High-Performance Electrocatalytic Conversion of N_2 to NH_3 Using Oxygen-Vacancy-Rich TiO_2 In Situ Grown on Ti_3C_2T_x MXene

摘要

To achieve the energy-effective ammonia (NH3) production via the ambient-condition electrochemical N-2 reduction reaction (NRR), it is vital to ingeniously design an efficient electrocatalyst assembling the features of abundant surface deficiency, good dispersibility, high conductivity, and large surface specific area (SSA) via a simple way. Inspired by the fact that the MXene contains thermodynamically metastable marginal transition metal atoms, the oxygen-vacancy-rich TiO2 nanoparticles (NPs) in situ grown on the Ti3C2Tx nanosheets (TiO2/Ti3C2Tx) are prepared via a one-step ethanolthermal treatment of the Ti3C2Tx MXene. The oxygen vacancies act as the main active sites for the NH3 synthesis. The highly conductive interior untreated Ti3C2Tx nanosheets could not only facilitate the electron transport but also avoid the self-aggregation of the TiO2 NPs. Meanwhile, the TiO2 NPs generation could enhance the SSA of the Ti3C2Tx in return. Accordingly, the as-prepared electrocatalyst exhibits an NH3 yield of 32.17 mu g h(-1) mg(-1) cat. at -0.55 V versus reversible hydrogen electrode (RHE) and a remarkable Faradaic efficiency of 16.07% at -0.45 V versus RHE in 0.1 m HCl, placing it as one of the most promising NRR electrocatalysts. Moreover, the density functional theory calculations confirm the lowest NRR energy barrier (0.40 eV) of TiO2 (101)/Ti3C2Tx compared with Ti3C2Tx or TiO2 (101) alone.