Construction of Graphene-Wrapped Pd/TiO2 Hollow Spheres with Enhanced Anti-CO Poisoning Capability toward Photoassisted Methanol Oxidation Reaction

The development of high activity and durable Pd-based electrocatalysts is highly desired for methanol oxidation reaction (MOR). Herein, the unique graphene-encapsulated Pd/TiO2 hollow sphere (PHTG) heterostructure is fabricated through a self-assembly strategy. The as-fabricated hierarchical PHTG exhibits the highest forward current for MOR of 2657 mA.mg(-1) and excellent mass activity of 3687 mA.mg(-1) with the aid of visible light irradiation, which is higher than all the reported TiO2-based photoassisted electrocatalysts. Impressively, the PHTG shows the highest long-time stability within 10,000 s (retained current density up to 1627 mA.mg(-1), which is 51% of the initial activity), compared to that of the state-of-art MOR catalysts. The detailed analyses (XPS, zeta potential, and CO-stripping) reveal that the superior performance of PHTG can be ascribed to the unique architectures of PHTG and the synergetic effect from the mutual interfaces of Pd NPs, hollow TiO2 sphere (HTS), and conductive graphene shell. Notably, the introduction of the HTS provides abundant oxygen species to the Pd surface, fast mass and electron transportation, and strong CO oxidation ability for oxidative removal of the poisonous carbonaceous materials.

Automated summary

In this study, a graphene-encapsulated Pd/TiO2 hollow sphere heterostructure was fabricated, exhibiting high activity and durability under visible light irradiation, outperforming other TiO2-based photoassisted electrocatalysts. Technically, PHTG shows the highest stability over a long period, attributed to its unique structure and synergistic effects.