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Development of scanning electrochemical microscopy for product selective screening of catalysts for carbon dioxide electroreduction to formate

University of British Columbia

The current work deals with the development of scanning electrochemical microscopy (SECM) as a product selective catalyst screening tool for CO₂ electroreduction to formate reaction (CO2RF) in aqueous media. CO2RF is a proposed route for utilizing CO₂ and surplus electrical energy produced by intermittent renewable sources. In CO2RF devices, CO₂ is electrochemically converted to formic acid or to a solution of formate ions. The resulting product can be either sold on the market, used for H₂ storage, or oxidized back to CO₂ to recover the electricity in direct liquid fuel cells. Our goal is to develop SECM for the simultaneous characterization of multiple CO₂ electroreduction (CO2RR) catalysts, probing their electrocatalytic activity in a product selective manner. To illustrate our method, we studied tin oxide-based catalyst, one of the most promising CO2RF catalyst. We submitted these catalysts to an electroreduction pre-treatment at −1.25 and −3 VAg/AgCl, respectively yielding a smooth oxide rich surface and an oxide poor surface covered in nanoparticles (30 to 70 nm diameter). The creation of spherical nanoparticles by electroreduction of tin oxide at −3 VAg/AgCl in an aqueous carbonate solution has, to our knowledge, never been reported. These two pre-treated catalysts, in conjunction with the un-pretreated surface, were simultaneously characterized by SECM, determining their CO2RF electrocatalytic activity relative to each other. The cyclic voltammetry (CV) tip detection mode provided product selective activity data for three different reaction products: formate, CO and H₂. We demonstrated that pre-electroreduction at −1.25 VAg/AgCl formed a surface with improved selectivity toward CO2RF. We also discussed the effect of SECM experimental parameters on the success of CO2RR catalyst characterization, as well as the challenges and limitations of the method. Our development in SECM opens the door to automated screening of CO2RR catalyst, which dovetails with the recent advances in model-based computational catalyst screening. While high screening throughput can be achieved using these various theoretical methods, they depend on experimental catalyst characterization and screening to validate their models. By automating the slowest step of the process, the experimental bottleneck on catalyst screening can hopefully be alleviated.

Text

2021-04-15

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/77805

Chemical and Biological Engineering

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/