Developing noble-metal-free electrocatalysts is important to industrially viable ammonia synthesis through the nitrogen reduction reaction (NRR). However,t he present transition-metal electrocatalysts still suffer from low activity and Faradaic efficiency due to poor interfacial reaction kinetics.H erein, an interface-engineered heterojunction, composed of CoS nanosheets anchored on aT iO 2 nanofibrous membrane,isdeveloped. The TiO 2 nanofibrous membrane can uniformly confine the CoS nanosheets against agglomeration, and contribute substantially to the NRR performance.T he intimate coupling between CoS and TiO 2 enables easy charge transfer,resulting in fast reaction kinetics at the heterointerface. The conductivity and structural integrity of the heterojunction are further enhanced by carbon nanoplating.T he resulting C@CoS@TiO 2 electrocatalyst achieves ah igh ammonia yield (8.09 10 À10 mol s À1 cm À2 )and Faradaic efficiency (28.6 %), as well as long-term durability.The electrocatalytic nitrogen reduction reaction (NRR) is ap romising alternative to the energy-consuming Haber-Bosch process toward ammonia synthesis since it can be operated under ambient conditions. [1] To enable efficient nitrogen fixation, highly active electrocatalysts are required, which are mostly noble metals such as Au, [2][3][4] Pt, [5] and Ru. [6,7] Recently,t he research focus turned to the development of low-cost electrocatalysts composed of earth-abundant elements,s uch as transition metals,s ince their unoccupied dorbitals were able to accept the electrons of nitrogen, and thus,break the highly symmetric electronic cloud of the NN bonds.A ss uch, various nanostructures of transition metal oxides, [8][9][10][11][12] sulfides, [13] nitrides, [14,15] and carbides, [16][17][18] were explored as possible NRR electrocatalysts.H owever,n anostructured transition-metal compounds suffer from low activity and Faradaic efficiency resulting from two inherent deficiencies,t hat is,s trong agglomeration tendencya nd poor conductivity.T herefore,s everal studies employed car-Supportinginformation and the ORCID identification number(s) for the author(s) of this article can be found under: https://doi.