Ordering-induced concentration effect: a mass transport boost for CO2 electroreduction

Abstract

Electrocatalytic reduction of CO₂ into CO holds great promise for addressing environmental challenges and industrial needs. However, the practical implementation is hindered by the hydrogen evolution reaction (HER), which competes for electrons and reduces the selectivity of the CO₂ reduction reaction (CO₂RR). Here, we have proposed a novel strategy to enhance CO₂RR selectivity using an ordered structure from a mass transport perspective for the first time. Ag nanowires (NWs) were selected as model catalysts and assembled into an ordered array. The ordered structure of Ag NWs induces an ordered micro electric field that crucially regulates the kinetic mass transports of both the CO₂RR and HER. This micro electric field is demonstrated to promote the preferential accumulation of CO₂ on the catalyst surface while concurrently repelling H₂O molecules. This dual action, which enriches the desired reactant and depletes the source for the competing reaction, tilts the balance in favor of CO₂ reduction over the HER, thereby enhancing selectivity towards CO production. Therefore, the ordered Ag NW arrays demonstrated highly efficient CO₂ electroreduction to CO, resulting in an impressive 97.3% faradaic efficiency (FE) of CO at a current density of 100 mA cm⁻², significantly outperforming their disordered counterparts. This innovative approach not only inspires the design of structural assembly in electrocatalysts from a mass transport perspective but also provides fundamental insights into the relationship between the ordering of structured catalysts and their CO₂RR performance.