Overview
Metal-nanoparticles play a central role in catalysis because their high surface-to-volume ratio exposes a large number of active sites while minimizing material use. At the nanoscale, atoms at edges, corners, and defects show unique electronic structures that can enhance reaction rates and selectivity [1,2] (Figure 1 A). As a result, catalytic processes in energy conversion increasingly rely on engineered nanomaterials to improve efficiency and reduce costs.
However, catalytic performance is not determined by particle size alone. The shape of nanoparticles governs which crystallographic facets are exposed, affecting binding energies and reaction pathways. Likewise, substrate type and coverage influence the accessibility of reactants and beneficial support effects. Inter-particle spacing is equally important, as particles placed too closely lead to diffusion domain overlaps, electronic coupling, or nanoparticle merging, changing catalytic behavior, whereas excessive spacing reduces cooperative effects and surface density [3].
In previous work, researchers from the group for Physics of Complex Fluids demonstrated that nanoparticles adhere more strongly to certain facets of substrate materials and how these interactions can be tuned by solution pH [4] (Figure 1 B). Once established this methodology grants a new level control over nanoparticle spacing, anchoring during reaction conditions and substrate effects.
Nanoparticle size effects and ability to control particle substrate interactions. A: Catalytic activity of gold nanoparticles in dependence of their size. B: Adhesion of silica nanospheres to different crystal facets in dependence of solution pH.
Research Objectives
In this project, we investigate how substrate identity (e.g., metal oxides, carbon supports) and solution composition (ionic strength, surfactants, pH) can be tuned to control nanoparticle deposition and in-situ reorganization during catalysis. Our goal is to establish design principles that enable stable, more active catalytic interfaces through guided nanoscale assembly.
To this end, we will prepare gold nanoparticle electrodes supported on both metal-oxide thin films as well as graphene-like materials. A deposition from nanoparticle suspensions under different pH and dewetting of sputtered gold-films will serve as the primary sources of nanoparticles on these substrates. Atomic force microscopy will be employed to investigate the size, spacing and anchoring of these nanoparticles in dependence of preparation method and substrate. The such created electrodes will be used to perform the oxygen evolution reaction, allowing to relate the afore mentioned parameters with catalytic activity. Afterwards nanoscale-microscopy and other in situ techniques native to PCF will be used to understand how the catalytic process changes the initial structure of the nanostructured electrode and how these changes can be influence by tuning solution pH, ionic strength and by adding certain additives such as surfactants.
Learning Objectives
In addition to the standard learning objectives for a Master’s project (research planning, academic writing, data presenting, how to work in a lab environment, etc.), you will learn how to:
· prepare electrochemical experiments and nanostructured electrode materials
· perform electrochemical experiments and atomic force microscopy
· evaluate and interpret electrochemical and AFM data.
· work with state-of-the art microscopic and/or spectroscopic methods
Contact Information
· Daily Supervision: Dr. Maximilian Jaugstetter
· Supervision: Prof. Dr. Frieder Mugele
[1] Rulle Reske, Hemma Mistry, Farzad Behafarid, Beatriz Roldan Cuenya, and Peter Strasser
Journal of the American Chemical Society 2014 136 (19), 6978-6986, DOI: 10.1021/ja500328k
[2] Hemma Mistry, Rulle Reske, Zhenhua Zeng, Zhi-Jian Zhao, Jeffrey Greeley, Peter Strasser, and Beatriz Roldan Cuenya, Journal of the American Chemical Society 2014 136 (47), 16473-16476, DOI: 10.1021/ja508879j
[3] Julia Linnemann, Kannasoot Kanokkanchana, and Kristina Tschulik
ACS Catalysis 2021 11 (9), 5318-5346, DOI: 10.1021/acscatal.0c04118
[4] Shaoqiang Su, Igor Siretanu, Dirk van den Ende, Bastian Mei, Guido Mul and Frieder Mugele, Advanced Materials 2021 33 (52), DOI: 10.1002/adma.202106229