Hexagonal Cobalt Nanosheets for High-Performance Electrocatalytic NO Reduction to NH₃

Electrocatalytic nitric oxide (NO) reduction not only provides an extremely promising strategy for ambient NH₃ generation but also alleviates the artificially disrupted N-cycle balance. However, exploring efficient electrocatalysts to enhance the NO electroreduction performance remains a significant challenge. Herein, a hexagonal-close-packed Co nanosheet (hcp-Co) is prepared and exhibits a high NH₃ yield of 439.50 μmol cm^-2 h^-1 and a Faraday efficiency of 72.58%, outperforming the face-centered cubic phase of the Co nanosheet (fcc-Co) and most reported electrocatalysts. Through the combination of density functional theory calculations and NO temperature-programmed desorption experiments, the superior catalytic NO reduction reaction (NORR) activity on the hcp-Co can be attributed to the unique electron structures and proton shuttle effect. A proof-of-concept device of Zn-NO batteries using the hcp-Co as the cathode is assembled and shows a power density of 4.66 mW cm^-2, which is superior to the reported performance in the literature so far.