Ammonia synthesis under mild conditions is of supreme interest. Photocatalytic nitrogen fixation with water at room temperature and atmospheric pressure is an intriguing strategy. However, the efficiency of this method has been far from satisfied for industrialization, mainly due to the sluggish cleavage of the N/N bond. Herein, we report a carbon-tungstic-acid (WO3 center dot H2O) hybrid for the co-optimization of N-2 activation as well as subsequent photoinduced protonation. Efficient ammonia evolution reached 205 mu mol g(-1)h(-1) over this hybrid under simulated sunlight. Nitrogen temperature-programmed desorption revealed the decisive role of carbon in N-2 adsorption. Photoactive WO3 . H2O guaranteed the supply of electrons and protons for subsequent protonation. The universality of carbon modification for enhancing the N-2 reduction was further verified over various photocatalysts, shedding light on future materials design for ideal solar energy utilization.