Mesoporous PtPd Alloy: High Entropy Oxide Heterostructures for Efficient Electrocatalytic Methanol Oxidation Reaction.

Abstract

The widespread adoption of direct methanol fuel cells (DMFCs) has been significantly hindered by the low activity of commercial noble metal catalysts toward the methanol oxidation reaction (MOR) and their susceptibility to CO poisoning. To address these challenges, a mesoporous PtPd-HEO (HEO = high entropy oxide) heterostructure is assembled in situ from a metal-organic framework (MOF)-derived high entropy alloy (HEA) in this work. Mass activity exceeding that of commercial Pt/C by more than an order of magnitude is demonstrated by this catalyst. A peak power density of 155 mW cm-2 and long-term operational stability are achieved in a DMFC assembled with mesoporous PtPd-HEO, surpassing the performance of cells based on Pt/C and PtPd/C. In situ spectroscopic studies combined with density functional theory (DFT) simulations reveal that the valence electronic structure of the PtPd alloy is modulated by the HEO component, resulting in improved selectivity for non-CO pathways and increased formation of reactive hydroxyl species. Superior MOR catalytic activity and durability for PtPd-HEO are attributed to this synergistic electronic tuning and the porous structure. The development of HEO-based mesoporous heterostructures is proposed as a promising strategy for the design of next-generation catalysts in energy conversion and sustainable technologies.