Rags to Riches: Meliorating the Electrocatalytic Reduction of Nitrate to Ammonia over Cu-Based Nanoalloys.

The selective electrocatalytic reduction of nitrate pollutants into valuable ammonia products has gained significant momentum thanks to the emerging circular economy model. However, this technology suffers from poor selectivity, low Faradic efficiency, and a competing parallel hydrogen evolution reaction. In this regard, the use of nanoalloys offers a promising approach to fine-tune the electronic structure by shifting the position of the d-band center and modulating the interaction with nitrate and other reaction intermediates and thus enhance the selectivity of desirable products, which may not be accessible over a pristine single metallic active site. Herein, we have systematically doped Cu (d 9 s 2 ) by Ni (d 8 s 2 ) and Zn (d 10 s 2 ) to produce Cu 0.85 Ni 0.15 /C and Cu 0.85 Zn 0.15 /C, respectively, from the corresponding bimetallic metal-organic framework materials. A thorough investigation of electrocatalytic nitrate reduction over the as-synthesized nanomaterials was done by studying the product yield, selectivity, Faradic efficiency, reaction order, rate, and activation energy. The synthesized carbon-supported nanoalloy of Cu 0.85 Zn 0.15 /C outperformed both Cu 0.85 Ni 0.15 /C and Cu/C, and the superiority was rationalized by the first-principles calculation, which unveiled the significance of the modulation of the d-bands in influencing the interaction of nitrate and other reaction intermediates with the surface, thereby enhancing the selectivity and catalytic efficacy.