Electrocatalytic N2 Fixation over Hollow VO2 Microspheres at Ambient Conditions

Graphical Hollow VO 2 microspheres can operate efficiently and stably to give an NH 3 yield of 14.85 μg h −1 mg −1 cat and a Faradaic efficiency of 3.97 % at −0.7 V (vs. the reversible hydrogen electrode) in 0.1 M Na 2 SO 4 , rivaling the performances of most reported aqueous-based electrocatalysts. Density functional theory calculations provide further insight into the catalytic mechanism involved. Electrochemical N 2 fixation has gained much attention as an environmentally friendly and sustainable process for NH 3 production at ambient conditions. Its efficiency depends greatly on identifying highly active electrocatalysts with good stability. In this work, we propose the use of VO 2 hollow microspheres as a robust non-precious metal catalyst for the N 2 reduction reaction (NRR). The catalyst operates efficiently and stably at neutral pH to high Faradaic efficiency (3.97 %) and NH 3 yield (14.85 μg h −1 mg −1 cat. ) under an applied potential of −0.7 V (vs. the reversible hydrogen electrode). Note that this catalyst also presents a high selectivity for NH 3 synthesis without N 2 H 4 generation. Density functional theory reveals that the energetically favorable pathway for NRR is *N 2 →*NNH→*NHNH→*NHNH 2 →*NH 2 NH 2 →*NH 2 +NH 3 →*NH 3 +NH 3 →2NH 3 , where the first hydrogenation step to form *NNH is the potential-determining step.