The crux for solar N-2 reduction to ammonia is activating N-2 into its high-energy intermediate. Applying a simultaneous multi-electron reduction process could avoid intermediate generation and decrease the thermodynamic barrier. However, this process is extremely difficult from a kinetic view and experiments so far have not shown it is accessible. Here we show the first direct evidence of trion induced multi-electron N-2 reduction on ultrathin MoS2. By applying light induced trions, N-2 molecular was activated and transformed into ammonia by a simultaneous six-electron reduction process, with a high ammonia synthesis rate of 325 mu mol/gh without the assistant of any organic scavengers or co-catalyst. Bulk MoS2 without trions did not exhibit any activity. This demonstrates multi-electron reduction may be realized in electron-rich semiconductors with high concentration of localized electrons such as trions. The methodology of simultaneous multi-electron reduction has wide implications for reactions beyond N-2 reduction and for materials beyond MoS2. (C) 2016 Elsevier B.V. All rights reserved.