P-d hybridized In-Co dual sites promote nitrite electroreduction to ammonia at high current density

Abstract

Electrochemical reduction of NO2- to NH3 (NO2RR) represents an attractive route to simultaneously mitigate hazardous nitrite and produce value-added NH3. Herein, main-group In atomically doped into CoS2 (In-CoS2) is firstly developed as an active and selective NO2RR catalyst. Atomic-level characterizations of In-CoS2 reveal that In dopant coordinates with its neighboring Co atom to form p-d hybridized In-Co dual active sites. In situ spectroscopic measurements combined with theoretical computations reveal that In-Co dual active sites can synergistically promote NO2- activation and hydrogenation to NH3, while concurrently inhibiting the competing hydrogen evolution, consequently resulting in a high NO2--to-toNH3 conversion efficiency. Impressively, a flow cell with In-CoS2 presents an unprecedented NH3 yield rate of 1834.6 µmol h−1 cm−2 with a corresponding NH3-Faradaic efficiency of 95.1% at a current density of 310.5 mA cm−2, as well as an exceptional durability for 100 h electrolysis.