“Efficient conversion of CO2 to methanol is one of the grand challenges of contemporary catalytic sciences to which Michael Higham’s work through START is making a key contribution,”Professor Richard Catlow FRS
Addressing the global CO2 emissions and energy challenges
Rising atmospheric carbon dioxide (CO2) levels attributed to burning fossil fuels is a major economic and environmental issue for Africa and globally, in particular the association with increasing global temperatures, which pose a significant risk for current and future generations.
Although global emissions of carbon dioxide CO2 have increased by almost 50 per cent since 1990, experts like the UN’s Intergovernmental Panel on Climate Change (IPCC) agree it is still possible to limit the increase in global mean temperatures using a wide array of technological measures and changes in behaviour. Such measures are set out in the UN’s Sustainable Development Goal 7 Energy.
One such approach involves Catalysis and renewable combustible liquid fuels to enable new technologies to remove CO2 from the atmosphere, converting it into valuable and versatile synthetic fuels. This would allow for an entirely closed carbon cycle, reflecting nature’s own carbon cycle1. The CO2 would be captured and converted into a liquid fuel; this fuel would then be burnt and the CO2 re-captured, closing the gap.
Shipping and aviation are amongst the largest consumers of fossil fuels and greatest contributors to CO2 atmospheric pollution yet cannot be easily converted to utilise electricity from renewable and non-polluting sources. For these applications, catalytic technology could be vital for providing alternative fuel sources.
Computational techniques to investigate both new and existing catalytic materials
Dr Michael Higham is a START-funded expert providing computational insights to support experimental work utilising capabilities at the UK’s national synchrotron – Diamond Light Source. His research entails applying computational techniques to investigate both new and existing catalytic materials to utilise CO2, in particular for methanol synthesis.
Methanol is an important industrial feedstock material and can be used as a renewable fuel when generated from atmospheric CO2; hydrogen obtained sustainably from efficient water splitting processes is another key area of catalytic research for energy applications.
Methanol can be used as both a conventional combustible fuel, as well as in Direct Methanol Fuel Cells (DMFC)2 , which offer an alternative to hydrogen fuel cells with fewer safety and engineering issues to be addressed. Furthermore, methanol can also be used as a starting material for subsequent catalytic processes to produce hydrocarbons, which are chemically equivalent to existing liquid fuels and allow for maximal utilisation of existing technologies.
Efficient conversion of CO2 to methanol and ZnO-supported catalysts
Dr Higham’s research has mostly focused on copper (Cu) based catalysts for methanol synthesis, which have been used extensively for the conversion of synthesis gas (a mixture of CO2, CO, H2O and H2 originating from coal gasification processes). In particular, the Cu/ZnO/Al2O3 catalyst has been used successfully for decades. However, much remains to be understood regarding how precisely these catalysts enhance methanol production.
“As part of my research, I have conducted extensive computational investigations into the mechanism of CO2 and CO hydrogenation to methanol over unsupported Cu catalysts, providing detailed insights into key intermediates and limiting elementary processes in the overall reaction” says Dr. Higham.
This work will provide a benchmark for future computational studies examining ZnO-supported catalysts, which in turn will provide atomic-scale insights into the origin of catalytic activity that will directly complement experimental synchrotron studies.
To this end, my project has also investigated the structure and morphology of Cu clusters supported on ZnO, in order to derive suitable models for the aforementioned computational investigations of supported Cu/ZnO catalysts3.”
It is expected that the work investigating unsupported Cu catalysts will be published imminently in a leading peer-review journal; meanwhile, a second manuscript concerning the growth of Cu clusters over ZnO supports is in preparation, and further calculations are underway to explore the methanol synthesis reaction over model Cu/ZnO catalysts, in collaboration with visiting Masters students from the University of Freiburg, Germany, and the National University of Singapore.
The importance of computational investigations in catalytic research
Dr Higham explains that computer simulations and modelling are vital components in catalytic research, supporting and corroborating by providing an atomic-scale insight into the phenomena that are responsible for macro-scale observations in actual experiments.
“We can test hypotheses for explanations of observed real-world behaviour, and on the flipside, we can use what we already know about well-studied systems to examine new, novel materials, and therefore help to direct future experimental studies.”
Addressing fossil fuel dependence in Africa
These approaches could offer hope to countries across Africa and also address key polluting industries such as aviation and shipping.
“Whilst there is a great deal of focus on renewable electricity sources such as wind and solar, sustainable and renewable combustible liquid fuels will make an important contribution to reducing humanity’s dependence on unsustainable and polluting fuel sources.
This is especially true for Africa and the rest of the developing world, where existing infrastructure could be readily and inexpensively adapted to accommodate such synthetic fuels, whereas infrastructure to enable widespread use of renewably generated electricity such as for transportation purposes would require substantial new investment.” explains Dr Michael Higham.
About the contributors:
Michael Higham completed a PhD in Chemical Science and Technology at the Institut Català d’Investigació Química (ICIQ, Catalan Institute of Chemical Research) in November 2017. Michael joined Professor Richard Catlow’s group at Cardiff University in August 2018, supported by the GCRF (Global Challenges Research Fund). Michael’s work forms part of the START (Synchrotron Techniques for African Research and Technology) project, providing computational insights to support experimental work utilising the synchrotron facilities at Diamond Light Source Ltd. Michael’s current research project concerns Cu-based catalysts for methanol synthesis from CO2.
Professor Richard Catlow is Foreign Secretary and Vice President of The Royal Society,
Professor of Catalytic and Computational Chemistry at Cardiff Catalysis Institute and Professor of Chemistry at UCL, and is a founder of the UK Catalysis Hub: https://ukcatalysishub.co.uk/
1 Olah, G. A.; Goeppert, A.; Prakash, G. K. S. Chemical Recycling of Carbon Dioxide to Methanol and Dimethyl Ether : From Greenhouse Gas to Renewable, Environmentally. J. Org. Chem. 2009, 74 (2), 487–498.
2 Hogarth, M. P.; Hards, G. A. Direct Methanol Fuel Cells: Technological Advances and Further Requirements. Platin. Met. Rev. 1996, 40 (4), 150–15
3 Collaboration with Alexey A. Sokol and David Mora-Fonz, both of University College London.