The efficient adsorption and activation of inert N-2 molecules on a heterogeneous electrocatalyst surface are critical toward electrochemical N-2 fixation. Inspired by the bimetallic sites in nitrogenase, herein, we developed a bi-metallic tin-titanium (Sn-Ti) structure in Sn-doped anatase TiO2 via an oxygen vacancy induced engineering approach. Density functional theory (DFT) calculations indicated that Sn atoms were introduced in the oxygen vacancy sites in anatase TiO2 (101) to form Sn-Ti bonds. These Sn-Ti bonds provided both strong sigma-electron accepting and strong pi-electron donating capabilities, thus serving as both N-2 adsorption and catalytic N-2 reduction sites. In 0.1 M KOH aqueous solution, the Sn-TiO2 electrocatalyst achieved a NH3 production rate of 10.5 mu g h(-1) cm(-2) and a corresponding Faradaic efficiency (FENH3) of 8.36% at -0.45 V vs. reversible hydrogen electrode (RHE). Our work suggests the potential of atomic-scale designing and constructing bimetallic active sites for efficient electrocatalytic N-2 fixation. (C) 2020 Elsevier Inc. All rights reserved.