Silver supported on titania as an active catalyst for electrochemical carbon dioxide reduction

Although significant research efforts have focused on the exploration of catalysts for the electrochemical reduction of CO₂, considerably fewer reports have described how support materials for these catalysts affect their performance, which includes their ability to reduce the overpotential, and/or to increase the catalyst utilization and selectivity. Here Ag nanoparticles supported on carbon black (Ag/C) and on titanium dioxide (Ag/TiO₂) were synthesized. In a flow reactor, 40wt % Ag/TiO ₂ exhibited a twofold higher current density for CO production than 40wt % Ag/C. Faradaic efficiencies of the 40wt % Ag/TiO₂ catalyst exceeded 90 % with a partial current density for CO of 101mA cm^-2; similar to the performance of unsupported Ag nanoparticle catalysts (AgNP) but at a 2.5times lower Ag loading. A mass activity as high as 2700mA mg _Ag^-1 cm^-2 was achieved. In cyclic voltammetry tests in a three-electrode cell, Ag/TiO₂ exhibited a lower overpotential for CO₂ reduction than AgNP, which, together with other data, suggests that TiO₂ stabilizes the intermediate and serves as redox electron carrier to assist CO₂ reduction while Ag assists in the formation of the final product, CO. TiO₂ supports for CO ₂ conversion: TiO₂ has been used as a catalyst support in fuel cells and for photo-electroreduction. This study reveals that TiO ₂ is a good support material for Ag nanoparticles used as catalyst (Ag/TiO₂) for the reduction of CO₂ to CO because of its unique role in the stabilization of the Ag particles as well as a key reaction intermediate.