(569ep) Ultratrace Ruthenium Anchored on Cu@Ni Foam for Accelerated H* Utilization in Nitrate Electroreduction to Near 100% Ammonia Selectivity

Electrochemical nitrate reduction reaction (NO₃RR) presents a compelling strategy for mitigating the environmental impact of nitrate in wastewaters, while concurrently facilitating the production of valuable chemicals, such as ammonia (NH₃). The preparation of an efficient, highly selective electrocatalyst for NH₃ synthesis is paramount. The primary challenges lie in enhancing the generation of adsorbed hydrogen (H*) through water splitting and optimizing H* utilization to improve ammonia selectivity. In this study, we introduce a novel one-step electrodeposition technique to synthesize ultratrace ruthenium anchored on copper@nickel foam (RuCu@NF), aimed at accelerating H* production and maximizing its utilization. Tested under conditions of 50 mM SO₄^2- and 50 mg L^-1 NO₃^--N, the RuCu@NF electrode demonstrated exceptional performance, achieving nearly 100% NH₃ selectivity and a faradaic efficiency (FE) of 96.8%, alongside robust electrocatalytic stability over more than 10 cycles. DFT calculations show that ruthenium atoms, when surrounded by copper, have more electrons near the Fermi level but lower hydrogen adsorption. Combining this with free radical and EPR studies reveals that although ultratrace ruthenium doping decreases hydrogen adsorption, it actually speeds up hydrogen production. Importantly, this process uses adsorbed hydrogen (H*) efficiently, avoiding unwanted hydrogen gas formation. Additionally, we developed an electrochemical coupling system that significantly enhanced the nitrate reduction rate by approximately 1.7-fold, with the selective conversion of benzyl alcohol to benzaldehyde reaching 90%. This research not only offers innovative approaches for designing high-performance, ammonia-selective electrocatalysts by focusing on the efficient cracking of water and the optimal use of H*, but also sheds light on integrating nitrate reduction with the synthesis of high-value-added chemicals.