CO2 Electroreduction on Different Mono- and Bi-Metallic Electrocatalysts: Synthesis, Characterization and Electrode Design

Abstract

It is well known that CO2 is a major green-house gas with significant influence on increase of overall global temperature. Recent work on CO2, however, has shown that it can be used as feedstock for production of value-added products such as alcohols, formate, CO, and methane or ethane [1]. Electrochemical conversion is one way of utilizing CO2 with the advantage of easier scale-up and operation under ambient temperature and pressure. This technology is currently in the developmental stage and can therefore benefit from the knowledge obtained from research in the field of the proton exchange membrane fuel cell (PEMFC) or even anion exchange membrane fuel cells (AEMFCs). Similar to the oxygen reduction reaction (ORR) in PEMFCs/AEMFCs, the reaction at the cathode of a CO2 electrolyzer requires an engineered electrocatalyst. Furthermore, it should be mentioned that contrary to the ORR, CO2 electroreduction reaction results in multiple reaction products that are generated both in liquid and gas phase and the hydrogen evolution reaction (HER) is a competing reaction. In order to make the CO2 electroreduction systems viable and prevent cost-heavy separation of products, electrocatalysts with high selectivity towards the desired product should be designed, synthesized, and scaled-up. Herein we report our recent results on synthetic development method – based on Sacrificial Support Method (SSM) for preparation of mono- and bi-metallic materials [2-5]. The method of the evaluation of electrocatalytic activity of un-supported catalysts for the CO2 electroreduction reaction was based on the rotating disk electrode (RDE) technique and online gas chromatography (GC). The sealed RDE cell was specially designed at Naval Research Laboratory and it was demonstrated that the reaction products generated on small surface area thin RDE films can be quantified by online GC. Liquid reaction products are separated and identified ex-situ by liquid chromatography or NMR (experiments performed at UNM). Figure 1 shows SEM morphology of copper-based electrocatalysts, XRD data and electrochemical performance from RDE experiments. It was shown that, by controlling the SSM parameters, it was possible to synthesize electrocatalysts selective to one product only (except hydrogen). Acknowledgements OAB is grateful to the Office of Naval Research for financial support of this project.