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)3O4 high-entropy oxide (HEO) nanoparticles were synthesized by a coprecipitation method followed by calcination. The results showed that the (CrMnFeCoCu)3O4 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)3O4 HEO were confirmed, which was attributed to the adjustable electronic structure by the variable chemical valence of adjacent elements in (CrMnFeCoCu)3O4 HEO. The (CrMnFeCoCu)3O4 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 CuFe2O4 (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)3O4 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.