Single Phase Electrocatalysts

Electrochemical reduction of atmospheric oxygen provides carbon emission-free pathways for the generation of electricity from chemical fuels and for the distributed production of green chemical oxidants like hydrogen peroxide. Recently, organic mixed ionic–electronic conducting polymers (OMIECs) have been reported as a new class of active electrode materials for the oxygen reduction reaction (ORR).  

Figure 1: ORR can proceed via two pathways. Shown here is qualitative comparison between the two; the outer-sphere and inner-sphere reaction pathways.

In the Salleo group, we seek to identify the operating mechanisms with which polymers can facilitate ORR.  The features of a polymeric film which contribute to its ability to perform as an electrocatalyst span many orders of magnitude, from the electronic structure of individual polymer chains to the microscale atomistic structure, to the interaction between the film surface and the electrolyte. 

Figure 2: An illustration of the charge distribution around an O2/polymer adsorbed intermediate, as calculated using DFT.

To address the different time and length scales we take a multi-faceted approach, including electronic-structure theory, the synthesis of a wide range of polymer materials with systematic changes in chemistry, as well as multi-faceted electrochemical characterizations.

Figure 3: Cyclic voltammetry (CV) techniques are used to characterize the redox behavior of polymer of interest for ORR. Peaks in the CV indicate where the polymer is transitioning from an undoped state to a doped state.

Within this scope, correlative operando techniques that combine robust electrochemistry with a probe to examine a variety of different materials properties while the material is operated electrochemically are of particular interest. These probes can range from Raman spectroscopy to different forms of microscopy all the way to X-ray scattering and can each provide unique insights about the mechanistic function of OMIECs. Using this knowledge, our goal is to design new and exciting polymers for ORR applications. 

Active members in this area: Ana De La Fuente Duran, Adam Marks, Nicholas Siemons, Alison Shad