Carbon Valorisation: Cutting-Edge Microscopy Techniques Unveil Breakthrough in CO2 Hydrogenation Catalysts

by Virginia Greco

Innovative characterization techniques were used for the first time to study with nanometric precision the interactions between catalysts and their supporting structures during CO₂ hydrogenation. The results presented in a study published in Advanced Materials and authored by scientists from the University of Antwerp, ICN2 and IREC will allow the design of bespoke catalysts to enhance reactions that are crucial for CO₂ conversion into green fuel.

Decarbonization of our economy and carbon valorisation (through conversion of CO₂ into usable chemicals or fuels) are key strategies to address the current alarming climate change emergency and limit our footprint on the planet. In this context, researchers are seeking chemical processes that can facilitate and enhance the conversion of CO₂ into methane (CH₄), which is a green fuel. Catalysts designed to speed up such reactions are therefore extremely important.

Scientists have recently realised that they must thoroughly observe how catalysts and other agents evolve during the chemical reaction in order to clearly understand the role played by each of them and take advantage of it –in other words, a before-and-after comparison does not give enough information. This is particularly relevant in cases in which –as it has been observed in situ—not only the catalyst itself but also support materials, used for example to stabilise small nanoparticles, intervene in the reaction.

A groundbreaking study lead by researchers from the EMAT (University of Antwerp, Belgium), the Catalan Institute of Nanoscience and Nanotechnology (ICN2, Barcelona) and the Catalonia Institute for Energy Research (IREC, Barcelona) pioneers the use of innovative in situ and operando characterization techniques to observe at the nanoscale the changes taking place on a complex catalyst during a chemical reaction (CO₂ hydrogenation) that is key to carbon valorisation. The work, recently published in the journal Advanced Materials, was coordinated by Prof. Sara Bals, from the University of Antwerp and Director of EMAT, and by ICREA Prof. Jordi Arbiol, leader of the Advanced Electron Nanoscopy Group at the ICN2; the in-situ work study was mainly performed by Dr Kellie Jenkinson (EMAT).

Specifically, the researchers used nanoparticles of nickel (Ni) dispersed on a porous cerium oxide (CeO₂) support. The evolution of this catalyst-support structure (Ni/MP-CeO₂) during hydrogenation was studied using in-situ and operando electron microscopy techniques in 2D and 3D –such as quantitative multimode electron tomography and electron energy loss spectroscopy.

This approach enabled the authors to identify active sites (parts of molecules or structures in which binding is more likely to occur) formed dynamically during the reaction and understand how different supports facilitate (or not) CO₂ hydrogenation. In particular, the investigation showcases the advantages of using mesoporous CeO₂ as a support material, demonstrating its ability to facilitate the hydrogenation reaction via the creation of Ce₃⁺active sites thanks to the synergistic effect of the Ni nanoparticles at CeO₂ surface.

By proving the significance of support materials in dictating reaction mechanisms, this study overcomes the traditional approach focusing on precious metal catalysts. It also provides new tools for the design of more efficient and targeted catalysts, crucial for advancing sustainable chemical transformations and addressing environmental challenges.

In addition, this research was made possible by the e-DREAM (the European Distributed Research infrastructure for Advanced electron Microscopy) initiative, which is meant to promote cooperation between European advanced electron microscopy laboratories, and to foster collaborative research and transnational user programmes. Both the EMAT (University of Antwerp) and ICN2 are founding members of this network.

Reference article:

Kellie Jenkinson, Maria Chiara Spadaro, Viktoria Golovanova, Teresa Andreu, Joan Ramon Morante, Jordi Arbiol,* Sara Bals* (2023). Direct Operando Visualization of Metal Support Interactions Induced by Hydrogen Spillover During CO₂ Hydrogenation. Advanced Materials, Volume35, Issue51. DOI: 10.1002/adma.202306447