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3D Model Catalysts to explore new routes to sustainable fuels

Periodic Reporting for period 4 - 3MC (3D Model Catalysts to explore new routes to sustainable fuels)

Reporting period: 2020-03-01 to 2020-11-30

"Currently fuels, plastics, and drugs are predominantly manufactured from oil. A transition towards renewable resources critically depends on new catalysts to convert small molecules (such as solar or biomass derived hydrogen, carbon monoxide, water and carbon dioxide) into more complex ones (such as hydrocarbons and oxygenates). Catalyst development often relies on trial and error rather than rational design, as the heterogeneity of these composite systems hampers detailed understanding of the role of each of the components.
In this project we used 3D model catalysts as a novel enabling tool to overcome this problem. Their well-defined nature allowed unprecedented precision in the variation of structural parameters (morphology, spatial distribution) of the individual components, while at the same time they mimic real catalysts closely enough to allow testing under industrially relevant conditions. Using this approach we adressed fundamental questions such as:
* What are the mechanisms (structural, electronic, chemical) by which non-metal promoters influence the functionality of copper-based catalysts?
* Which nanoalloys can be formed, how does their composition influence the surface active sites and catalytic functionality under reaction conditions?
* Which size and interface effects occur, and how can we use them to tune the activity and selectivity towards desired products?

Our 3D model catalysts were assembled from ordered mesoporous silica and carbon support materials and consisted mainly of Cu-based promoted and bimetallic nanoparticles, although also some other bimetallic systems were explored (Co-Ni, Au-Ag, Au-Pd). The combination with high resolution imaging, active site characterization and testing under realistic conditions allowed detailed insight into the role of the different components.

Most important achievements of this project include:
* Insight into how Cu-based catalysts for the formation of CO and H2 into fuels and chemical building blocks such as methanol can have a longer lifetime and work more effectively, and how this is influenced by interface effects (with the support), the sieze of the Cu particles, and small amounts of additive (""promoters"")
* Concrete information on the impact of switching to CO2 as feed for building chemicals and fuels, and how the catalyst can be adjusted to account for that
* First results on copper-based catalysts for electrochemical CO2 reduction, and the importance of a second component (much prominently CuSx and Cu-ZnOx
* fundamental understanding of the behaviour of nano-alloys, also under reaction conditions, and how the atoms of tow different metals will redistribute, and how that affect the efficiency of the catalysts."
PhD1, Lisette Pompe, has worked on the project of promoters for Cu based catalysts. She has prepared supported Cu nanoparticles on different supports, and investigated and published how most stable catalysts can be made (comparing for instance precipitation by impregnation routes). She unraveled the effect in conversion of synthesis gas to methanol of the Cu particle size, and interestingly discovered how the particle size can be tuned by adapting the reduction conditions (varying reducing agent, concentration, ramp rate). She then continued with investigating catalysts stability, a critical factor in the large scale production of fuels and chemicals from small molecules. The well defined nature of hermodel catalysts allowed to build a model and fundamental and practical understanding of how morphology (interparticle distances, polydispersity, etc) influenced the life time of the catalysts.

Remco Dalebout (PhD2) started with investigating pore-confined bimetallic nanoparticles. Together with Jan Willem the RIjk he also established equipment and protocols that allow to measure the conversion of syngas and CO2 to higher alcohols, fuels and other building blocks. He investigated especially the interplay between promoters and reactant feed (aiming for pure CO2 with renewable H2 as the only feed) and understanding how the catalysts should be tuned to accomodate for this specific feed. With the help of operando experiments at the synchrotron he established for the first time the exact nature of the promoter, MnOx or ZnOx for Cu catalysts under working conditions. Jessi van der HOeven also worked on bimetallic nanoparticles, establishing more fundamental knowledge, such as how with two metal components in one nanoparticle, the atomic distribution changed under working conditions ,and how this could be used to design efficient catalysts. She also contributed to the toolbox of analysis techniques for this type of systems

PhD3, Marisol Tapia Rosales, later succeeded has started 1 October 2016, worked on the electrochemical CO2 reduction using Cu-based catalysts. SHe developed methods to prepare electrode consisting of copper nanoparticles on highly conductive carbon supports, which allowed new fundamental insights. Especially noteworthy were the achievements in understanding electronic tuning by the addition of S to the Cu, and the influence of ZnOx and morphology.

Lastly Peter Ngene (PD1), together with the PI, facilitated the above research, but also participated in related investigations with others to promote renewable energy storage and conversion, such as interesting results also obtained in the field of electrochemical energy storage in batteries.

All outcomes of research have been published (or publication is expected soon, for instance a paper having been accepted in Nature Materials), and results have been actively disseminated also at scientific conferences and in workshops. Furthermore they have led to follow-up projects, for instance supported by an industrial partner to further advance the possibilities of direct conversion of CO2 and renewable hydrogen to sustainable fuels and building blocks.
We obtained unprecedented new insight into the role of the different components (particle size, composition, support and promoters) in supported heterogeneous Cu catalysts; critical for the rational design of novel catalysts for more sustainable production of chemicals and fuels from renewable resources.
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