Accelerating Electrocatalytic Nitrate Reduction to Ammonia via Weakening of Intermediate Adsorption on Cu-Based Catalyst

Abstract

Cu-based materials are commonly used in electrocatalytic nitrate reduction reactions (NO₃RR). NO₃RR is a “two birds, one stone” approach, simultaneously removing NO₃ ⁻ pollutants and producing valuable ammonia (NH₃). However, the strong coordination between the NO₃ ⁻ intermediate and the catalytic active sites seriously hinders the conversion efficiency. Here, we determined that, through encapsulation strategies, the carbon layer could weaken the NO₃ ⁻ intermediate binding to active sites, resulting in higher NH₃ yields. We experimentally fabricated electrocatalysts, i.e., Cu nanoparticles encapsulating (or loaded on) N-doped carbon nanofibers (NCNFs) called Cu@NCNFs (Cu-NCNFs), using electrostatic spinning. As a result, Cu@NCNFs can achieve NH₃ yields of 17.08 mg/(h·mg_cat) at a voltage of − 0.84 V and a Faraday efficiency of 98.15%. Meanwhile, the electrochemical properties of the Cu nanoparticles on the surface of carbon fibers (Cu-NCNFs) are lower than those of the Cu@NCNFs. The in situ Raman spectra of Cu@NCNFs and Cu-NCNFs under various reduction potentials during the NO₃RR process show that catalyst encapsulation within carbon layers can effectively reduce the adsorption of N species by the catalyst, thus improving the catalytic performance in the nitrate-to-ammonia catalytic conversion process.

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