Marc Georg Willinger

• Professor
• Chair of Electron Microscopy at Technical University of Munich

Hydrogen production by electrocatalytic water splitting will play a key role in the realization of a sustainable energy supply. Owing to their relatively high stability and activity, iridium (hydr)oxides have been identified as most promising catalysts for the oxidation of water. Comprehensive spectroscopic and theoretical studies on the basis of R...

Analytical methods that provide direct real-space information about the dynamics of catalysed reactions often require simplified model systems and operate under high-vacuum conditions. There is thus a strong need for the development of methods that enable observation of active catalysts under relevant working conditions. Here, in situ scanning elec...

Dependent on the application or characterization method catalysts are exposed to different gas pressures, which results in different structures. The quantitative determination of the structure and composition of a catalyst as a function of its gas environment allows the establishment of structure–performance relationships. Herein, we determine the...

Copper-zinc-alumina catalysts are used industrially for methanol synthesis from feedstock containing carbon monoxide and carbon dioxide. The high performance of the catalyst stems from synergies that develop between its components. This important catalytic system has been investigated with a myriad of approaches, however, no comprehensive agreement...

Active catalysts are typically metastable, and their surface state depends on the gas-phase chemical potential and reaction kinetics. To gain relevant insights into structure-performance relationships, it is essential to investigate catalysts under their operational conditions. Here, we use operando TEM combining real-time observations with online...

Magnesium oxide serves as promising sorbent for CO2 capture, storage and release. The CO2 uptake can be enhanced through the addition of molten alkali nitrate- and bicarbonate promoters, such as NaNO3 and Na2CO3. The mechanisms through which these promotors affect the kinetics of CO2 uptake have so far not been fully uncovered. Here, using a combin...

Platinum (Pt) oxides are vital catalysts in numerous reactions, but research indicates that they decompose at high temperatures, limiting their use in high-temperature applications. In this study, we identify a two-dimensional (2D) crystalline Pt oxide with remarkable thermal stability (1,200 K under nitrogen dioxide) using a suite of in situ metho...

The interplay between order and disorder is crucial across various fields, especially in understanding oscillatory phenomena. Periodic oscillations are frequently observed in heterogeneous catalysis, yet their underlying mechanisms need deeper exploration. Here, we investigate how periodic oscillations arise during methane oxidation catalysed by pa...

Catalysts based on palladium are among the most effective in the complete oxidation of methane. Despite extensive studies and notable advances, the nature of their catalytically active species and conceivable structural dynamics remains only partially understood. Here, we combine operando transmission electron microscopy (TEM) with near-ambient pre...

Alloying metals to form intermetallics has been proven effective in tuning the chemical properties of metal-based catalysts. However, intermetallic alloys can undergo structural and chemical transformations under reactive conditions, leading to changes in their catalytic function. Elucidating and understanding these transformations are crucial for...

The application of hydrogen proton exchange membrane fuel cells (PEMFC) in greenhouse gas emission free heavy-duty vehicles requires extremely durable PEMFC components with service lives in the range of 30,000 h. Hence suitable test and analysis methods are required that reflect realistic operation scenarios, but significantly accelerate aging. For...

The mechanism of nacre formation in gastropods involves a vesicular system that transports organic and mineral precursors from the mantle epithelium to the mineralization chamber. Between them lies the surface membrane, a thick organic structure that covers the mineralization chamber and the forming nacre. The surface membrane is a dynamic structur...

Additive microfabrication processes based on localized electroplating enable the one‐step deposition of micro‐scale metal structures with outstanding performance, e.g., high electrical conductivity and mechanical strength. They are therefore evaluated as an exciting and enabling addition to the existing repertoire of microfabrication technologies....

In this work, we present a recent advancement in high‐temperature instrumentation in the form of a heating stage that enables studies to be performed in the temperature range of 20–1250°C under high‐vacuum, millibar, and atmospheric pressure conditions (10 ⁻⁷ –1000 mbar). The newly developed laser‐based heating solution is described in detail. Its...

The application of hydrogen proton exchange membrane fuel cells (PEMFC) in greenhouse gas emission free heavy-duty vehicles requires extremely durable PEMFC components with service lives in the range of 30,000 hours. Hence suitable test and analysis methods are required that reflect realistic operation scenarios, but significantly accelerate aging....

Propane Dehydrogenation is a key technology, where Pt-based catalysts have widely been investigated in industry and academia, with development exploring the use of promoters (Sn, Zn, Ga, etc.) and additives (Na, K, Ca, Si, etc.) towards improved catalytic performances. Recent studies have focused on the role of Ga promotion: while computations sugg...

Propane Dehydrogenation is a key technology, where Pt-based catalysts have widely been investigated in industry and academia, with development exploring the use of promoters (Sn, Zn, Ga, etc.) and additives (Na, K, Ca, Si, etc.) towards improved catalytic performances. Recent studies have focused on the role of Ga promotion: while computations sugg...

Catalysis is a highly complex phenomenon involving fundamental processes on multiple length scales. The full-scale complexity of catalysis is only poorly understood, and how atomic-scale processes influence long-range order in the materials is not well documented experimentally. The result is that we still, to a large degree, develop new catalysts...

Catalysts based on palladium are among the most effective in the complete oxidation of methane. Despite extensive studies, the nature of their catalytically active species and conceivable structural dynamics remains elusive. Here, we combine operando transmission electron microscopy (TEM) with near-ambient pressure X-ray photoelectron spectroscopy...

The properties of two-dimensional (2D) van der Waals materials can be tuned through nanostructuring or controlled layer stacking, where interlayer hybridization induces exotic electronic states and transport phenomena. Here we describe a viable approach and underlying mechanism for the assisted self-assembly of twisted layer graphene. The process,...

Platinum nanoparticles (NPs) supported by titania exhibit a strong metal‐support interaction (SMSI)[1] that can induce overlayer formation and encapsulation of the NP's with a thin layer of support material. This encapsulation modifies the catalyst's properties, such as increasing its chemoselectivity[2] and stabilizing it against sintering.[3] Enc...

Platinum nanoparticles (NPs) supported by titania exhibit a strong metal‐support interaction (SMSI) [1] that can induce overlayer formation and encapsulation of the NP's with a thin layer of support material. This encapsulation modifies the catalyst's properties, such as increasing its chemoselectivity [2] and stabilizing it against sintering. [3]...

Oxidative dehydrogenation of propane with carbon dioxide (CO2-ODP) characterizes the tandem dehydrogenation of propane to propylene with the reduction of the greenhouse gas of CO2 to valuable CO. However, the existing catalyst is limited due to the poor activity and stability, which hinders its industrialization. Herein, we design the finned Zn-MFI...

Atom-by-atom control of a catalyst surface is a central yet challenging topic in heterogeneous catalysis, which enables precisely confined adsorption and oriented approach of reactant molecules. Here, exposed surfaces with either consecutive Pd trimers (Pd 3 ) or isolated Pd atoms (Pd 1 ) are architected for Pd 2 Ga intermetallic nanoparticles (NPs...

Hydrogen spillover from metal nanoparticles to oxides is an essential process in hydrogenation catalysis and other applications such as hydrogen storage. It is important to understand how far this process is reaching over the surface of the oxide. Here, we present a combination of advanced sample fabrication of a model system and in situ X-ray phot...

The motion of liquid droplets is studied across many physics subfields and manipulation of nanoscale droplets on demand holds great promise in, e.g., nanotechnology. In this study, AuGe droplets on a germanium substrate are manipulated by an electron beam in a scanning electron microscope. The electron beam exposure creates a local temperature grad...

The typical industrial catalyst used for methanol synthesis is a multi‐component catalyst based on Cu/ZnO/Al2O3. The synergies between various phases of this catalyst play a vital role in defining the overall catalytic function and performance. To gain insights into the role and interaction between the relevant components and phases, ex situ and in...

Manipulating with micro-objects inside an electron microscope is a challenging task, especially with liquid droplets. However it is possible by using the electron beam in SEM. The gold-germanium microdroplets move in the direction of the temperature gradient created by the electron beam. If we move the electron beam, the droplets follow the beam an...

Oxides are essential catalysts and supports for noble metal catalysts. Their interaction with hydrogen enables, e.g., their use as a hydrogenation catalyst. Among the oxides considered reducible, substantial differences exist in their capability to activate hydrogen and how the oxide structure transforms due to this interaction. Noble metals, like...

One dimensional graphene nanostructures are one of the most promising materials for next generation electronics. Here, the chemical vapor depostion growth of graphene nanoribbons (GNRs) and graphene nanospears (GNSs) on a copper surface is reported. The growth of GNRs and GNSs is enabled by a vapor–liquid–solid (VLS) mechanism guided by on‐surface...

The thermal carburization of MoO3 nanobelts (nb) and SiO2-supported MoO3 nanosheets under a 1 : 4 mixture of CH4 : H2 yields Mo2C-nb and Mo2C/SiO2. Following this process by in situ Mo K-edge X-ray absorption spectroscopy (XAS) reveals different carburization pathways for unsupported and supported MoO3. In particular, the carburization of α-MoO3-nb...

The dynamic interactions between noble metal particles and reducible metal-oxide supports can depend on redox reactions with ambient gases. Transmission electron microscopy revealed that the strong metal-support interaction (SMSI)-induced encapsulation of platinum particles on titania observed under reducing conditions is lost once the system is ex...

Direct growth of large-area vertically stacked two-dimensional (2D) van der Waal (vdW) materials is a prerequisite for their high-end applications in integrated electronics, optoelectronics and photovoltaics. Currently, centimetre- to even metre-scale monolayers of single-crystal graphene (MLG) and hexagonal boron nitride (h-BN) have been achieved...

The thermal carburization of MoO3 nanobelts (nb) and SiO2-supported MoO3 nanosheets under a 1 : 4 mixture of CH4 : H2 yields Mo2C-nb and Mo2C/SiO2. Following this process by in situ Mo K-edge X-ray absorption spectroscopy (XAS) reveals different carburization pathways for unsupported and supported MoO3. In particular, the carburization of α-MoO3-nb...

Copper and zinc oxide are a dream team in transforming carbon dioxide and carbon monoxide together with hydrogen to the valuable base chemical methanol. Inspired by the cover art of the music masterpiece “Wish you were here” by Pink Floyd the picture featuring the Research Article (DOI: 10.1002/anie.202200301) by Jeroen A. van Bokhoven et al. highl...

The copper‐zinc‐alumina (CZA) catalyst is one of the most important catalysts. Nevertheless, understanding of the complex CZA structure is still limited and hampers further optimization. Critical to the production of a highly active and stable catalyst are optimal start‐up procedures in hydrogen. Here, by employing operando X‐ray absorption spectro...

Kupfer und Zinkoxid sind ein Dreamteam bei der Umwandlung von Kohlendioxid und Kohlenmonoxid mit Wasserstoff in die wertvolle Basischemikalie Methanol. Inspiriert vom Cover von Pink Floyds Meisterwerk „Wish you were here“ illustriert das Titelbild, das zum Forschungsartikel (DOI: 10.1002/ange.202200301) von Jeroen A. van Bokhoven et al. gehört, das...

Fossil-free ironmaking is indispensable for reducing massive anthropogenic CO2 emissions in the steel industry. Hydrogen-based direct reduction (HyDR) is among the most attractive solutions for green ironmaking, with high technology readiness. The underlying mechanisms governing this process are characterized by a complex interaction of several che...

The copper‐zinc‐alumina (CZA) catalyst is one of the most important catalysts. Nevertheless, the still limited understanding of the complex CZA structure hampers further optimization. Critical to the production of a highly active and stable catalyst are optimal start‐up procedures in hydrogen. Here, by employing operando X‐ray absorption spectrosco...

Fossil-free ironmaking is indispensable for reducing massive anthropogenic CO2 emissions in the steel industry. Hydrogen-based direct reduction (HyDR) is among the most attractive solutions for green ironmaking, with high technology readiness. The underlying mechanisms governing this process are characterized by a complex interaction of several che...

The properties of two-dimensional (2D) van der Waals (vdW) materials can be tuned through nanostructuring or controlled layer stacking, where interlayer hybridization induces exotic electronic states and transport phenomena. Here, we describe an assisted self-assembly of twisted layer graphene. The process, which can be implemented in standard chem...

Graphene nanoribbons (GNRs) are considered one of the most promising materials for next generation electronics, however a reliable and controllable synthesis method is still lacking. Here, we report the CVD growth of GNRs on a copper surface and the corresponding mechanisms of growth. One-dimensional GNR growth is enabled by a vapor-liquid-solid (V...

Water splitting will become important to store excess renewable electrical energy into hydrogen. Although the oxygen-evolution reaction (OER) by water oxidation is a critical reaction for water splitting, further investigations are needed to find the details of the OER mechanism for various electrocatalysts. More in particular for homogeneous elect...

The active state of heterogeneous catalysts is typically metastable and can only be generated under actual reaction conditions. In article number 2101772, Xing Huang, Marc‐Georg Willinger, and co‐workers report an operando transmission electron microscopy study to characterize chemical dynamics and surface sites of metal catalysts, as well as their...

Metal catalysts play an important role in industrial redox reactions. Although extensively studied, the state of these catalysts under operating conditions is largely unknown, and assignments of active sites remain speculative. Herein, an operando transmission electron microscopy study is presented, which interrelates the structural dynamics of red...

We explore three different potential mechanisms to introduce 4 mol% ZnO sintering additive to the promising yttrium-doped barium zirconate (Ba(Zr,Y)O3-δ, BZY) proton conductor. The mechanisms involve Zn substitution for Y, Zr, or B-site cation excess. The addition of ZnO promotes high densification levels (up to 98% of the theoretical value) at 130...

div>Metal catalysts play an important role in industrial redox reactions. Although extensively studied, the state of these catalysts under operating conditions is largely unknown and assignments of active sites remain speculative. Herein, we present an operando transmission electron microscopy study that interrelates structural dynamics of redox me...

Multiferroic materials demonstrating coexistence of magnetic and ferroelectric orders are promising candidates for magnetoelectric devices. While understanding the underlying mechanism of interplaying of ferroic properties is important, tailoring their properties to make them potential candidates for magnetoelectric devices is challenging. Here, th...

Synthesizing high‐quality two‐dimensional nanomaterials of nonlayered metal oxide is a challenge, especially when long‐range single‐crystallinity and clean high‐energy surfaces are required. Reported here is the synthesis of single‐crystalline MgO(111) nanosheets by a two‐step process involving the formation of ultrathin Mg(OH)2 nanosheets as a pre...

Ultrathin single crystalline MgO nanosheets that are preferentially oriented in the [111] direction are prepared through topotactic decomposition of Mg(OH)2 nanosheets under dynamic vacuum. The surface is highly defect‐rich with under‐coordinated O and Mg ions and F‐centers, which makes the MgO nanosheets highly active in interacting with CO probe...

Synthesizing high-quality two-dimensional nanomaterials of non-layered metal oxide is a grand challenge because it requires long range single-crystallinity and clean high-energy surfaces. Here, we report the synthesis of single-crystalline MgO(111) nanosheets via a two-step process involving the formation of ultrathin Mg(OH)₂ nanosheets...

Starting from subsurface Zr0-doped “inverse” Pd and bulk-intermetallic Pd0Zr0 model catalyst precursors, we investigated the dry reforming reaction of methane (DRM) using synchrotron-based near ambient pressure in-situ X-ray photoelectron spectroscopy (NAP-XPS), in-situ X-ray diffraction and catalytic testing in an ultrahigh-vacuum-compatible recir...

The fabrication of power semiconductor devices based on 4H-silicon carbide (SiC) typically includes doping by ion implantation and postimplantation annealing to activate the implanted dopants. The high-temperature annealing process can initiate various diffusion mechanisms that alter the initial implantation profile in terms of spatial distribution...

How a catalyst behaves microscopically under reaction conditions, and what kinds of active sites transiently exist on its surface, is still very much a mystery to the scientific community. Here we present an in situ study on the red-ox behaviour of copper in the model reaction of hydrogen oxidation. Direct imaging combined with on-line mass spectro...

Ag doped TiO2 photocatalysts (Ag@TiO2) were prepared with an aim to extend the absorption range of TiO2 into the visible region, for tentative application under solar irradiation. Photocatalyst synthesized by the novel method using chitosan for reduction of Ag+ to Ag0 nanoparticles was compared to similar catalysts previously reported. The photocat...

Light elements in the interstitial site of transition metals have strong influence on heterogeneous catalysis via either expression of surface structures or even direct participation into reaction. Interstitial atoms are generally metastable with a strong environmental dependence, setting up giant challenges in controlling of heterogeneous catalysi...

Heterogeneous catalysts in the form of atomically dispersed metals on a support provide the most efficient utilization of the active component, which is especially important for scarce and expensive late transition metals. These catalysts also enable unique opportunities to understand reaction pathways through detailed spectroscopic and computation...

Heterogeneous catalysts play a pivotal role in the chemical industry. The strong metal-support interaction (SMSI), which affects the catalytic activity, is a phenomenon researched for decades. However, detailed mechanistic understanding on real catalytic systems is lacking. Here, this surface phenomenon was studied on an actual platinum-titania cat...

Common methods to produce supported catalysts include impregnation, precipitation, and thermal spray techniques. Supported electrocatalysts produced by a novel method for thermal spray deposition were investigated with respect to their structural properties, elemental composition, and electrochemical performance. This was done using electron micros...

Herein, we report TiC as precursor of a highly active and novel TiO2-TiC composite for the catalytic oxidation of HBr into Br2, which is a key technology for bromine looping in the halogen-mediated process for natural gas valorisation. In addition, we investigate the mechanism of TiO2 formation that is pivotal in deriving synthesis-structure-perfor...

The effect of NaNO3 and its physical state on the thermal decomposition pathways of hydrated magnesium hydroxycarbonate (hydromagnesite, HM) towards MgO was examined by in situ total scattering. Pair distribution function (PDF) analysis of these data allowed us to probe the structural evolution of pristine and NaNO3-promoted HM. A multivariate curv...

Plasma nitriding was applied to ferritic stainless steel substrates to improve their performances as interconnects for solid oxide fuel cell devices. The samples underwent electrical conductivity test and SEM/EDS, TEM/EDS, environmental-SEM analyses. The first stages of corrosion were recorded in-situ with the e-SEM. Nitriding is effective in limit...

High-quality AB-stacked bilayer or multilayer graphene larger than a centimetre has not been reported. Here, we report the fabrication and use of single-crystal Cu/Ni(111) alloy foils with controllable concentrations of Ni for the growth of large-area, high-quality AB-stacked bilayer and ABA-stacked trilayer graphene films by chemical vapour deposi...

Understanding how catalysts work during chemical reactions is crucial when developing efficient catalytic materials. The dynamic processes involved are extremely sensitive to changes in pressure, gas environment and temperature. Hence, there is a need for spatially resolved operando techniques to investigate catalysts under working conditions and o...

Heterogeneous catalysts in the form of atomically dispersed metals on a support provide the most efficient utilization of the active component, which is especially important for scarce and expensive late transition metals. These catalysts also enable unique opportunities to understand reaction pathways through detailed spectroscopic and computation...

Heterogeneous catalysts in the form of atomically dispersed metals on a support provide the most efficient utilization of the active component, which is especially important for scarce and expensive late transition metals. These catalysts also enable unique opportunities to understand reaction pathways through detailed spectroscopic and computation...

Wafer-scale monocrystalline two-dimensional (2D) materials can theoretically be grown by seamless coalescence of individual domains into a large single-crystal. Here we present a concise study of the coalescence behavior of crystalline 2D films using a combination of complementary in situ methods. Direct observation of overlayer growth from the ato...

ZnO has prominent electron transport and optical properties, beneficial for photovoltaic application, but its surface is prone to the formation of defects. To overcome this problem, we deposited nanostructured TiO2 thin film on ZnO nanorods to form a stable shell. ZnO nanorods synthesized by wet-chemistry are single crystals. Three different proced...