Copper-Infused MXene from MAX Phase for Enhanced Electrochemical Ammonia Production

The electrochemical conversion of nitrate to value-added ammonia is a green alternative to the energy-intensive Haber-Bosch process. However, due to inefficient catalysts, guiding the reaction route towards selective ammonia synthesis is still challenging. Here, we report a highly efficient Cu-infused V₂C catalyst, synthesized via the molten salt synthesis method using selective CuCl₂ etching. The optimized catalyst exhibits a faradaic efficiency of ∼83% and an ammonia yield of 320 μg cm⁻² h⁻¹ at -0.7 V vs RHE. We performed ¹⁵N isotopic labeling to ensure the purity and origin of ammonium ions. The synthesis approach was further applied to Ti₃C₂ MXene, which, upon Cu infusion, achieved a faradaic efficiency of ∼70% and an improved ammonia yield of approximately 450 μg cm⁻² h⁻¹ at -0.6 V vs RHE. Our results demonstrate that Cu-infused MXene catalysts achieve high selectivity, faradaic efficiency, and ammonia yield, highlighting the broad applicability of this method across different MXenes derived from various transition metals. Moreover, the Cu infusion approach can be expanded to incorporate other metals, offering versatile potential for developing MXene-based catalysts for a range of applications, from ammonia synthesis to CO₂ reduction.