Active Interfacial Perimeter in NbN-Supported CoCu Alloys for Electrocatalytic Nitrate Reduction to Ammonia

Ammonia (NH3) is a promising zero-carbon and hydrogen-rich fuel, in addition to its critical role in the manufacture of agricultural fertilizers and various chemicals. Electrocatalytic nitrate reduction reaction (NO3–RR) holds potential for NH3 synthesis yet faces challenges as complex multielectron/proton transfer pathways. Promoter-supported catalysts have shown particular advantage in hindering the agglomeration of the active sites, while the catalytic performance is further boosted by generating abundant active perimeter sites at the metal–support interface. Here, CoCu nanoparticles are successfully anchored on a spin promoter of niobium nitride (CoCu/NbN-NPs) by the high-temperature thermal shock (HTS) strategy. CoCu/NbN-NPs exhibit better NO3–RR activity than the single-metal counterparts (Cu/NbN-NPs and Co/NbN-NPs), and achieve a high Faradaic efficiency (FE) of nearly 100% and NH3 yield of 35.5 μg min–1 cm–2 at −0.3 V in NaNO3-containing alkaline electrolyte. The NbN support also enables CoCu/NbN-NPs to show catalytic stability and structural robustness during prolonged electrolysis. In situ electrochemical investigations reveal that the NO3–RR activity is enhanced synergistically by Cu and Co sites, which accelerate the conversion of intermediates. Theoretical studies demonstrate that the bimetallic model shows a 1.12 eV lower energy barrier for the rate-determining step than the Cu-only model. Notably, the binding of intermediates is collectively optimized by their preferential adsorption at the interfacial perimeters, thereby accelerating the NO3–RR. The NbN support modulates the electronic structure of the anchored CoCu alloys by achieving electron transfer from the support to the alloys at the interfacial perimeters. The enhanced NO3–RR activity of CoCu/NbN-NPs over that of the alloys on other conductive supports can be specifically attributed to the large active interfacial perimeter and the consequent strong electronic interactions. This study provides valuable insights into the reaction mechanism at the interfacial perimeters of supported catalysts and offers a promising design principle for developing high-performing, promoter-supported catalysts.