Plasma-Assisted Catalyst Active Phase Regeneration in Formate-Selective Carbon Dioxide Electroreduction

Abstract

Electrochemical carbon dioxide conversion to more valuable products such as formate (its protonation leads to formic acid, a versatile liquid fuel) is an appealing approach to mitigating the greenhouse gas emission and storing a surplus of renewable energy, but the catalysts developed to date are typically plagued by rapid deactivation. Catalyst deactivation often results in a very low selectivity, in the form of a multitude of products, including H2, formate, methanol, CO, and hydrocarbons instead of more preferably a single product, which normally originates from CO-induced phase transformation of hydride catalyst active phases (e.g., Pd hydride). This phase transformation is typically manifested by a high sensitivity of Faradaic Efficiency (FE) and catalyst active phase to small changes of potentials, pH, and temperature. Despite recent developments in catalysts for electrochemical CO2 conversion, least effort has been devoted to regenerating catalyst active phases, especially for Pd-based catalysts when they are targeted for converting CO2 to formate. Effective regeneration of the catalyst active phase would allow enhanced efficiency and catalytic activity in CO2 conversion, greater supply of formate as a fuel, and reduced greenhouse effect. To address the above issues, non-thermal plasma has been utilized to regenerate the hydride catalyst active phase by exacting H from water and assisting in H sorption, and thus eliminate the CO-induced phase transformation through the repulsive interaction between CO and H. This work intends to establish a new framework of multi-electron/proton and heterogeneous electrochemical kinetics driven/mediated by free charged species in plasma.