(238d) Anchoring Pt Catalyst with ZrO2 on Carbon Black for Enhanced ORR Durability

Carbon black-supported platinum catalysts (Pt/C) remain the mainstream oxygen reduction reaction (ORR) catalysts for proton exchange membrane fuel cells (PEMFCs). However, the high cost of Pt and its degradation during operation hinder the practical application of PEMFCs. To solve this problem, zirconia (ZrO₂) has been considered for anchoring platinum nanoparticles (NPs) onto carbon surfaces due to its excellent acid/base resistance, aiming to reduce Pt loading and enhance the durability of Pt/C catalysts. In this project, a facile deposition of ultra-thin ZrO₂ layers onto the surface of Vulcan XC72 carbon black was achieved through the condensed layer deposition technique. Subsequent high-temperature annealing resulted in uniformly distributed ZrO₂ nanoparticles (~2.0 nm), as confirmed by transmission electron microscopy (TEM). The deposition of Pt NPs (~3.5 nm) was accomplished by ethylene glycol reduction of potassium tetrachloroplatinate under heating conditions. The final composition of ZrO₂-anchored Pt/C catalyst (Pt/ZrO₂/C) was determined to be 22.9 wt% Pt, 4.9 wt% ZrO₂, and 72.2 wt% C through thermogravimetric analysis. The catalysts were characterized by high-resolution TEM, energy dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy, confirming the presence, formation and distribution of Pt and Zr. Corresponding ORR and catalyst durability tests demonstrated excellent activity and stability of Pt/ZrO₂/C in acid media. After 10,000 cycles between 0.6 and 1.1 V_RHE in 0.1 M perchloric acid, there was only ca. 10 mV shift in the half-wave potential, with no significant change in the electrochemical surface area. It was demonstrated that ZrO₂ can be an anchoring metal oxide to enhance the catalyst durability.