(197c) Bifunctional Pd/MoOx Electrocatalyst Promotes Oxidative Carbonylation for the Electrosynthesis of Organic Carbonates

Oxidative carbonylation is an important class of industrial chemical reactions used to prepare commodity chemicals such as organic carbonates. Dimethyl carbonate (DMC) is one of the most widely produced organic carbonates and is increasing in demand for its use as a battery solvent and in polycarbonate production. Current thermochemical routes for DMC synthesis are hampered by high system complexity, corrosive byproducts, and explosive reactant mixtures.

Here, we investigate the direct electrochemical synthesis of DMC as an alternative approach to thermochemical oxidative carbonylation. Thus far, research on direct DMC electrosynthesis has exhibited low selectivity due to undesirable C-C coupling to form oxalate byproducts. We identify that DMC formation requires optimizing the adsorption strengths of two key intermediates, CO_ads and CH₃O_ads. By modulating the catalyst microenvironment using ionomers and deuterated methanol, we identify CO binding strength as the dominant descriptor for steering selectivity from the oxalate to carbonate pathway, while abundant CH₃O_ads is needed to promote carbonyl coupling. This finding prompts us to develop a Pd/MoOₓ catalyst that leverages metal-support interactions to optimize CO binding and further accelerate alcohol activation. X-ray spectroscopies, in situ Raman spectroscopy, and CO chemisorption reveal how MoOₓ enriches electron density on Pd, strengthening π-backbonding to enhance CO adsorption while promoting methanol dissociation—dual functions that lead to 96% Faradaic efficiency (FE) to DMC in a batch reactor. Finally, we demonstrate that our strategy extends to the carbonylation of longer chain alcohols, enabling the synthesis of diethyl and dipropyl carbonate from ethanol and propanol.