Symmetry-Breaking -Block Antimony Single Atoms Trigger N-Bridged Titanium Sites for Electrocatalytic Nitrogen Reduction with High Efficiency.

The electrochemical nitrogen reduction reaction (eNRR) under mild conditions emerges as a promising approach to produce ammonia (NH) compared to the typical Haber-Bosch process. Herein, we design an asymmetrically coordinated -block antimony single-atom catalyst immobilized on nitrogen-doped TiCT (Sb SA/N-TiCT) for eNRR, which exhibits ultrahigh NH yield (108.3 μg h mg) and excellent Faradaic efficiency (41.2%) at -0.3 V vs RHE. Complementary spectroscopies with theoretical calculations reveal that the nitrogen-bridged two titanium atoms triggered by an adjacent asymmetrical Sb-NC moiety act as the active sites for facilitating the protonation of the rate-determining step from *N to *NH and the kinetic conversion of key intermediates during eNRR. Moreover, the introduction of Sb-NC promotes the formation of oxygen vacancies to expose more titanium sites. This work presents a strategy for single-atom-decorated ultrathin two-dimensional materials with the aim of simultaneously enhancing NH yield and Faradaic efficiency for electrocatalytic nitrogen reduction.