Efficient electrocatalytic conversion of CO2 to ethanol enabled by imidazolium-functionalized ionomer confined molybdenum phosphide

An effective electrochemical carbon dioxide reduction reaction (eCO(2)RR) requires the discovery of a catalytic system that is highly active and selective for multi-carbon products together with superior CO2 diffusion at a catalyst layer to minimize the reduction barriers. Here, we found a catalytic system that uses molybdenum phosphide (MoP) nanoparticles covered by imidazolium-functionalized ionomer (Im) that promotes CO2 diffusion at the catalyst layer toward the catalyst surface, where CO2 is reduced to ethanol (C2H5OH). The electrochemical results with the MoP-Im co-catalyst show a C2H5OH production Faradaic efficiency and a cathodic energy efficiency of 77.4% and 63.3%, respectively, at a potential as low as - 200 mV vs. RHE. The electrochemical experiments along with our physicochemical characterizations indicate that the Im improves CO2 diffusion and balances water content resulting in a higher CO2-to-water ratio at the catalyst layer and fine-tunes the electronic properties of Mo atoms at the MoP surface. In-situ Raman spectroscopy reveals that a high number of adsorbed *CO intermediates on the surface and a higher binding strength of *CO intermediates on the Mo surface sites in the presence of imidazolium molecules are the main reasons for a superior C-C coupling and thereby the improved C2H5OH formation.

Automated summary

This study found a catalytic system using molybdenum phosphide nanoparticles covered by imidazolium-functionalized ionomer, which effectively reduces carbon dioxide to ethanol. The imidazolium-functionalized ionomer improves the diffusion of CO2 and balances the water content in the catalyst layer, resulting in higher CO2-to-water ratio and fine-tuning of the electronic properties of the catalyst surface.