Lines of indium(III) sulfides are deposited by atomic-layer additive manufacturing (ALAM) based on the reaction of indium tris(acetylacetonate) with hydrogen sulfide established in atomic layer deposition (ALD). At 160 °C, solid accretion occurs at a rate of 0.04 Å per pass. The layers are continuous, free of observable pinholes, dense, and very smooth, with a root-mean-squares roughness on the order of 0.5 nm found for deposits up to 25 nm thick. The material is nearly stoichiometric, with a S/. In ratio of 1.6 found experimentally by energy-dispersive X-ray microanalysis in cross-section examination by transmission electron microscopy, and it is polycrystalline. This work delivers In2S3 as a dopant or interfacial layer in opto-electronic devices to be prototyped and optimized by ALAM.

Optimizing the performance of organic solar cells hinges on a comprehensive understanding of their nanostructures, yet traditional characterization methods often fall short, delivering incomplete structural snapshots. We introduce elastically filtered 3D electron diffraction as technique to bridge full reciprocal- and real-space structural analysis within a single transmission electron microscope. Using model bulk heterojunction DRCN5T:PC71BM, 3D electron diffraction reproduces key structural parameters obtained from grazing-incidence wide-angle X-ray scattering, including lattice spacings, coherence lengths, and mosaicity, while also providing true in-plane access and direct registration with high-resolution imaging, diffraction imaging and nano-spectroscopy on the same sample. Application to another archetypal blend, P3HT:PC71BM, demonstrates the generality of the method. Our findings underscore the transformative potential of 3D electron diffraction, particularly in analyzing beam-sensitive organic thin films. The method enables correlative structural characterization of organic solar cells and opens pathways for application to a wide range of other nanostructured materials.

Operando microscopy methods applied in electrocatalysis come with critical limitations such as statistical relevance, interfering probe-sample interactions, and mass-transport-related phenomena on the one hand. On the other hand, those methods provide unique insights into dynamic processes that nanomaterials undergo during operation, insights that are inaccessible otherwise. Overcoming these challenges is, therefore, essential to disentangle, for instance, degradation mechanisms of electrocatalysts, knowledge that is urgently needed to drive forward our energy transition in a reasonable manner. This Mini-Review names the details of these challenges, provides recently published solutions, and depicts how operando microscopies can be embedded into correlative workflows to unfold their full potential. This way, insights gained from investigating model systems employing electrochemical liquid-phase electron microscopy, operando X-ray methods, and scanning electrochemical probe microscopies have the potential to lead to major breakthroughs in the development of next-generation energy materials.

Making solution-cast organic solar cells industrially available generally comes at the cost of significant performance losses compared to device prototypes manufactured under laboratory conditions. Adjusting solvent evaporation kinetics is postulated to recover efficiency. Yet, a comprehensive characterization of their effect, independently of other property-defining parameters, is lacking. Thus, the present objective is to isolate the influence of the solvent drying rate on solution-deposited organic active layer nanomorphologies and performances. To this end, a specially designed gas quenching technique is employed to fabricate PM6:Y6 donor-acceptor films under systematic variations of evaporation conditions. Using an extensive investigation protocol that combines insights from numerical simulations and experimental measurements, process-structure-performance relationships are unraveled. It is found that higher drying rates imply finer and more dispersed nanomorphologies with increased fractions of amorphous material. This enhances electric charge generation, thereby improving short-circuit current density and overall cell performance. The open-circuit voltage is also boosted under accelerated evaporation due to changes in the aggregation mode of the Y6 small molecule that induce higher effective bandgaps. The results demonstrate that the developed gas-quenching technique is a valuable tool for optimizing the performance of upscaled organic photovoltaics, as it is readily compatible with high-throughput equipment, such as roll-to-roll coating machines.

Ga-Pt liquid metal catalysts have emerged as promising catalysts, offering improved catalytic performance compared to pure platinum for reactions such as propane dehydrogenation. Previous studies suggest that the active species formed in Ga-Pt catalysts differ from traditional metallic Pt. In this study, we explore multiple potential active Pt species by focusing on the surface-derived electronic and chemical structures assessed via X-ray photoelectron spectroscopy (XPS) and the correlating structural composition analyzed by scanning transmission electron microscopy (STEM). While XPS indicates that Pt is present in different chemical environments, STEM reveals different topographic structures varying from Pt single atom to Pt agglomerates and Ga-Pt intermetallic compounds (IMCs). The variation in the chemical, electronic, and topographic structure of Pt depends on its amount, as well as on the surrounding environment (e.g., gallium-oxide shell versus liquid Ga matrix). Further, XPS and STEM in situ investigations at elevated temperature (T) shed light on the high dynamic surfaces, demonstrating the dissolution of Ga-Pt IMCs due to the enhanced solubility of Pt in Ga with increasing T. The chemical and electronic structure of the Pt species is discussed in conjunction with density-functional theory and molecular dynamics simulations, providing an unprecedented conceptual understanding of Ga-Pt catalysts.

Abstract Fused filament fabrication (FFF) 3D printing provides an accessible route to fabricating retrievable photocatalytic architectures with tunable geometry and composition. Here, we address the limited recoverability and reusability of conventional powder-based photocatalysts by translating a metal-free semiconductor catalyst to 3D printed electrodes. Graphitic carbon nitride (g-C3N4) was functionalized with carbonized polydopamine (cPDA) to create a modified photocatalyst with improved photophysical behavior, consistent, more effective charge separation, and longer-lived photoexcited states, which correlates with enhanced photocatalytic activity. The optimized formulation was compounded into an extrudable PLA-based composite filament and printed into electrodes containing either g-C3N4 or g-C3N4/cPDA. The printed g-C3N4/cPDA electrodes show enhanced photocatalytic rhodamine B degradation under simulated sunlight compared with unmodified printed electrodes. In contrast to suspended powders, the electrodes enable straightforward retrieval, improved operational stability, and reuse without postseparation steps. Furthermore, we demonstrate that electrode performance can be increased by scaling the surface area, highlighting geometry as a simple handle for upscaling. This work demonstrates the potential of photocatalytic 3D printed electrodes made from abundant materials via low-energy processing as a scalable and sustainable route for wastewater treatment.

The ALD precursor tetrakis(dimethylamido)tin and water are exploited towards the atomic-layer additive manufacturing (ALAM) of SnO2 lines. ALAM exploits the surface chemistry principles of ALD (atomic layer depositions) but adds a laterally constrained precursor delivery. Motion of the precursor delivery nozzle over the substrate surface thus deposits the material in a 3D printing mode while maintaining the sub-nanometers thickness control of ALD. We find that the precursor canister temperature can be lowered by approximately 20 degrees C from ALD to ALAM, corresponding to a lower precursor consumption. The temperature window of controlled deposition reaches from 150 degrees C to 250 degrees C, whereas 200 degrees C yields the best stoichiometry and highest growth rate. The material is amorphous initially and crystallizes upon annealing at 500 degrees C in N2 or air. The lines deposited have a flat top profile and a constant thickness along their length.

Ti-deficient TiO2 nanosheets derived from lepidocrocite-type titanate delamination show a p-type conductivity with a band gap widened by the quantum confinement effect to 3.7 eV. This shift in the extended band positions─and thus in the electron transfer level─allows a direct photocatalytic nitrate reduction to ammonia without the use of any hole scavengers; this in contrast to classic TiO2. The deposition of Pt single atoms as cocatalysts onto the nanosheets significantly enhances the activity and selectivity toward ammonia, which outperforms classic Pt nanoparticles used as cocatalyst. The present study therefore reports not only on the unique photocatalytic properties of these Ti-deficient TiO2 nanosheets but also on the beneficial use of the modified electronic properties that enable entirely novel applications, such as the technologically highly important reduction of nitrate to ammonia.

Antimony sulfide (Sb2S3), a compound of earth-abundant elements with a highly anisotropic, quasi-layered crystal structure, has triggered growing interest as a solar absorber in photovoltaics and as a phase-change material in memory devices. However, challenges remain in achieving high-quality thin films with controlled nucleation and growth for optimal performance. Here, we investigate the phase transformation, crystal structure and properties, as well as the growth and degradation of atomic layer-deposited Sb2S3 thin films using in situ TEM and correlative ex situ analysis. The as-deposited amorphous films crystallized at 243 °C, forming grains with an [100] out-of-plane texture that developed into tens to hundreds of micrometer-long, leaf-shaped grains. Introducing an ultrathin ZnS interfacial layer increased nucleation density, resulting in few-micrometer-sized, more uniform grains while retaining the overall [100] texture. In situ observations and subsequent crystal orientation analysis with cutting-edge 4D-STEM and EBSD revealed that the grains grew faster along the [010] ribbon direction and that the bare films underwent early-stage degradation, forming holes in amorphous regions during annealing. The ZnS interlayer mitigated degradation, stabilizing the films and improving their uniformity. These findings offer valuable insights for optimizing Sb2S3 thin films for applications as both solar cell materials and phase-change materials.

Stacking orders and topological defects substantially influence the physical properties of 2D van der Waals (vdW) materials. However, the inherent features of 2D materials challenge the effectiveness of single characterization techniques in identifying stacking sequences, necessitating correlative approaches. Using bilayer MoS2 as a benchmark, we differentiate its polytypism and specific dislocations through transmission electron microscopy (TEM) and Raman spectroscopy. Perfect and partial dislocations were revealed in TEM, which are closely linked to the stacking sequences, thus indirectly indicating the 2H and 3R polytypes. Quantitative analysis of reciprocal lattice from 3D electron diffraction and low-frequency Raman spectroscopy further validated these polytypes owing to their reliance on crystal symmetry. Surprisingly, we unexpectedly resolved both polytypes despite starting with 2H bulk crystal, pointing to a possible phase transition during mechanical exfoliation. The correlative TEM-Raman approach can be extended to other 2D materials, paving the way for property alteration via stacking and defect engineering.

This document is the unedited not peer-reviewed Author’s version of a Submitted Work to Chemistry of Materials. The controlled assembly of supraparticles using spray-drying enables the synthesis of nanoporous materials. Changing the size of the constituent nanoparticles or their agglomeration states provides access to a diverse range of pore frameworks. This turns supraparticles into ideal scaffolds in heterogeneous catalysis. The combination of supraparticles with atomic layer deposition (ALD) as a surface functionalization technique offers excellent control over the deposition of a functional material and its distribution over the scaffold on the nanoscale. This work reports the combination of SiO2 supraparticles as tunable scaffolds and their loading with a platinum-based ALD catalyst. The deliberate adjustment of the scaffold pore framework via spray-drying and its effects on the catalyst deposition are highlighted. Furthermore, varying numbers of Pt ALD cycles are applied to explore the capability of the combinational approach with respect to catalyst loading and Pt efficiency. High-resolution electron microscopy reveals ultra-small Pt clusters deposited on the supraparticles after the very first ALD cycle. Using the hydrogenation of 4-nitrophenol as a demonstration, the impact of the pore framework and the Pt deposition variation in ALD on the catalytic functionality is investigated.

A comprehensive investigation of the impact of hydrogen (H2) pretreatments on Ga-Pt supported catalytic active liquid metal solution (SCALMS) for propane dehydrogenation (PDH) is reported. Our approach bridges from model system investigations to real-world catalytic systems, which are tested in continuously operating PDH reactors. The microscopic and spectroscopic findings on model Ga-Pt systems suggest changes in the electronic structure and surface chemistry during SCALMS sample oxidation and H2 pretreatment, indicating potential modifications of the active sites involved in PDH. H2 pretreatments of technical Ga-Pt SCALMS prepared by ultrasonication (US) led to significantly improved activity, i.e., the conversion of propane increased from 10% for the untreated catalyst to 26% for the H2 pretreated (5 h at 823 K) catalyst. We attribute this enhanced activity to the removal of a gallium oxide (GaO x ) shell, as confirmed by synchrotron-based in situ X-ray photoelectron spectroscopy (XPS) as well as in situ transmission electron microscopy (TEM) investigations of Ga-Pt model alloys. These findings are supported by density functional theory (DFT) and machine learned force field (ML-FF) calculations. Increasing the temperature of the H2 treatment to 923 K reduced the deactivation rate of the catalyst to as low as 0.01 h-1, which is 3 times more stable than what was observed for the untreated catalyst. This deactivation is ascribed to bulk restructuring of the alloy, leading to the formation of less active Pt species as confirmed by spectroscopic and microscopic analysis. Our work not only elucidates the fundamental properties, i.e., typology, electronic structure, and reactivity, of isolated Pt atoms in Ga-Pt SCALMS but also proposes underlying mechanisms for the activation and deactivation of PDH catalysts.

Silver nanowire (AgNW) networks have emerged as one of the most promising materials for flexible transparent conductive electrodes. These wires offer excellent electrical, optical, and mechanical properties and can be applied using low-cost printing techniques with the potential for upscaling. To elucidate the mechanical properties of nanowire networks for use in flexible electronics, it is essential to first characterize the behavior of individual wires adhered to the polymer surface under mechanical loading of the polymer. This study investigates the mechanical response of isolated nanowires during uniaxial in situ tensile testing of the polymer using correlative microscopy, which combines the advantages of light and electron microscopy. By changing the orientation of the nanowires with respect to the tensile straining axis of the polymer, the nanowires experience either tensile (for parallel orientation) or compressive forces (for perpendicular orientation) according to the polymer's elastic-plastic Poisson's ratio, which links lateral contraction of the polymer to tensile strain. Aligned and isolated AgNWs were applied to flat surfaces of two polymers, PET and PDMS, which serve as model systems to investigate the effect of the substrate on the mechanical response of the nanowires. We observe a strong influence of the polymer type on the wire deformation behavior and fracture, which we attribute to the different adhesion strength of the wires on PET and PDMS. While the wires on PET undergo multiple fractures, breaking into segments of roughly equal length under tensile loading, those on PDMS typically fracture only once, accompanied by early sliding of the wire on the substrate. Compression tests revealed localized plastic deformation by nanowire kinking with the formation of new grain boundaries for both polymer substrates. Electron microscopy studies revealed different deformation configurations depending on the amount of load applied. In addition, cyclic compressive tests provided insight into the fatigue behavior of the wires. Here, newly formed grain boundaries acted as potential fracture sites, whereas the purely elastic deformation remained fully reversible up to 1000 cycles.

Interest in organic solar cells (OSCs) is constantly rising in the field of photovoltaic devices. The device performance relies on the bulk heterojunction (BHJ) nanomorphology, which develops during the drying process and additional post-treatment. This work investigates the effect of thermal annealing (TA) on the all-small molecule DRCN5T:PC71BM blend with phase field simulations. The objective is to determine the physical phenomena driving the evolution of the BHJ morphology for a better understanding of the post-treatment/morphology relationship. Phase-field simulation results are used to investigate the impact on the final BHJ morphology of the DRCN5T crystallization-related mechanisms, including nucleation, growth, crystal stability, impingement, grain coarsening, and Ostwald ripening, of the amorphous-amorphous phase separation (AAPS), and of diffusion limitations. The comparison of simulation results with experimental data shows that the morphological evolution of the BHJ under TA is dominated by dissolution of the smallest, unstable DRCN5T crystals and anisotropic growth of the largest crystals.

3D printing of conductive structures via fused deposition modelling has emerged as a mainstream manufacturing technique for electrochemical devices owing to the affordability and availability of thermoplastic-carbon-based filaments. On the current market, the existing filaments are limited in terms of their electrical conductivity and functionality. To address this, the development of multi-material filaments incorporating additional functional materials along with conductive carbons strategically produces 3D-printed electrodes with enhanced functionalities. In parallel, filament fabrication allows for precise control over the material composition and properties, such as chemical, thermal, and mechanical properties of the filament. In this work, we explored the fabrication of a multi-material filament combining photocatalytic carbon nitride, C3N4, and conductive carbon nanotubes, CNTs. Our C3N4-CNTs electrodes 3D-printed from it outperformed CNTs electrodes in hydrogen evolution and photocatalytic degradation of an organic dye. Our findings suggest that multi-material filaments may transcend the current filament-extrusion printing technique and expand its potential beyond electrochemistry.

Thermally-induced agglomeration of Pt single atoms (SAs) on anatase TiO2 thin films is exploited for tuning their activity in photocatalytic H2 generation. After thermal treatment at temperatures ranging from 350 to 650 degrees C in an Ar atmosphere, a more than fivefold higher photocatalytic activity is achieved under optimized conditions. The Pt species obtained after annealing at different temperatures are monitored via ex situ and in situ transmission electron microscopy. For in situ measurements, a gas cell system operating at 700 mbar is utilized. Structural data obtained in the temperature range from 250 to 950 degrees C demonstrate the co-existence of SA species and agglomerates over the whole temperature range, and give fundamental insights into thermal and light-induced agglomeration processes, including nucleation, growth and ripening of Pt species on TiO2. Under optimized annealing conditions Pt is present as a mixture of SAs, 2D rafts and nanoparticles. Data show that annealing can stabilize the Pt species against light-induced agglomeration and detailed analysis reveals such SAs (realized under optimized annealing conditions) provide the most active sites (in comparison with various agglomerates). We further emphasize the importance of conducting atomic-scale structural characterization both before and after photocatalysis to accurately establish the process-structure-property-performance relationships of SAs in photocatalysis.

The stabilization of single-atom catalysts on semiconductor substrates is pivotal for advancing photocatalysis. TiO2, a widely employed photocatalyst, typically stabilizes single atoms at oxygen vacancies-sites that are accessible but prone to agglomeration under illumination. Here, we demonstrate that cation vacancies in Ti-deficient TiO2 nanosheets provide highly stable anchoring sites for Pt single atoms, enabling persistent photocatalytic hydrogen evolution. Ultrathin TiO2 nanosheets with intrinsic Ti4+ vacancies are synthesized via lepidocrocite-type titanate delamination and Pt single atoms are selectively trapped within these vacancies through a simple immersion process. The resulting Pt-decorated nanosheets exhibit superior photocatalytic hydrogen evolution performance, outperforming both Pt nanoparticle-loaded nanosheets and benchmarked Pt single-atom catalysts on P25. Crucially, Pt atoms anchored at Ti4+ vacancies display remarkable resistance to light-induced agglomeration, a key limitation of conventional single-atom photocatalysts. Density functional theory calculations reveal that Pt incorporation into Ti4+ vacancies is highly thermodynamically favorable and optimizes hydrogen adsorption energetics for enhanced catalytic activity. This work highlights the critical role of cation defect engineering in stabilizing single-atom co-catalysts and advancing the efficiency and durability of photocatalytic hydrogen evolution.

The influence of the polarity of ceramic substrates on the structural evolution of thin metal films during annealing at elevated temperatures is investigated, including the competing processes of solid state dewetting (SSD) and grain growth, as well as the atomic structure of the epitaxial interface. For this purpose, Au thin films on polar O-ZnO(0001) and Zn-ZnO(0001) surfaces are annealed at elevated temperatures and times. Whereas SSD dominates on the O-terminated surface, pronounced grain growth is observed on the Zn-terminated surface. The texture analysis revealed that up to 600 degrees C, both samples exhibit a fiber texture with slightly dominating Au (111)[110] || ZnO(0001)[1120] orientation relation (OR 2). At 800 degrees C, Au on Zn-ZnO exhibits a transformation to a mazed bicrystal structure with Au(111)[110] || ZnO(0001)[1010] orientation relation (OR 1). Comparison of various interface structures in density-functional theory (DFT) indicates that atomically sharp interfaces between the Au(111) films and the ideal bulk-truncated polar ZnO surfaces are energetically favored for both substrate polarities in excellent agreement with atomically resolved electron microscopy. Due to the larger period of the coincidence site lattice in OR 2, the corresponding interface can be described as semi-coherent with clearly separated misfit dislocations. In contrast, the much smaller period of the (approximate) coincidence site lattice in OR 1 leads to a largely incoherent interface with local reconstructions. However, in the experimental situation, even a small rotational deviation from the perfect OR 1 can introduce an interfacial screw dislocation network superimposed on the incoherent interface structure, effectively making the interface semi-coherent.