Quantitative Relationship between Support Porosity and the Stability of Pore-Confined Metal Nanoparticles Studied on CuZnO/SiO₂ Methanol Synthesis Catalysts

Abstract

Metal nanoparticle growth represents a major deactivation mechanism of supported catalysts and other functional nanomaterials, particularly those based on low melting-point metals. Here we investigate the impact of the support porous structure on the stability of CuZnO/SiO2 model methanol synthesis catalysts. A series of silica materials with ordered cagelike (SBA-16 mesostructure) and disordered (SiO2-gel) porosities and varying pore sizes were employed as catalyst supports. Nitric oxide moderated nitrate decomposition enabled the synthesis of catalytically active Cu nanoparticles (3-5 nm) exclusively inside the silica pores with short interparticle spacings. Under relevant reactive conditions, confinement of the Cu particles in cagelike silica pores notably enhances catalyst stability by limiting Cu particle growth as compared to catalysts deposited in SiO2-gel host materials with also 3D and highly interconnected though unconstrained porosity. For both pore morphologies, we find a direct relationship between catalyst stability and support porosity, provided the narrowest characteristic pore dimension is employed as a porosity descriptor. For cagelike porosities this corresponds to the size of the entrances to the nanocages. Our results point to nanoparticle diffusion and coalescence as a relevant growth mechanism under reactive conditions and underscore the significance of the narrowest pore constrictions to mitigate growth and improve catalyst stability. This finding contributes to the establishment of general and quantitative structure-stability relationships which are essential for the design of catalysts and related functional nanostructures with long lifetimes under operation conditions.

Impact of the synthesis route of supported copper catalysts on the performance in the methanol synthesis reaction

“…catalysts was stable during the methanol synthesis at similar conditions [23]. During synthesis of these catalysts, co-impregnation of copper and zinc led to the incorporation of zinc in the silica support, resulting in a zinc-silicate, which is more stable than ZnO and SiO 2 separately [60].…”

“…Irrespective of the mechanism, particle growth is generally considered to depend on the reaction conditions [14], the metal-support interaction [15][16][17], the particle size (distribution) [18,19] and the interparticle spacing [20][21][22], and also on the geometry of the support [9,15,16,23,24]. It has for instance been shown that particle migration can be restricted by encagement or entrapment [23][24][25][26][27]. The geometry of the support can also affect the thermodynamic stability of a supported nanoparticle since the chemical potential of a supported nanoparticle depends on the contribution of the metal-support interfacial energy [3,28].…”

CuO/SBA-15 materials synthesized by solid state grinding: Influence of CuO dispersion and multicycle operation on DeSO performances

“…The CuO sintering process is correlated with this alteration. In fact this effect is closely related to the metal loading and the textural properties of the support [60,61].…”

Comparison between a Water-Based and a Solvent-Based Impregnation Method towards Dispersed CuO/SBA-15 Catalysts: Texture, Structure and Catalytic Performance in Automotive Exhaust Gas Abatement

“…Although the micropores are blocked and no longer accessible, the mesopores are still reachable. The existence of copper oxide particles inside the mesopores is advantageous for the copper oxide dispersion, since pore confinement will prevent further metal oxide particle growth within the pores [31]. Finally, when comparing the average pore size of the materials, a significant increase can be recognized for the ADP sample.…”