Understanding the diffusion-driven colloidal deposition of laser-generated ligand-free nanoparticles on dispersed catalyst supports

纳米基催化剂的新发展具有巨大的经济潜力。制备非均相催化剂的一种灵活方法是将纳米颗粒胶体沉积在支撑材料上。粒子沉积可由液体中带电粒子的静电吸引相互作用引起。然而，扩散驱动过程也很重要，特别是在富含缺陷的载流子材料的情况下可以观察到。虽然粒子吸附在静电吸引区表明不可避免的自发和非特异性沉积机制，但在静电排斥区，特别是在富含缺陷的吸附剂上，预计会发生选择性和特异性吸附。因此，静电驱动的颗粒吸附由于电荷密度高而导致团聚，而在静电排斥（扩散控制）区域，颗粒可以均匀沉积。由于静电斥力区存在能量垒，不利于多个纳米粒子同时吸附。这些方面在文献中研究较少，特别是在无配体条件下。这种无配体胶体无疑是胶体颗粒动力学研究的理想模型材料。因此，本项目的目的是通过系统的研究来了解扩散驱动的颗粒吸附，从而在多相催化剂的生产中实现有针对性的控制。在一个有充分根据的假设的基础上，将发展一个效应机制，它将描述各种表面缺陷对颗粒吸附的作用。为此，将使用无配体纳米颗粒，并选择具有不同氧空位、面和官能团的载体。不同的表征方法被用来阐明纳米颗粒-缺陷的相互作用：光电子能谱（粒子氧化、电子结构、粒子-载流子相互作用）、拉曼光谱（载流子-纳米粒子相互作用的振动带）、电子显微镜（粒子大小、形状和分布）、x射线衍射（晶体结构）、红外光谱（官能团）、热重（粒子质量负载）、BET法（催化剂表面）、紫外-可见光谱（带隙、沉积效率、胶体稳定性）、zeta电位（胶体稳定性，表面电荷）和电催化（催化活性和稳定性ORR）的测量。最后，通过系统的研究，建立一个广泛的模型来阐明扩散驱动颗粒沉积的机理，并将其转移到不同的材料体系中。

The new and further developments of nano-based catalysts has a great economic potential. A flexible method for the preparation of heterogeneous catalysts is the colloidal deposition of nanoparticles on support materials. Particle deposition can be initiated by electrostatically attractive interactions of charged particles in liquids. However, diffusion driven processes are also important, which can be observed in particular in the case of defect-rich carrier materials. While particle adsorption in the electrostatically attractive regime suggests an inevitably spontaneous and nonspecific deposition mechanism, a selective and specific adsorption is expected especially on defect-rich adsorbents, in the case of the electrostatically repulsive region. Thus electrostatically-driven particle adsorption causes agglomeration due to the high charge density, while in the electrostatically repulsive (diffusion-controlled) area the particles can be deposited homogeneously. Due to an existing energy barrier in the electrostatic repulsive region, the adsorption of several nanoparticles at the same time is unfavorable. These Aspects have been less studied in the literature, in particular for ligand-free conditions. Such ligand-free colloids are undoubtedly ideal model materials for colloidal particle dynamic investigations. Therefore, the aim of this project is to gain an understanding of the diffusion-driven particle adsorption by systematic investigations and thus to enable targeted control in the production of heterogeneous catalysts. On the basis of a well-founded hypotheses, an effect mechanism will be developed, which will describe the role of various surface defects on particle adsorption. For this purpose, ligand-free nanoparticles will be used and supports with different oxygen vacancies, facets and functional groups will be selected. Various characterization methods are used to elucidate the nanoparticle-defect interaction: photoelectron spectroscopy (particle oxidation, electronic structure, particle-carrier interaction), Raman spectroscopy (vibrational band of carrier-nanoparticle interaction), electron microscopy (particle size, shape and distribution), X-ray diffraction (crystal structure), IR spectroscopy (functional groups), thermogravimetry (particle mass loading), BET method (catalyst surface), UV-VIS spectroscopy (band gap, deposition efficiency, colloidal stability), measurement of zeta potential (colloidal stability, surface charge) and electrocatalysis (catalytic activity and stability ORR). Finally, by means of systematic studies a wide-ranging model to elucidate the mechanism of diffusion-driven particle deposition will be established and transferred to different material systems.