ASU researchers develop artificial enzyme to harness light for renewable energy systems

August 19, 2021

Harnessing energy from light and transforming it into other usable forms is fundamental to many renewable energy systems as well as the production of clean fuels. Research and development of efficient artificial photosynthesis to develop clean fuels and sequester carbon dioxide from the atmosphere are primary goals and challenges of future renewable energy systems. Key components of these systems include the development of artificial enzymes capable of catalyzing the oxidation of water and transferring electrons as part of a renewable energy system.

Using an artificial enzyme embedded in a transparent, conductive material, researchers at Arizona State University's School of Molecular Sciences report in Catalysts their success in developing a highly efficient system to convert light energy into chemical energy. SMS Researchers Seo and Ghirlanda Download Full Image

“The artificial enzyme we used is based on the protein cytochrome c, but with a cobalt atom in place of the iron atom in the bound cofactor; this simple substitution enables catalysis of water oxidation,” said Carla Casadevall, lead author on the paper. 

Casadevall, who has since earned her PhD, was a visiting graduate student in School of Molecular Sciences Professor Giovanna Ghirlanda’s lab.

“Carla’s expertise was on small-molecule catalysts, and at ASU she learned to work with proteins; her combination of these areas facilitated the development of this system, integrating a cobalt-containing active site into a protein matrix that tuned the environment around the active center to allow for enhanced oxygen evolution," Ghirlanda said. 

This innovative system converts light energy into chemical energy by transferring electrons with an efficiency of 97% within an electrochemical cell. To accomplish this, the new protein was absorbed onto transparent antimony-doped tin oxide (ATO) developed in School of Molecular Sciences Professor Don Seo’s lab, which allows passage of light and simultaneously conducts the electrons produced in the reaction to the other side of the electrochemical cell — in this case producing hydrogen.  

Ghirlanda explained the significance of this research: “Mixed systems in which protein-based catalysts interfaced directly with electrodes can be used to convert solar light into electricity and/or chemicals and fuels, by coupling the electrons obtained on one side of the reaction to a second set of reductive catalysts that can convert carbon dioxide and other substrates to valuable chemicals. Transparent, conductive materials such as those developed by Professor Seo are key to developing this technology.”

“This paper is a clear example of the crosspollination environment at (the School of Molecular Sciences) in which the knowledge and skills of, for example, protein experts integrate discoveries in engineering and molecular catalysis to produce an emergent semiartificial catalyst with superior performance," said Tijana Rajh, director of the school. "This exemplifies why ASU is ranked as No. 1 in innovation for the sixth year!”

James Klemaszewski

Science writer, School of Molecular Sciences


Q&A with Department of Physics Chair Patricia Rankin

August 19, 2021

With the start of a new semester this fall, Patricia Rankin, Department of Physics chair, talks about her visions for the department and answers some questions about herself.

Question: What is your overall vision for the Department of Physics? Patricia Rankin, Department of Physics chair. Photo by Xu Wei Download Full Image

Answer: I want to produce the physicists of tomorrow — innovative, adaptive, collaborative and in high demand!

Q: Where do you see the school in 10 years?

A: I want to have built on past and current successes — we have some cutting edge facilities here, the Compact X-ray Free Electron Laser, or CXFEL being just the latest, that allow us to do research at the frontiers of physics. When people decide what physics department they want to be a part of, I want our department to be the one they choose. In short, I want us to not just produce the physicists of the future but to have become the model for physics departments in the future — the one they all aspire to be.

Q: Why should you study physics?

A: If you want to understand the natural laws governing the world you live in, study physics! It’s a foundational science that you can take in many directions as you pursue your career. It teaches you to problem solve and think critically. If you want to understand something like how gravity can bend light, study physics. If you want to understand the maximum amount of power a solar panel can generate, study physics. Mostly though, study it because you enjoy being amazed by how basic ideas can explain complex phenomena.

Q: How do you work through setbacks as a woman in STEM?

A: This is a complex question because I think it is sometimes hard to know if a setback you face has anything to do with the fact you are a woman. Anyone pursuing a career in physics will face setbacks and find people who will help. We are starting to understand that not everyone faces the same setbacks or gets the same help in overcoming them. At a group level there are marginalized aspects of an identity, and privileged ones, but how different aspects of an identity intersect and the overall impact on individuals varies immensely.

I had an education at a girls-only school from age 11 to 18 years that built my self-confidence, a supportive family, and lots of people who helped me in my career and that got me through setbacks. I think it is important to reach out for help when you need it and have a network to draw on. It helps to have interests outside of physics. Now when I look back I can see that the setbacks helped me get to where I am now and put me in a position to help remove barriers for others, and that it was worth persevering.

Q: Why is it important to you for physics to be more inclusive?

A: Multiple reasons — I want everyone to have the opportunity to succeed. Moreover, everyone brings their own perspectives in and has a unique set of skills. It doesn’t make sense to limit the power we have to advance by only using some of the skills at our disposal.

Q: Why did you go into physics?

A: I liked the fact I could start from some basic assumptions and figure things out I didn’t already know. As an example, you can take a drop of oil of known volume, watch how it spreads out on a water surface and use the area the drop spreads out over to determine how big an oil molecule is. Also, you can use the number of radioactive decays in a given amount of time to help date how old an object is. The examples are endless — who wouldn’t want to be a physicist?

Q: What is your favorite physics concept/physicist?

A: The connection between symmetries of nature and conservation laws. The fact that energy is conserved means that when you repeat an experiment sometime later you get a consistent result (time invariance/symmetry). This connection comes from work by Emmy Noether, which makes her my choice for favorite physicist.

Q: What’s a good book/source/website to read to get involved in physics?

A: Whichever one you will pick up or click on. There are so many. The PHET website has a lot of fun simulations you can use to start to explore physics with.

Q: What do you do to relax?

A: Read. I like mysteries, especially historical ones. Meet with friends; dance around the house to old pop songs.

Q: How do you recommend managing stress?

A: Reach out for support from family, friends and colleagues. Have activities you enjoy doing that are not related to what you are working on or studying. Realize that it's often smarter to take a break than continue to be frustrated trying to solve a problem or get something done. Take a holistic approach to life and make sure you build in recovery time from periods of intense focus.

Q: What’s the weirdest food item you like?

A: So, I was born and raised in the U.K., which means that I grew up eating things that may sound weird but aren’t — like toad in the hole, which is actually sausages in batter. Now that I have moved to Arizona I have developed a taste for iced tea made with sparkling water, which seems weird to me and which I would not have expected to like from the description.

Q: What do you miss about growing up in the U.K.?

A: Castles; old ruins in general. I also miss really green and lush vegetation.

Q: What is something people don’t know about you?

A: I am really good at doing the twist.

Kiersten Moss

Marketing Assistant, Department of Physics