The low reaction rate of the oxygen reduction reaction (ORR) on platinum electrocatalysts seriously reduces practical efficiencies of hydrogen/air Polymer Electrolyte Membrane (PEM) fuel cells. The design of improved ORR electrocatalysts requires understanding how catalyst activity and stability are controlled by catalyst structure and composition. To prepare strained Pt core-shell particles, an "electrochemical de-alloying synthesis" has been developedIn agreement with computational DFT predictions, experimental results show that compressively strained pure platinum lattices are very active for the oxygen reduction reaction exhibiting a factor of 6x over the activity of unstrained platinum.
Intellectual merit: This project targets the fundamental investigation of the hypothesis that lattice strain is an effective means to tune the surface reactivity of Pt for the ORR. In particular, it will focus on the synthesis, structure-property relationships, and the in-situ X-ray characterization of Pt core-shell nanoparticle electrocatalysts with lattice strain. Specific objectives of the project are: (i) to study the process of de-alloying as a synthetic strategy to prepare Pt particles with controlled lattice strain, (ii) to characterize structure-activity and structure-stability relationships of strained Pt core shell structures using experimental real space (microscopy) and reciprocal space (X-ray diffraction (XRD), small angle scattering (SAXS) and absorption (XAS)) methods as well as DFT computational techniques, (iii) to develop in-situ characterization methods to study the controlling parameters for the strain generating de-alloying process using synchrotron based X-ray methods, such as SAXS and XRD.
Broader impact: Successful development of an ORR catalyst system will overcome a serious technological limitation of today's hydrogen fuel cells. Beyond ORR, the project will clarify whether lattice strained noble metal lattices can benefit other electrocatalytic reactions. This project also provides an opportunity for undergraduate students to contribute to the development of electrochemical energy conversion technologies. New courses on the hydrogen economy are developed with research being an integral part of the course curriculum. The PI and the Houston Museum of Natural Sciences (HMNS) will continue to reach out together to K-12 students to spark fascination about clean energy issues. The PI is also reaching out to young future business leaders in course modules in the MBA program at the U of Houston business school.
