Researchers at Stockholm University have for the first time been able to study the surface of a copper-zinc catalyst when carbon dioxide is reduced to methanol. A better knowledge of the catalytic process and the possibility of finding even more efficient materials opens the door for a green transition in the chemical industry.

The researchers results have been published in the scientific journal Science.

Methanol is currently one of the most important petrochemical basic chemicals, with an annual production of 110 million tones, and can be converted into tens of thousands of different products and used for the manufacture of, for example, plastics, detergents, pharmaceuticals and fuels.

Methanol also has the potential to become a future energy carrier where, for example, aviation fuel can be produced using captured carbon dioxide for recycling and hydrogen from electrolysis of water instead of using natural gas. A future green transformation of the chemical industry, similar to the one with green steel, where wind or solar energy drives electrolytic cells is therefore a possibility.

Schematic cartoon of two scenarios of equal Zn in Cu that would result in different Zn/Cu ratio in the XP spectrum analysis. (A) represents a totally covered sample surface with a thin layer of Zn, and (B) represents a surface of deeply penetrating Zn and Cu islands alternating on the surface. Image Credit: Stockholm University. Click image for the largest view.

Anders Nilsson, professor of Chemical Physics at Stockholm University explained, “The challenge has been to experimentally investigate the catalyst surface with surface-sensitive methods under real reaction conditions at relatively high pressures and temperatures. Those conditions have for many years not been achievable and different hypotheses about zinc being available as oxide, metallic or in alloy with copper arose but could not be unambiguously verified.”

Peter Amann, first author of the publication noted, “It is fantastic that we have been able to shed light into this complex topic of methanol formation over copper-zinc catalyst after many years of effort.”

David Degerman, PhD student in Chemical Physics at Stockholm University said, “What is special is that we have built a photoelectron spectroscopy instrument in Stockholm that allows studies of catalyst surfaces under high pressures and thereby directly been able to observe what happens when the reaction takes place. We have opened a new door into catalysis with our new instrument.”

Chris Goodwin, researcher in Chemical Physics at Stockholm University added, “We have succeeded using our instrument to demonstrate that zinc is alloyed with copper right at the surface and this provides special atomic sites where methanol is created from carbon dioxide. During industrial processes, a small amount of carbon monoxide is mixed in, which prevents the formation of zinc oxide from carbon dioxide.”

Patrick Lömker, postdoc at Stockholm University commented, “To have our Stockholm instrument at one of the brightest x-ray sources in the world at PETRA III in Hamburg has been crucial to conduct the study. We can now imagine the future with even brighter sources when the machine upgrades to PETRA IV.”

Nilsson concluded, “We now have the tools to conduct research leading to possible other catalyst materials that can be used better to fit together with electrolysis-produced hydrogen for the green transition of the chemical industry, which today is completely fossil-based and accounts for 8% of the world-wide carbon dioxide emissions.”

The study was conducted in collaboration with the University of Innsbruck and Vienna Technical University, Austria and DESY in Hamburg and the Fritz-Haber Institute in Berlin, Germany. The study included former employees at the University Peter Amann, Hsin-Yi Wang, Markus Soldemo, Mikhail Shiplin, Jörgen Gladh, Joakim Halldin Stenlid and Mia Börner.

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Your humble writer is smiling as its a sure bet one can tell this team is pretty happy with their results. Justifiably so, too. Once the CO2 and hydrogen can be cheaply obtained and reformed into the non-pressurized liquid methanol we would have also solved the hydrogen storage issue. Right now one can combust methanol in an internal/external combustion engine and there are fuel cells pretty well developed that can use methanol as fuel. This could well be the alternative short cut that just might be economical enough to compete with petroleum someday.


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