The topic
When asked about sustainable energy, many people first think of windmills and solar cells, in other words of electricity. But it is also possible to produce fuels in a climate-neutral way. The way plants carry out photosynthesis provides a good model: with the help of sunlight, sustainable syngas can be produced from CO2 and water - and subsequently converted to all of the products that normally come from crude oil. Burning the fuels releases no more CO2 than the amount that was bound when they were produced. The fuels could be used with existing systems (cars, airplanes, heating equipment), which as a result would no longer damage the climate.
The research question
The biochemistry of photosynthesis has been well studied. CO2 and water are used to produce sugar, with oxygen as a by-product - and the necessary energy comes from the sun. The process is complex and takes place via a number of intermediate steps. Chlorophyll has an essential role in absorbing light, enzymes enable and promote the reaction and the correct spatial organization is important.
What functions in nature can in principal be made to work in the laboratory, so the CD Laboratory for Sustainable Syngas Chemistry took the process as its model. Of course, the Lab aimed to produce not sugar but synthetic gas, or syngas for short. This mixture of hydrogen (H2) and carbon monoxide (CO) is currently produced in megaton quantities from fossil fuels - so not sustainably - and forms the starting material for numerous products of the petrochemical industry, such as plastics, fertilizers and medicines. If syngas could be generated sustainably along the lines of photosynthesis, it could be used to produce a sustainable fuel.
The work of the CD Laboratory
The scientists in the CD Laboratory for Syngas Chemistry were faced with two major challenges. Which materials would make suitable catalysts, able to kick-start the reaction and so take on the role of the photosynthetic enzymes? The group undertook a very detailed study of these enzymes and was then able to synthesize cheap and stable molecules with comparable properties: newly developed molecular catalysts to generate carbon monoxide from carbon dioxide and to make hydrogen from water.
The second key question related to the materials that absorb sunlight and the surfaces on which the catalysts should be arranged. Which materials would be suitable and how should the catalysts be arranged on them so that the sun’s energy can be taken up and used as efficiently as possible?
Results: yes we can
After seven years of work in the CD Laboratory, Prof. Reisner and his team were able to show that the idea really works. There is a prototype in Cambridge that can be described as an “artificial leaf”. It is a few millimetres thick, several square centimetres big, made up of numerous layers and completely immersed in water. When exposed to sunlight at room temperature it makes syngas from water and CO2, with oxygen as a by-product - exactly as in photosynthesis. This discovery has enabled the CD Laboratory to make new catalysts to convert organic and plastic waste for use by the petrochemical industry.
