Nanoporous surface high-entropy alloys enable tandem catalysis and ultrafast hydrogen spillover for efficient nitrate electroreduction to ammonia

The electrochemical nitrate (NO3−) reduction reaction (NO3−RR) provides a promising strategy for ammonia (NH3) synthesis and NO3− 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 NO3−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 mgcat.−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 NO3−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 NO3−RR performance. This work offers an opportunity to design highly active and selective NO3−RR electrocatalysts with potential for practical application.