Kwabena Bediako: Getting the fundamentals down

Portrait of Kwabena Bediako.

“In Ghana,” says Kwabena Bediako, one of the College of Chemistry’s new assistant professors, “everyone knows I was born on Tuesday.” Bediako, whose first name is pronounced Kwab-na, continues, “There is a tradition in Ghana to name children by the day of the week they were born. So we know Kofi Annan, the former U.N. Secretary General, was born on Friday, and our first president, Kwame Nkrumah, was born on Saturday.”

Although born in Ghana’s capital city of Accra in 1986, Bediako’s upbringing was international. His British mother met his Ghanaian father in Bordeaux, France, where they were both studying French. His father was studying for his first Ph.D. in African francophone literature. Both parents would go on to earn Ph.D.s in theology.

Bediako did spend time in his mother’s hometown of Blackburn, just north of Manchester, and in Edinburgh, Scotland. He also accompanied his father to Pasadena, CA, where he was lecturing. “But whenever I returned to Ghana, I would get off the plane in Accra and the humidity would greet me with a big warm hug.” That memory provided him with some comfort when he found himself attending a small midwestern college, where his campus job over the winter was shoveling snow.

Bediako grew up an hour north of Accra in the town of Akropong, and attended middle and high school at the Akosombo International School, another hour further north. “The school in Akosombo,” he says, “was created to educate the children of the expatriates who came there to build a huge hydroelectric dam on the Volta River.” Completed in 1965, the dam created Lake Volta, which has the largest surface area of any artificial lake in the world.’

Although the dam provided cheap electricity for both aluminum smelters and Ghana’s power grid, it had some unintended consequences, including providing habitat for mosquitos. “When I was in school in Akosombo,” Bediako recalls, “we got malaria about as often as Americans get the flu. This left a strong impression on my older brother, Yaw, who also studied there. He became an immunologist who researches malaria in Kenya and the U.K.”

Bediako finished his high school studies in 2004. He states, “I became intrigued by chemistry in high school, thanks to my teacher Charles Karikari. However, I didn’t have the opportunity to spend time in a lab.” Bediako moved to the United States to begin his college career at Calvin College, a small religious liberal arts college in Grand Rapids, MI. He says. “At Calvin, I had a great inorganic chemistry professor, Douglas Vander Griend, and I became fascinated with inorganic coordination chemistry. I wrote an undergrad thesis with Vander Griend as my adviser, and along with other students, I co-authored two published papers with him.”

Graduating with a chemistry B.S. in 2008, Bediako was ready to move onto graduate school when he changed course, moved to suburban Chicago, and, began working for Honeywell UOP. “I made catalysts and absorbents and spent a year getting some industry experience. I figured I’d spent several years in academia, so I wanted to know what it was like on the other side of the fence.”

In 2009, Bediako began his Ph.D studies at MIT, where he worked with Dan Nocera. “I was interested in energy and the environment. There wasn’t much solar power in Ghana, and I wondered why. The Nocera lab was working on water splitting with cobalt and other metal catalysts for solar energy storage, culminating in an artificial leaf.”

In 2013, Nocera moved to Harvard, and Bediako moved with him. “I got my master’s at MIT in 2013, and my Ph.D. at Harvard in 2015,” he says. Bediako’s thesis was entitled “The Electrocatalytic Evolution of Oxygen and Hydrogen by Cobalt and Nickel Compounds.”

The Bediako lab works its magic by starting from nanoscale building blocks and creating electrochemically active structures in the mesoscale range, where quantum mechanics give them unique functionality.

About his thesis research Bediako says, “Artificial photosynthesis requires the execution of two half-reactions, one that oxidizes water to O2 — the oxygen evolution reaction — and the other that reduces hydrogen ions to H2 — the hydrogen evolution reaction. My oxygen evolution reaction studies focused on the catalytic behavior of structurally disordered first-row transition metal oxides.

“At a fundamental level, understanding how protons and electrons may be managed and coupled to improve their activity is important for the design of new electrocatalysts. I enjoyed working on a problem that was motivated by renewable energy, but also involved learning very fundamental mechanistic details of how bonds are rearranged to make new molecules.”

For his postdoc, Bediako remained at Harvard, but switched from chemistry to physics. He worked in the lab of Phillip Kim, which was focused on properties of low-dimensional nanoscale materials. The group uses modern semiconductor fabrication techniques to make materials based on carbon nanotubes, organic and inorganic nanowires and two-dimensional crystals.

In the language of physics, macroscopic objects exhibit behaviors that can be explained by classical mechanics. As these objects get smaller (while they are still composed of many molecules), they enter the mesoscopic realm where the explanation of their behavior requires quantum mechanics.

Says Bediako, “In the Kim lab, we started with a clear mesoscopic target and asked, can we make it? It is possible to make some nanoscale and larger mesoscale structures by deposition from liquid-phase suspensions. These techniques are scalable, but the processes are random enough that you’re never quite sure what structures you created.

“In the Kim lab, I learned how to isolate the layers of our nanoscale lattices and precisely place them to create superlattices. That appeals to me. These techniques might not scale at this point in time, but to understand the fundamentals you have to know what you are working with. And who knows, in the future we may find that it’s possible to layer these materials on a massive scale like we do the pages of a newspaper.

Says Bediako, “Not only are there thousands of layered materials to choose from, at the nanoscale we have some extra tricks to help expand the nature of the structures we create — quantum confinement effects, strong electronic correlations and van der Waals forces. These van der Waals forces can act over atomic distances and can lead to additional modifications to the heterostructure lattices. We can also insert atoms, ions and molecules into the van der Waals gap between layers. The structures I create are called layered van der Waals crystals or van der Waals heterostructures.

“If you have ever seen a gecko climb a wall, or scamper across a ceiling, you’ve seen van der Waals forces in action,” he adds. “The geckos have special structures on their toes that allow them to use these forces to cling to surfaces.

“I think from an early age I appreciated that academic research, and the process of searching for answers to questions about the world around us, has great intrinsic value. I came to recognize that it is just as worthwhile to be a chemist in a lab as it is to be a doctor in a hospital. I don’t think that was a common point of view among Ghanaian kids when I was younger. Back then, if you were interested in science, you studied to become a doctor or engineer. So like my parents, I ended up in academia — but I felt drawn to become a scientist and not a theologian.”

Bediako will officially join the faculty on July 1, although he has already made several visits from Harvard to talk with students about his research program. Here’s how he explains the goals of his lab: “Research in my group will involve the mesoscopic investigation of charge transfer and charge transport in two-dimensional materials and heterostructures, with an emphasis on studying electrochemical energy conversion in fuel cells, batteries and other energy applications. We’ll also study twodimensional semiconductors and quantum electronics. Many of the challenges to creating new materials for energy conversion are related to challenges in next-generation electronics and computing as well.

“To do this, we’ll synthesize and isolate atomically thin inorganic crystals, precisely assemble these layers into novel multicomponent materials and use them to build electrochemical and electronic devices. We will employ a range of optical spectroscopy, electron microscopy, and low-temperature quantum probes to measure the properties of these devices. Working as chemists we’ll study how to manipulate the interfaces of materials to overcome problems at the interface of chemistry and physics.”