The electrochemical nitrate (NO 3 − ) reduction reaction (NO 3 − RR) provides a promising strategy for ammonia (NH3) synthesis and NO 3 − wastewater treatment. However, the reaction still suffers from sluggish kinetics and unsatisfactory NH3 selectivity owing to the complex multi-step reaction process with eight-electron transfer and multiple intermediates. Here we report a hierarchical nanoporous CuCoNiPdRuAl catalyst with a high-entropy CuCoNiPdRu surface as an efficient electrocatalyst for NO 3 − RR. By virtue of the high-entropy surface offering multiple catalytic sites and nanoporous architecture that facilitate mass transport, the np-CuCoNiPdRuAl exhibits a high NH3 Faradic efficiency of 97.4% and an impressive NH3 yield rate of 30.47 mg h−1 mg cat −1 . Experimental and theoretical studies indicate that the high-entropy CuCoNiPdRu surface creates multiple catalytic sites, which not only enable the acceleration of every step of the NO 3 − RR via a tandem reaction mechanism but also provide a facile channel for ultrafast *H spillover for enhanceing the hydrogenation of intermediates, ultimately leading to enhanced NO 3 − RR performance. This work offers an opportunity to design highly active and selective NO 3 − RR electrocatalysts with potential for practical application.
