High‐Performance Electrocatalytic Conversion of N₂ to NH₃ Using Oxygen‐Vacancy‐Rich TiO₂ In Situ Grown on Ti₃C₂T<i>_x</i> MXene

Abstract

Abstract To achieve the energy‐effective ammonia (NH 3 ) 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 TiO 2 nanoparticles (NPs) in situ grown on the Ti 3 C 2 T x nanosheets (TiO 2 /Ti 3 C 2 T x ) are prepared via a one‐step ethanol‐thermal treatment of the Ti 3 C 2 T x MXene. The oxygen vacancies act as the main active sites for the NH 3 synthesis. The highly conductive interior untreated Ti 3 C 2 T x nanosheets could not only facilitate the electron transport but also avoid the self‐aggregation of the TiO 2 NPs. Meanwhile, the TiO 2 NPs generation could enhance the SSA of the Ti 3 C 2 T x in return. Accordingly, the as‐prepared electrocatalyst exhibits an NH 3 yield of 32.17 µg 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 TiO 2 (101)/Ti 3 C 2 T x compared with Ti 3 C 2 T x or TiO 2 (101) alone.