Electrochemical synthesis of ammonia has the advantages of low energy consumption and promising environmental protection, as compared to the traditional Haber-Bosch process. However, the commercial utilization of this novel system is limited by the low Faradaic efficiency, poor ammonia yield and high overpotential due to the strong N[tbnd]N bond and the dominant competing reaction of hydrogen evolution reaction (HER). Herein, a BiOCl-modified two-dimensional (2D) titanium carbide MXenes nanocomposite (BiOCl@Ti3C2Tx) is proposed as a promising electrocatalyst for ambient nitrogen (N2) reduction reaction with excellent catalytic performance and superior long-term stability at low overpotential. In 0.1 M HCl, this catalyst attains a high Faradic efficiency of 11.98% and a NH3 yield of 4.06 µg h−1 cm−2 at -0.10 V (vs. RHE), benefiting from its strong interaction of Bi 6p band with the N 2p orbitals, combined with its large specific surface area and the facile electron transfer.