The metalorganic chemical vapor deposition (MOCVD) preparation of InGaAs is the mainstream approach for commercial production, but the atomic-scale microkinetic mechanisms of its growth process remain to be thoroughly elucidated. The existing atomic-level simulations of the complete InGaAs MOCVD growth process are relatively scarce and suffer from limitations such as restricted model sizes and inadequate consideration of multiprecursor cooperative effects. Therefore, this study employs the β2(2 × 4)-As surface of GaAs(001) as the substrate, selecting trimethylindium (TMIn), trimethylgallium (TMGa), and AsH3 as the In, Ga, and As sources, respectively. Our research primarily focuses on the surface reaction steps of InGaAs MOCVD, thereby neglecting gas-phase reactions, and assuming that precursor molecules remain intact when adsorbed on the GaAs surface. Based on density functional theory, periodic surface models were constructed to systematically calculate the reaction energies and energy barriers for the adsorption and decomposition of different precursors, both individually and coadsorbed, thereby clarifying the relationship between rate-limiting steps and deposition efficiency. We found mix precursor reduces the barrier of the rate-limiting step by about 0.2 eV compared to the single-precursor case, demonstrating a synergistic relationship in TMGa and TMIn. The results in our study also reveal the physical nature of surface reaction kinetics, defect formation, and impurity control during InGaAs MOCVD growth.
Meeting the global challenge of clean and sustainable energy calls for continuous advancements in functional materials designed for energy conversion, storage, and catalysis. The performance of such materials is inherently linked to their atomic and electronic configurations, as well as the interfacial dynamics that dictate their operational behavior. Synchrotron-based X-ray techniques offer powerful analytical capabilities, enabling precise characterization with exceptional elemental sensitivity and spatial resolution. Among these, X-ray absorption and emission spectroscopies stand out for their ability to unravel complex material architectures and elucidate interactions between key components. The integration of in situ and operando approaches further allows for real-time tracking of atomic and electronic structural changes under realistic operating environments—providing vital mechanistic insights to inform rational material design. Understanding the influence of solid–liquid interfaces on electrochemical processes demands careful investigation of surface chemistry at the electrode–electrolyte junction. In this presentation, I will showcase examples of dynamic transformations in surface composition and structure that critically affect a material’s catalytic performance for water splitting across various media. I will also highlight how NSRRC beamlines play a central role in advancing this research. Our findings emphasize the indispensable value of in situ and operando X-ray characterization techniques in uncovering the true mechanistic pathways of catalytic reactions. These insights serve as a bridge between fundamental design principles and the practical challenges encountered in real-world energy systems, where additional complexities must be addressed. References [1] Li,Y.; Peng,C.K.; Sun,.; Nicole, S.L.D.; Chang, Y.C.; Chen, S.Y.; Zhou, Y.; Lin, Y.G.; Lee, J.M.; Operando Elucidation of Hydrogen Production Mechanisms on Sub-Nanometric High-Entropy Metallenes. Nature Communications, 2024, 15, 10222. [2] Peng, C.K.; Lin, Y.C.; Chiang, C.L.; Qian, Z.; Huang, Y.C.; Dong, C.L.; Li, J.F.; Chen, C.T.; Hu, Z.; Chen, S.Y.; Lin, Y.G.; Zhang-Rice singlets state formed by two-step oxidation for triggering water oxidation under operando conditions. Nature Communications, 2023, 14, 529. [3] Lim, S.C.; Chiang, C.L.; Peng, C.K.; Wu, W.B.; Lin, Y.C.; Lin, Y.R.; Chen, C.L.; Lin, Y.G.; Realizing the bifunctional electrocatalysis via local charge rearrangement of α-CrOOH-modulated Co@CoMoOx for overall water splitting. Chemical Engineering Journal, 2023, 452, 139715. [4] Li, Y.; Peng, C.K.; Hu, H.; Chen, S.Y.; Choi, J.; Lin, Y.G.; Lee, J.M.; Interstitial boron-triggered electron-deficient Os aerogels for enhanced pH-universal hydrogen evolution. Nature Communications, 2022, 13, 1143. [5] Lin, Y.C.; Peng, C.K.; Lim, S.C.; Chen, C.L.; Nguyễn, T.N.; Wang, T.T.; Lin, M.C.; Hsu, Y.J.; Chen, S.Y.; Lin, Y.G.; Tailoring the Surface Oxygen Engineering of a Carbon-Quantum-Dot-Sensitized ZnO@H-ZnO1-x Multijunction toward Efficient Charge Dynamics and Photoactivity Enhancement. Applied Catalysis B: Environmental, 2021, 285, 119846.
Controlling elemental mixing in nanoparticles composed of immiscible elements remains a central challenge in high-entropy materials design. Here, we demonstrate a kinetic pathway that enables a transition from elementally segregated to high-entropy AgNiCoCr nanoparticles using nanosecond laser-induced dewetting of metallic thin films. During this nonequilibrium process, nanoparticles form through a sequence of morphological transformations and ultimately evolve into near-spherical structures with thickness-dependent sizes. In the chosen model system, Ag is thermodynamically immiscible with Ni and Co, whereas Ni, Co, and Cr are mutually miscible at equiatomic compositions. By varying the thickness and configuration of the metallic thin-film layers, the liquid-phase lifetime during laser irradiation is systematically tuned, thereby regulating mass transport and solidification dynamics. Ultrathin film stacks produce smaller nanoparticles (up to ∼40 nm) that rapidly solidify on nanosecond time scales, kinetically trapping metal atoms into a chemically disordered high-entropy phase. In contrast, thicker films remain molten for longer durations during dewetting, leading to the formation of larger nanoparticles with pronounced elemental segregation into AgNiCoCr core–shell or Janus structures. Supported by atomistic simulations, this work demonstrates that solidification kinetics, rather than thermodynamic immiscibility, governs chemical order in laser-processed nanoparticles, providing a versatile strategy for engineering high-entropy nanoparticles from immiscible elements.
Compositionally complex solid solutions (frequently referred to as high entropy alloys) provide a unique route for designing high-performance electrocatalysts, where the polyelemental surface composition can be seamlessly tuned to optimize activity, selectivity, and stability. However, the mechanistic understanding of these electrocatalysts remains limited by the lack of a model system with a crystallographically defined surface that is compatible with correlative, multi-scale characterization. Here, we present epitaxial films as a model platform for studying compositionally complex electrocatalysts. Using magnetron sputtering, we realize (111) epitaxial Ir-Pd-Pt-Rh-Ru films on a (0001) sapphire substrate via a (111) Pt buffer layer, confirmed via X-ray diffraction and transmission electron microscopy. The growth approach is applicable across a broad composition range and produces smooth surfaces (root mean square roughness <1 nm) with micrometer-sized grains in the nanoscale films. For these films, we demonstrate direct structure-activity mapping at the nanoscale through precise co-localization using micro-indents and performing correlative atomic force microscopy, electron backscatter diffraction, and scanning electrochemical cell microscopy. Our work establishes a model platform for fundamental scale-bridging characterization and paves the way for rational design of compositionally complex electrocatalysts.
Nanocrystal surfaces generally undergo reconstructions that differentiate them from the bulk structures, often in nontrivial ways. Understanding these terminations is critical across diverse fields, from heterogeneous catalysis to the formation of topological states and the synthesis of semiconductor nanomaterials. Determining surface structures is currently an interdisciplinary task, most often involving high-resolution electron microscopy and surface electron diffraction. These methods, however, do not provide a global view of the ensemble of structures present in a sample. Here, we show how surface-sensitive solid-state nuclear magnetic resonance (SSNMR) spectroscopy methods can bridge this gap. In this context, we investigated the surface structure of lanthanum aluminate (LaAlO3) perovskite nanoparticles. Four distinct surface terminations have previously been observed for this material, but their relative abundances were unknown. Using an array of double- and triple-resonance SSNMR methods probing the relative proximities of surface 1H, 27Al, 17O, and 139La nuclei, we conclude the surface to be majority terminated (80%) by AlO x with substantial (20%) LaO x terminated regions.
Mechanochemistry, the study of how mechanical energy drives chemical transformations, has rapidly evolved into a powerful and influential discipline at the intersection of chemistry and materials science. This article provides an integrated and critical overview of recent advances in mechanochemical methodologies within organic and inorganic chemistry, while also examining the challenges and opportunities that accompany this emerging technology. Mechanochemistry represents a promising and evolving field, though it still requires careful approaches to address challenges in scalability, mechanistic understanding, and technological implementation. Continued innovation in instrumentation, process design, and theoretical modelling will be essential for unlocking the full potential of mechanically driven chemistry. As global interest in sustainable, energy-efficient chemical processes intensifies, mechanochemistry is poised to play an increasingly prominent role, offering one of the most compelling pathways toward greener synthesis. This review is designed not only to serve as a resource encompassing a broad spectrum of literature, but also as a practical guide for researchers seeking to advance and expand the mechanochemical landscape.