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Journal articles made easy: Photocatalytic water oxidation

Description

This article looks at photocatalytic water oxidation and producing an artificial water photooxidation system, including  how this could be used to generate renewable energy. It will help you understand the research the journal article is based on, and how to read and understand journal articles. The research article was orginaly published in our Chemical Science journal.

Type of Activity

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working independently

Audience

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TeacherStudent

Age Group

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Undergraduate & Postgraduate
journal-articles-made-eas...

Professor Burkhard Koenig, one of the authors of the article, answers some additional questions on his group's work.


Explain the focus and findings of your article and why it is of current interest?

Catalytic water splitting by visible light is one of the great challenges of our times, as it is closely connected with the sustainable energy production of the future. Typical catalytic systems work either in solution (homogeneous) or as solid (heterogeneous), but natural photosynthesis, which may serve as a model, uses a different approach: dyes and redox enzymes (biocatalysts) bound to fluid membranes. The key difference of membrane-bound processes to solution phase reactions is going from three dimensions to two dimensions, which has drastic implications on the concentration dependence of bimolecular processes. The difference to solid (heterogeneous) catalysts is that they are static, while membranes are fluid and dynamic; they can adapt and rearrange during reactions, which may enable processes like self-repair. 


What distinguishes your work from other photosystems in bilayer membranes that have been reported in recent years? 

We report the first example of a water photooxidazing system that is membrane bound. Homogeneous and heterogeneous catalysts for water oxidation have been reported. The key difference of the membrane bound system is that it still works at very low concentrations, where homogeneous systems fail.


What was the motivation behind the research?

I like to use inspirations from nature to design functional chemical systems. 


How big an impact do you see your work potentially having?

At the current stage of development this is (like always) difficult to foresee.


Which part of you work proved the most challenging?

Optimizing the conditions and establishing reaction conditions that ensure good reproducibility of the water oxidation performance.


Could you expand more on the applications you see the membranes being employed in, considering the amount of oxygen they are able to generate?

Regarding applications in functional devices for artificial photosynthesis, two approaches may be considered: 

1. To combine the water oxidation unit with the hydrogen generation unit in solution, and to use a redox shuttle for a soft “device” pretty much like the Z-scheme of PSII and PSI; 

2. To immobilize the two units on the respective anode and cathode for a wired device.


The concentration/stability of the photosensitiser is identified as being the limiting factor and you report a 60% recovery of initial TON when a new photosensitiser is embedded into the membrane. How does this compare to the more traditional homogeneous systems that have been reported and is the reuse of your vesicles more complicated to achieve?

The stability of the photosensitizer is indeed a limitation in all reported systems. This limitation remains also in the membrane bound catalysts. Regeneration of catalyst is simple (addition of new amphiphilic sensitizer) and the recovery is comparable to homogeneous systems to the best of my knowledge, but there are not many reports regarding this aspect.


Do you have any plans for future work extending from this study? 

As already mentioned above, we certainly will try to combine photooxidation and -reduction and we will use the functionalized membranes as coating for electrodes. The suggested "more active role of the membrane" is interesting and indeed the membrane could be more than a support for the catalyst. 

ADDITIONAL INFORMATION

Journal articles made easy are journal articles from a range of Royal Society of Chemistry journals that have been re-written into a standard, accessible format. They contain links to the associated Chemistry World article, ChemSpider entries, related journal articles, books and Learn Chemistry resources such as videos of techniques, and resources on theory and activities. They should facilitate students understanding of scientific journal articles and how to extract and interpret the information in them.