Electrochemical nitrogen fixation via bimetallic Sn-Ti sites on defective titanium oxide catalysts

The efficient adsorption and activation of inert N2 molecules on a heterogeneous electrocatalyst surface are critical toward electrochemical N2 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 (1 0 1) to form Sn–Ti bonds. These Sn–Ti bonds provided both strong σ-electron accepting and strong π-electron donating capabilities, thus serving as both N2 adsorption and catalytic N2 reduction sites. In 0.1 M KOH aqueous solution, the Sn-TiO2 electrocatalyst achieved a NH3 production rate of 10.5 μg 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 N2 fixation.