MoSe₂ Nanosheets on Multilayer Ti₃C₂ MXenes with Optimized Se Vacancies for Improved Electrocatalytic N₂ Reduction

The electrochemical transformation of nitrogen (N 2 ) into valuable ammonia (NH 3 ) is a highly coveted process that poses a formidable challenge owing to the inherent inertness of the N 2 molecule. The creation step in the development of this process is the development of a long-lasting electrocatalyst. Herein, we presented a simple one-step hydrothermal method for assembling MoSe 2 nanosheets on multilayer Ti 3 C 2 MXenes (MoSe 2 /Ti 3 C 2 composite) to serve as a reliable and effective catalyst for the nitrogen reduction reaction (NRR). The present study employs two detection methods, namely, ultraviolet–visible (UV–vis) and ion chromatography, to determine the ammonia yield of MoSe 2 /Ti 3 C 2 composite catalysts. MoSe 2 /Ti 3 C 2 composites show outstanding NRR activity with a superior NH 3 yield rate of 60.87 μg·h –1 ·mg cat. –1 at −0.55 V vs reversible hydrogen electrode (RHE) and Faraday efficiency of 9.3% at −0.25 V vs RHE, markedly better than individual MoSe 2 or Ti 3 C 2 MXene components. In addition, this composite also has excellent stability and durability during the recycling test. In addition, we have demonstrated the existence of Se vacancies in the catalyst through electron paramagnetic resonance (EPR). The density functional theory calculation (DFT) reveals that abundant Se vacancies play a significant role in enhancing the NRR activity by increasing the conductivity and reducing reaction barriers for intermediate formation. This work opens up an avenue for designing MXene-based electrocatalysts by constructing heterostructures for NRR.