Ampere-Level Nitrate Electroreduction to Ammonia over Monodispersed Bi-Doped FeS₂.

Abstract

Electrochemical conversion of NO₃^- into NH₃ (NO₃RR) holds an enormous prospect to simultaneously yield valuable NH₃ and alleviate NO₃^- pollution. Herein, we report monodispersed Bi-doped FeS₂ (Bi-FeS₂) as a highly effective NO₃RR catalyst. Atomic coordination characterizations of Bi-FeS₂ disclose that the isolated Bi dopant coordinates with its adjacent Fe atom to create the unconventional p-d hybridized Bi-Fe dinuclear sites. Operando spectroscopic measurements combined with theoretical calculations disclose that Bi-Fe dinuclear sites can synergistically enhance the hydrogenation energetics of NO₃^--to-NH₃ pathway, while suppressing the competitive hydrogen evolution, leading to a high NO₃RR selectivity and activity. Consequently, the specially designed flow cell equipped with Bi-FeS₂ exhibits a high NH₃ yield rate of 83.7 mg h^-1 cm^-2 with a near-100% NO₃^--to-NH₃ Faradaic efficiency at an ampere-level current density of 1023.2 mA cm^-2, together with an excellent long-term stability for 100 h of electrolysis, ranking almost the highest performance among all reported NO₃RR catalysts.