Optimizing Nitrate Electroreduction toward Nearly 100% Ammonia Selectivity through Synergistic RuCu Catalysts and Integrated Coupled Anodic Reaction for High-Value Products.

Abstract

Copper-based catalysts have been widely used in the field of the nitrate reduction reaction (NO₃RR) to ammonia, demonstrating high nitrate reduction rates. However, their low selectivity for ammonia production poses significant limitations in practical applications. In this study, we present that the incorporation of Ru into the Cu@Ni foam can achieve nearly 100% selectivity for NH₃ and a high faradaic efficiency of 96.8% in the NO₃RR. Ru not only facilitates the generation of adsorbed hydrogen but also suppresses the HER reaction. This can be attributed to the unique electron distribution exhibited by Ru atoms when surrounded by Cu, leading to a decreased electron-accepting capability. Consequently, this reduction results in a diminished Lewis acidity and a decreased H* adsorption. Importantly, it was confirmed that the incorporation of Cu with Ru serves as "anchor" for atomic H* generated from Ru, inhibiting HER and ensuring the availability of H* for subsequent ammonia production. The synergistic effect between Ru and Cu enhanced the efficiency and selectivity of reduction of nitrate to NH₃. Remarkably, substituting oxygen evolution reaction (OER) with a coupled anodic reaction for the oxidation of benzyl alcohol to benzaldehyde can significantly accelerate the nitrate reduction rate by 1.7 times and achieves a 90% benzaldehyde conversion rate. This research not only introduces innovative strategies for designing high-performance ammonia-selective electrocatalysts but also highlights the potential industrial applications for the synthesis of high-value products.