Tailoring the d‑Band Center of High-Entropy Perovskite Oxide Nanotubes for Enhanced Nitrate Electroreduction

High-entropy perovskite oxides exhibit promising application prospects in the field of electrocatalysis, owing to their flexible elemental composition, plentiful active sites, and superior structural stability. Herein, high-entropy perovskite oxide nanotubes are prepared with La, Nd, Pr, Er, Eu at A-site by electrospinning as efficient electrocatalysts for nitrate reduction reaction (NO₃RR). Electrochemical tests demonstrate that LaNd_0.25Pr_0.25Er_0.25Eu_0.25CuO₄ nanotubes (LNPEEC NTs) display outstanding NO₃RR performance, achieving a NH₃ Faraday efficiency (FE_NH3) of 100% at -0.7 V versus reversible hydrogen electrode (RHE) and a yield rate_NH3 of 1378 µg h^-1 mg^-1 _cat. at -1.0 V_RHE, outperforming Nd₂CuO₄ nanotubes (NC NTs). Furthermore, LNPEEC NTs also exhibit excellent stability even after 10 cycles at -0.7 V_RHE and -1.0 V_RHE. X-ray absorption spectroscopy confirms that multi-component regulation of A-site optimizes the coordination environment of Cu at B-site, increasing the unsaturated Cu sites and thus providing more active sites. Additionally, density functional theory calculations reveal that the doping of multi-component rare-earth elements at A-site in LNPEEC NTs modulates the d-band center of Cu at B-site and reduces the reaction energy barrier of the rate-determining step, thus enhancing the adsorption of NO₃ ^- and promoting the NO₃RR performance.