Ambient Electrochemical Nitrogen Fixation over a Bifunctional Mo–(O–C2)4 Site Catalyst

Abstract

The electrochemical synthesis of NH3 and NO3- by the N2 reduction reaction (NRR) and the N2 oxidation reaction (NOR) under ambient conditions utilizing H2O as the hydrogen and oxygen source has aroused great attention. Here, we report the fabrication of oxygen-coordinated molybdenum (Mo) single atoms anchored on carbon (Mo-O-C) using bacterial cellulose (BC) as the impregnation regulator and carbon source. As a result, the as-synthesized Mo-O-C as an electrocatalyst exhibits superior bifunctional NRR and NOR activities with high stability. A superb NH3 yield rate of 248.6 ± 12.9 μg h-1 mgcat.-1 and a faradaic efficiency (FE) of 43.8 ± 2.3% can be obtained at -0.20 V (vs RHE) by the Mo-O-C-catalyzed NRR, and Mo-O-C can also afford a NO3- yield rate of 217.1 ± 13.5 μg h-1 mgcat.-1 with a FE of 7.8 ± 0.5% at 2.35 V (vs RHE) for the NOR. The synchrotron-based X-ray absorption spectra and theoretical calculation results unveil that the O-coordinated molybdenum configuration of Mo-(O-C2)4 anchored on carbon is the most stable single-atom structure as the catalytic active sites for N2 adsorption, activation, and bifunctional hydrogenation/oxidation reactions.