Confinement effects in CO2 electroreduction – mechanistic investigations on surfactant-tailored porous Cu electrodes

• Applicants: Professor Dr. Holger Dau; Professorin Dr.-Ing. Christina Roth
• Subject Area: Physical Chemistry of Solids and Surfaces, Material Characterisation ; Solid State and Surface Chemistry, Material Synthesis
• Term: since 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 495717797

The electrochemical conversion of CO2 (CO2RR) into chemical feedstocks does not only offer the possibility of a CO2-neutral fuel cycle, but also a sustainable synthesis route towards industrially required basic and value chemicals. Controlling the selectivity towards multi-carbon products and suppressing the hydrogen evolution remains one major scientific challenge in the CO2RR technology. Copper occupies a special position as a catalyst for CO2RR due to its ability to produce hydrocarbons and oxygenates with significant efficiency. Here, we exploit the confinement effect of tailored 3D porous Cu structures tuning the selectivity towards multi-carbon products (C2+). The electrodes will be fabricated by a facile hydrogen-bubble templated electrodeposition method to establish structure / property relations between the porous catalyst structure and their CO2RR activity. Surfactants will be utilized to tailor pore size, size distribution and morphology. The presence of confined spaces in the catalysts can support the C-C coupling of the lower reaction intermediates or products to C2 or higher hydrocarbons/oxygenates, but this is insufficiently understood. Adapted physical methods for investigation under operation conditions (Operando Raman & X-ray spectroscopy & video microscopy) together with electrochemical characterization and determination of the CO2RR product spectrum may pave the road towards understanding of the spatial confinement effect on product selectivity at an unprecedented level. The key elements of the work program are: 1) Exploit the bubble-templated electrodeposition approach to produce a new variety of 3D hierarchical pore morphologies (micrometer pores) of Cu catalysts by controlling the hydrogen bubble size (break-off diameter of the bubble) by means of synthesis parameters and surfactants. 2) Establish structure parameters and quantitative morphology descriptors for micrometer pores and nanoporous regions. 3) Identify correlations between porosity characteristics and product spectrum by relating quantitative morphology descriptors and the product spectrum from analytical chemistry. This project combines the substantial expertise of the two groups in electrochemical (synthesis & characterization) and operando spectroscopic investigation, to understand the factors decisive in the selectivity and activity of hierarchically porous bimetallic catalysts towards CO2RR.

• DFG Programme: Research Grants