Highly Selective Electroreduction Of Carbon Dioxide To Carbon Monoxide On A Silver Catalyst With Truncated Hexagonal Bipyramidal Shape

The continuing overconsumption of traditional fossil fuels will eventually raise atmospheric levels of CO₂ and lead to an energy crisis.Many researchers have proposed a number of ways to convert carbon dioxide into energy,reducing its content in the atmosphere and easing energy crisis.Electricity can be provided via renewable sources such as solar,tide and wind energy,without giving rise to any CO₂ emissions.Nonetheless,activation of CO₂ by breaking the very stable C=O bond is a major challenge.Therefore,an excellent catalyst is needed to improve the catalytic performance.In this paper,to improve the activity,selectivity and stability of silver electrodes towards CO₂ electroreduction to CO,three-dimensional frameworks comprised of the metallic silver electrocatalyst particles were constructed on bulk silver surfaces using a successive double-potential pulses method.With the help of X-ray diffraction,field-emission scanning electron microscopy,high-resolution transmission electron microscopy and X-ray photoelectron spectroscopy,it was found that the as-synthesized silver particles exhibited a truncated hexagonal bipyramidal morphology,which was assembled from silver seeds with two {111} bases as well as laterally exposed {100} and {111} facets.Potential-dependent results revealed that the modified electrode exhibited an earlier onset potential,higher Faradaic efficiency and greater current density for CO evolution when compared to its smooth-surface counterpart.Moreover,as opposed to the bulk silver electrode losing its activity as a function of time,the activity of the improved electrode was durably stable over three successive 4 h periods.It is proposed that,in addition to the relatively vast electrochemical surface area that the exposed edges of the silver particles play a major role in enhancing the intrinsic activity and selectivity of the silver electrocatalyst by stabilizing the surface-adsorbed COOH species.Meanwhile,the existence of a large proportion of low-index {111} planes facilitates the desorption of the reduction intermediates of adsorbed CO species,suppressing the deactivation of the silver electrode towards CO₂ reduction.The observations presented herein arepotentially significant in the design of useful electrodesand procedures for generation of valuable carbon-containingproducts using CO₂ as the carbon source.