Correlating Site Density and Catalytic Activity for Non-Precious ORR Electrocatalysts

Sunday, October 11, 2015: 14:00
Regency A (Hyatt Regency)
P. Strasser, N. Ranjbar (Technical University Berlin), J. Steinberg (Technical University Berlin), and U. Kramm (Technical University Darmstadt)
Carbon materials doped with iron and nitrogen (Fe-N-C) are highly active, precious metal-free catalysts for the electrochemical conversion of molecular oxygen in fuel cells, metal air batteries, and electrolytic processes1-4. However, accurate measurement of their intrinsic turn-over-frequency (TOF) and active site density based on metal centers in bulk and surface has remained difficult to date, which has hampered a more rational catalyst design. Here, we report a successful quantification of bulk and surface-based active site density and associated TOF values of mono- and bimetallic Fe/N-doped carbons using a combination of chemisorption, desorption, and 57Fe Mößbauer spectroscopy techniques. Our general approach yields novel experimental descriptors for intrinsic activity and active site utilization, aiding in the catalyst development process and enabling a previously unachieved level of understanding of reactivity trends owing to a deconvolution of site density and intrinsic activity.             

1.            Wu, G.; Zelenay, P., Nanostructured Nonprecious Metal Catalysts for Oxygen Reduction Reaction. Acc. Chem. Res. 2013, 46, 1878-1889.

2.            Sahraie, N. R.; Paraknowitsch, J. P.; Göbel, C.; Thomas, A.; Strasser, P., Noble-Metal-Free Electrocatalysts with Enhanced ORR Performance by Task-Specific Functionalization of Carbon using   Ionic Liquid Precursor Systems. J. Am. Chem. Soc. 2014, 136, 14486-14497.

3.            Chung, H. T.; Won, J. H.; Zelenay, P., Active and stable carbon nanotube/nanoparticle composite electrocatalyst for oxygen reduction. Nature Communications 2013, 4.

4.            Wu, G.; More, K. L.; Johnston, C. M.; Zelenay, P., High-Performance Electrocatalysts for Oxygen Reduction Derived from Polyaniline, Iron, and Cobalt. Science 2011, 332, 443-447.