Fuel Cells (FCs) as a new energy source requires highly active catalysts for the sluggish oxygen reduction reaction (ORR) on the cathode. The development of alternative Pt-free ORR catalysts to replace the current-in-use Pt-based catalyst is pressing due to the scarcity and high price of Pt. Imitating the structure of the enzymes that catalyze ORR offered a promising approach to developing these catalysts. Inspired by the structure of cytochrome c oxidase (CcO) and laccase that both contain porphyrinic iron active centers, our group fabricated a Fe based single atom electrocatalyst (E-SAC) from a Fe-porphyrin-based metal organic frameworks (MOF) precursor. MOF with confined and tunable structures of the metal centers are excellent candidates for mimicking the structure of active centers in enzymes. Due to the low conductivity of most of the MOFs, high temperature and longtime pyrolysis is often required to carbonize the organic linkers for electrochemical application. This process often associates with serious metal aggregation that needs to be removed with tedious post-treatment. Our groups for the first time reports a microwave heating method that transforms the designed metal atoms in the MOF to single atom active sites without aggregation. This method not only enabled fast conversion of a MOF to an E-SAC, but also minimized metal diffusion and aggregation, ensuring exclusive single metal atoms dispersion in a conductive carbon matrix. Naturally the tedious post-treatment procedures associated with aggregate formation can be omitted, which can largely cut the cost for practical fabrication. Using Fe-PCN-222 MOF as an example, with microwave irradiation as short as 5 seconds, the Fe-PCN222 MOF precursor was quickly carbonized to Fe-E-SAC. Various electrochemical techniques have been applied to study the resulting Fe-E-SAC and demonstrated excellent electrocatalytic activity and selectivity in reduction of molecular oxygen to water, a great promise for fuel cell applications.

Fabrication of bioinspired enzymatic single-atom electrocatalysts using metal organic frameworks as precursors for oxygen reduction reactions in fuel cells

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.