Phase-dependent Electrocatalytic Nitrate Reduction to Ammonia on Janus Cu@Ni Tandem Catalyst

Electrosynthesis of NH3 from nitrate anion (NO3–) reduction (NO3–RR) is a cascade reaction, which is considered a great potential alternative to the Haber–Bosch route to reduce CO2 emissions and alleviate the adverse effects of excessive NO3– contamination in the environment. Frequently, solid solution alloys (SSAs) with a single-phase active site may struggle to fully utilize their benefits during the entire process of nitrate (NO3–) reduction, which involves multiple intermediate reactions. In this study, we showed that by separating Cu and Ni in a Janus Cu@Ni catalyst structure, we can achieve high performance in NO3–RR, yielding a high Faradaic efficiency (92.5%) and a production rate of NH3 (1127 mmol h–1 g–1) at −0.2 V versus RHE, compared to CuNi SSA (82.6%, 264 mmol h–1 g–1). Here, we demonstrate that a Janus Cu@Ni catalyst with short-range ordered catalytic sites favors the adsorption of NO through a bridge-bond mode. Simultaneously, a hydrogen spillover process was observed, in which Ni dissociates H2O to generate *H which spontaneously migrates to adjacent catalytic sites to hydrogenate the *NOx intermediates. This facilitates N–O bond cleavage, resulting in the NH3 production rate nearly 5 times higher than that of CuNi SSA, where NO was linearly bonded on its surface. The study of this catalytic effect, a cooperative tandem enhancement, provides insights into the design of multifunctional heterogeneous catalysts for electrochemical NH3 synthesis.