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Ammonia (NH3) is an indispensable chemical raw material and plays an important role in daily life.Herein,we for the first time assemble semi-metallic 1Tphase MoS2 on the surface Ti3C2 MXene (1T-MoS2/Ti3C2 composite) by one-step hydrothermal method as an efficient non-noble metal electrocatalyst for nitrogen fixation.In 0.1 M Na2SO4,1T-MoS2/Ti3C2 composites with optimum 10 wt% 1T-MoS2 reach a highest ammonia yield rate of 31.96 μg h-1 mg-1cat.at-0.95 V vs.RHE and a highest FEs of 30.75% at-0.7 V vs.RHE,which is much better than pure 1T-MoS2,pure Ti3C2 MXenes,IT-MoS2/Ti3C2 composites and 2H-MoS2/Ti3C2 composites.Furthermore,the 1T-MoS2/Ti3C2 composites exhibit significant selectivity and excellent chemical stability with no significant decrease in the ammonia yield rate and FEs of the 6 cycles.The synergy effect between semi-metallic 1 Tphase MoS2 and Ti3C2 MXene promotes the improvement of its NRR performance.15N isotopic labeling experiment confirms that nitrogen in produced ammonia originates from N2 in electrolyte.DFT calculations reveal the optimal reaction path of NRR with both associative distal and alternating pathways.This work provide a promising idea for the rational design of non-noble metal-based NRR electrocatalysts.