Non-Precious Catalysts Based on Porous Media for Polymer Electrolyte Membrane Fuel Cells (PEMFCs)

Oxygen reduction reaction (ORR) is the key process in many electrochemical technologies, such as fuel cells and metal-air batteries. However, the ORR is kinetically sluggish, necessitating the use of an electrocatalyst. Currently, platinum-based catalysts are the state-of-the-art catalyst for the ORR and are widely used in fuel cell technologies. However, platinum is classed as a critical raw material due to its scarcity, putting supply chains at risk and potentially limiting the widespread adoption. Recently, transition-metal coordinated nitrogen doped carbon (M-N-C) materials have emerged as promising alternatives, offering activity from earth-abundant elements and tunability through structure and composition. In this work, we explore combining transition metal and nitrogen in a porous carbon structure of varying surface area and morphology. We develop catalysts that offer both high efficiency and durability. The catalysts were synthesised using a simple pyrolysis and were tested using various advanced techniques such as XRD, XPS, BET, SEM, TEM. A central contribution of this work is the application of time-resolved spectroscopies to ORR electrocatalysts. Using transient absorption spectroscopy (TAS) and terahertz spectroscopy, we directly observe charge-carrier dynamics in M-N-C materials. TAS reveals long-lived trapped states localised at metal-Nₓ sites, providing the first spectroscopic evidence that these centres act as charge-trapping sites which facilitate electron transfer during ORR. This dynamic perspective bridges structural characterisation with catalytic function, establishing a mechanistic understanding of electronic behaviour of these catalysts. Overall, this work advances both material design and fundamental understanding of non-precious ORR catalysts, demonstrating ultrafast optical spectroscopy can guide the rational development of next-generation electrocatalysts.