Microenvironment Regulation of the Ti3C2Tx 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 Ti3C2Tx 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 NH3 yield rate of 17.81 μg h-1mgcat-1 at -0.55 V (vs RHE) in a Na2SO4 solution, which were 3.5-fold in FE and 6.5-fold in NH3 yield rate higher than those of the pristine Ti3C2Tx. 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 N2 chemisorption ability, which cumulatively contribute to the boosted eNRR efficiency.