Periodic Reporting for period 2 - CASCAT (Catalytic cascade reactions. From fundamentals of nanozymes to applications based on gas-diffusion electrodes)
Période du rapport: 2021-03-01 au 2022-08-31
Climate change and its impact on life on our planet can only be mitigated if humankind manages to restrict further massive pollution, especially by emission of CO2 and NOx. In order to contribute to technological solutions, we develop knowledge and new experimental devices to in-depth investigate electrocatalyst-modified gas-diffusion electrodes for CO2 reduction. On the one hand, we develop new catalyst materials to convert CO2 into value-added chemicals such as ethylene or higher alcohols. On the other hand, we are convinced that an in-depth understanding of the complex set of parameters is of utmost importance to allow optimizing devices for CO2 reduction.
The overall objectives of CASCAT are to gain a deep understanding of electrocatalysis for CO2 reduction using gas diffusion electrodes. This is achieved by searching and characterizing new catalyst materials, developing new technologies for the fabrication of gas diffusion electrodes by airbrush-type spray coating, assembling the catalyst material(s) at the optimal location inside the gas diffusion electrode, and making use of (nano)electrochemical techniques, spectroelectrochemical techniques to elucidate properties of the working gas diffusion electrode.
The overall objectives of CASCAT are to gain a deep understanding of electrocatalysis for CO2 reduction using gas diffusion electrodes. This is achieved by searching and characterizing new catalyst materials, developing new technologies for the fabrication of gas diffusion electrodes by airbrush-type spray coating, assembling the catalyst material(s) at the optimal location inside the gas diffusion electrode, and making use of (nano)electrochemical techniques, spectroelectrochemical techniques to elucidate properties of the working gas diffusion electrode.
We designed Ag core/porous Cu shell catalyst particles and could demonstrate synergistic cascade reactions during CO2 reduction with the enhanced formation of ethylene, ethanol and propanol. By careful design of gas-diffusion electrodes, we found measures to mitigate the parasitic hydrogen evolution reaction by managing the electrolyte wetting inside the electrode by adjusting the hydrophobicity and porosity. We developed automatic measurement setups with in-line product analysis, nanoelectrochemical methods for characterizing single electrocatalyst nanoparticles, and in-situ electrochemistry/Raman spectroscopy methods to identify intermediate products during CO2 reduction. Most importantly, we developed and applied a nanoelectrode-based method which allows us to measure the local pH value in the gas diffusion electrode in dependence on the applied current density. First results concerning the implementation into model flow-through electrolyzer systems were obtained. Furthermore, we worked on the reduction of NOx and found that Cu/Co-based catalyst works synergistically for the reduction of nitrate to ammonia with nearly 95% yield.
Until the end of the project, we expect to develop improved electrocatalysts for CO2- and NOx-reduction and combinations of catalysts as a basis for cascade reactions enabling high selectivity for value-added chemicals and suppressing the parasitic hydrogen evolution reaction. We want to characterize the catalysts, the mechanistic details of the complex reaction pathways while keeping scalable synthesis, operational stability at high currents and abundance of the constituting elements in the focus to potentially enable industrial applications.