Deconvoluting the Individual Effects of Nanoparticle Proximity and Size in Thermocatalysis

Abstract

Nanoparticle (NP) size and proximity are two physical descriptors applicable to practically all NP-supported catalysts. However, with conventional catalyst design, independent variation of these descriptors to investigate their individual effects on thermocatalysis remains challenging. Using a raspberry-colloid-templating approach, we synthesized a well-defined catalyst series comprising Pd 12 Au 88 alloy NPs of three distinct sizes and at two different interparticle distances. We show that NP size and interparticle distance independently control activity and selectivity, respectively, in the hydrogenation of benzaldehyde to benzyl alcohol and toluene. Surface-sensitive spectroscopic analysis indicates that the surfaces of smaller NPs expose a greater fraction of reactive Pd dimers, compared to inactive Pd single atoms, thereby increasing intrinsic catalytic activity. Computational simulations reveal how a larger interparticle distance improves catalytic selectivity by diminishing the local benzyl alcohol concentration profile between NPs, thus suppressing its readsorption and consequently, undesired formation of toluene. Accordingly, benzyl alcohol yield is maximized using catalysts with smaller NPs separated by larger interparticle distances, overcoming activity−selectivity trade-offs. This work exemplifies the high suitability of the modular raspberrycolloid-templating method as a model catalyst platform to isolate individual descriptors and establish clear structure−property relationships, thereby bridging the materials gap between surface science and technical catalysts.

Colloidal Templating in Catalyst Design for Thermocatalysis

“…Apart from the recent advances on the characterization front in electron tomographic analysis , and numerical wetting calculations of RCT catalysts (Figure c1–c3), we point out complementary progress in single-particle tracking of 3DOM structures. − Direct and real-time 3D visualization of individual fluorescent trackers diffusing within and between macropores was recently demonstrated using a refractive index matching imaging system. , Importantly, the diffusive transport results were readily extended from the single macropore level to the bulk 3DOM structure due to the predictable periodicity and pore interconnectedness in 3DOM structures . This ease of extrapolating physical properties (e.g., diffusive transport, thermal transport, optical, mechanical) toward the bulk, combined with the high synthetic modularity and thermomechanical stability of RCT catalysts, uniquely positions the RCT method as an excellent model catalyst platform to elucidate clear structure–property relationships in thermocatalysis, ,,, which will be discussed in Section .…”

“…Calcination is preferred for the RCT approach as NP sintering is mostly circumvented by partial NP embedding within the support . Moreover, apart from removing the polymeric templates, calcination also fully forms the support structure, removes the stabilizing ligands decorating the colloidal NPs to expose the metallic NP surfaces for catalysis, , while providing the energy input to access kinetically inaccessible NP shapes and compositions (e.g., alloying of multimetallic NPs and stabilizing specific crystal facets). ,, …”

“…Copyright 2024 Springer Nature. (h)–(i) adapted with permission from ref . Copyright 2024 American Chemical Society.…”

“…To further exemplify the ability of the RCT catalyst platform to exert independent control over catalyst design parameters, we designed a set of Pd 12 Au 88 /SiO 2 RCT catalysts comprising alloyed NPs at three different sizes (3.6, 4.5, and 5 nm) and two distinct interparticle distances (12 and 21 nm) . This study expanded on the preceding work and separately examined the isolated effect(s) of NP size at various fixed interparticle distances.…”

Controlling nanoparticle placement in Au/TiO2 inverse opal photocatalysts

“…Our observations are consistent with our previous findings in related thermocatalytic gas- and liquid phase evaluation where NP embedding within the support matrix substantially increased the catalyst stability and consequently, the overall catalytic performance. 37–42…”