An MnO2–Ti3C2Tx MXene nanohybrid: an efficient and durable electrocatalyst toward artificial N2 fixation to NH3 under ambient conditions

Abstract

Industrial synthesis of NH₃ relies mainly on the traditional Haber–Bosch process, which is highly energy-intensive with enormous greenhouse gas emission. Electrochemical N₂ reduction provides an eco-friendly approach for energy-saving NH₃ synthesis, but it requires highly efficient electrocatalysts under ambient conditions. In this communication, an MnO₂-decorated Ti₃C₂T_x (T = F, OH) MXene nanohybrid (MnO₂–Ti₃C₂T_x) is proposed as a highly active electrocatalyst for the N₂ reduction reaction with strong durability. In addition, only the NH₃ product without N₂H₄ can be detected during the NRR, revealing the excellent selectivity of MnO₂–Ti₃C₂T_x for NH₃ formation. A high NH₃ yield of 34.12 μg h⁻¹ mg_cat⁻¹ and a high faradaic efficiency of 11.39% are achieved at −0.55 V vs. a reversible hydrogen electrode in 0.1 M HCl. Density functional theory calculations further reveal that the unsaturated surface Mn atoms act as active sites to adsorb and activate the inert N₂ molecules for the NRR process, and the rate-determining step is the first hydrogenation process.