Scanning transmission X-ray microscopy of nano structured thin film catalysts for proton-exchange-membrane fuel cells

• STXM is used to analyse nano structured thin film (NSTF) catalyst fabrication.
• STXM is used to follow assembly into a PEM-FC as anode.
• STXM is used to track changes during start-up/shut-down & reversal testing.
• The perylene 149 support of NSTF is lost during these tests.
• Its loss does not affect performance during its lifetime.

Scanning transmission X-ray microscopy (STXM) has been applied to characterize nano structured thin film (NSTF) catalysts implemented as electrode materials in proton-exchange-membrane (PEM) fuel cells. STXM is used to study all chemical constituents at various stages in the fabrication process, from the perylene red (PR149) starting material, through the formation of the uncoated perylene whiskers, their coated form with Pt-based catalyst, and toward the NSTF anode fully integrated into the catalyst coated membrane (CCM). CCM samples were examined prior to operational testing and after several different accelerated testing protocols: start-up/shut-down (SU/SD), and reversal tests. It was found that, while the perylene support material is present in the pre-test samples, it was completely absent in the post-test samples. We attribute this loss of perylene material to the presence of cracks in the catalyst combined with intensive hydrogenation processes happening at the anode during operation. Despite the loss of the perylene support, the platinum shells forming the NSTF anode catalyst layer performed well during the tests.