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

Abstract

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 (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.