A two-dimensional MXene-supported CuRu catalyst for efficient electrochemical nitrate reduction to ammonia

Abstract

As a carbon-free energy source and carrier, NH₃ is an essential component used in agriculture, industry, and medicine. Currently, the main process for industrial ammonia production is the Haber–Bosch process, which is highly energy intensive with the emission of large amount of CO₂. In contrast, electrochemical ammonia synthesis is a promising alternative for the Haber–Bosch process owing to its environmentally friendly nature, low energy consumption, and zero CO₂ emission. Meanwhile, as a widespread source of nitrogen in industrial wastewater and contaminated groundwater, nitrate has received extensive attention as the source for the synthesis of NH₃. In this study, a Ru–Cu/Cu₂O@Ti₃C₂ catalyst was successfully prepared by combining highly conductive Ti₃C₂ MXene with Ru–Cu/Cu₂O@C. In 0.1 M KOH and KNO₃ electrolyte, the Ru–Cu/Cu₂O@Ti₃C₂ exhibited excellent nitrate reduction reaction (NO₃RR) performance, achieving the highest faradaic efficiency of 48.3% at −0.7 V with a corresponding NH₃ yield of 128.35 μmol cm⁻² h⁻¹. The excellent catalytic performance of Ru–Cu/Cu₂O@Ti₃C₂ was attributed to the synergistic interactions between multivalent Cu/Cu⁺, abundant metal active centers of Ru, and the excellent electrical conductivity of the two-dimensional Ti₃C₂ MXene. This study may provide a practical pathway for converting nitrate wastewater to valuable ammonia products.