Modulating Nitrogen Adsorption Mode and Microenvironment of Active Sites for Boosting Electrochemical Nitrogen Reduction

Electrochemical reduction of N₂ (NRR) offers a sustainable approach for ammonia (NH₃) synthesis, serving as a complementary to the traditional emission- and energy-intensive Haber-Bosch process. However, it faces challenges in N₂ activation and competing with pronounced hydrogen evolution reaction (HER). Herein an efficient electrocatalyst comprised of ultrafine Ru nanoclusters (NCs) confined by a hydrophobic molecular layer is developed on the surface of 2D Ti₃C₂T_x for NRR. These experimental and theoretical calculation results demonstrate that 1) ultrafine Ru NCs dispersed on the Ti₃C₂T_x surface form paired active sites for N₂ chemisorption in a unique tilted configuration with low-energy activation 2) the hydrophobic molecular layer modulates the local microenvironment surrounding catalytically active sites, enabling efficient N₂ accumulation while repelling H₂O diffusion to the active sites on the Ti₃C₂T_x surface, thereby leading to an increased N₂ concentration and suppressed HER. As a result, an exceptionally high NH₃ yield rate of 33.5 µg h^-1 mg^-1cat and Faradaic efficiency of 65.3% are obtained at -0.25 V versus reversible hydrogen electrode (RHE) in 0.1 m Na₂SO₄, outperforming those previously reported Ti₃C₂T_x-derived electrocatalysts. This work provides a valuable strategy for the rational design of advanced electrocatalysts by manipulating active sites and local microenvironments for efficient electrocatalysis.