NbO2 Electrocatalyst Toward 32% Faradaic Efficiency for N2 Fixation

The electrocatalytic N-2 reduction reaction (NRR) to produce ammonia is an attractive but highly challenging approach, due to the extreme inertness of N-2 molecules and significantly lower N-2 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 N-2 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 mu g h(-1) mg(cat.)(-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.