Promoting electroreduction of nitrite to ammonia over electron-deficient Pd modulated by rectifying Schottky contacts

Abstract

Electrochemical nitrite reduction reaction (NO₂⁻RR) is a potential sustainable route for regulating the nitrogen cycle and ambient ammonia (NH₃) synthesis. However, it remains a challenge to precisely regulate the reaction pathways and inhibit competing reactions (e.g. hydrogenolysis) for efficient and selective NH₃ production in an aqueous solution environment. Here, we utilize the Schottky barrier-induced surface electric field to construct high-density electron-deficient Pd nanoparticles by modulating the N content in the carbon carrier to promote the enrichment and immobilization of NO₂⁻ on the electrode surface, which ensures the ultimate selectivity for NH₃. With these properties, Pd@N_0.14C with the highest N content achieved excellent catalytic performance for the reduction of NO₂⁻ to NH₃ with the 100% Faraday efficiency at −0.5 and −0.6 V vs. reversible hydrogen electrode (RHE) for NH₃ production, which was significantly better than Pd/C and Pd@N_xC samples with lower N content. This study opens new avenues for rational construction of efficient electrocatalysts for nitrite removal and NH₃ electrosynthesis.