Scanning Electrochemical Microscopy (SECM) for Accelerated Screening of CO₂ Electroreduction to Formate Catalyst

Abstract

CO 2 electroreduction to formate (CO2RF) is the key reaction in many renewable energy storage schemes, sequestering CO 2 into a formate solution at ambient condition 1 . However, CO2RF catalysts are still afflicted by poor selectivity and low activity 2,3 . Compounding the issue, CO2RF catalyst screening is still dominated by slow, one catalyst sample at a time experimental method. Theoretical catalyst screening is also affected, with increasingly faster computational models waiting for sluggish empirical validation 4 . Our objective is to develop scanning electrochemical microscopy (SECM) as a high-throughput CO2RF catalyst screening tool using multi-catalyst arrays. Our SECM method was tested on arrays of Sn/SnO x catalysts (x = 1,2), evaluating the effectiveness of pre-electroreduction treatment on final activity. Theoretically, SnO/SnO 2 mixtures are the most promising catalysts for CO2RF , but in practice, they are thermodynamically unstable at potentials at which aqueous CO 2 reduction takes place 5,6 . Sn/SnO x catalyst pre-electroreduction at −1.25 V Ag/AgCl yielded an agglomerated surface with increased SnO x composition and CO2RF activity. Conversely, pre-electroreduction at −3 V Ag/AgCl deposited a film of nanoparticles (≈70μm) on the surface but decreased CO2RF activity and SnO x composition. In a single SECM experiment, the CO2RF activity of unreduced Sn/SnO x surface and of the two reduced surfaces was determined, demonstrating the technique’s potential for accelerating CO2RF catalyst screening. We will also discuss the advantages and challenges of using SECM for high-throughput CO 2 reduction catalyst study. S. Fukuzumi, Joule , 1 , 689–738 (2017) . C. E. Moore and E. L. Gyenge, ChemSusChem , 10 , 3512–3519 (2017). B. Khezri, A. C. Fisher, and M. Pumera, J. Mater. Chem. A , 5 , 8230–8246 (2017) . M. Zhong et al., Nature , 581 , 178–183 (2020). A. Dutta, A. Kuzume, M. Rahaman, S. Vesztergom, and P. Broekmann, ACS Catal. , 5 , 7498–7502 (2015). S. Wang, J. Wang, and H. Xin, Green Energy Environ. , 2 , 168–171 (2017). Figure 1