Photosynthesis and Artificial Photosynthesis:Learning Biology Through Its Engineering Application

AFACCT Conference 2014 Prince George’s Community College, Largo,

MDPoster Session (Sessions 2C And 6C)

January 9 And 10, 2014

RET in EngineeringNSF Grant No: 1009823

Directorate for Engineering

Yuda AnrianyAnrianya@pgcc.edu

Prince George’s Community College

BackgroundWhat is photosynthesis? Although many students can correctly answer that it is a process in which light energy is converted into food, few would be able to describe the process of energy conversion in photosynthesis.

What happens if the students are told that the same molecular process of natural photosynthesis is used in artificial photosynthesis to capture solar energy in a solar cell? (1) In my BIO1140 class, the answers are excitement and engagement.

The topic of artificial photosynthesis is one that I used to engage students in learning photosynthesis at the molecular level. By introducing students to the applications of biology in another fields, students were able to see the extent of the importance of the concept they learn. Since solar cell is a subject that students can relate to, students were more motivated to learn the concept much more deeply.

This curriculum element was developed as part of my participation in the Research Experience for Teachers (RET) program in which my summer research in Dr. Sheryl Ehrman’s laboratory in the Department of Chemical and Biochemical Engineering at the University of Maryland was implemented in Principles of Biology: Cellular and Molecular Biology (BIO1140) course at Prince George’s Community College.

Photosynthesis vs. Artificial Photosynthesis Both photosynthesis and artificial photosynthesis use light energy to split water molecule.

In natural photosynthesis, the light energy is captured by the chlorophyll in the reaction centers in the two photosystems that work together. The energy is used to excite electrons originated from water molecules, releasing hydrogen ions and oxygen (see Figure 1). The electrons then travel through a series of proteins which eventually result in the generation of ATP and NADPH energy that is used to form chemical bonds during conversion of CO2 to glucose. This process is highly efficient: almost 100% of light energy that hits the reaction center is used to excite electrons.

The photovoltaic system in solar cells also captures light energy by a semi conductor such as silicon to excite electrons, which then travels and produce energy in a form of current. Artificial photosynthesis is employed in Photo Electrochemical Cells (PEC), where instead of forming chemical bonds or producing currents, the light energy that has been harnessed is used to split water molecules to produce H2 and O2 (see Figure 1) in solar cells that are so called artificial leaf (2). Hydrogen fuel can be stored and used as an alternative source of energy in place of fossil fuels. The engineering aspect of artificial photosynthesis is still the subject of current research, due to its low efficiency and/or the high cost.

In this project, students had an opportunity to learn both photosynthesis and artificial synthesis through a case study, and to have a hands-on experience to build a mini solar cell called DSSC that uses organic dye and nanocrystalline titanium dioxide. This solar cell is inexpensive, although the efficiency is very low.

Figure 1. Conversion of Light Energy in a Leaf (A) and in a Solar Cell (B)(4, 5)

http://www.lbl.gov/Publications/YOS/Apr/synthetic_leaf.jpg

A B

Solar cell

Educational Objectives To engage students in learning the concept of energy conversion in photosynthesis and its application in artificial photosynthesis

To promote critical thinking in comparing and contrasting photosynthesis and artificial photosynthesis

Essential Questions (3)

How does photosynthesis take place with only two simple ingredients?How does the chlorophyll pigment convert sunlight energy to chemical energy?How is the photosynthesis reactions used as a basis for constructing hydrogen solar cell?

The Understanding Process (3)

Start

•A Case Study introduces the concept of photosynthesis in simple terms

Case I

•Self study, group and class discussion on natural photosynthesis process reinforces understanding of concept

Lab Activity

• Building a DSSC solar cell introduces application of concept

Case II

• Literature research on models of hydrogen solar cells (PEC), class presentation on photosynthesis and artificial photosynthesis promotes exploration and critical thinking

End

•Understanding of the concept of photosynthesis and its application

In-Class Activities

Students in BIO 1140 built the Dye-sensitized Solar Cell (DSSC) and presented their research on PEC designs as part of

the project in learning photosynthesis. The solar cell is pictured in the center.

Evaluation: The Most Important Concepts Learned

Significant role of a water molecule on photosynthesis/artificial photosynthesis

Process of making solar energy into another ATP (photosynthesis) and H2+O2 (PEC) Other ways to create energy, that unlike fossil fuels won’t negatively affect earth; lots of substances that can do job of chlorophyllImportance and need of artificial photosynthesisEnergy transfers between photosystems I & II

Evaluation: Students’ Comments“Learn how scientists and engineers work together”“Photosynthesis is not just for plants, but can be used to generate clean energy”“In depth knowledge of a very thorough topic (fossil fuels, global issue) that cannot be forgotten”“Being able to compare it to something else meant fully understanding photosynthesis” “Requiring to explain material to the class motivated me to learn material thoroughly”“Helpful, but too much work on top of other things”“Conducting research [on PEC] was challenging because of unfamiliar terms”“Working in groups was difficult because impossible to get together”

Challenges Encountered and Lessons Learned

Developing and integrating curriculum element:Writing a case study was challenging Integration was overwhelming because lab and presentation were

added to a preexisting lab and lecturePresenting the curriculum element:Gratifying to see students’ engagement in learning using methods

different from traditional lectureEvaluating curriculum element:Manual analysis of survey was challenging

ConclusionThe interdisciplinary method to teach photosynthesis has promoted students’ engagement in learning basic Biology, as shown in the survey results. Students enjoyed learning through untraditional means and got memorable lessons. This may stem from the close relevance of the application of the photosynthesis to students’ real lives. Students were more willing to delve deeper into the concept knowing the value of what they learn. The use of a case study, which is inquiry based, a hands-on activity, and the availability of resources also had facilitated the learning.

In the future, I plan to gauge students’ understanding by comparing exam grades from a class that does and does not use the project.

Finally, I believe that this approach of combining two different fields of study can also be applied in other disciplines as long as it is highly relevant to student’s life and that the relationship between the two fields is clearly defined.

Other, possible interdisciplinary applications Political Science and Journalism Math and Finance Steroid Abuse (Chemistry and Health) Neurogenerative Disease- (Chemistry and Biology) Drug Addition (Chemistry and Sociology)

This project was completed during participation in the RET program in the laboratory of Prof. Sheryl Ehrman in the Department of Chemical and Biomolecular Engineering at the University of Maryland. Many thanks to Dr. Ehrman and Dr. Chia-Ying Chiang for their assistance in learning about PEC. Thanks to Dr. Ehrman, Dr. Isabel Lloyd, and Dr. Leigh Abts for their help in developing the curriculum element. The curriculum implementation was also supported by the RET program.

Acknowledgement

1. Gust, Devens. 1996. Why Study Photosynthesis? http://photoscience.la.asu.edu/photosyn/study.html

2. Regalado, Antonio. 2010. Reinventing the Leaf. Scientific American 303, 86 – 89. 3. Wiggins, Grant and Jay McTighe (2006). Understanding by Design. Pearson: Merrill Prentice

Hall. 4. Yarris, Lynn. Tapping into Solar Energy Riches: Berkeley Lab’s Helios Project and the Solar

Energy Research Center. Lawrence Berkeley National Laboratory. http://www.lbl.gov/Publications/YOS/Apr/index.html

5. http://www.nature.com/nphoton/journal/v6/n8/images/nphoton.2012.175-f1.jpg

References