Reduction Reaction by Porphyrin-Based Catalysts for Fuel Cells

In 2007, the field of oxygen reduction reaction (ORR) by porphyrins was partially reviewed by Y. Kiros. The new development reported under the current review is the effect of surface state (composition) on porphyrin's activity toward oxygen reduction in fuel cells, and the highlight of the analogue of fuel cell cathode activity and the oxygen reduction activity in nature. This field also needs a fresh look vs. its overall importance. The porphyrins themselves are moderate oxygen reduction catalysts, and their activity needs to be enhanced. In perspectives of fuel cells, the methods that are practiced and reviewed here are the use of carbon and gold support, pyrolysis and co-deposition with transition metal oxides. Reasons for the porphyrin enhancements and catalysis have been scrutinized. Although great progress has been achieved, there are still some challenges ahead (concerning the ORR mechanism on porphyrins and the activity and stability enhancement for porphyrins to meet practical applications). Therefore, exploring ORR mechanisms on porphyrin, the continuation of the characterization efforts and enhancing porphyrins catalytic performance (a paper in preparation from this group), as well achieving better catalyst durability, are major focuses for fuel cell research in the future.