Scanning Electrochemical Microscopy (SECM) for High-Throughput Screening of Tin Oxide Derived Catalyst Arrays for CO₂ Electro-Reduction to Formate

Abstract

Formate produced from the electro-reduction of CO 2 has been proposed as a safe liquid alternative to hydrogen gas in renewable energy storage schemes 1 . However, catalysts for electro-reduction of CO 2 to formate reaction still suffer from poor stability and activity 2,3 . Furthermore, the CO 2 electroreduction catalysis discovery and screening process is generally hampered by slow, one catalyst sample at a time, experimental procedures. Our overall objective is to develop SECM as a reliable high-throughput technique for screening of electrocatalyst arrays. Here, using SECM, we evaluated the activity of three different tin oxide derived catalysts arranged in an array. Tin(IV) dioxide, has been previously shown to be one of the most promising catalysts for formate generation, while also being thermodynamically reduced to metallic tin at the potential at which CO2RR happens in an aqueous medium 4,5 . We created two different tin oxide derived catalysts by subjecting mirror-polished native tin oxide to electro-reduction at a constant potentials prior to the CO 2 reduction experiments. Electro-reduction of the native tin oxide surface at -3.00 V vs. Ag/AgCl yielded a tin(IV) dioxide deficient surface covered in nanospheres (≈70 um) while electro-reduction at -1.25 V vs. Ag/AgCl create a slightly porous surface exhibiting high proportion of tin(IV) dioxide. Fine tuning the SECM technique to analyze three samples (the two electroreduced and one native tin oxide surface) in an array, we demonstrate the successful evaluation of the electrocatalytic activities of these catalysts and we discuss the advantages and challenges of using SECM to screen catalysts for CO 2 reduction. 1. S. Fukuzumi, Joule , 1 , 689–738 (2017) https://doi.org/10.1016/j.joule.2017.07.007. 2. C. E. Moore and E. L. Gyenge, ChemSusChem , 10 , 3512–3519 (2017) http://doi.wiley.com/10.1002/cssc.201700761. 3. B. Khezri, A. C. Fisher, and M. Pumera, J. Mater. Chem. A , 5 , 8230–8246 (2017) http://xlink.rsc.org/?DOI=C6TA09875D. 4. A. Dutta, A. Kuzume, M. Rahaman, S. Vesztergom, and P. Broekmann, ACS Catal. , 5 , 7498–7502 (2015). 5. S. Geiger, O. Kasian, A. M. Mingers, K. J. J. Mayrhofer, and S. Cherevko, Sci. Rep. (2017). Figure 1