Yong Wang

Reduced oxide surfaces often undergo complex reconstructions in which atomic rearrangements and reduction-induced electronic redistribution are strongly coupled, obscuring the electronic principles that govern their stability. Here, we address this problem on the prototypical rutile TiO_{2}(110) surface by combining machine-learning-accelerated global structure search, first-principles calculations, simulated scanning tunneling microscopy, and data-driven electronic-structure analysis. We identify previously unreported Ti_{3}O_{2}-(2×1) and Ti_{3}O_{4}-(2×1) reconstructions, with Ti_{3}O_{2}-(2×1) being more stable than the previously proposed Ti_{3}O_{2}-(1×2) model by up to 0.67 eV per minimal reconstruction unit and reproducing the experimentally observed rosettelike STM motifs. Analysis of 80 Ti_{3}O_{2} reconstruction configurations reveals that their thermodynamic stability is governed by the integrated hybridization between occupied Ti 3d states associated with Ti^{3+} small polarons and O 2p states of the reconstructed oxide lattice. This polaronic lattice state hybridization distinguishes low-energy reconstructions from the broader configurational ensemble and explains the stabilization of the newly found ground-state structure. The Ti^{3+}-derived states are also present near the Fermi level, which facilitates electron transfer to adsorbates, allowing the reconstructed surface to combine thermodynamic stability with chemical activity. These results establish polaronic lattice state hybridization as a microscopic mechanism for stabilizing reduced TiO_{2} surface reconstructions and suggest a broader electronic principle governing reconstruction of defect-rich reducible oxide surfaces.

In-situ intraparticle mineralization of widespread metalloids in groundwater is challenging but critical for global freshwater security. However, electronic and steric hindrances of complex oxygen-containing configurations prevent efficient oxygen dissociation and mineralization. Here, arsenic oxyanions are selectively and stably mineralized within d-orbital-modulated nanoscale Fe⁰ particles following enhanced d-p orbital-coupled oxygen dissociation, yielding ~100% removal efficiency, ~100% electron utilization, and ~94% metalloid intraparticle mineralization as resolved from thousands of single nanoparticles. Universal As, Sb, and Se intraparticle mineralization demonstrate excellent long-term stability (up to 98-fold of conventional nanoscale Fe⁰) in various groundwater matrices, where σ-bonded species show preferential intraparticle mineralization over π-bonded configurations. Field deployment is verified through macroscale material synthesis, minimal leaching of Fe and S in permeable reactive barriers, and economic advantages. This work establishes targeted d-p orbital-coupled bond dissociation as a transformative paradigm for metalloid-contaminated groundwater remediation and proposes a scalable in-situ remediation strategy that bridges atomic-level precision with field-ready practicality.

Atomically dispersed catalysts (ADCs) have drawn considerable attention in recent years for their promising activity in heterogeneous catalysis. Conventional catalyst sintering theory largely ignores the entropy effect and suggests that ADCs are normally thermodynamically unstable due to their high surface free energies, which becomes an obstacle for practical applications. Here, we present a generalized thermodynamic framework to demonstrate how the previously ignored entropy effect induces the self-redispersion of supported NPs. Through machine-learning-assisted molecular dynamics simulations, in situ Cs-corrected environmental scanning transmission electron microscopy, and synchrotron-based ambient-pressure X-ray photoelectron spectroscopy experiments, we reveal an entropy-driven phenomenon: the supported NPs redisperse into untrapped ADCs upon heating and reversibly sinter upon cooling in three systems (Pd-CeO2, Cu-TiO2, Ag-TiO2), contrary to the traditional understanding that “high temperature promotes sintering”. We further establish the entropy-driven catalyst redispersion theory, analogous to two-dimensional dissolution, where thermodynamically stable ADCs are ubiquitous up to their saturation concentration. It redefines the basic understanding of sintering, dispersion, and coexistence behavior between NPs and ADCs, thereby offering multiple strategies for obtaining thermodynamically stable ADCs.

Polar surfaces, known for their unique electronic and chemical properties, play vital roles in catalysis and electronics, yet their atomic structures remain difficult to resolve due to intrinsic instability often mitigated by surface reconstruction. However, the role of entropy, particularly vibrational entropy, in stabilizing such reconstructions is not well understood. Herein, we combine in situ atomic-resolution spherical aberration-corrected scanning transmission electron microscopy, density-functional theory calculations, and a differential evolution algorithm for global structural search to resolve the (1×1) reconstructed structure of the classical polar rutile TiO_{2}(111) surface. Crucially, we demonstrate that this reconstruction is predominantly stabilized by vibrational entropy at high temperatures. These findings not only highlight the importance of vibrational entropy in surface reconstructions but also advance our understanding of compensation mechanisms on polar surfaces by highlighting entropy as a critical stabilizing factor.

Iron (Fe) oxidation represents a prototypical system for understanding gas-solid reactions, directly impacting corrosion science, heterogeneous catalysis, and oxide-heterostructure design. Although the oxide configurations and oxidation pathways have been extensively documented, the atomic-scale structural dynamics that couple gas-surface reactions to solid-state phase transitions remain limited. Here, using in situ atomic-resolution environmental scanning transmission electron microscopy (ESTEM), we prepare atomically flat metal α-Fe(001) surfaces via thermal annealing and reveal a fundamentally different oxidation pathway from Fe to Fe₃O₄ during cooling under the ESTEM base vacuum. We demonstrate that metastable FeO plays a dynamically sustained role in two intermediate states. First, FeO nucleates on Fe(001) as distinct nanoscale islands below 300 °C, exhibiting a truncated square-pyramidal morphology. Second, FeO is retained as capping layers on the oxide during the transformation of the inner FeO into Fe₃O₄, creating an inverted phase hierarchy (FeO/Fe₃O₄/Fe). The FeO layers provide an active pathway for Fe diffusion, with their growth and transition dominating the subsequent oxide expansion. Despite the distinct growth behaviors of FeO on the (001) and {111} surfaces of oxide, their phase transitions are driven by a common basic unit. Structurally, the FeO-to-Fe₃O₄ transition is achieved via the translocation of octahedral Fe to tetrahedral sites, accompanied by outward diffusion. This work unveils the atomic-scale dynamics governing the coupled surface and interfacial reactions during the Fe oxidation via an island growth mode and establishes a new paradigm for understanding the unconventional oxide configurations in multilayer oxide-forming metals.

Engineering the metal‐support interfacial structure in supported heterogeneous catalysts opens wide opportunities to tailor catalytic performance, particularly by exploiting strong metal‐support interactions (SMSI) that modify active‐site electronic and geometric properties to tune adsorption energetics, activity and stability. However, designing SMSI that simultaneously meets the geometric requirement of sufficient active site exposure, and the electronic requirement remains challenging. Here, we achieved an intermediate encapsulation by forming crystallographically defined CeO _x overlayers on Ru/CeO ₂ via a Ru‐precursor‐mediated route. Using Ru ₃ (CO) ₁₂ as the precursors creates a locally reducing environment on CeO ₂ {100}, inducing localized surface modification and formation of truncated‐pyramid‐shaped SMSI overlayers on Ru with a height of ∼2–3 atomic layers (Ru/CeO ₂ ─CO). By contrast, catalysts prepared from Ru(NO)(NO ₃ ) ₃ (Ru/CeO ₂ ─NO ₃ ) show no SMSI encapsulation. Ru/CeO ₂ ─CO exhibits significantly higher oxygen‐vacancy concentrations both overall and within the SMSI layer, which promotes electron transfer from the interface and overlayer to the Ru nanoparticles. The formation of electron‐rich Ru species, without blocking a significant number of active sites, facilitates nitrogen activation and enhances catalytic ammonia synthesis. This work presents a novel strategy to construct intermediate SMSI encapsulation and also provides mechanistic insight into precursor‐dependent activity at the nanoscale.

Nanocrystal phase thermostability is critical for their applications, yet fundamentally governed by complex thermodynamic and kinetic variables. Understanding the stabilizing mechanisms and dominant factors requires atomic-level insights into dynamic evolution across surface and bulk regions under extreme conditions. Herein, we present a comprehensive in-situ investigation of individual single-crystalline anatase TiO ₂ nanorods using spherical aberration-corrected scanning transmission electron microscopy. By simultaneously acquiring environmental secondary electron images for surface topography and high-angle annular dark-field images for bulk atomic structures, we reveal the extraordinary phase stability of individual anatase nanorods governed by surface effects, distinct from aggregated nanorods. Anatase TiO ₂ nanorods undergo morphology reshaping and surface atomic reconstruction above 600 °C, involving transformation from high-index surfaces to (101) facets and the formation of (1 × 4)-reconstructed (001) surfaces. Remarkably, individual anatase TiO ₂ nanorods maintain the anatase structure even up to 1250 °C without transforming into the rutile phase. The restructuring lowers the total energy of the system, and acts as a kinetic “surface-locking” effect preventing rutile nucleation. Beyond elucidating the restructuring mechanisms and intrinsic thermostability of TiO ₂ nanocrystals, this work also establishes an effective pathway for simultaneously probing the complex structural evolution of nanomaterials across both surface and bulk regions.

Sintering is one of the major causes of catalyst deactivation, which requires redispersion to restore catalytic activity. However, conventional redispersion methods often require harsh high‐temperature conditions or introduce contaminants, both of which can degrade catalyst integrity and limit their practical applicability. Here, a novel redispersion method that achieves highly dispersed Pt/CeO ₂ via NO treatment at an exceptionally low temperature of 200 °C, is visualized by in situ transmission electron microscopy (TEM) and confirmed by density functional theory (DFT). Interestingly, NO, although a milder oxidant compared to O ₂ , promotes more effective Pt redispersion on the CeO ₂ (100) surface. This behavior is governed by the kinetic behaviors of the Pt species formed under different oxidative atmospheres. Under NO, two‐coordinated Pt atoms are formed, each bonded to two surface oxygen atoms. These species exhibit high mobility across the surface, enabling efficient redispersion at low temperatures. In contrast, exposure to O ₂ leads to the formation of four‐coordinated Pt atoms bonded to four surface oxygen atoms, which significantly restricts surface diffusion and inhibits redispersion under the same temperatures. This ultralow‐temperature redispersion mechanism is not limited to Pt/CeO ₂ , but can also be extended to other catalyst systems, offering an energy‐efficient and halogen‐free alternative to conventional redispersion techniques.