Multi-functional Mo-doping in MnO2 nanoflowers toward efficient and robust electrocatalytic nitrogen fixation

Electrocatalytic N2 reduction reaction (NRR) represents a sustainable and promising technology for producing NH3 at ambient conditions. Herein, we demonstrated that Mo-doping could change the MnO2 from an inert material into one that can efficiently and robustly catalyze NRR in neutral media. The developed Mo-doped MnO2 nanoflowers (Mo-MnO2 NFs) exhibited a significantly enhanced NRR performance with an NH3 yield of 36.6 μg h−1 mg−1 (-0.5 V) and an FE of 12.1 % (-0.4 V), far outperforming undoped MnO2 NFs and comparing favorably to most reported NRR catalysts. Density functional theory calculations revealed the electron-deficient character of Mo dopants that delivered multi-functions for NRR enhancement: (1) inducing a defect level to promote the conductivity of MnO2, (2) serving as the key NRR active sites, (3) activating the inert Mn sites for enhancing the intrinsic NRR activity of MnO2, (4) retarding the binding of Lewis acid H+ to suppress the hydrogen evolution reaction.