Construction of a Graphene-Wrapped Pd/SiO₂@TiO₂ Core–Shell Sphere for Enhanced Photoassisted Electrocatalytic Methanol Oxidation Property

Abstract

Direct methanol fuel cells (DMFCs) are promising future green energy conversion devices, and their activity and stability can be improved using photofunctional electrodes with the assistance of light illumination. Herein, the graphene-wrapped Pd/SiO 2 @TiO 2 core−shell sphere (PTSG) was synthesized via a facile electrostatic self-assembly method. Benefiting from structural advantages and component optimization, the PTSG exhibits remarkable intrinsic MOR electrocatalytic activity (1569 mA•mg −1 ) and the 1.88 times enhancement (2921 mA•mg −1 ) under the light irradiation for a methanol oxidation reaction in the alkaline medium. The metal-support interactions among Pd NPs, SiO 2 @TiO 2 , and graphene offer the electrocatalyst more active metallic Pd for methanol oxidation. Moreover, further analysis reveals that SiO 2 @TiO 2 endows the catalyst with more surface oxygen-containing groups, high methanol-adsorption capacity, and high light utilization compared to the pure TiO 2 , which enables the PTSG with more available active sites, superior durability, and light harvesting. This work provides a new sight for designing high-performance photoassisted MOR electrocatalysts.

Supported nanostructured photocatalysts: the role of support-photocatalyst interactions

“…Silica (SiO 2 ) is another excellent support material for photocatalysts particles [27,29,[51][52][53][54][55] that has been reported to improve the dispersion or decrease the agglomeration of supported photocatalysts particles and increase the surface area and adsorption capacity toward a variety of pollutant molecules [27,43,44,[56][57][58][59][60]. Hence, the SiO 2 -TiO 2 system often exhibits better photocatalytic activity than pure titania [29,57,[61][62][63].…”

Platinum–palladium-on-reduced graphene oxide as bifunctional electrocatalysts for highly active and stable hydrogen evolution and methanol oxidation reaction

“…18 However, on the one hand, Pt is expensive due to its scarcity, on the other hand, Pt-based catalysts are destabilized owing to CO poisoning, and their wide applications are presently still facing great challenges. 19,20 The Pd-based catalysts have excellent catalytic performance and stability for the MOR in alkaline solution owing to their appropriate d-band centers that make them insensitive to CO. 21 The price of Pd is lower than that of Pt, but both have similar face-centered cubic structures and extremely high lattice matching. The hydrogen absorption energy (Gibbs free energy-ΔG H ) of Pt is only slightly below zero, while the ΔG H of Pd is close to −0.13 eV, and the combination of Pt with Pd leads to an increase in ΔG H relative to Pd.…”

Nitrogen-Doped Graphene Aerogel Microspheres Used as Electrocatalyst Supports for Methanol Oxidation

“…Direct methanol fuel cells (DMFCs) have become a promising renewable energy source and have attracted widespread interest owing to the outstanding energy conversion efficiency, higher energy density, and lower pollution rate. − Until now, Pt-containing nanosystems have been the most popularly studied catalysts for DMFCs owing to the fascinating catalytic properties. − However, some shortcomings of Pt-containing catalysts hinder the commercialization of DMFCs, for example, high cost, low utilization, unsatisfactory catalytic activity, poor durability, and poor toxicity resistance in the methanol oxidation reaction (MOR). , Catalyst poisoning resulting from the strong interaction between the intermediate substances (such as CO) and the Pt NPs result in the decline of the catalytic performance . Furthermore, the dispersion state , of Pt NPs on the carrier or the stability between the Pt NPs and the carrier − also affect the catalytic performance.…”