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

Abstract

Despite the intense research efforts directed to electrocatalytic nitrogen reduction reaction (eNRR), the NH3 yield and selectivity are still not up to the standard of practical application. Here, high-entropy perovskite oxides with composition Bax(FeCoNiZrY)0.2O3−δ (Bx(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 NH3 yield and Faraday efficiency for B0.9(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 (*NNH2 → *NNH3) 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. [Figure not available: see fulltext.]