Modulation of the binding of the reactant or product species with catalysts is an effective approach to optimize the photocatalytic activity. Herein, we explored the relationship between the binding of reactant (N-2) and product (NH3) with catalyst and the photocatalytic nitrogen fixation activity. The surface reactivity of nitrogen with water was tuned by introducing Co into the MXene@TiO2 catalysts, which the TiO2 nanoparticle derived from the in-situ growth on the surface of MXene nanosheets. Co modified adjusted the chemisorption equilibrium of the catalyst for reactant (N-2) and product (NH3), thus promoted product desorption and efficiency of the active site. Remarkably, the optimal catalyst (MXene/TiO2/Co-0.5%) exhibited outstanding NH4+ production rate (110 mu mol g(-1) h(-1)) and excellent stability in pure water without any hole sacrificial agent under Ultraviolet-Visible (UV-vis) light in N-2 and air ambient. (C) 2020 Elsevier Inc. All rights reserved.