Sustainable activation of the PtCln/Fe–N–C cathode for PEFCs through repeated subnanometer sizing and coarsening

Abstract

In recent years, the development of polymer electrolyte fuel cells has been in transition from application in fuel cell vehicles and residential cogeneration systems to heavy-duty vehicles such as trucks and buses. Therefore, higher durability and performance are required for each component material, and the development of cathode catalysts is particularly important. We have recently developed a PtCl_n/Fe–N–C catalyst that is 8 times more active than standard Pt/C and maintains activity for 100 000 cycles under accelerated stress testing. This is because Pt ions dissolved from PtCl_n are redeposited and interact with Fe and N sites in the support as subnanometer Pt particles (Pt_subnano), which results in an increased electrochemical surface area and specific activity for the oxygen reduction reaction. In the present research, Cl in PtCl_n was determined to play an important role in promoting the formation of Pt_subnano, and the details of the Pt_subnano formation process, which is the repetitive aggregation and subnano-sizing of Pt in a very short period of the potential cycle, were elucidated by in situ X-ray absorption fine structure analysis.