Cage-bell Pt-Pd nanostructures with enhanced catalytic properties and superior methanol tolerance for oxygen reduction reaction

Concave Pt-Zn Nanocubes with High-Index Faceted Pt Skin as Highly Efficient Oxygen Reduction Catalyst

High dosage of expensive Pt to catalyze the sluggish oxygen reduction reaction (ORR) on the cathode severely impedes the commercialization of proton exchange membrane fuel cells. Therefore, it is urgent to cut down the Pt catalyst by efficiently improving the ORR activity while maintaining high durability. Herein, magic concave Pt-Zn nanocubes with high-index faceted Pt skin (Pt78 Zn22 ) are proposed for high-efficiency catalysis toward proton exchange membrane fuel cells. These unique structural features endow the Pt-skin Pt78 Zn22 /KB with a mass activity of 1.18 mA μgPt -1 and a specific activity of 3.64 mA cm-2 for the ORR at 0.9 V (vs RHE). Meanwhile, the H2 -O2 fuel cell assembled by this catalyst delivers an ultrahigh peak power density of ≈1449 mW cm-2 . Both experiments and theoretical calculations show that the electronic structure of the surface is adjusted, thereby shortening the length of the Pt-Pt bond and reducing the adsorption energy of OH*/O* on the Pt surface. This work demonstrates the synergistic effect of the oxidation-resistant metal Zn and the construction of Pt-rich surface engineering. Also, it guides the future development of catalysts for their practical applications in energy conversion technologies and beyond.

Fabrication and catalytic application of tandem reactor module using Au nanoparticles-coated glass beads as packing materials

A tandem reactor module using Au nanoparticles (NPs)-coated glass beads as packing materials is designed and fabricated for the catalytic reduction of 4-NP. Au NPs-coated glass beads are firstly prepared...

Sphere-to-Multipod Transmorphic Change of Nanoconfined Pt Electrocatalyst during Oxygen Reduction Reaction

An oxygen reduction reaction (ORR) catalyst/support system is designed to have Pt nanoparticles nanoconfined in a nanodimensionally limited space. Holey crumpled reduced graphene oxide plates (hCR-rGO) are used as a carbon support for Pt loading. As expected from interparticular Pt-to-Pt distance of Pt-loaded hCR-rGO longer than that of Pt/C (Pt-loaded carbon black as a practical Pt catalyst), the durability of ORR electroactivity along cycles is improved by replacing the widely used carbon black with hCR-rGO. Unexpected morphological changes of Pt are electrochemically induced during repeated ORR processes. Spherical multifaceted Pt particles are evolved to {110}-dominant dendritic multipods. Nanoconfinement of a limited number of Pt within a nanodimensionally limited space is responsible for the morphological changes. The improved durability observed from Pt-loaded hCR-rGO originates from 1) dendritic pod structure of Pt exposing more active sites to reactants and 2) highly ORR-active Pt {110} planes dominant on the surface.

Swollen hexagonal liquid crystals as smart nanoreactors: implementation in materials chemistry for energy applications

Materials are the key roadblocks for the commercialization of energy conversion devices in fuel cells and solar cells. Significant research has focused on tuning the intrinsic properties of materials at the nanometer scale. The soft template mediated controlled fabrication of advanced nanostructured materials is attracting considerable interest due to the promising applications of these materials in catalysis and electrocatalysis. Swollen hexagonal lyotropic liquid crystals (SLCs) consist of oil-swollen surfactant-stabilized 1D, 2D or 3D nanometric assemblies regularly arranged in an aqueous solvent. Interestingly, the characteristic size of the SLCs can be controlled by adjusting the volume ratio of oil to water. The non-polar and/or polar compartments of the SLCs can be doped with guest molecules and used as nanoreactors for the synthesis of various metals (Pt, Pd, Au, etc.), conducting polymers and composite nanostructures with controlled size and shape. 1D, 2D and 3D mono- and bimetallic nanostructures of controlled composition and porosity can also be fabricated. These materials have demonstrated impressive enhancements of their electrochemical properties as compared to their bulk counterparts and have been identified as promising for further implementation in energy harvesting applications. In this review article, recent research materials are described regarding the development of functional materials with much improved performances for catalysis applications. This review addresses a brief overview of swollen hexagonal mesophases as nanoreactors, describes examples of nanostructured materials synthesized in these nanoreactors, shows several examples of the energy conversion applications in solar light harvesting, fuel cells etc. and also summarizes the associated reaction mechanisms developed in the recent literature for enhanced catalytic activity.

Shape-Controlled Synthesis of Pt Nanopeanuts

Exploring the novel shape of Pt nanoparticles is one of the most useful ways to improve the electrocatalytic performance of Pt in fuel cells. In this work, the Pt nanopeanuts consisting of two nanospheres grown together have been fabricated through a two-step polyol method. The high resolution scanning electron microscope (SEM) images and energy dispersive x-ray (EDX) spectrum collected at adjacent part point out the Pt nanopeanut is apparently different from the two physical attached nanospheres. To understand the growth mechanism of this nanopeanut, the final products in different synthesis situations are studied. The results indicate the interesting morphology of Pt nanopeanuts mainly benefit from the chemical reagent (FeCl₃) while the size and homogeneity are greatly affected by the temperature. Furthermore, the electrocatalytic activity of the Pt nanopeanuts has also been demonstrated here. Our two-step synthesis of Pt nanopeanuts not only enlarges the group of Pt nanoparticles, but also provides a beneficial strategy for the synthesis of novel metal nanoparticles.

Tuning metal cluster catalytic activity with morphology and composition: a DFT study of O2 dissociation at the global minimum of PtmPdn (m + n = 5) clusters

The catalytic property for O₂ dissociation of the pure Pt₅ cluster can be further improved by introducing the Pd atoms based on the morphology and composition.