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.

References

[1] Y. Hori, Electrochemical CO₂ reduction on metal electrodes, in: C.e.a. Vayenas (Ed.) Modern Aspects of Electrochemistry, vol. 42, Springer, New York, 2008.

[2] A. Serov, K. Artyushkova, N. I. Andersen, S. Stariha, P. Atanassov "Original Mechanochemical Synthesis of Non-Platinum Group Metals Oxygen Reduction Reaction Catalysts Assisted by Sacrificial Support Method", Electrochim. Acta (2015) doi:10.1016/j.electacta.2015.02.108

[3] A. Serov, N. I. Andersen, A. J. Roy, I. Matanovic, K. Artyushkova, P. Atanassov, “CuCo2O4 ORR/OER Bi-Functional Catalyst: Influence of Synthetic Approach on Performance”, J. of The Electrochem. Soc., 162 (4) (2015) F449-F454

[4] C. Santoro, A. Serov, C. W. Narvaez Villarrubia, S. Stariha, S. Babanova, A. J. Schuler, K. Artyushkova, P. Atanassov. “Double‐Chamber Microbial Fuel Cell with a Non‐Platinum‐Group Metal Fe–N–C Cathode Catalyst”, ChemSusChem, 8 (2015), 828-834.

[5] N. I. Andersen, A. Serov, P. Atanassov “Metal Oxides/CNT Nano-Composite Catalysts for Oxygen Reduction/Oxygen Evolution in Alkaline Media”, Appl. Catal. B: Environmental, 163 (2015), 623-627.

[6] Z. Zhang, K.L. More, K. Sun, Z. Wu, W. Li, Chemistry of Materials, 23 (2011) 1570.

[7] S. Trasatti, O.A. Petrii, Pure and Applied Chemistry, 63 (1991) 711.