Current research in our group is motivated by two main, interrelated technologies: electrochemical energy storage (flow batteries) and carbon dioxide capture. In many cases, there are themes common to both research areas, such as aqueous (electro)chemistry, flow cells, and thermodynamic analyses.
Aqueous Organic Redox Flow Batteries
Renewable energy from intermittent sources such as solar and wind is a necessary part of a sustainable future. However, as these sources supply energy for a larger proportion of the grid, a drastic increase in energy storage deployment will be required. After all, how can you use a solar panel at night? Redox flow batteries are a promising option for electochemical energy storage at the grid scale, because of their unique structure. In a flow battery (unlike the battery in your phone), energy is stored in dissolved reactants kept in tanks, and these electrolytes are pumped into an electrochemical cell to charge and discharge. The size of the tanks and the size of the reactor (electrodes, membrane) can be scaled independently, meaning that the battery's capacity to store energy and the power at which it can discharge can be scaled independently. This is especially useful for grid scale energy storage because the duration of discharge (energy to power ratio) is critical.
Our lab researches aqueous organic redox flow batteries: the reactants are organic, metal-organic, or organometallic redox active species dissolved in water. These reactants are synthesized from earth abundant atoms, and are potentially cost-effective. Since the early days of aqueous organic flow batteries, featuring the quinone-bromide flow battery and our first alkaline flow battery (DHAQ), our team has come a long way in designing and evaluating new, extremely stable battery chemistries that enable decadal lifetimes of these systems. However, there is more to be done! We are investigating new chemistries to further improve lifetime, lower cost, increase energy density, and improve cell voltage, among other important characteristics. We continue to collaborate closely with Roy Gordon's chemistry lab to these ends. We also investigate the properties of porous electrodes and ion exchange membranes and their interactions with aqueous electrolytes, deepening understanding of electrochemical systems in order to spur further innovation. See here for a timeline hilighting some milestones of our group's flow battery research, and here for a 2018 talk by Mike on this topic!
Carbon Dioxide Capture
Human activity has (and continues to) increase the concentration of carbon dioxide in the atmosphere, leading to disasterous climate impacts in the present and future. There is no substitute for decarbonization of our energy systems (see above), but there is compelling evidence that nearer-term emissions will continue in some sectors for physical or social reasons (e.g. food security). We anticipate the need for carbon dioxide capture as part of a sustainable future, especially applied as negative emisions technologies such as those that can capture CO2 directly from ambient air, so our group is applying our (electro)chemical engineering skills to take on this technological challenge.
Our carbon dioxide capture methods utilize the concept of alkalinity. Alkalinity a property of aqueous solutions, related to the pH, that determines the concentrations of dissolved inorganic carbon in a solution eqilibrated with CO2-containing gas (like the air). One of our approaches to CO2 capture involves an electrochemical flow cell, where redox mediators undergo proton-coupled electron transfer reactions to swing the electrolyte pH, and thus reversibly absorb and release CO2 from the solutions! Our group has also recently developed a new concept for swinging the alkalinity concentration with other separations processes (e.g. reverse osmosis membranes or capacitive deionization), and we are currently working on demonstrating it in the lab.