Enhancing the selective electrochemical conversion of nitrate via π back-donation on Lewis acid sites induced by noble-metal doped CoP

Abstract

Electrochemical conversion of nitrate into ammonium through an electrocatalytic NO₃⁻ reduction reaction (NO₃⁻RR) system and a Zn–NO₃⁻ battery system provides a green way to achieve environmental governance and energy conversion. To achieve efficient electrochemical conversion of nitrate, it is necessary that the electrocatalyst has excellent NO₃⁻ adsorption capacity and an easily regulated electronic structure to achieve the adsorption of NO₃⁻ and meet the requirements of an eight-electron nine-proton reaction. To realize the adsorption of NO₃⁻ and the adjustment of the electronic structure, the strategy of introducing Lewis acid sites into the lattice of noble metal Pd doped CoP has been successfully carried out, and it has been verified that it can promote the adsorption and transformation of NO₃⁻, and partly adjust the electronic structure of Pd/CoP. The ammonium selectivity through the electrochemical activity test increased by nearly a factor of 1.5 from 58.47% to 88.94%. The DFT calculation shows that Pd/CoP can efficiently anchor dissociated NO₃⁻ through Lewis acid–base interaction, and magnify the reaction intensity between NO₃⁻ and Pd/CoP to realize the highly selective conversion of nitrate to ammonium. In addition, the Pd/CoP-based Zn–NO₃⁻ battery also showed an open-circuit voltage of 1.38 V vs. Zn/Zn²⁺ and a peak current density of 1.55 mW cm⁻². This work provides a reference strategy for the design of high-performance electrocatalysts by introducing Lewis acid sites and regulating the electronic structure of active sites.