Xingchen Liu

(a) CO oxidation rates as a function of O ₂ concentration at 170 °C. (b) Stepwise formation energies for oxygen vacancies (O _v ) on pristine CeO ₂ (110) (pink) and CeO ₂ (110) containing a cerium vacancy (Ce _v ) (blue).

In iron-based Fischer–Tropsch synthesis (FTS) catalysts, χ-Fe5C2 (Hägg carbide) is regarded as the key active phase; however, its dynamic structural evolution and stabilization mechanism under realistic reaction conditions remain unclear. To elucidate the carburization mechanism of the Fe5C2(111) surface under realistic reaction conditions at the atomic scale, this study develops a simulation-analysis framework named GRL (GCMC-RF-LAS). This framework integrates Grand Canonical Monte Carlo (GCMC) simulations based on the Reactive Force Field (ReaxFF), the Random Forest (RF) algorithm, and a self-developed local coordination environment-based structural identification method (FeC-LAS, Fe–C Local Atomic Structure Classifier). The results indicate that the carburization process on the Fe5C2(111) surface can be divided into three stages, with both the rate and extent of carburization strongly influenced by temperature. Notably, temperature exerts a significantly stronger regulatory effect on kinetics than on thermodynamics. Importance analysis using Random Forest reveals that the number of carbon atoms surrounding an iron atom (cnFeC) is the most significant descriptor contributing to surface energy. Thermodynamic phase diagrams further confirm that structures with high carbon coverage are more stable. Dynamic analysis of the subsurface structure using the FeC-LAS method reveals that the proportion of the Fe5C2 phase continuously decreases, while the content of the metastable intermediate phase Fe2C initially increases and subsequently enters a regime of wide-range dynamic oscillation. Moreover, the steady-state proportions of these two phases show no clear linear correlation with the carbon chemical potential, and a more detailed statistical analysis of the Fe2C proportion further confirms this lack of monotonic correlation with temperature and pressure, underscoring that kinetics dominate the subsurface evolution. Collectively, these observations indicate that kinetics dominate the carburization process on the Fe5C2(111) surface. The GRL framework established in this study provides a systematic approach for resolving catalyst surface phase evolution under realistic reaction conditions at the atomic scale, deepening the understanding of the dynamic structural evolution and deactivation micromechanisms of iron-based Fischer–Tropsch catalysts.

Identifying metal anchoring sites and their role in dynamic evolution is an important fundamental problem for catalysis research. For industrially used Al2O3 supports, precisely identifying metal anchoring sites remains challenging due to the intricate, diverse nature of their surface structures. Here, we deposited Pt nanoparticles onto hydroxyl groups (–OH) and lattice oxygen sites on hydroxyl-rich and partially dehydrated alumina. Different from the prevailing report of AlV consumption, AlVI transforms to AlV during Pt deposition on lattice oxygen sites. Moreover, different anchoring sites alter catalytic performance by driving the structural evolution of Pt atoms during hydrogenation. Pt nanoparticles bonded to hydroxyl groups are stable, while those nucleated on lattice oxygen undergo atomic redistribution to form more active sites for aromatic hydrogenation. These insights establish a direct link between initial coordination environment and dynamic behavior, advancing molecular-level understanding of metal–support interactions.

The selective oxidation of CH4 to C2 oxygenates under mild conditions is a significant pathway for CH4 valorization, yet it remains extremely challenging due to the inertness of methane, the competing overoxidation, and sluggish C–C coupling kinetics. Here, we show that the N,S co-doped carbon nanotube-supported Fe5 clusters catalyst (Fe5/NSC) with adjacent Fe sites drives sequential C–H activation and C–C coupling to ethanol with a C2H5OH productivity of 1939.6 μmol·gcat–1·h–1 and a selectivity of 83.9% at 25 °C and 0.5 MPa CH4 without the assistance of CO. Comprehensive experimental investigation and density functional theory calculations reveal the critical role of adjacent Fe sites in the selective formation of C2H5OH. The adjacent Fe sites featured in Fe5/NSC synergistically facilitate the dissociation and/or partial oxidation of CH4 to distinct C1 intermediates (*OCH2 and *CH3) and subsequent OCHx–CHx coupling between them to form the key CH3CH2O* intermediate for C2H5OH production, as opposed to the conventional CHx–CO coupling pathway that primarily yields acetic acid.

The selective aerobic oxidation of alkanes plays a pivotal role in the sustainable conversion of hydrocarbons. However, designing catalysts that facilitate the selective generation of radicals while avoiding side reactions (such as over‐oxidation) remains a major challenge. Herein, we demonstrate the enhanced spin polarization and lattice oxygen migration on CoO _x /Fe ₂ O ₃ catalyst for cyclohexane oxidation under solvent‐free conditions. We introduce highly dispersed CoO _x clusters on iron oxide nanorods (Co/FeNR) through atomic layer deposition, forming interfacial Co–O–Fe active sites. The high‐spin Co atoms modulate the spin‐state of neighboring Fe atoms via double‐exchange interaction, promoting the adsorption and dissociation of triplet molecular oxygen. Meanwhile, Co effectively enhances the mobility of lattice oxygen, further forming the interface‐confined radical intermediate. Both spin polarization‐promoted oxygen activation and lattice oxygen migration drive the transformation of interface‐confined radicals, thus suppressing side reactions and enhancing selectivity. Benefiting from these effects, the 5Co/FeNR achieves 14.6% conversion and 82.7% selectivity for KA oil and mass‐specific reaction rate of 830.7 mmol·g _cat ⁻¹ ·h ⁻¹ , which is approximately 6 times that of FeNR. This study provides valuable insights into the rational design of efficient oxidation catalysts.

The selective aerobic oxidation of alkanes plays a pivotal role in the sustainable conversion of hydrocarbons. However, designing catalysts that facilitate the selective generation of radicals while avoiding side reactions (such as over‐oxidation) remains a major challenge. Herein, we demonstrate the enhanced spin polarization and lattice oxygen migration on CoO _x /Fe ₂ O ₃ catalyst for cyclohexane oxidation under solvent‐free conditions. We introduce highly dispersed CoO _x clusters on iron oxide nanorods (Co/FeNR) through atomic layer deposition, forming interfacial Co–O–Fe active sites. The high‐spin Co atoms modulate the spin‐state of neighboring Fe atoms via double‐exchange interaction, promoting the adsorption and dissociation of triplet molecular oxygen. Meanwhile, Co effectively enhances the mobility of lattice oxygen, further forming the interface‐confined radical intermediate. Both spin polarization‐promoted oxygen activation and lattice oxygen migration drive the transformation of interface‐confined radicals, thus suppressing side reactions and enhancing selectivity. Benefiting from these effects, the 5Co/FeNR achieves 14.6% conversion and 82.7% selectivity for KA oil and mass‐specific reaction rate of 830.7 mmol·g _cat ⁻¹ ·h ⁻¹ , which is approximately 6 times that of FeNR. This study provides valuable insights into the rational design of efficient oxidation catalysts.

Understanding the structure-property relationship is of pivotal importance for the rational design of efficient solid catalysts yet persists as a significant challenge due to the inherent complexity of solid materials. Here, we present an efficient strategy to decipher the interfacial catalysis in metal-oxide nanocatalysts during CO₂ hydrogenation through synergistically integrated experimental and theoretical investigations with machine learning (ML) algorithms. Using model Pd/CeO₂ catalysts as a proof-of-concept system, the matched experimental and ML-predicted results demonstrate that given sufficient oxygen vacancy concentrations on the support matrix the catalytic performance is primarily governed by the nature of supported metals. Specifically, atomically dispersed Pd species exhibit exceptional intrinsic activity for CO production, which is attributed to its enhanced H spillover and hydrogenation capacities but weakened CO binding affinity. Further ML analysis indicates the sum surface d charge of supported metal as the principal factor governing catalytic performance among four types of typical intrinsic features influencing catalytic hydrogenation processes, which could be directly evaluated by a geometric descriptor of average coordination number of the metal on the support, associated with the metal particle size. This work provides a generalizable theoretical framework for understanding metal-oxide interfaces in CO₂ hydrogenation and opens up a novel approach for catalytically fundamental studies to unravel the complex nature of heterogeneous catalysis.

Accurate identification of material structures is crucial for establishing reliable structure-property relationships, yet this task is often hindered by the coexistence of multiple metastable phases and their facile transformations under reaction conditions. Although spectroscopic techniques are powerful tools for probing structural motifs, the lack of comprehensive reference data remains a critical bottleneck for experimental analysis. Here, we propose a unified strategy that integrates structure prediction, thermodynamic stability calculations, machine learning models, and Mössbauer spectroscopy simulations, tailored for iron-based intermetallic compounds. By constructing quantitative relationships between local structural features and Mössbauer parameters with machine learning, and by leveraging a theoretical spectral database to interpret experimental spectra, we successfully identified candidate iron sulfide metastable phases that were previously unresolved. This data-driven framework provides a robust complement to experimental approaches, enabling more accurate and efficient identification of metastable phases in dynamically evolving systems.

The binary 2-butynyl alcohol-H₂O complex was explored using pulsed-jet Fourier transform microwave spectroscopy with complementary quantum chemical calculations. Distinct tunneling-induced splittings in the rotational spectra reveal two large-amplitude motions: internal rotation of water (V₂ = 4.33 kJ mol^-1) and concerted tunneling of water and the hydroxyl group (B₂ = 6.61 kJ mol^-1). The observed isomer is stabilized by dual OH···O_w and O_w-H···π_C≡C hydrogen bonds. Electronic structure analyses indicate that methyl substitution strengthens the O_w-H···π_C≡C interaction, oppositely modulating these two tunneling pathways─restricting water rotation while facilitating skeletal torsion. These findings demonstrate how substituent effects control tunneling cooperativity in hydrogen-bonded systems, offering mechanistic insight into substituent-controlled quantum hydrogen dynamics in weakly bound clusters.

Hydrogen bonds are fundamental interactions that govern molecular aggregation. Although the O-H···O hydrogen bond is dominant in simple hydroxylic dimers, how this dominance is perturbed by substituents remains a key question. This study investigates the 2-butyn alcohol dimer using pulsed-jet Fourier transform microwave spectroscopy and theoretical calculations to quantitatively assess the impact of an alkynyl substituent on the dominant O-H···O hydrogen bond. The observed isomer is stabilized by a primary -H···O hydrogen bond and secondary O-H···π and C-H···π interactions. Quantum theory of atoms in molecules analysis revealed that the -H···O hydrogen bond energy contributes merely 55.0% to the total dimerization energy─the lowest value observed among a series of hydroxylic dimers, including water, alcohols, and phenols. This systematic comparative analysis reveals that introducing substituents, particularly those with π-systems or elongated alkyl chains, consistently reduces the energetic contribution ratio of the O-H···O hydrogen bond. The 2-butyn alcohol dimer, with its significantly weakened relative energy contribution ratio of the dominant hydrogen bond, approaches a threshold where the dominance of the O-H···O hydrogen bond could be challenged, providing a crucial perspective for understanding hierarchical molecular self-assembly.