Size Effects in Nanoparticle Catalysis at Nanoparticle Modified Electrodes: The Interplay of Diffusion and Chemical Reactions

Abstract

Electron transfer reactions mediated via nanoparticles immobilized on an electrode surface are considered in respect of catalytic processes in which solution phase species are either oxidized or reduced to form products exclusively via electron transfer with negligible reaction at the underlying supporting electrode. Specifically simulation is used to explore the effect of the nanoparticle size both for individual nanoparticles as well as ensembles of nanoparticles and a kinetic diagram developed. For a single nanoparticle its size controls the rates of diffusion of species to and from the particle so that the relative extent of the catalysis is reduced for larger particles. For an array of nanoparticles the response of the whole is sensitive not only to the particle size but also to the particle coverage since the inter-particle distance influences the extent, or otherwise, of the local overlap of the diffusion layers of neighbouring particles and hence also the extent of the catalysis. Both particle size and coverage are essential parameters to consider in evaluating possible electrocatalytic nanoparticles.

Design of the vanadium dioxide temperature self-regulator in the terahertz regime

“…如果不考虑材料光学及热学性质 的变化, 光热效应将导致粒子的平衡温度随着光 强增加而不断上升. 然而, 在光电对抗 [1] 、 化学催 化 [2,3] 、 生物医学成像 [4][5][6][7][8][9] 等需要较强光强或光强 不能准确控制的情况下, 常常需要将材料温度保持 在某一固定值, 这就要求材料的光吸收能够随入射 光强发生非线性改变. 相变材料是一类在适当条件 下可以触发结构或物理性质剧烈改变的物质.…”

“…为简单起见, 我们在模拟中取固定 值C VO 2 ≈ 3 × 10 6 J m −3 K −1[36] . 球体积V = 4πr3 /3, 表面积A = 4πr 2 . h c 代表粒子与环境的热对流系数.…”

Halide-Enhanced Catalytic Activity of Palladium Nanoparticles Comes at the Expense of Catalyst Recovery

“…NP catalysis rather literally occurs around the boundary between homogeneous and heterogeneous catalysis and has been referred to as "semi-heterogeneous catalysis" [9]. Catalysis by nanoparticles poses intriguing questions and gives rise to interesting ideas, such as the question whether reactions occur on the surface of the nanoparticles or in solution (vide infra) and the idea that reactions may be diffusionlimited or chemistry-limited depending on nanoparticle size [10]. Model reactions for studying catalysis by metallic nanoparticles have been proposed [11].…”

Electrocatalytic Oxidation of Hydroxide Ions by Co3O4 and Co3O4@SiO2 Nanoparticles Both at Particle Ensembles and at the Single Particle Level

“…Moreover, the diffusion layer overlap of those particles tends to mask their true catalytic activity and often occurs especially when with a high nanoparticle loading on the electrode surface. Over the last two decades, an emerging technique of particle‐electrode impacts, or ‘nano‐impacts’, has been demonstrated to provide insights at the single particle level for many electro‐catalysis processes including hydrogen oxidation on Pt NPs and Pd NPs, methanol oxidation on Pd NPs, oxygen reduction and hydrogen peroxide reduction on single enzymes . The area of catalytic impacts has been recently reviewed .…”