Electrosynthesis of Value-Added Chemicals Using Water As a Proton Source

Abstract

Electrifying chemical productions is a potential approach to decarbonizing the chemical industry. The electrochemical processes, when powered by renewable electricity, have lower carbon footprints than conventional thermochemical routes. Using water as the proton source avoids the energy-intensive dry-reforming process to produce H2 from fossil fuels, and electrochemical reaction using voltage as driving force instead of elevated pressure enables the reaction to happen at ambient temperature and pressure. Electrosynthesis of value-added ethylamine and ethylene glycol are used as two examples in this presentation. Herein, we report an electrocatalytic route to produce ethylamine selectively through an electroreduction of acetonitrile at ambient temperature and pressure. Among all the electrocatalysts, Cu nanoparticles exhibited the highest ethylamine Faradaic efficiency (FE, ~96%) at -0.29 V versus reversible hydrogen electrode (RHE). In a flow cell configuration, an ethylamine partial current density of 846 mA cm-2 was achieved using the Cu catalyst at -0.73 V vs. RHE in a 1 M NaOH electrolyte containing 12 wt.% acetonitrile. Under a constant current density operation at 100 mA cm-2, the Cu catalyst also showed a stable 20-hour performance in a continuous acetonitrile electroreduction with an 86% ethylamine FE. Moreover, the reaction mechanism of acetonitrile electroreduction was investigated by density functional theory calculations, in which the calculated free energy changes of the rate-limiting steps in acetonitrile reduction and hydrogen evolution reaction suggest a better ethylamine selectivity for Cu than other conventional hydrogenation catalysts (i.e., Ni and Pt).