Photochemische Energieumwandlung und künstliche Photosynthese
Photochemical Energy Conversion Artificial Photosynthesis

Photochemical Energy Conversion and Artificial Photosynthesis

For the transition to a renewable energy based energy supply, the greatest challenge is the energy storage to compensate for the daily and yearly variability of wind and solar energy. Owing to their high energy density and temporally unlimited storage capacity, fuels, such as hydrogen, methane or liquid hydrocarbons, present the ideal storage medium.
In the module we will discuss in-depth state of the art routes to store solar energy directly in form of chemical energy. These routes involve absorption of solar light (mainly by a semiconductor), and accumulation of the minority charge carriers at the semiconductor surface followed by charge transfer of an electron or hole to a chemical species, such as water or carbon dioxide. Artificial pathways to solar fuels will be compared to natural photosynthesis. The module will provide foundations of the various areas being necessary to understand the production of fuels from sunlight: semiconductor physics, semiconductor surfaces, the solid-liquid interface,  electron transfer theories, experimental techniques, state of the art of water splitting and carbon dioxide reduction.

After successful completion of the module the students are familiar with the prospects of photochemical energy conversion for future energy storage technologies. In particular, the students are able to:

• explain the physical foundations needed for photochemical energy conversion
• determine the efficiency of individual energy transfer processes with physical concepts
• assess the rank of solar fuels in a future renewable energy scenario
• estimate the applicability of different production routes of solar fuels
• compare photochemical energy conversion to alternative concepts

Bachelor in Physics or Chemistry

The module consists of a lecture and exercise classes.

Lecture: The teaching an learning content is presented, discussed, and explained in a structured and detailed manner. Basic knowledge of the physical and chemical aspects in this field is imparted, as well as various aspects of technical systems and devices are discussed. Universal methodic and physical concepts are highlighted by cross referencing between different topics. The students are involved in scientific discussions to stimulate their analytic thinking in physical problems. Regular attendance is, hence, highly recommended.

Exercise: The presentation of the learning content is enhanced by examples and calculations. They are intended to deepen the students understanding of the course material. The students are welcome to discuss any problems with the teacher.

beamer presentation, board work, practise sheets, accompanying internet sites, complementary literature

• R. Memming: Semiconductor Electrochemistry, Wiley-VCH, (2015)
• A.J. Bard & L.R. Faulkner: Electrochemical Methods, Wiley, (2001)
• W. Schmickler & E. Santos: Interfacial Electrochemistry, Springer, (2010)
• K. Krischer & K. Schönleber: Physics of energy conversion, De Gruyter, (2015)

There will be an oral exam of 30 minutes duration. Therein the achievement of the competencies given in section learning outcome is tested exemplarily at least to the given cognition level using comprehension questions, reflection of simple formulas for the description of elementary relations, and sample calculations for order-of-magnitude estimates.

For example an assignment in the exam might be:

• Describe and explain the charge carrier gerneration in semiconductors by sunlight.
• Name the various factors determing the efficiency of a photoelectrochemical device.
• Name and explain the most important loss factors of the electrochemical processes in a photoelectrochemical device.

Participation in the exercise classes is strongly recommended since the exercises prepare for the problems of the exam and rehearse the specific competencies.