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 cm². We conclude with directions for the further synthesis and study of semimetallic disulfides developing CO-selective electrocatalysts.