Unveiling the role of Ru nanoclusters in Ru-CuOx nanowires for electrochemical nitrate reduction to ammonia

Electrochemical nitrate reduction reaction (NO 3 RR) is a sustainable strategy to treat wastewater and produce ammonia. However, it is still a challenge to prepare electrocatalysts with high activity and selectivity. Herein, the CuO x nanowires supported Ru nanoclusters (Ru-CuO x ) were fabricated via a three-step procedure for efficient nitrate conversion and highly selective ammonia generation. The prepared Ru-CuO x shows a high ammonia yield rate of 2286.5 μg h −1 cm −2 at −0.7 V vs. RHE and Faradaic efficiency (FE) of 80.1% at −0.4 V vs. RHE. Additionally, the nitrate conversion rate exceeds 90% at the potential range from −0.2 to −0.7 V vs. RHE, and the ammonia selectivity can reach 97.7% at −0.7 V vs. RHE in 100 mg L −1 NaNO 3 solution. The systematic characterizations clarify that the introduction of Ru not only regulates the electronic structure of CuO x and accelerates the reconstruction of CuO x to Cu but also promotes H 2 O dissociation to generate active hydrogen. Moreover, in-situ Raman spectroscopy reveals that the formed Ru-Cu is considered the actual active species during the NO 3 RR. Density functional theory (DFT) calculations further prove that the obtained Ru-Cu facilitates the adsorption of nitrate and lowers the Gibbs free energy of the rate-determining step, thus improving the NO 3 RR performance.