Shape-dependent catalytic activity of palladium nanocrystals for the oxidation of carbon monoxide

Abstract

It is of great interest to study the shape effect on the catalytic activity of metal nanocrystals, which exposed different crystallographic facets upon adopting various shapes. The investigations on shape-dependent catalysis of supported metal nanocrystals need to be conducted over nanocrystals with well-defined shapes and cleaned surface. The palladium nanocrystals with cubic, octahedral, and spherical morphologies were synthesized and well dispersed onto the inert silica support after removing the capping agents, which were used as the heterogeneous catalysts for carbon monoxide (CO) oxidation. It was found that the crystal facets of Pd nanoparticles played an essential role in determining the catalytic oxidation properties. As a result, the octahedral and spherical nanoparticles that predominantly exposed the Pd {111} crystal facets exhibited significantly better catalytic activity than the palladium nanocubes that possessed the Pd {100} crystal facets as the basal plane for the CO catalytic oxidation. It was inferred that the appropriate adsorption strength of CO molecules on Pd {111} planes was beneficial to the enhancement of the catalytic activity.

Palladium‐Based Nanomaterials: A Platform to Produce Reactive Oxygen Species for Catalyzing Oxidation Reactions

“…In the system of Pd-SiO 2-nanospheres demonstrated by Wang et al, no remarkable size effect on the CO oxidation effi ciency was observed. [ 97 ] In a different report, however, Xia et al found that Pd nanocubes with sizes <10 nm exhibited excellent activity against the samples at large sizes. [ 27 ] Given that these works used different experimental conditions (e.g., O 2 content, fl ow speed, synthetic methods for nanocrystals, and support materials), it seems infeasible to systematically compare their fi ndings and make solid conclusions.…”

“…[ 97 ] This indicates that a certain factor other than oxygen activation changes the overall performance of CO oxidation. It is known that Pd surfaces can be readily poisoned by strongly adsorbed CO, [ 98 ] and as such, O 2 activation may also be infl uenced by CO molecules.…”

The Orientation of Silver Surfaces Drives the Reactivity and the Selectivity in Homo‐Coupling Reactions

“…To optimize the efficiency of a defined reaction, it is important not only to find the most relevant catalytic material but also to process it with an adequate morphology ,. In particular facetted surfaces of metal catalysts exhibit different activities depending on their crystallographic orientation . While catalytic processes usually refer to the chemical transformations of small organic molecules, in the so‐called on‐surface synthesis approach well‐defined surfaces of single crystal metals can be used to steer the flat‐lying adsorption and the coupling reaction of larger aromatic or aliphatic compounds.…”

An integrated micromechanical model and BP neural network for predicting elastic modulus of 3-D multi-phase and multi-layer braided composite

“…Over the last decades, extensive investigations have been mainly conducted [8][9][10][11][12][13][14][15][16][17] about the modeling of traditional 3-D braided composites. Following assumptions were introduced [17] to simplify the finite element modeling and improve the computing efficiency: (1) The tow cross-section is hexagonal and identical for all the tows; (2) The braiding process is quite stable so that the braided structure is uniform and all the tows are straight within the braided preform.…”

“…The advantage of this approach is not only in obtaining global properties of the composite but also mechanical behaviors can be related to the composite microstructure. A majority of micromechanics models for predicting the elastic properties of 3-D braided composites have been reported in the literature [8][9][10][11][12][13][14][15][16][17]. In comparison, the studies for 3-D MPML braided composite are limited and inadequate owing to the fact that MPML composite has just been developed in recent decades.…”