Nanoscale Spatial Distribution of Supported Nanoparticles Controls Activity and Stability in Powder Catalysts for CO Oxidation and Photocatalytic H₂ Evolution

Abstract

Supported metal nanoparticles are essential components of high-performing catalysts, and their structures are intensely researched. In comparison, nanoparticle spatial distribution in powder catalysts is conventionally not quantified, and the influence of this collective property on catalyst performance remains poorly investigated. Here, we demonstrate a general colloidal self-assembly method to control uniformity of nanoparticle spatial distribution on common industrial powder supports. We quantify distributions on the nanoscale using image statistics and show that the type of nanospatial distribution determines not only the stability, but also the activity of heterogeneous catalysts. Widely investigated systems (Au−TiO 2 for CO oxidation thermocatalysis and Pd−TiO 2 for H 2 evolution photocatalysis) were used to showcase the universal importance of nanoparticle spatial organization. Spatially and temporally resolved microkinetic modeling revealed that nonuniformly distributed Au nanoparticles suffer from local depletion of surface oxygen, and therefore lower CO oxidation activity, as compared to uniformly distributed nanoparticles. Nanoparticle spatial distribution also determines the stability of Pd−TiO 2 photocatalysts, because nonuniformly distributed nanoparticles sinter while uniformly distributed nanoparticles do not. This work introduces new tools to evaluate and understand catalyst collective (ensemble) properties in powder catalysts, which thereby pave the way to more active and stable heterogeneous catalysts.

Template-assisted synthesis of Ag/AgCl hollow microcubes and their composition-dependent photocatalytic activity for the degradation of phenol

“…According to the mechanism, photocatalytic performance of Ag/ AgCl hollow microcubes was related to the hot electron concentration of Ag and the separation efficiency of photoinduced carriers was dependent on the amount of Ag nanoparticles in Ag/AgCl and on the nanoscale spatial distribution of supported Ag nanoparticles. 21,22 Based on the experimental results of photocatalytic degradation of phenol, the as-obtained Ag/AgCl hollow microcubes (the ratio of Ag to AgCl ¼ 1 : 3) showed the highest photocatalytic capability under visible-light illumination. The reason might be ascribed to two aspects including the content of Ag and the surface porous structure of Ag/AgCl hollow microcubes in our experiments.…”

“…Although this method is efficient for the preparation of hollow structure Ag/AgCl, the distribution of hetero interfaces between Ag and AgCl in the shell and the Ag/AgCl ratio are hard to manipulate; meanwhile, the amount and distribution of noble metals in plasmonic photocatalysts have an important inuence on the photocatalytic performance. 21,22 In fact, an oxidation method was proposed to prepare Ag/AgBr nanowires, which is a simple experimental method, easy to operate, and the molar ratio of Ag to AgBr can be easily adjusted by controlling the concentration of the oxidizing agent composed of halide. 23 Furthermore, the in situ oxidation of Ag can form a close connection between Ag and AgBr and it is conducive to effective carrier transfer.…”

Photocatalytic Activity of Supported Metal Nanoparticles and Single Atoms

“…[71] Spatial distribution of NPs in the support has an impact on the photocatalytic performance. [72] Two COF-based Schottky heterojunctions, namely AuSP/COF and AuCP/COF, were synthesized using Au NPs with sparsely (AuSP) or closed-packed (AuCP) distributions and then applied for photocatalytic degradation of decabromodiphenyl ether and dehalogenation of phenacyl bromide. The Au-loaded composites were prepared by oil-in-water emulsion solvent evaporation technique.…”

Dual promotional effect of CuxO clusters grown with atomic layer deposition on TiO2 for photocatalytic hydrogen production

“…The overpopulation of cocatalyst clusters and overlap of PPA marks the decay of activity of the photocatalyst as a function of the cocatalyst loading. The photocatalytic activity decay resulting from PPA overlap can be attributed to local depletion of the reaction intermediates on the catalyst surface, which has a strong negative effect on the reaction rate in the case of densely spaced surface islands [58].…”