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 (101) 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 μgh^-1cm^-2 and a corresponding Faradaic efficiency (FE_NH3) 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.