NbO2 Electrocatalyst Toward 32% Faradaic Efficiency for N2 Fixation

Abstract The electrocatalytic N2 reduction reaction (NRR) to produce ammonia is an attractive but highly challenging approach, due to the extreme inertness of N2 molecules and significantly lower N2 concentration compared to the surrounding water molecules. Herein, NbO2 nanoparticles are demonstrated as an efficient NRR electrocatalyst with significantly improved electrochemical performances. Compared to Nb2O5 with a similar crystal structure unit but different linkage, the Nb4+ cation not only provides empty d‐orbitals for strong N2 adsorption, but also a single d‐electron to further enable back donation to activate the NN triple bond. As a result, the NbO2 nanoparticles present an outstanding ammonia production rate of 11.6 µg h−1 mgcat.−1 at −0.65 V versus reversible hydrogen electrode (RHE) and an excellent electrochemical stability, significantly higher than those of the Nb2O5 nanorods under similar conditions. More importantly, a peak faradaic efficiency of ammonia production of 32% is obtained for NbO2 at −0.60 V versus RHE, which is one of the highest reported NRR faradaic efficiencies to date.