Electrokinetic Analysis-Driven Promotion of Electrocatalytic CO Reduction to n-Propanol.

ABSTRACT

The electrocatalytic carbon dioxide or carbon monoxide reduction reaction (CO2RR or CORR) features a sustainable method for reducing carbon emissions and producing value-added chemicals. However, the generation of C3 products with higher energy density and market values, such as n-propanol, remains highly challenging, which is attributed to the unclear formation mechanism of C3+ versus C2 products. In this work, by the Tafel slope analysis, electrolyte pH correlation exploration, and the kinetic analysis of CO partial pressure fitting, it is identified that both n-propanol and C2 products share the same rate-determining step, which is the coupling of two C1 intermediates via the derivation of the Butler-Volmer equation. In addition, inspired by the mechanistic study, it is proposed that a high OH─ concentration and a water-limited environment are beneficial for promoting the subsequent *C2-*C1 coupling to n-propanol. At 5.0 m [OH-], the partial current density of producing n-propanol (jn-propanol) reached 45 mA cm-2, which is 35 and 1.3 times higher than that at 0.01 m [OH-] and 1.0 m [OH-], respectively. This study provides a comprehensive kinetic analysis of n-propanol production and suggests opportunities for designing new catalytic systems for promoting the C3 production.