Surface Atomic Structure Research Articles

Large-area single-crystal TMD growth modulated by sapphire substrates.

Transition metal dichalcogenides (TMDs) have recently attracted extensive attention due to their unique physical and chemical properties; however, the preparation of large-area TMD single crystals is still a great challenge. Chemical vapor deposition (CVD) is an effective method to synthesize large-area and high-quality TMD films, in which sapphires as suitable substrates play a crucial role in anchoring the source material, promoting nucleation and modulating epitaxial growth. In this review, we provide an insightful overview of different epitaxial mechanisms and growth behaviors associated with the atomic structure of sapphire surfaces and the growth parameters. First, we summarize three epitaxial growth mechanisms of TMDs on sapphire substrates, namely, van der Waals epitaxy, step-guided epitaxy, and dual-coupling-guided epitaxy. Second, we introduce the effects of polishing, cutting, and annealing processing of the sapphire surface on the TMD growth. Finally, we discuss the influence of other growth parameters, such as temperature, pressure, carrier gas, and substrate position, on the growth kinetics of TMDs. This review might provide deep insights into the controllable growth of large-area single-crystal TMDs on sapphires, which will propel their practical applications in high-performance nanoelectronics and optoelectronics.

How Water Binds to Microcline Feldspar (001).

Microcline feldspar (KAlSi3O8) is a common mineral with important roles in Earth's ecological balance. It participates in carbon, potassium, and water cycles, contributing to CO2 sequestration, soil formation, and atmospheric ice nucleation. To understand the fundamentals of these processes, it is essential to establish microcline's surface atomic structure and its interaction with the omnipresent water molecules. This work presents atomic-scale results on microcline's lowest-energy surface and its interaction with water, combining ultrahigh vacuum investigations by noncontact atomic force microscopy and X-ray photoelectron spectroscopy with density functional theory calculations. An ordered array of hydroxyls bonded to silicon or aluminum readily forms on the cleaved surface at room temperature. The distinct proton affinities of these hydroxyls influence the arrangement and orientation of the first water molecules binding to the surface, holding potential implications for the subsequent condensation of water.

Operando Surface X-Ray Diffraction Studies of Co Oxide Catalyst Films for Electrochemical Water Splitting

The need for environmental friendly and sustainable energy conversion has triggered renewed interest into the electrochemical and photoelectrochemical splitting of water. A key challenge in this field is the development of economically viable electrocatalyst materials for the oxygen evolution reaction (OER). Transition-metal oxide catalysts, in particular the cobalt (hydr)oxide materials, have been found as promising candidates, since they are earth-abundant, efficient and scalable over a wide range of electrochemical conditions [1]. They present good catalytic properties and stability in alkaline solution under ambient conditions. Although a wide variety of different catalysts with rather diverse nanoscale morphologies have been synthesized and studied, the atomic scale surface structure usually is still unknown or poorly defined. This makes it difficult to compare their electrocatalytic activity and correlate it with ab initio theoretical studies, which hinders the development of clear structure-reactivity relationships and unambiguous determination of the OER reaction mechanism.We presentsystematic comparative studiesof structurally well-defined, 18-35nm thick Co3O4 films, prepared by electrodeposition or physical vapor deposition (PVD) on Au(111), Au(100) and Ir(100) single crystals. In all cases a well ordered epitaxial Co3O4(111) arrangement results, but the film morphology differs substantially, as shown by AFM and surface X-ray diffraction (SXRD). In order to elucidate the quantitative relationship between the catalyst surface structure and the OER reactivity, synchrotron-based operando SXRD and electrochemical measurements were performed simultaneously under reaction conditions, using a dedicated operando cell which allows massive gas evolution and current densities of up to 150 mA/cm2 [2,3].We find that the Co3O4(111) layers prepared by PVD on Ir(100) stay perfectly stable in the pre-OER and OER potential regime, whereas all electrodeposited films exhibit reversible changes in the oxide structure and oxidation state, in agreement with a previous study of Co3O4 catalysts [2]. Specifically, we observe the reverse formation of an ultrathin X-ray-amorphous CoOx(OH)y skin layer above 1 V vs. RHE and the gradual buildup of tensile lattice strain in the underneath, remaining Co3O4 layer with increasing potential. These structural changes occur for all electrodeposited samples, albeit to a different extent, depending on the film morphology [3]. Studying the relationship between the effective thickness of this skin layer and the OER reactivity, we found clear evidence that the entire skin layer is a three dimensional OER zone, which strongly exceeds one monolayer.Our results suggest that even subtle changes of the surface morphology have large influence on the OER activity of the Co3O4 catalyst, which may be expected also for other spinel-type transition metal oxides. On the one hand, this reveals that great care as to be taken in comparing the OER activity of differently prepared catalysts. On the other hand, these observations may provide a base for targeted preparation of highly reactive oxide catalysts.[1] C. C. L. McCrory et al., Journal of the American Chemical Society 2015, 137, 4347.[2] F. Reikowski, et al., ACS Catalysis, 2019, 9, 3811.[3] T. Wiegmann, et al., ACS Catalysis, 2022, 12, 256.

Deconvoluting the Role of Electrolyte pH, Structural Sensitivity, and Electric Field Effects on the Electrochemical Hydrogenation of Phenol

Traditional thermochemical hydrogenation (TCH) methods that are used in the U.S. chemical and petroleum industries to produce value-added fuels are highly energy intensive. To achieve hydrogenation, they require high temperature and pressure, along with an external source of hydrogen that usually comes from steam methane reformation. Electrochemical hydrogenation (ECH) is an attractive alternative that replaces the thermal driving force with an applied electrical potential, allowing ECH to operate near ambient conditions. The participating protons come from the aqueous electrolyte solution rather than externally produced hydrogen. These features of ECH lower its energy demand compared to TCH and result in less greenhouse gas emissions. ECH is also promising for the processing of biomass feedstocks and could be powered directly by renewable energy, further minimizing the environmental impact.The addition of an aqueous electrolyte and electric field means that insights from TCH should not be directly translated to ECH systems, however, this is often the case in the literature. Fundamental studies on ECH of aromatic hydrocarbons (AHs) are necessary to address current limitations including: competition with the hydrogen evolution reaction (HER) resulting in lower faradaic efficiency, low rates compared to TCH, and little control over selectivity and degree of hydrogenation. For instance, the role of electrolyte pH on phenol ECH remains poorly understood. While some groups have reported negligible phenol turnover rates in electrolytes of pH 10 and above on Pt/C and Pd/C catalysts [1], Song et al. have shown that turnover rates and efficiency are highest on Rh/C at pH 10 [2]. Yet, the idea that low pH (3-5) is best has persisted and the source of the pH dependence remains unknown.In this work we use phenol as a simple representative AH for lignocellulosic bio-oil. We have shown with rotating disk electrode voltammetry that the presence of phenol in electrolytes of pH ~10 enhances HER rates on Pt, Pd, and Au catalysts. Considering that the pKa of phenol is also 10.0, we propose that interfacial phenol molecules channel protons to the catalyst surface by way of facile proton dissociation/reassociation, lowering the barrier for adsorbed H formation in alkaline electrolytes. While this may explain, in part, the low phenol turnover rates observed at higher pH, we further investigate why the opposite is observed on Rh/C catalysts. The role of atomic surface structure is also critical to the adsorption geometry and coverage of AHs. We use well-defined, low-index Pt single crystals to identify the true structural sensitivity for the ECH of AHs. We show with select stepped single crystal surfaces that there is a synergetic role between terrace width/step density that defines activity, balancing coverage of AH molecules, formation of surface adsorbed H, and transfer of that H to AH reactants. We use a low-volume, membrane-separated flow cell for chrono-amperometry followed by product analysis to correlate pH, structural sensitivity, and applied potential to phenol ECH rates and faradaic efficiency. With an understanding of the role of atomic surface structure and the true source of pH dependence, we propose strategies for enhancing phenol turnover rates at lower overpotentials, improving faradaic efficiency, and controlling selectivity.

Altering the electronic structure and surface chemical environment of Pt{100} facets via synergizing with Ir species for enhanced oxygen-reduction activity and stability

Shape-controlled metal-based nanomaterials provide a special platform to regulate the surface physicochemical properties for optimizing the electrocatalytic performance, due to their homogeneously arranged surface atomic structures. Accordingly, owing to the solely {100} facets-ended surfaces, highly uniform Pt nanocubes (NCs) are utilized in this study, to probe the effects of synergizing with Ir species (a very effective metal for various electrocatalysis) on the electrocatalytic performance for the oxygen reduction reaction (ORR). Electrochemical results present that carbon-supported Pt1Ir1 NCs with surface Ir–O species (Pt1Ir1–O NCs/C) have much enhanced electrocatalytic activity and electrochemical stability than both Pt NCs/C and commercial Pt/C. Physicochemical characterization and theoretical calculation analyses further elucidate the mechanism of the improved electrocatalytic performance: the strong electronic interaction between Pt and Ir, the lowered d-band center of the surface metal atoms, and especially the synergistic effect induced by the surface Ir–O species. This study not only develops a highly active and stable ORR electrocatalyst, but also demonstrates an effective and universal research paradigm to explore the surface engineering effects on the electrocatalytic performance, which can be further applied in other crystalline facets for other (electro)catalytic reactions.

Surface-dependent generation of reactive oxygen species at pyrite–water interface

The generation of reactive oxygen species (ROS) at the pyrite–water interface is an important discovery for both early Earth’s and present environments in the past two decades. In these revealed reactions, pyrite can oxidize water to ROS and reduce O2 and ROS to water. However, the two types of reactions are controversial. The underlying physical theory responsible for the reactions has yet to be elucidated. In this study, we established a surface structure-dependent model of oxidation and reduction potentials (ORP) for semiconductors. Surface atomic structure-dependent electronic structures were adopted to estimate the ORP of pyrite. We apply this model to gain insights into the generation of ROS at the pyrite–water interface. The results demonstrate that the surface structure of pyrite controls its ORP, and ROS production can only occur on certain pyrite facets. The {210} and {111} facets with certain defects (e.g., 210-2S′ and 111-3S, respectively) could oxidize either H2O or OH− to O2, and ROS form during the oxidation of pyrite surfaces by O2. This suggests that surface effects play a crucial role in governing the ORP of semiconducting minerals. Accurately calculating surface ORP could potentially be used to better understand redox reactions and develop more efficient catalysts.

Porphyrin-based Bi-MOFs with Enriched Surface Bi Active Sites for Boosting Photocatalytic CO2 Reduction.

The inherent challenges in using metal-organic frameworks (MOFs) for photocatalytic CO2 reduction are the combination of wide-range light harvesting, efficient charge separation and transfer as well as highly exposed catalytic active sites for CO2 activation and reduction. We present here a promising solution to satisfy these requirements together by modulating the crystal facet and surface atomic structure of a porphyrin-based bismuth-MOF (Bi-PMOF). The series of structural and photo-electronic characterizations together with photocatalytic CO2 reduction experiment collectively establish that the enriched Bi active sites on the (010) surface prefer to promote efficient charge separation and transfer as well as the activation and reduction of CO2 . Specifically, the Bi-PMOFs-120-F with enriched surface Bi active sites exhibits optimal photocatalytic CO2 reduction performance to CO (28.61 μmol h-1 g-1 ) and CH4 (8.81 μmol h-1 g-1 ). This work provides new insights to synthesize highly efficient main group p-block metal Bi-MOF photocatalysts for CO2 reduction through a facet-regulation strategy and sheds light on the surface structure-activity relationships of the MOFs.

Mn induces a 1×3 reconstruction in the ferromagnetic L21 Mn2FeGa (001) surface

The Mn2FeGa compound is an ordered ferrimagnetic Heusler alloy characterized by its unique inverse magnetostriction and exceptional magnetic properties. In this study, we employ density functional theory (DFT) to conduct a theoretical analysis of the atomic structure of the (001) surface of Mn2FeGa. We utilize the surface energy formalism to systematically evaluate and compare the stability of various surface atomic configurations under different chemical potential conditions. Notably, our investigation identifies three energetically stable surfaces: MnGa-terminated, Ga-terminated, and MnGa2-terminated surfaces, featuring a 3×1 surface reconstruction, prevalent under Ga-rich conditions. Understanding the atomic arrangements and surface effects of Mn2FeGa is pivotal for optimizing its properties for specific device applications.

In situ preparation and determination of CeO2 high-index surface atomic structures

Understanding the properties regarding the high-index surfaces of the oxide nanocrystals is of great importance, but it remains challenging to obtain atomic-level information due to the lack of efficient preparation methods for high-index surfaces. Herein, we presented a work to in situ prepare and determine the intrinsic atomic structures of nanocrystalline CeO2 high-index surfaces via in situ spherical aberration (Cs)-corrected scanning transmission electron microscopy (STEM). By utilizing a reshaping process driven by the Wulff reconstruction, high-index surfaces of CeO2 nanocrystals including {210} {311}, and {533} were successfully prepared. Combined STEM with the density functional theory calculations, these high-index surface structures were determined with atomic precision, and interestingly {533} exhibited a unique atomic pit feature with low-coordinated Ce atoms exposure and unique electrical properties. This work has revealed new information about CeO2 high-index surfaces through experiments, enhancing our understanding of these surfaces, and also providing a new route for preparing high-index surfaces.

Photocatalytic Co‐Reduction of N2 and CO2 with CeO2 Catalyst for Urea Synthesis

AbstractThe effective conversion of carbon dioxide (CO2) and nitrogen (N2) into urea by photocatalytic reaction under mild conditions is considered to be a more environmentally friendly and promising alternative strategies. However, the weak adsorption and activation ability of inert gas on photocatalysts has become the main challenge that hinder the advancement of this technique. Herein, we have successfully established mesoporous CeO2‐x nanorods with adjustable oxygen vacancy concentration by heat treatment in Ar/H2 (90 % : 10 %) atmosphere, enhancing the targeted adsorption and activation of N2 and CO2 by introducing oxygen vacancies. Particularly, CeO2‐500 (CeO2 nanorods heated treatment at 500 °C) revealed high photocatalytic activity toward the C−N coupling reaction for urea synthesis with a remarkable urea yield rate of 15.5 μg/h. Besides, both aberration corrected transmission electron microscopy (AC‐TEM) and Fourier transform infrared (FT‐IR) spectroscopy were used to research the atomic surface structure of CeO2‐500 at high resolution and to monitor the key intermediate precursors generated. The reaction mechanism of photocatalytic C−N coupling was studied in detail by combining Density Functional Theory (DFT) with specific experiments. We hope this work provides important inspiration and guiding significance towards highly efficient photocatalytic synthesis of urea.

Photocatalytic Co-Reduction of N2 and CO2 with CeO2 Catalyst for Urea Synthesis.

The effective conversion of carbon dioxide (CO2 ) and nitrogen (N2 ) into urea by photocatalytic reaction under mild conditions is considered to be a more environmentally friendly and promising alternative strategies. However, the weak adsorption and activation ability of inert gas on photocatalysts has become the main challenge that hinder the advancement of this technique. Herein, we have successfully established mesoporous CeO2-x nanorods with adjustable oxygen vacancy concentration by heat treatment in Ar/H2 (90 % : 10 %) atmosphere, enhancing the targeted adsorption and activation of N2 and CO2 by introducing oxygen vacancies. Particularly, CeO2 -500 (CeO2 nanorods heated treatment at 500 °C) revealed high photocatalytic activity toward the C-N coupling reaction for urea synthesis with a remarkable urea yield rate of 15.5 μg/h. Besides, both aberration corrected transmission electron microscopy (AC-TEM) and Fourier transform infrared (FT-IR) spectroscopy were used to research the atomic surface structure of CeO2 -500 at high resolution and to monitor the key intermediate precursors generated. The reaction mechanism of photocatalytic C-N coupling was studied in detail by combining Density Functional Theory (DFT) with specific experiments. We hope this work provides important inspiration and guiding significance towards highly efficient photocatalytic synthesis of urea.

(Invited) Oxide-Water Interfaces from Ab Initio Based Deep Neural Network Simulations

Photo-electrocatalysis involving complex oxide-water interfaces is a highly promising technology for the sustainable production of fuels. However, probing these complex interfaces and gaining atomistic insights is still very challenging for current experimental methods, and is often only possible through accurate computational simulations. While first principles-based simulations provide the best accuracy, they are also limited to small system sizes and time-scales due to their high computational cost. Machine learned potentials that reproduce the accuracy of first-principles methods, while at the same time allowing the exploration of larger systems and timescales, are a promising approach to circumvent this issue. In this talk, I will discuss recent applications of deep neural network based molecular dynamics simulations to understand the structure and dynamics of interfacial water on photoelectrochemically relevant oxide surfaces. Focusing on TiO2 and IrO2 surfaces, we examine interfacial proton transfer and discuss how the water dissociation fraction and hydroxyl lifetimes depend on the surface atomic and electronic structures.

Adsorption behavior of oxygen on Ti0.5Al0.5N (001) surface with X-doped (X = La, Ce, Y, Hf, Zr, Ta, Cr, Si): A first-principles study

In this work, we systematically investigate the effect of X-doped atom (X = La, Ce, Y, Hf, Zr, Ta, Cr, Si) on the adsorption behavior of oxygen for Ti0.5Al0.5N (001) surface through first-principles calculations. The calculated results show that the order of formation energies for substituting Al is Y < Hf < La < Ce < Zr < Ta < Cr < Si. The adsorption energy results reveal that the doping can improve the adsorbability of oxygen, where the enhancement effect for Cr and Si is poor. Notably, the bonding structures of Ta, Cr, and Si prefer to form O-X bond, which is different from the hybrid bonds of Al-O-X and Ti-O-X by La, Ce, Y, Hf, and Zr doping, agreeing well with the two types of oxidation products experimentally observed. Among these eight doping atoms, Cr and Si can enhance effectively the oxidation resistance of Ti0.5Al0.5N (001) surface due to the compact surface atomic structure, poorer adsorbability of oxygen, and forming the Al2O3 protection layer together with Cr2O3 and SiO2. Moreover, the results of partial density of state show that O(s) orbital is hardly involved in covalent bonding when O atom interacts with La, Ce, Y, and Cr atoms.

Origin of surface and subband states at the InAs(111)A surface

The atomic structure of surfaces and interfaces plays a vital role in the electronic quality and properties of quantum devices. The interplay between the surface and confined bulk subband states in terms of their susceptibility has been investigated in relation to crystal defects on an InAs(111)A-$(2\ifmmode\times\else\texttimes\fi{}2)$ reconstructed surface, using low-temperature scanning tunneling microscopy and spectroscopy. We measure the two-dimensional quantized subband states arising from the confined potential imposed by downward bending of the conduction band edge. Furthermore, we show evidence of the existence of surface Bloch states within the confined bulk band gap projected on the surface spectrum which have originated from the surface reconstruction. As expected, larger confined bulk band gaps at the surface and conduction band offset are measured to be 0.58 and 0.31 eV, respectively. We further show the scattering of these quantum states at different surface defects and demonstrate that surface states are more susceptible to the defect potential when compared with the corresponding subband states. This apparent contrast follows from the length scale at which these defect potentials actively interact on or near the surface. Our observed experimental results are supported by empirical tight-binding simulations for the subband states and first-principles density functional theory simulations for the surface states present on the surface.

Carboxyl regulated Bi2WO6 nanosheets with negative conduction band sites for improving visible light reduction of Cr(VI)

This paper focuses on a new synthesis strategy using organic molecules to customize the surface structure of Bi2WO6 nanosheets, and applies them to the visible-light reduction of Cr(VI) in sewage. Interestingly, the Bi2WO6 nanosheets modified by citric acid molecules with rich carboxyl groups exhibit a conduction band position of −0.87 eV. Meanwhile, the material with large specific surface area (146.60 m2·g−1) promotes the adsorption of pollutants to 6.71 mg·g−1. Furthermore, the material also produces surface oxygen vacancies, which provides impetus for the separation of carriers. In addition, more than 95% of the catalytic efficiency and complete crystal diffraction peaks after six cycles indicate that the catalyst has good cycles and light corrosion resistance. This work provides a novel strategy to adjust the surface atomic structure by functional groups to achieve efficient photocatalyst.

Significantly enhanced surface oxygen vacancies over W18O49 via Mo doping and plasma-induced surface reconstruction for oxidative desulfurization

The non-stoichiometric structure of tungsten oxide (W18O49) makes it easy to form oxygen vacancies near the low-valence W atoms, so the W18O49 can be applied to oxidative desulfurization. To further improve the desulfurization activity of W18O49 to meet the increasingly stringent environmental requirements, Mo doping and plasma-induced surface reconstruction cooperative strategies are developed. The incorporation of Mo species into the W18O49 surface by replacing W sites can adjust the atomic and electronic structure of the catalyst surface and form more oxygen vacancies. After Mo doping into the W18O49, the plasma bombarded the surface of material to destroy part of the surface structure, thus producing the reactive sites with low coordination numbers. This reconstructed atomic surface also accompany to generate more oxygen vacancies, thus greatly improving the catalytic activity. Compared to pure W18O49, significantly improves oxidative desulfurization performance can be achieved over Mo-W18O49-P, and deep desulfurization is realized within 3 h. Moreover, the optimal Mo-W18O49-P shows better stability than pure W18O49, which can be recycled for 12 times. This work provides an accessible pathway for cooperative enhancing the catalytic oxidative desulfurization activity of oxide catalysts.

Design of grain boundaries enriched nickel molybdate for enhanced catalytic oxidative desulfurization

Grain boundaries (GB), a favorable atomic configuration, can provide highly active surfaces by modulating electronic structures in the catalysts. Whereas, it is usually be ignored owing to the large structural variations and the difficulty in its precise design. Herein, a novel strategy is proposed to prepare nickel molybdate with rich GB (RGB-NMO) via a facile one-step growth assisted by cetyltrimethylammonium bromide. Experimental results reveal that the optimized morphology can increase the exposure of active sites and facilitate the mass transfer during the oxidative desulfurization (ODS) reaction. Moreover, the engineered GB can modulate the surface atomic composition and electronic structure, leading to the increase of hydrogen peroxide activation capacity. Benefiting from these features, the synthesized RGB-NMO not only exhibits attractive desulfurization efficiency, but also shows a satisfactory cycling stability. Overall, this manuscript provides new inspirations for design of functional materials rich in GB towards excellent ODS treatment.

Ferroelectricity in Niobium Oxide Dihalides NbOX2 (X = Cl, I): A Macroscopic- to Microscopic-Scale Study.

2D materials with ferroelectric and piezoelectric properties are of interest for energy harvesting, memory storage and electromechanical systems. Here, we present a systematic study of the ferroelectric properties in NbOX2 (X = Cl, I) across different spatial scales. The in-plane ferroelectricity in NbOX2 was investigated using transport and piezoresponse force microscopy (PFM) measurements, where it was observed that NbOCl2 has a stronger ferroelectric order than NbOI2. A high local field, exerted by both PFM and scanning tunneling microscopy (STM) tips, was found to induce 1D collinear ferroelectric strips in NbOCl2. STM imaging reveals the unreconstructed atomic structures of NbOX2 surfaces, and scanning tunneling spectroscopy was used to probe the electronic states induced at defect (vacancy) sites.

Atomistic Origins of Reversible Noncatalytic Gas-Solid Interfacial Reactions.

Noncatalytic gas-solid reactions are a large group of heterogeneous reactions that are usually assumed to occur irreversibly because of the strong driving force to favor the forward direction toward the product formation. Using the example of Ni oxidation into NiO with CO2, herein, we demonstrate the existence of the reverse element that results in the NiO reduction from the countering effect of the gaseous product of CO. Using in situ electron microscopy observations and atomistic modeling, we show that the oxidation process occurs via preferential CO2 adsorption along step edges that results in step-flow growth of NiO layers, and the presence of Ni atoms on the flat NiO surface promotes the nucleation of NiO layers. Simultaneously, the NiO reduction happens via preferential step-edge adsorption of CO that leads to the receding motion of atomic steps, and the presence of Ni vacancies in the NiO surface facilitates the CO-adsorption-induced surface pitting. Temperature and CO2 pressure effect maps are constructed to illustrate the spatiotemporal dynamics of the competing NiO redox reactions. These results demonstrate the rich gas-solid surface reaction dynamics induced by the coexisting forward and reverse reaction elements and have practical applicability in manipulating gas-solid reactions via controlling the gas environment or atomic structure of the solid surface to steer the reaction toward the desired direction.

Toward In Situ Atomistic Design of Catalytic Active Sites via Controlled Atmosphere Transmission Electron Microscopy

ConspectusHeterogeneous catalysts are widely used in a variety of industrial fields, including environmental protection, energy conversion, and chemical production. Their performance during reactions is usually determined by a small fraction of sites at the catalyst surfaces/interfaces, namely, the active sites. Actually, since the concept of the “active sites” was proposed by Hugh Taylor in the 1920s, determining the active site at the atomic level and understanding the molecular processes that happened at the active site have become the top priority in catalysis research. Researchers tried different methods to acquire various information related to the surface/interface active sites, pursuing their rational design at the atomic level. Although great achievements have been made in catalyst surface study, in situ atomistic design of active sites remains challenging, due to the lack of direct information and effective manipulation means concerning the active sites. Specifically, many critical issues regarding the active sites under reaction conditions remain to be solved: (1) precisely identifying the active sites, which is the foundation for understanding the catalytical mechanism and rational design of the catalyst; (2) accurately manipulating the surface/interface active sites at the atomic scale, which is the basis for realizing the desired performance; (3) maintaining these designed active sites operating in a long-term with high efficiency without deactivation, which is extremely important to the practical applications of the catalysts. All these aspects rely on the fundamental understanding of the interactions between different surface/interface configurations of the catalyst and external environments (gas, pressure, temperature, etc.).In this Account, we present the recent progress in our group on the studies of surface/interface active sites via controlled atmosphere transmission electron microscopy (CATEM). We first briefly introduce the advances in CATEM technologies, including the window (closed) approach and aperture (open) approaches. Then, the challenge of identifying active sites is discussed, and our efforts in this target by determining surface atomic structures, tracking the active components, visualizing reacting molecules, and in situ evaluating catalytic performance are demonstrated. The next section focuses on the in situ manipulating active sites by controlling external environmental factors (e.g., gas, temperature, and pressure), including tailoring the catalyst shape, surface components, and interface with atomic precision. The fourth section discusses the strategies for the long-term stable operation of the active sites based on our in situ studies in understanding the deactivation mechanisms. In the end, we provide our perspectives on the future opportunities and some scientific and technical challenges in this booming area. This Account highlights the in situ atomic level design of the active sites based on the CATEM route, which provides an applicable strategy for deep understanding and the rational design of the catalyst active sites.