Designing interfacial structures for selective electrocatalysis

Selectivity of electrocatalysis in fuel cells stresses on the tolerance of electrode catalysts to cross-over species. A typical polymer electrolyte membrane fuel cell (PEMFC) employs a Nafion-based membrane to separate the Pt-based cathode and anode. Nevertheless, the intrinsic porosity of Nafion membranes allows reactants and products to cross over from one electrode chamber to the other. As a result, the poor selectivity of Pt leads to mixed reactivity at both electrodes and thus, decreased output voltage and power density. In principle, the membrane can be eliminated if cathode and anode catalysts are selective to the desired half reaction. Herein, the thesis aims to develop selective cathode and anode catalysts. For the cathode, transition metal chalcogenides are selective catalysts for the oxygen reduction reaction. We investigate the structure, activity, surface dynamics, and mechanism of a nickel sulfide catalyst during the oxygen reduction catalysis. By employing the selective nickel sulfide catalyst as the cathode, we construct a proof-of- concept membrane-free fuel cell which significantly outperforms an unselective Pt-cathode congener. For the anode, there is still a paucity of intrinsically selective fuel oxidation catalysts. To achieve high 02 tolerance, we design a new configuration of electrocatalysis by employing a solid oxide-based mixed electron-proton conductor (MEPC) as a condensed membrane to segregate the catalyst and electrolyte while only transporting H-atom equivalents, thus blocking 02 and impurities dissolved in the electrolyte from reaching the catalyst surfaces. We investigate the activity, selectivity, and mechanism of the catalyst/MEPC membrane composite electrode.

Name thesis:degree_name

Doctoral

Department dc:contributor.department

Massachusetts Institute of Technology. Department of Chemistry

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2019

Author dc:creator

• Yan, Bing,Ph. D.Massachusetts Institute of Technology.

Advisor dc:contributor.advisor

• Yogesh Surendranath.

• Chemistry.

Statement dc:rights

• MIT theses are protected by copyright. They may be viewed, downloaded, or printed from this source but further reproduction or distribution in any format is prohibited without written permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

https://hdl.handle.net/1721.1/122454

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/122454