Behind The Publication: exploring Cu-promoted ZnZrOx catalysts for CO2 to methanol synthesis

Team portrait, from left to right: Dr. Thaylan Pinheiro Araújo, Dr. Jordi Morales Vidal, Dr. Mikhail Agrachev, and Patrik Willi.

In a recent collaborative publication, a team of experimental and computational experts from four NCCR Catalysis member groups investigated a sustainable class of catalyst promoters and their workings. Learn more about the work from Dr. Thaylan Pinheiro Araújo (aCe lab, ETHZ), Dr. Jordi Morales Vidal (TheorHetCat Group, ICIQ), Dr. Mikhail Agrachev (EPR Research Group, ETHZ), and Patrik Willi (Functional Materials Laboratory, ETHZ) in this Behind The Publication

Can you briefly introduce the concept of your project and your roles?
Thaylan: The production of chemicals places a burden on our planet; our study addresses the sustainable production of methanol, a key building block for the chemical industry, through CO2 valorization. We aimed to systematically investigate the promotion of mixed zinc-zirconium oxides (ZnZrOx), a promising catalyst family for CO2 hydrogenation to methanol. Building upon our past collaborative endeavors within the NCCR Catalysis framework, multiple groups with distinct expertise joined forces to tackle this challenge. Among diverse hydrogenation metals examined, we - surprisingly! - identified copper as the most effective promoter, exceeding even palladium, and provided atomic-level rationalization of the working state of the new Cu-promoted ZnZrOx catalyst. Our findings show the potential for an earth-abundant, more sustainable promoter class.
My primary role in this project was to closely collaborate with all team members, facilitating the exchange of insights and ultimately synthesizing their invaluable contributions into the cohesive narrative of our study.

The team used a standardized flame spray pyrolysis approach to prepare ZnZrOx catalysts with small amounts (0.5 mol%) of diverse hydrogenation metals (Re, Co, Au, Ni, Rh, Ag, Ir, Ru, Pt, Pd, and Cu).

How did the collaboration between your groups and disciplines come about?
Catalysis, with its multidisciplinary nature spanning various scales, inherently requires complementary expertise. The collaboration among our groups with diverse know-how - from standardized catalyst synthesis and evaluation to in-depth characterization and theoretical simulations - flowed seamlessly in this study. Indeed, our collaboration felt instinctive, given our successful history of tackling other challenging questions within the NCCR Catalysis since 2021, when we first came together to investigate metal promotion in In
2O3-catalyzed methanol synthesis via CO2 hydrogenation.

How did your experience working with characterization and mechanism analysis help advance your understanding of the catalyst?
Mikhail: Our team’s broad expertise in different fields helped us work on these complex catalysts. From the point of view of EPR methodology, the main novelty was to bring concepts from magnetism and solid-state physics together with traditional EPR approaches to get a structural and mechanistic understanding of the catalytic process. Also, performing the measurements in-situ/operando is still uncommon in the field. Of course, close collaboration and exchange of results and ideas between the researchers was essential to achieve our results, as one can hardly answer the big questions in catalysis by applying a single method.

Were there any unexpected challenges during the collaboration, and how did you address them?
Mikhail: The initial challenge was communicating with researchers from different disciplines. My background is in spectroscopic/physical chemistry, and my approach is often very different from that of collaborators, who are chemical engineers and computational chemists. However, as I learned over several years of close and fruitful collaborations, the ability to approach challenges from different perspectives makes it possible to solve problems in sustainable chemistry. Thanks to these collaborations and changes in perspective, we made relevant scientific contributions, and I became more open-minded, both scientifically and personally.

What message or insight do you hope readers take away from your collaborative work?
Patrik: This collaboration demonstrates the potency of interdisciplinary work in tackling current challenges in catalysis and sustainable chemistry. Scientifically, each contribution – from state-of-the-art characterization to modeling and preparation – was indispensable for obtaining and understanding these novel catalysts. The shared goals and clear communication throughout the project were vital to its success. Personally, our joint endeavor forged lasting bonds across the research groups, and we hope our example encourages others to unlock the full potential of collaborative work.

Visualization of Cu0 species forming Zn-rich low-nuclearity CuZn clusters on the ZrO2 surface during the reaction, which correlates with the generation of oxygen vacancies in their vicinity.

Where do you see the intersection of catalyst development, computational chemistry and mechanism elucidation research heading in the field of heterogeneous catalysis?
Jordi: The intersection between experiments and modeling is crucial for the efficient design of novel materials and processes. The synergy between these two fields leverages their strengths and is greater than the sum of their parts. In our work, the in-depth experimental characterization was pivotal for building representative models of the Cu-ZnZrOx system for density functional theory simulations. We used these models to provide insights at the atomic level to reveal synthesis-structure-performance relationships. This approach paves the way for performing high-throughput screening of catalytic materials coupled with machine learning to accelerate the discovery of relevant catalysts for green methanol production.

What role has NCCR Catalysis played in developing this work?
Thaylan: The program was pivotal in developing this work by fostering collaboration among groups, facilitating larger-scale projects, and providing access to a broad community of researchers in Switzerland and beyond. Our groups could not have accessed the necessary resources and achieved these synergistic efforts individually, and the consortium framework enhanced the scope and impact of our research.

Publication details:

Low-nuclearity CuZn ensembles on ZnZrOx catalyze methanol synthesis from CO2. T. Pinheiro Araújo, G. Giannakakis, J. Morales-Vidal, M. Agrachev, Z. Ruiz-Bernal, P. Preikschas, T. Zou, F. Krumeich, P.O. Willi, W.J. Stark, R.N. Grass, G. Jeschke, S. Mitchell, N. López, J. Pérez-Ramírez. Nat. Commun. 2024, 15, 3101. DOI: 10.1038/s41467-024-47447-6.

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