Papers by Markus Niederberger
Journal of Materials Chemistry A
We present a one-pot microwave synthesis of Pd modified titanium dioxide nanocrystals for macrosc... more We present a one-pot microwave synthesis of Pd modified titanium dioxide nanocrystals for macroscopic aerogel monoliths, which are efficient visible-light photocatalysts for methanol oxidation in a heated gas flow reactor.
ACS Applied Nano Materials, 2018
Electrodes for metal-ion batteries should combine high specific capacity with fast cycling rate c... more Electrodes for metal-ion batteries should combine high specific capacity with fast cycling rate capabilities. Although the use of mesoporous particles is an attractive approach to reconcile these contradicting performance parameters, synthetic protocols to create such particles are typically time-consuming, require environment-unfriendly chemistries and are limited to small batches. We present a simple and scalable processing route to synthesize mesoporous TiO 2 particles through freezing, drying and grinding of gelled aqueous suspensions of 5 nm sized TiO 2 nanoparticles. Freezing enables partial densification of the nanoparticle network present in the initial gel, thus leading to mesoporous particles combining high density with easily accessible specific surface area for metal ion insertion. The resulting mesoporous particles can be assembled into hierarchical porous anodes that exhibit superior volumetric capacity in comparison to xerogel and aerogel reference compositions. The aqueous-based nature and the simplicity of the freezing process makes this synthetic approach a promising route for the fabrication of architectured electrodes for the next generation of metal-ion batteries.
Advanced Science, 2022
Photocatalysis has the potential to make a major technological contribution to solving pressing e... more Photocatalysis has the potential to make a major technological contribution to solving pressing environmental and energy problems. There are many strategies for improving photocatalysts, such as tuning the composition to optimize visible light absorption, charge separation, and surface chemistry, ensuring high crystallinity, and controlling particle size and shape to increase overall surface area and exploit the reactivity of individual crystal facets. These processes mainly affect the nanoscale and are therefore summarized as nanostructuring. In comparison, microstructuring is performed on a larger size scale and is mainly concerned with particle assembly and thin film preparation. Interestingly, most structuring efforts stop at this point, and there are very few examples of geometry optimization on a millimeter or even centimeter scale. However, the recent work on nanoparticle-based aerogel monoliths has shown that this size range also offers great potential for improving the photocatalytic performance of materials, especially when the macroscopic geometry of the monolith is matched to the design of the photoreactor. This review article is dedicated to this aspect and addresses some issues and open questions that arise when working with macroscopically large photocatalysts. Guidelines are provided that could help develop novel and efficient photocatalysts with a truly 3D architecture.
Nonaqueous synthesis of high-purity indium and tin oxide nanocrystals and their application as gas sensors
Proceedings of IEEE Sensors, 2004.
ABSTRACT
Applied Catalysis B: Environmental, 2020
Nanoparticle-based aerogels are 3-dimensional (3D) assemblies of macroscopic size that maintain t... more Nanoparticle-based aerogels are 3-dimensional (3D) assemblies of macroscopic size that maintain the intrinsic properties of the initial nanoparticles. Accordingly, they bear immense potential to become an emerging platform for designing new and efficient photocatalysts. However, to take full advantage of this strategy, understanding of the multiscale processes occurring in such 3D-architectures is essential. Here, we prepared aerogels by co-assembling spherical Au, Pd, and PdAu with TiO 2 nanoparticles and investigated their photocatalytic properties for hydrogen generation. During gelation, the anatase nanoparticles undergo oriented attachment, homogeneously entrapping the metal nanoparticles in the growing network. The aerogels offer a high porosity with a mean pore size of ca. 34 nm and a large surface area of about 450 m 2 g −1. The porous structure enhances the light-harvesting, reagent transport, and electron migration process, generating 3.5-fold more hydrogen in comparison to the corresponding powders.
From 1D to 3D – macroscopic nanowire aerogel monoliths
Nanoscale, 2016
Here we present a strategy to assemble one-dimensional nanostructures into a three-dimensional ar... more Here we present a strategy to assemble one-dimensional nanostructures into a three-dimensional architecture with macroscopic size. With the assistance of centrifugation, we successfully gel ultrathin W18O49 nanowires with diameters of 1 to 2 nm and aspect ratios larger than 100 into 3D networks, which are transformed into monolithic aerogels by supercritical drying.
Vanadium Oxide Nanotubes with Diamine Templates
MRS Proceedings, 1999
ABSTRACTDiamine vanadium oxide nanotubes (DA-VOx-NTs) have been prepared in high yields applying ... more ABSTRACTDiamine vanadium oxide nanotubes (DA-VOx-NTs) have been prepared in high yields applying two different synthesis routes, namely either a sol-gel reaction followed by a hydrothermal treatment or an exchange reaction. The first route is analogous to the well-known preparation of VOx-NTs containing monoamines: a vanadium(V) alkoxide is mixed with an α, ω- diamine (H2N[CH2]nNH2 with 12≤n≤20), the resulting adduct is hydrolyzed, and, after aging, a hydrothermal treatment leads to the nanotubes in pure form. The exchange of the monoamine template in VOx-NTs against diamines represents an alternative access to DA-VOx-NTs. This reaction occurs readily and is also applicable for diamines with short CH 2 chains like, e.g., in ethylene diamine. The TEM characterization of the DA-VOx-NTs confirms the tubular morphology which is widely preserved in the products of the exchange reactions. The characteristic feature of as-synthesized DA-VOx-NTs is a thick tube wall with many VO, layers whi...
The development of visible light-active photocatalysts is essential for increasing the conversion... more The development of visible light-active photocatalysts is essential for increasing the conversion efficiency of solar energy into hydrogen (H 2). Here, we present a facile method for nitrogen doping of monolithic titanium dioxide (TiO 2) nanoparticlebased aerogels to activate them for visible light. Plasma-enhanced chemical vapor deposition at low temperature enables efficient incorporation of nitrogen into preformed TiO 2 aerogels without compromising their advantageous intrinsic characteristics such as large surface area, extensive porosity, and nanoscale properties of the semiconducting building blocks. By balancing the dopant concentration and the defects, the nitridation improves optical absorption and charge separation efficiency. The nitrogen-doped TiO 2 nanoparticle-based aerogels loaded with palladium (Pd) nanoparticles show a significant enhancement in visible light-driven photocatalytic H 2 production (3.1 mmol h −1 g −1) with excellent stability over 5 days. With this method, we introduce a powerful tool to tune the properties of nanoparticle-based aerogels after synthesis for a specific application, as exemplified by visible light-driven H 2 production.
Journal of Materials Chemistry A
Combination of materials with fast Li-ion storage in both positive and negative electrodes result... more Combination of materials with fast Li-ion storage in both positive and negative electrodes results in a high-rate lithium ion battery full cell with a long life-span.
Journal of Materials Chemistry A
The relationship between the interlayer metal ions and the Na-ion storage performance of layered ... more The relationship between the interlayer metal ions and the Na-ion storage performance of layered metal vanadates is systematically explored.
Polymers
Poly(phenylene methylene)s (PPMs) with high molar masses were isolated by polymerization of benzy... more Poly(phenylene methylene)s (PPMs) with high molar masses were isolated by polymerization of benzyl chloride catalyzed with tungsten(II) compounds and subsequent fractionation. Four different tungsten(II) catalysts were successfully exploited for the polymerization, for which a strict temperature profile was developed. The PPMs possessed roughly a trimodal molar mass distribution. Simple fractionation by phase separation of 2-butanone solutions allowed to effectively segregate the products primarily into PPM of low molar mass (Mn = 1600 g mol−1) and high molar mass (Mn = 167,900 g mol−1); the latter can be obtained in large quantities up to 50 g. The evolution of the trimodal distribution and the monomer conversion was monitored by gel permeation chromatography (GPC) and 1H NMR spectroscopy, respectively, over the course of the polymerization. The results revealed that polymerization proceeded via a chain-growth mechanism. This study illustrates a new approach to synthesize PPM with ...
ACS Omega
We present a sol-gel processed hematitetitania-based photoanode, which exhibits a photocurrent of... more We present a sol-gel processed hematitetitania-based photoanode, which exhibits a photocurrent of up to 2.5 mA/cm 2 at 1.23 V RHE under simulated AM 1.5 G illumination (100 mW/cm 2 ) thanks to the addition of an amorphous cocatalyst with the nominal composition Fe 20 Cr 40 Ni 40 O x . To unveil the role of the cocatalyst interconnected to the photoanode, we performed impedance measurements. According to the one order of magnitude higher value for the capacitance associated with surface states (C SS ) compared to the bare photoanode, the function of the catalyst-photoanode interface resembles that of a p-n-like junction. In addition, the charge transfer resistance associated with charge transfer processes from surface states (R ct,ss ) was unchanged at potentials between 0.8 and 1.1 V RHE after adding the cocatalyst, indicating that the catalyst has a negligible effect on the hole transport to the electrolyte. The understanding of the role of oxygen evolution catalysts (OECs) in conjunction with the photoanodes is particularly important for water splitting because most OECs are studied separately at considerably higher potentials compared to the potentials at which photoanode materials are operated.
Mater. Horiz.
A newly developed prototype of a flow reactor enables the exploitation of nanoparticle based aero... more A newly developed prototype of a flow reactor enables the exploitation of nanoparticle based aerogel monoliths as macroscopically sized photocatalysts in gas phase reactions.
Nanoscale, Jan 7, 2015
TiO2 has been considered as a promising anode material for lithium ion batteries. However, its po... more TiO2 has been considered as a promising anode material for lithium ion batteries. However, its poor rate capability originating from the intrinsically low lithium ion diffusivity and its poor electronic conductivity hampers putting such an application into practice. Both issues can be addressed by nanostructure engineering and conductive surface coating. Herein, we report a template-assisted synthesis of micron sized TiO2 fibers consisting of a mesoporous network of anatase nanoparticles of about 7.5 nm and coated by N doped carbon. In a first step, an amorphous layer of TiO2 was deposited on cobalt silicate nanobelts and subsequently transformed into crystalline anatase nanoparticles by hydrothermal treatment. The N doped carbon coating was realized by in situ polymerization of dopamine on the crystalline TiO2 followed by annealing under N2. After removal of the template, we obtained the final mesoporous TiO2 fibers@N doped carbon composite. Electrochemical tests revealed that the ...
Self-assembly in inorganic and hybrid systems: beyond the molecular scale
Dalton Transactions, 2008
The availability of well defined inorganic nanocrystals allows the construction of aligned struct... more The availability of well defined inorganic nanocrystals allows the construction of aligned structures with characteristic architectural elements in the nanometer range, the mesoscale. Contrary to alignment driven by external conditions and fields, we focus on strict "self-effects", where the organization is already encoded in the shape and mutual interaction potentials of the particles. This Perspective discusses the potential of this approach for generating valuable functional inorganic mesostructures.
Nano Today
Nanoparticle-based aerogels are one of the few examples of 3-dimensional nanoparticle assemblies ... more Nanoparticle-based aerogels are one of the few examples of 3-dimensional nanoparticle assemblies that can achieve macroscopic sizes while fully retaining the size-specific properties of the initial nanobuilding blocks. A typical synthesis involves three main steps: i) Preparation of a stable dispersion containing all the building blocks with the desired composition, size, shape and crystallinity, ii) controlled destabilization of the dispersion into a gel, and iii) drying of the gels under preservation of the 3-dimensional nanoparticle architecture. In this review, we focus on the first two steps. We discuss the stability of colloidal dispersions, offering an overview of the different interparticle forces and how they can experimentally be modulated. In the next section, we discuss the gelation process in its entirety, including gelation mechanisms, and, most importantly, how it can rationally be controlled under consideration of the interparticle forces in the dispersion. Finally, the review concludes with an overview of the synthesis pathways to nanoparticle-based aerogels, divided into the gelation of sterically and charge-stabilized particles.
3D Printed Scaffolds for Monolithic Aerogel Photocatalysts with Complex Geometries
Small
Transient Rechargeable Battery with a High Lithium Transport Number Cellulosic Separator
Advanced Functional Materials
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Papers by Markus Niederberger