“I live vicariously through the researchers and their experiments”

Kevin Sivula is passionate about harvesting energy from light. Professor of chemical engineering at EPFL’s Laboratory for Molecular Engineering of Optoelectronic Nanomaterials, Sivula is driven by curiosity and has a particular fascination for the role of color and interactions with light in chemical systems. Last autumn, the US born researcher was named director of EPFL’s Institute of Chemical Sciences and Engineering.

“My personal interests have been from a very young age in the color of materials but has ended up being focused on solar light harvesting, like when light is absorbed by a material, and then how we can harvest that resulting excited state, for producing electricity or also to store it directly as fuel with an added chemical value that could be used for an eventual sustainable circular economy,” says Sivula.

“Everything that has color, like the dyes in your clothes, has that color because it’s absorbing or interacting somehow with visible light. But what’s the actual interaction of a light absorption event? Well light is bumping an electron to a higher energy level in a molecular material like those dyes in clothes. And when that electron falls back down to a lower, more stable energy level, it most likely releases a small vibration as heat. The whole idea about solar light harvesting and solar energy is to try to use that excited state before it turns into heat,” explains Sivula.

Sivula grew up near Minneapolis, Minnesota, and recalls receiving a chemistry kit from his father, an aeronautical and mechanical engineer who indirectly instilled in him the hands-on importance of engineering. “I was really drawn to that chemistry set as a kid,” says Sivula. “It got me investigating the properties of materials, oxidative states, color changes. The set came with a phenopen, a pH indicator that vividly changes color by simply adding vinegar or ammonia water. I was more interested in the phenopen’s ability to change color rather than the properties of the solution!”

By the time he was 11 or 12 years old, Sivula knew that chemical engineering was his thing, although he admits, “I didn't really know what chemical engineering was, and it wasn’t until I was probably 17 or 18 that I actually started to look into the details of that career path.”

Graduate studies to professorship

Sivula chose to study chemical engineering in undergrad at the University of Minnesota because of its reputable chemical engineering program, and he felt fortunate that it was close to home and family. Coming from a non-academic family, he would have continued in industry after his Bachelor’s if it hadn’t been for polymer expert Frank Bates encouraging strong students to do a PhD, and getting paid while doing so.

Sivula pursued his PhD at Berkeley under the direction of professor Jean Fréchet, and it's no surprise that Sivula was captivated by polymer P3HT that changes color during a process called spin coating. Sivula explains, “The polymer is orange to begin with in solution. It’s thinly coated on a surface by simply placing some solution onto glass and then spinning it. Very quickly, the polymer changes color from orange to dark purple! This dramatic change of color happens because the dissolved polymer switches to a solid state, and that rearranges electron orbitals which ultimately affect the color.” The subject of Sivula’s PhD was to use this material in a solar cell that could convert sunlight into electricity. “My PhD was on the interface between materials and chemistry, and I had to engineer the device which meant that I had to understand the electronics and how to make a functional solar cell. It was a great challenge,” recalls Sivula.

Immediately afterwards, Sivula pursued a postdoc abroad and in the field of artificial photosynthesis with EPFL professor Michael Graetzel where he was quickly promoted to group leader for solar fuels. By 2011, he was accepting a tenure track professorship at EPFL where he continues to conduct research on developing novel optoelectronic materials and harvesting energy for greener fuels.

Constantly challenging himself to push the limits

Sivula says that he has been lucky and at the right place at the right time to get to where he is now. Yet he is someone who has constantly challenged himself to push the limits, be it to find the solution, to be the top of his class, or to confront his own ideas with experiment. He insists, “It’s not enough to work hard in academia. Even having a brilliant formation and top grades wasn’t enough, I had to go out and push my way through.”

So Sivula learned to step out of his comfort zone, like when he was eager to join Michael Graetzel’s lab but hadn’t yet received a response to his application. “Michael was coming to a conference in San Francisco, so I took the opportunity to introduce myself to him directly and express my interest in joining his group for the artificial photosynthesis project. That caught his attention, and he encouraged me to follow up by email. But when I didn’t hear back right away, I reached out to a postdoc in the group, who helped connect me with Michael’s secretary—and that led to my interview.”

He also learned to trust his instinct, like one of several eureka moments when he was investigating how to layer rust (iron oxide) onto solar cells to make a solar water splitting cell. “Every time somebody tried to put a thin film of iron oxide onto glass, the device performed very poorly, and my idea was that perhaps we just have to heat it to a higher temperature to get particles to better adhere to each other. But beyond 500 degrees Celsius, the glass substrate would essentially melt. So I tried a different type of glass, the same material in glass stovetops which is made of aluminium borosilicate glass. I discovered that the optimal temperature was just below 800 degrees Celsius. This led to a whole new line of research.”

What Sivula loves most about academia?

“The best time in my research career was as a postdoc, just having sixty to eighty hours a week in the lab and figuring things out, understanding how the materials work. This was the time in my life when I actually made what I would consider a real discovery,” says Sivula. “But now I get to live vicariously through the experiments of my researchers and students. I still enjoy thinking about how to explain the results, thinking about the next experiments to do to gain more insight on what's going and advance our materials toward practical implementation.”