High-entropy perovskite oxides: A versatile class of materials for nitrogen reduction reactions

Despite the intense research efforts directed to electrocatalytic nitrogen reduction reaction (eNRR), the NH 3 yield and selectivity are still not up to the standard of practical application. Here, high-entropy perovskite oxides with composition Ba x (FeCoNiZrY) 0.2 O 3− δ (B x (FCNZY) 0.2 ( x = 0.9, 1) are reported as eNRR catalysts. The eNRR activity of high-entropy perovskite oxide is enhanced by changing the nonstoichiometric metal elements at the A-site, thus generating additional oxygen vacancies. The NH 3 yield and Faraday efficiency for B 0.9 (FCNZY) 0.2 are 1.51 and 1.95 times higher than those for B(FCNZY) 0.2 , respectively. The d-band center theory is used to theoretically predict the catalytically active center at the B-site, and as a result, nickel was identified as the catalytic site. The free energy values of the intermediate states in the optimal distal pathway show that the third protonation step (*NNH 2 → *NNH 3 ) is the rate-determining step and that the increase in oxygen vacancies in the high-entropy perovskite contributes to nitrogen adsorption and reduction. This work provides a framework for applying high-entropy structures with active site diversity for electrocatalytic nitrogen fixation.