Copper nanowires decorated with TiO2−x from MXene for enhanced electrocatalytic nitrogen oxidation into nitrate under vacuum assistance

The green synthesis of nitrate (NO3−) via electrocatalytic nitrogen oxidation reaction (NOR) is a promising strategy for artificial nitrogen fixation, which shows great advantages than traditional nitrate synthesis based on Haber–Bosch and Ostwald processes. But the poor N2 absorption, high bond energy of N≡N (941 kJ·mol−1), and competing multi-electron-transfer oxygen evolution reaction (OER) limit the activity and selectivity. Herein, we fabricated MXene-derived irregular TiO2−x nanoparticles anchored Cu nanowires (Cu-NWs) electrode for efficient electrocatalytic nitrogen oxidation, which exhibits a NO3− yield of 62.50μg·h−1·mgcat−1 and a Faradaic efficiency (FE) of 22.04%, and a significantly enhanced NO3− yield of 92.63 μg·h−1·mgcat−1, and a FE of 40.58% under vacuum assistance. The TiO2−x/Cu-NWs electrode also shows excellent reproducibility and stability under optimal experimental conditions. Moreover, a Zn-N2 reaction device was assembled with TiO2−x/Cu-NWs as an anode and Zn plate as a cathode, obtaining an extremely high NO3− yield of 156.25 μg·h−1·mgcat−1. The Zn-nitrate battery shows an open circuit voltage (OCV) of 1.35 V. This work provides novel strategies for enhancing the performance of ambient N2 oxidation to obtain higher NO3− yield.