Two-dimensional MXene-based materials are potential of presenting unique catalytic performances of electrocatalytic reactions. The surface functionalization of MXene-based catalysts is attractive for developing efficient electrocatalysts toward nitrogen reduction reaction. Herein, we reported a Ti3C2Tx MXene with a medium density of surface functionalized fluorine terminal groups, as an excellent N2 reduction reaction electrocatalyst with enhanced adsorption and activation of N2. The Ti3C2Tx MXene catalyst showed a production rate of ammonia as 2.81 × 10–5 μmol·s−1·cm−2, corresponding to a partial current density of 18.3 μA·cm−2 and a Faradic efficiency of 7.4% at − 0.7 V versus reversible hydrogen electrode in aqueous solutions at ambient conditions, substantially exceeding similar Ti3C2Tx MXene catalysts but with higher or lower densities of surface fluorine terminal groups. Our work suggests the capability of developing surface functionalization toolkit for enhancing electrochemical catalytic activities of two-dimensional MXene-based materials.