| Pacific Rim Symposium on Surfaces, Coatings and Interfaces (PacSurf 2016) | |
| Thin Films | Thursday Sessions |
| Session TF-ThM |
| Session: | Advanced Protective Coatings/Stress Evolution, Nanostructure, and Physical Properties of Thin Films |
| Presenter: | Beatriz Roldan Cuenya, Ruhr University Bochum, Germany |
| Correspondent: | Click to Email |
The electrocatalytic reduction of CO2 to industrial chemicals and fuels is a promising pathway to sustainable electrical energy storage and to an artificial carbon cycle, but is currently hindered by the low energy efficiency and low activity displayed by traditional electrode materials.
Using colloidal synthesis, nanoparticles (NPs) with well-defined size and interparticle distance were prepared and tested as catalysts for CO2 electroreduction. Cu NP catalysts displayed a drastic increase in activity and selectivity for H2 and CO with decreasing NP size below 5 nm. Hydrocarbon (methane and ethylene) selectivity was increasingly suppressed with decreasing NP size. For Au NPs, a drastic increase in current density was observed with decreasing NP size, along with a decrease in faradaic selectivity towards CO. The H2/CO product ratio could be specifically tailored for different industrial processes by tuning the size of the Au NPs. In addition, we demonstrated that interparticle distance (IP) is also a critical parameter for controlling reactivity. For largely spaced NPs, selectivity to CO is enhanced, since this reaction intermediate is less likely to readsorb on neighboring NPs after formation. On the contrary, for closely spaced NPs we find that hydrocarbon selectivity is enhanced, since the re-adsorption of reaction intermediates on neighboring NPs can facilitate the multi-step pathway required for hydrocarbon production. This study addresses previously unexplored aspects of how product selectivity can be controlled using mesoscale transport processes during CO2 electroreduction.
Another critical parameter for selectivity control in nanostructured electrocatalysts is the chemical state. We will discuss new oxide-derived metal catalysts that can reduce CO2 with lowered overpotential and improved ethylene selectivity. We will also present critical insights into the catalyst reaction mechanism which were unraveled using structural and chemical information on the sample obtained under operando conditions via X-ray absorption fine-structure spectroscopy. Finally, the role of the NP shape, in particular, the presence of (100) facets in Cu nanocubes and the evolution of the NP structure and dispersion under reaction conditions will be discussed based on operando electrochemical AFM data.