Jillian Dempsey

Jillian Dempsey

Vitals

Current affiliation: University of North Carolina, Chapel Hill

Age: 34

Ph.D. alma mater: California Institute of Technology

Role models: Harry B. Gray, her Ph.D. adviser, “for his selfless dedication to young scientists”; and the late “queen of carbon science,” Mildred Dresselhaus, “for being a pioneer for women in science.”

If I were an element, I would be: Ruthenium. “I like to have fun with photons!”

Growing up in New Jersey, Jillian Dempsey was surrounded by the pharmaceutical industry. It would have been natural for her to become part of it, and in fact, that was her plan. But Dempsey switched course in college when she saw how physical inorganic chemistry could curb humanity’s addiction to fossil fuels.

Dempsey and her team at the University of North Carolina, Chapel Hill, are now studying next-generation catalysts for artificial photosynthesis. Like natural photosynthesis, this process creates energy-rich compounds from water, carbon dioxide, and sunlight. Whereas plants make sugars, artificial leaves would produce fuels including hydrogen and methane.

Molecular fuels, especially hydrocarbons, dominate the shipping and transportation industries, in which sustainable but bulky technologies have struggled to make inroads. Batteries and solar panels gobble up an aircraft’s weight budget, for example, leaving no room for ticketed passengers or valuable cargo. Comparatively lightweight molecular fuels, such as methane, are much better suited for these applications. Artificial photosynthesis promises a sustainable way of making them without extracting them from deep in Earth.

Research at a glance

Artificial photosynthesis promises to make high-energy fuels from cheap, abundant reactants. But even the simple step of splitting water to obtain hydrogen requires complex chemistry, as depicted in this cartoon. Dempsey studies the mechanisms of hydrogen-evolution catalysts, such as those shown, to improve the process.

Artificial photosynthesis promises to make high-energy fuels from cheap, abundant reactants. But even the simple step of splitting water to obtain hydrogen requires complex chemistry, as depicted in this cartoon. Dempsey studies the mechanisms of hydrogen-evolution catalysts, such as those shown, to improve the process.
Credit: Yang H. Ku/C&EN

But converting cheap and abundant reactants into valuable fuels requires a reshuffling of both protons and electrons through reactions known as proton-coupled electron transfers. Dempsey’s research combines electrochemical methods with time-resolved spectroscopy to reveal how well different catalysts choreograph these reactions under different conditions.

“She’s worked out ways to tell exactly how these reactions go,” says electron-transfer-chemistry expert Harry B. Gray of California Institute of Technology, who was Dempsey’s doctoral adviser. Her research, coupled with her excellence as a teacher and mentor, have established her as an emerging leader in chemistry, Gray adds. “I can’t think of anyone who does more for the chemical enterprise.”

Dempsey’s work is already helping researchers design improved catalysts, Gray says, and she’s doing that with an eye toward cost. For instance, her team is particularly interested in cobalt and nickel complexes that are cheaper than more conventional platinum catalysts.

Although it will be years before artificial photosynthesis is ready to fill fuel tanks on a commercial scale, Dempsey may already be sharing a glimpse of the chemistry that will help power the future.

Three key papers

Linear Free Energy Relationships in the Hydrogen Evolution Reaction: Kinetic Analysis of a Cobaloxime Catalyst” (ACS Catalysis 2016, DOI: 10.1021/acscatal.6b00667)

Potential-Dependent Electrocatalytic Pathways: Controlling Reactivity with pKa for Mechanistic Investigation of a Nickel-Based Hydrogen Evolution Catalyst” (J. Am. Chem. Soc. 2015, DOI: 10.1021/jacs.5b08297)

Photo-Induced Proton-Coupled Electron Transfer Reactions of Acridine Orange: Comprehensive Spectral and Kinetics Analysis” (J. Am. Chem. Soc. 2014, DOI: 10.1021/ja505755k)

Stories in C&EN about Dempsey’s work:

The inorganic kids are alright

Vitals

Current affiliation: University of North Carolina, Chapel Hill

Age: 34

Ph.D. alma mater: California Institute of Technology

Role models: Harry B. Gray, her Ph.D. adviser, “for his selfless dedication to young scientists”; and the late “queen of carbon science,” Mildred Dresselhaus, “for being a pioneer for women in science.”

If I were an element, I would be: Ruthenium. “I like to have fun with photons!”

Luke Connal
Daniel DiRocco