Microenvironment Regulation of the Ti 3 C 2 T x MXene Surface for Enhanced Electrochemical Nitrogen Reduction.

The overwhelmingly competitive hydrogen evolution reaction (HER) is a bottleneck challenge in the electrocatalytic nitrogen reduction reaction (eNRR) process. Herein, we develop a general and effective strategy to suppress the HER via covalent surface functionalization to modulate the local microenvironment of the electrocatalyst. A hydrophobic molecular layer with tunable coverage density was coated on the surface of Ti 3 C 2 T x MXene, and the one with appropriate coverage density significantly improved the eNRR efficiency with an excellent faradaic efficiency (FE) of 38.01% at -0.35 V and a high NH 3 yield rate of 17.81 μg h -1 mg cat -1 at -0.55 V (vs RHE) in a Na 2 SO 4 solution, which were 3.5-fold in FE and 6.5-fold in NH 3 yield rate higher than those of the pristine Ti 3 C 2 T x . Experimental results combined with molecular dynamics (MD) simulations reveal that the hydrophobic molecular layer on the surface greatly limits the proton transfer and benefits higher exposure of active sites with enhanced N 2 chemisorption ability, which cumulatively contribute to the boosted eNRR efficiency.