diversification chemical valence and richer oxygen vacancies in (CrMnFeCoCu) 3 O 4 HEO were confirmed, which was attributed to the adjustable electronic structure by the variable chemical valence of adjacent elements in (CrMnFeCoCu) 3 O 4 HEO. The (CrMnFeCoCu) 3 O 4 HEO presented a higher oxygen evolution reaction catalytic activity with a lower overpotential of 313 mV at a current density of 10 mA·cm –2 than that of CuFe 2 O 4 (402 mV) and superior long-term durability with a 89.7% current retention rate after testing for 24 h. The excellent catalytic performance of (CrMnFeCoCu) 3 O 4 HEO could be attributed to the self-regulating electronic structure of multiple elements and richer oxygen vacancies in the HEO. These findings promote the HEO as a candidate material for electrocatalytic application.