Enabling Effective Electrocatalytic N₂ Conversion to NH₃ by the TiO₂ Nanosheets Array under Ambient Conditions

Abstract

NH₃ serves as an attractive hydrogen storage medium and a renewable energy sector for a sustainable future. Electrochemical reduction is a feasible ambient reaction to convert N₂ to NH₃, while it needs efficient electrocatalysts for the N₂ reduction reaction (NRR) to meet the challenge associated with N₂ activation. In this Letter, we report on our recent experimental finding that the TiO₂ nanosheets array on the Ti plate (TiO₂/Ti) is effective for electrochemical N₂ conversion to NH₃ at ambient conditions. When tested in 0.1 M Na₂SO₄, such TiO₂/Ti attains a high NH₃ yield of 9.16 × 10^-11 mol s^-1·cm^-2 with corresponding Faradaic efficiency of 2.50% at -0.7 V vs reversible hydrogen electrode, outperforming most reported aqueous-based NRR electrocatalysts. It also shows excellent selectivity for NH₃ formation with high electrochemical stability. The superior NRR activity is due to the enhanced adsorption and activation of N₂ by oxygen vacancies in situ generated during electrochemical tests.