Reshaping the Cathodic Catalyst Layer for Anion Exchange Membrane Fuel Cells: from Heterogeneous Catalysis to Homogeneous Catalysis

In anion exchange membrane fuel cells, catalytic reactions occur at a well-defined three-phase interface, wherein conventional heterogeneous catalyst layer structures exacerbate problems such as low catalyst utilization and limited mass transfer. We developed a structural engineering strategy to immobilize a molecular catalyst tetrakis(4-methoxyphenyl)porphyrin cobalt(II) (TMPPCo) on the side chains of an ionomer (polyfluorene, PF) to obtain a composite material (PF-TMPPCo), thereby achieving a homogeneous catalysis environment inside ion flow channels, with greatly improved mass transfer and turnover frequency due to 100% utilization of the catalyst molecules. The unique brand-new structure of the homogeneous catalysis system comprising interconnected nanoreactors exhibits advantages of low overpotential and high fuel cell power density. This strategy of reshaping of the catalyst layer structure may serve as a new platform for applications of many molecular catalysts in fuel cells.