(Invited) Tuning Ag Nanoparticle Size for Selective Electrocatalytic Reduction of CO2 to CO

Abstract

Coinage metals (Au, Ag and Cu) have shown propensity to reduce CO2 under electrochemical condition. For Au and Cu, nanoparticle size has been used as a lever to tune their activity and selectivity and it was found that the competing hydrogen evolution reaction (HER) becomes an issue for small catalyst particles. For the Ag case, which has been shown to produce CO, the effect of the particle size remains a subject of ongoing discussion because of the lack of thorough benchmark studies. In this presentation, we highlight our detailed investigation of electrochemical CO2 reduction on Ag to ascertain whether size variation can be used to tune the reactivity of the catalyst material. Our combined density functional theory, microkinetic modeling, and experiment demonstrate a strong size-dependence for pristine Ag particles in the sub-10 nm range. The modeling reveals that the enhanced activity can be correlated to the population of a moderately high index facet. Experimental results validated these predictions and we identified an optimal particle diameter that balanced selectivity and activity. The availability of synthetic method to make Ag nanoparticle with different sizes and predictive computational methods that factor in the kinetic aspects could potentially enhance future outlook for material design.