Morphological and structural design through hard-templating of PGM-free electrocatalysts for AEMFC applications

Abstract

This study delves into the critical role of customized materials design and synthesis methods in influencing the performance of electrocatalysts for the oxygen reduction reaction (ORR) in anion exchange membrane fuel cells (AEMFCs). It introduces a novel approach to obtain platinum-free (PGM-free) electrocatalysts based on the controlled integration of iron active sites onto the surface of silica nanoparticles (NPs) by using nitrogen-based surface ligands. These NPs are used as hard templates to form tailored nanostructured electrocatalysts with an improved iron dispersion into the carbon matrix. By utilizing a wide array of analytical techniques including infrared and X-ray photoelectron spectroscopy techniques, X-ray diffraction and surface area measurements, this work provides insight into the physical parameters that are critical for ORR electrocatalysis with PGM-free electrocatalysts. The new catalysts showed a hierarchical structure containing a large portion of graphitic zones which contribute to the catalyst stability. They also had a high electrochemically active site density reaching 1.47 × 10¹⁹ sites g⁻¹ for SAFe_M_P1AP2 and 1.14 × 10¹⁹ sites g⁻¹ for SEFe_M_P1AP2, explaining the difference in performance in fuel cell measurements. These findings underscore the potential impact of a controlled materials design for advancing green energy applications.