Abstract
Obtaining valuable C(3+) products directly from the electrocatalytic reduction of CO(2) or CO is an attractive but challenging task, due to the much more complicated reaction pathways and sluggish kinetics of C(3+) products than their C(1) and C(2) counterparts. As different C(3+) products and competitive C(2) side-products may share the common rate-determining step (e.g. the carbon-carbon coupling), the regulation of subsequent selectivity-determining step(s) is critical for promoting the selectivity of C(3+) products. Herein, we focused on tuning the selectivity competition between n-propanol (n-C(3)H(7)OH, an important C(3+) alcohol) versus ethanol (C(2)H(5)OH, a major C(2) side product), based on the constant potential computations on the Cu surface with different step sites. The critical selectivity-determining steps for the n-C(3)H(7)OH and C(2)H(5)OH pathways have been identified, and the impact of Cu step sites on the competitive relation between n-C(3)H(7)OH and C(2)H(5)OH has been explored. Moreover, a descriptor related closely to the n-propanol selectivity has been developed, showing that controlling the competitive hydrogenation of C(2) intermediates and C(1)-C(2) coupling processes is vital to differentiate the selectivity of n-propanol from ethanol. This work can inspire the screening and rational design of unconventional electrocatalytic sites for generating more value-added C(3+) products from the electrocatalytic CO(2) reduction.