Designing the Macroporous Structure of Three-Way Catalyst Particles: The Influence of Template Concentration on Framework Thickness and Mass Transfer

Abstract

Mass transfer is an essential process that can extend the performance and utilization of nanoporous materials in various applications. Therefore, improving mass transfer in nanoporous materials has always attracted much interest, and macroporous structures are currently being studied to enhance mass transfer performance. The introduction of macroporous structures into three-way catalysts (TWC), which are widely utilized to control the emission of polluted gases from vehicles, provides the potential to enhance their mass transfer property and catalytic performance. However, the formation mechanism of macroporous TWC particles has not yet been investigated. On the other hand, the influence of the framework thickness of the macroporous structure on the mass transfer enhancement is still unclear. Therefore, this report investigates the particle formation and framework thickness of the macroporous TWC particles synthesized using the template-assisted aerosol process. The formation of macroporous TWC particles was precisely controlled and investigated by altering the size and concentration of the template particles. The template concentration played a crucial role in maintaining the macroporous structure and controlling the framework thickness between the macropores. Based on these results, a theoretical calculation showing the influence of template concentration on the particle morphology and framework thickness was developed. The final results showed that increasing the template concentration can positively affect the nanoporous material’s framework thickness reduction and mass transfer coefficient improvement.

CO Oxidation Enabled by Three-Way Catalysts Comprising Pd/Rh Nanoparticles Supported on Al2O3 and CeZrO4 Confined in Macroporous Polystyrene Latex Templates

“…In contrast, the superior catalytic performance of the macroporous TWC particles is attributed to their convective diffusion property, where macropores are preferable for reactant transportation within the structure (Figure 7c). 44 The improved convective diffusion within the particles facilitates contact between the reactants and the interior catalyst surface, thereby enhancing the overall catalytic performance. Therefore, producing macroporous catalyst particles shows great potential for enhancing catalytic performance by improving the mass transfer efficiency within the particles.…”

“…34,42−45 Recently, Le et al efficaciously synthesized macroporous TWC particles via a straightforward aerosol process with the assistance of template particles. 44,45 This work demonstrated that the hierarchically ordered macroporous structure exhibits a higher mass transfer efficiency than the aggregate structure due to the facility of macropores. Therefore, macroporous TWC particles hold significant promise for achieving excellent catalytic performance owing to their high mass transfer efficiency within the structure.…”

“…In light of these difficulties, one potential solution relies on the design of hierarchically ordered macroporous-structured particles composed of TWC NPs. Among the various existing structures, macroporous structures have gained significant attention because of their exceptional properties. – Previously, our group successfully synthesized hierarchically ordered macroporous-structured particles using various materials, demonstrating the feasibility of this approach. – Remarkably, studies have demonstrated the crucial role of macroporous structures in improving mass transfer efficiency, electrocatalytic performance, and protein adsorption. ,– Recently, Le et al efficaciously synthesized macroporous TWC particles via a straightforward aerosol process with the assistance of template particles. , This work demonstrated that the hierarchically ordered macroporous structure exhibits a higher mass transfer efficiency than the aggregate structure due to the facility of macropores. Therefore, macroporous TWC particles hold significant promise for achieving excellent catalytic performance owing to their high mass transfer efficiency within the structure.…”

“…The macroporous TWC particles were synthesized by a template-assisted spray process, which has been described elsewhere. , Briefly, the precursor solution comprised TWC NPs (Mitsui Mining & Smelting Co., Ltd., Japan) and laboratory-fabricated PSL 154 nm at desired concentrations. The TWC NPs are composed of supports (i.e., Al 2 O 3 and CeZrO 4 ), which exhibit high thermal stability and surface areas, as well as catalyst metals (i.e., Pd and Rh), displaying excellent catalytic performance in the gas conversion (Figure a).…”

“…Additionally, Figure b,c shows the scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images of TWC NPs used in this study. The PSL 154 nm template was controllably produced following a previously reported procedure, ,, and its morphology and particle size distribution are presented in Figure d,e. The precursor solution was then introduced into the spray apparatus heated at 250, 350, 500, and 700 °C under N 2 carrier gas flowing at a rate of 2.0 L min –1 (Figure a).…”