Our group examines electrocatalysts for both cathodic and anodic fuel cell reactions. We have examined novel Pt-alloy electrocatalysts in order to better understand how both the composition and crystalline phases present in the catalyst infleunce electrocatalytic activity.
We are also interested in understanding how the strong-metal support interactions (SMSI) can influence electrochemical reactions. For example, TiO2 can enhance the oxygen reduction reaction on Pt nanoparticles. Furthermore, the presence of TiO2 can slow down Pt nanoparticle coalescence, improve its durability in fuel cells. However, TiO2 is not electrically conductive, so introducing it into fuel cell catalyst layers without increasing ohmic losses presents a major challenge.
Recently, we have developed a fuel cell catalyst support based on a novel conducting doped metal oxide material, Ti3O5-Mo-Si (hereafter referred to as TOMS). Unlike TiO2, TOMS materials have enahanced enhanced electronic conductivity, and still stabilize the Pt catalyst and enhance its fuel cell performance. These new materials have the potential to replace the carbon support commonly used in current fuel cell electrodes.
More details on our research in this area can be found in the following publications:
Today’s fuel cells rely on platinum to act as a catalyst for both oxidation of hydrogen and reduction of oxygen. While platinum is ideal for this application, its use is not sustainable in the long term. Platinum is not only a rare precious metal but it is also very expensive. To make fuel cells both more sustainable and cheaper, a non-precious metal alternative to platinum is required. Given the slow kinetics of oxygen reduction, the cathode typically requires more platinum than the anode. Thus, non-noble alternatives to oxygen reduction at the cathode would significantly reduce the amount of platinum required. Metals such as iron or cobalt, heated under inert atmosphere in the presence of nitrogen on high surface area carbon black yield highly active catalysts towards oxygen reduction
Our work employs a chemisorption approach which involves grafting nitrogen-containing functionalities directly onto the carbon surface that can coordinate iron species. The main advantage of chemisorption over physisorption is that we have more control over the placement of both the nitrogen and iron species, which leads to a higher number of active sites being formed. Our work explores the impacts of nitrogen content, heat treatment temperature, carbon black, on the activity towards oxygen reduction. Methods of characterization including thermogravimetric analysis, inductively coupled plasma – optical emission spectrometry, and rotating ring-disk electrode voltammetry are utilized to evaluate various properties of the catalysts generated. As the adjacent plot demonstrates, iron based catalysts were generated that are comparable Dodelet’s, which are among the best non-noble catalysts currently available.
More details on our research in this area can be found in the following publications:S. G. Mavilla, B. J. MacLean, E. B Easton, "Preparation and Characterization of Non-Precious Metal Fuel Cell Catalysts via Chemical Modification of Carbon Surfaces", ECS Trans.,53 (12) 31 – 41 (2013). doi: 10.1149/05312.0031ecst