Active Sulfur Sites in Semimetallic Titanium Disulfide Enable CO2 Electroreduction

Electrocatalytic CO2-to-CO conversion represents one pathway to upgrade CO2 to a feedstock for both fuels and chemicals (CO, deployed in ensuing Fischer-Tropsch or bioupgrading). It necessitates selective and energy-efficient electrocatalysts-a requirement met today only using noble metals such as gold and silver. Here, we show that the two-dimensional sulfur planes in semimetallic titanium disulfide (TiS2) provide an earth-abundant alternative. In situ Fourier transform infrared mechanistic studies reveal that CO2 binds to conductive disulfide planes as intermediate monothiocarbonate. The sulfur-CO2 intermediate state steers the reduction kinetics toward mainly CO. Using TiS2 thin films, we reach cathodic energy efficiencies up to 64% at 5 mA cm(2). We conclude with directions for the further synthesis and study of semimetallic disulfides developing CO-selective electrocatalysts.