Neighboring Oxygen Research Articles

Tuning the local electronic structure of oxygen vacancies over copper-doped zinc oxide for efficient CO2 electroreduction

Oxygen vacancies in metal oxides can serve as electron trap centers to capture CO 2 and lower energy barriers for the electrochemical CO 2 reduction reaction (CO 2 RR). Under aqueous electrolytes, however, such charge-enriched active sites can be occupied by adsorbed hydrogen (H∗) and lose their effectiveness for the CO 2 RR. Here, we develop an efficient catalyst consisting of Cu-doped, defect-rich ZnO (Cu–ZnO) for the CO 2 RR, which exhibits enhanced CO Faradaic efficiency and current density compared to pristine ZnO. The introduced Cu dopants simultaneously stabilize neighboring oxygen vacancies and modulate their local electronic structure, achieving inhibition of hydrogen evolution and acceleration of the CO 2 RR. In a flow cell test, a current density of more than 45 ​mA ​cm −2 and a CO Faradaic efficiency of > 80% is obtained for a Cu–ZnO electrocatalyst in the wide potential range of −0.76 ​V to −1.06 ​V vs. Reversible Hydrogen Electrode (RHE). This work opens up great opportunities for dopant-modulated metal oxide catalysts for the CO 2 RR. • A low-valence Cu-doping strategy is proposed to tune the local electronic structure of oxygen vacancies in ZnO. • The tuned local electronic structure of oxygen vacancies can weaken the adsorption of H∗ and optimize the affinity for CO∗. • The Cu-doped and defect-rich ZnO exhibits enhanced CO Faradaic efficiency and current density compared to pristine ZnO.

Introducing Brønsted acid sites to accelerate the bridging-oxygen-assisted deprotonation in acidic water oxidation

Oxygen evolution reaction (OER) consists of four sequential proton-coupled electron transfer steps, which suffer from sluggish kinetics even on state-of-the-art ruthenium dioxide (RuO2) catalysts. Understanding and controlling the proton transfer process could be an effective strategy to improve OER performances. Herein, we present a strategy to accelerate the deprotonation of OER intermediates by introducing strong Brønsted acid sites (e.g. tungsten oxides, WOx) into the RuO2. The Ru-W binary oxide is reported as a stable and active iridium-free acidic OER catalyst that exhibits a low overpotential (235 mV at 10 mA cm−2) and low degradation rate (0.014 mV h−1) over a 550-hour stability test. Electrochemical studies, in-situ near-ambient pressure X-ray photoelectron spectroscopy and density functional theory show that the W-O-Ru Brønsted acid sites are instrumental to facilitate proton transfer from the oxo-intermediate to the neighboring bridging oxygen sites, thus accelerating bridging-oxygen-assisted deprotonation OER steps in acidic electrolytes. The universality of the strategy is demonstrated for other Ru-M binary metal oxides (M = Cr, Mo, Nb, Ta, and Ti).

Adsorption of toxic and non-toxic metals with new model of CX[4]: Experimental and computational investigation, Spectroscopic, QTAIM, and Antibacterial activity analyses

• New models of adsorption of cations are determined. • Electronic properties and the charge transfer were evaluated. • The interactions between cations and AC-CX[4] are performed using QTAIM theory. • AC-CX[4]-Eu 3+ has checked for a biological application. The presence of toxic metals in the environment is a big problem because it can be harmful to human health. Consequently, it is necessary to control the percentage of metals (for example, magnesium) in human body. In this paper, a very efficient model was proposed to detect the toxic or know the presence of the non-toxic metals at the same time. The selected models are capable of adsorbing cations in all active sites, even if they are present in different positions. The structural stability, adsorption sites and charge transfer have been investigated. The models, where all adsorption sites are filled involving azo-ethoxycarbonylmethoxy-calix[4]arene-X 2+,3+ (Pb, Cd, Mg, and Eu), are stable and selective for toxic or non-toxic cations. The Hirshfeld surfaces (HS) have been computed at the active sites, where Mg 2+ , Pb 2+ and Cd 2+ cations are adsorbed. Theoretical and experimental investigations of the luminescence properties have demonstrated that when adding the three cations in the acceptor sites a very high charge transfer is observed, indicating that the compound is well selective for the three cations. According to the QTAIM theory, a toxic or non-toxic metal may be fixed through strong hydrogen bonding interactions between the guest and its neighboring oxygen atoms. The molecular docking simulation showed that the most stable system azo-ethoxycarbonylmethoxy-CX[4]-Eu 3+ exhibits a potential anti-bacterial activity.

On-line optical absorption of electron-irradiated yttria-stabilized zirconia

The kinetics of color-center formation and decay in electron-irradiated cubic yttria-stabilized zirconia (ZrO 2 : Y 3+ ) has been followed by on-line UV/Vis absorption spectroscopy. The growth and decay with time of absorption spectra have been measured upon electron irradiation and subsequent beam shut-off for energies of 0.8, 1.0, 1.75, and 2.5 MeV. Spectra have been fitted with two broad absorption bands centered at about 3.0 eV and 3.8 eV for high beam current intensity. These bands are assigned to so-called T-centers, i.e. Zr 3+ ions in trigonal point symmetry, which are produced by ionization processes induced by either photon irradiation or charged particle irradiation. A red-shift of the absorption spectra is observed for lower current intensities irrespective of electron energy: these spectra have been fitted with two broad absorption bands centered at about 3.0 eV and 3.3 eV. This modification is attributed to a change in the local environment of Zr 3+ ions due to the formation of neighboring oxygen vacancies by elastic collisions, which depends on the electron energy and flux. A common behavior of an increase in differential absorbance to similar saturation values after accumulation of the irradiation dose and decays with time to similar non-zero asymptotic values has been observed, irrespective of the electron energy and flux. However, the rise time and lifetime deduced from the growth and decay curves of the absorbance are dependent on the electron energy. The increase and saturation of the T-center growth rate with electron energy can be attributed to competitive channels of hole trapping at the oxygen and zirconium vacancies induced by elastic collisions. The present on-line experiments reveal the complex process of point-defect generation resulting from the interplay of displacement damage and electronic excitation. • Color centers induced by electron irradiation in yttria-stabilized zirconia (ZrO 2 : Y) single crystals is studied by on-line optical absorption spectroscopy in the UV–visible range. • Point-defect growth and decay is followed for electron energies ranging between 0.8 and 2.5 MeV. • Absorption bands near 3.3 eV are assigned to the so-called T-center, i.e. Zr 3+ ions in a trigonal point symmetry induced by electronic excitations. • The increase of the T-center growth rate versus electron energy is correlated with the free hole trapping on the Zr and O vacancies induced by elastic collisions.

Characterization of Y and Mn co-substituted BaZrO3 ceramics: Material properties as a function of the substituent concentration

Innovations in materials science are the key element for solving technological challenges. Various energy and environmental applications require designing materials with tailored compositions, microstructures and specific target-oriented performance. Y and Mn co-substituted BaZrO 3 , e.g. BaZr 0.85 Y 0.15 Mn 0.05 O 3-δ , has previously attracted attention as a membrane material for H 2 separation from gas mixtures due to its mixed proton-electron conductivity leading to appreciable levels of H 2 -flux at elevated temperatures and its good thermo-chemical stability under reducing environments. In the present work, we developed ceramic materials within the BaZr 0.8 Y 0.2-x Mn x O 3-δ series, where x = 0.02–0.15. The study of their functional properties in dependence of the Y-to-Mn ratio disclosed that thermal expansion and hydration decrease by increasing the Mn content as well as the total electrical conductivity. In addition to that, XPS analysis and near edge X-ray absorption fine structure spectra (NEXAFS) in the vicinity of O K-edge and Mn L 2,3 -edges indicated that the Mn atoms oxidation state in the surface and in the bulk range from Mn 2+ to Mn 4+ depending on the ambient conditions that can be encountered in MPEC electrodes, which it is suggested to be related with a hydration mechanism mediated by Mn oxidation and subsequent proton attachment to oxygen neighbors, similar to LSM. • Y and Mn co-substituted BaZrO 3 forms single cubic perovskites form up to 10 mol% of Mn. • Mn plays a role as a sintering aid, optimized for a 5 mol% Mn. • Better hydration behavior, respectively proton conductivity, is observed for materials with closer composition to BZY (as BZYM2). • XPS and NEXAFS disclosed that the majority of surface Mn in BZYM10 is present as Mn 2+ , while different oxidation states contributing to the electronic transport are ascertained in the bulk. • Mn substituted BZY materials are compatible with other cell components, although exposure to acid gases as CO, CO 2 form Ba carbonates.

Highly efficient synthesis of unsymmetrical organic carbonates from alcohols and diethyl carbonate over mesoporous carbon-supported MgO catalysts

• Mesoporous carbon (MC) supported MgO catalysts were prepared by impregnation method. • MgO are highly dispersed on the surface of MC through metal-support interaction. • MgO/MC can efficiently catalyze transesterification of diethyl carbonates with alcohols. • Various unsymmetrical organic carbonates can be obtained at ambient temperature. • MgO/MC exhibit high stability and recyclability for transesterification reaction. Transesterification of dialkyl carbonate with various alcohols is a very attractive route for synthesizing unsymmetrical organic carbonates. Intensive efforts have been focused on developing highly active and stable heterogeneous catalysts that can efficiently catalyze the transesterification reaction at mild conditions. In this work, the synthesis of unsymmetrical organic carbonates was conducted over a series of mesoporous carbon-supported MgO (MgO/MC) catalysts. The composition-optimized MgO/MC catalyst exhibited remarkably high activity, selectivity and stability for the transesterification of diethyl carbonates with various alcohols at the commonly used reaction temperature of 125 °C, and could even work well at ambient temperature. The uniformly dispersed MgO species should be the main active sites for the transesterification reaction, while the neighboring oxygen- and nitrogen-containing groups existed on the surface of MC support may also play positive role in synergistically activating the reagents, thus leading to efficient production of the corresponding unsymmetrical organic carbonates at very mild conditions.

Strong electronic interaction of indium oxide with palladium single atoms induced by quenching toward enhanced hydrogenation of nitrobenzene

The realization of efficient and fully controllable synthesis of single atom catalysts is an exciting frontier, yet still challenging in the modern catalysis field. Here we describe a straightforward high-temperature quenching approach to precisely construct isolated palladium atoms supported over cubic indium oxide, with individual palladium atoms coordinated with four neighboring oxygen atoms. This palladium catalyst achieves exceptional catalytic efficiency in the selective hydrogenation of nitrobenzene to aniline, with more than 99% chemoselectivity under almost 100% conversion. Moreover, it delivers excellent recyclability, anti-CO poisoning ability, storage stability, and substrate tolerance. DFT calculations further reveal that the high catalytic activity stems from the optimized electronic structure and the charge states of palladium atoms in the defect-containing indium oxide. Our findings provide an effective approach to engineering single atom catalysts at the atomic level and open the door to a wide variety of catalytic reactions. • Pd single atoms supported over In 2 O 3 was created by a quenching approach. • DFT calculations reveal the support can provide anchoring sites for Pd atoms. • This catalyst shows high catalytic efficacy in hydrogenation of nitrobenzene. • The high catalytic activity stems from the unique coordination environment.

Reversible dehydrogenation and rehydrogenation of cyclohexane and methylcyclohexane by single-site platinum catalyst

Developing highly efficient and reversible hydrogenation-dehydrogenation catalysts shows great promise for hydrogen storage technologies with highly desirable economic and ecological benefits. Herein, we show that reaction sites consisting of single Pt atoms and neighboring oxygen vacancies (VO) can be prepared on CeO2 (Pt1/CeO2) with unique catalytic properties for the reversible dehydrogenation and rehydrogenation of large molecules such as cyclohexane and methylcyclohexane. Specifically, we find that the dehydrogenation rate of cyclohexane and methylcyclohexane on such sites can reach values above 32,000 molH2 molPt−1 h−1, which is 309 times higher than that of conventional supported Pt nanoparticles. Combining of DRIFTS, AP-XPS, EXAFS, and DFT calculations, we show that the Pt1/CeO2 catalyst exhibits a super-synergistic effect between the catalytic Pt atom and its support, involving redox coupling between Pt and Ce ions, enabling adsorption, activation and reaction of large molecules with sufficient versatility to drive abstraction/addition of hydrogen without requiring multiple reaction sites.

Unraveling the State of Charge-Dependent Electronic and Ionic Structure–Property Relationships in NCM622 Cells by Multiscale Characterization

LiNi0.6Co0.2Mn0.2O2 (NCM622) undergoes crystallographic and electronic changes when charging and discharging, which drive the cathode material close to or even beyond its stability window. To unravel the charge compensation mechanism of NCM622, spatially resolved atomic force microscopy (AFM) measurements in electrochemical strain microscopy (ESM) and conductive AFM (C-AFM) modes are obtained, and the spectroscopic information and crystallographic information are compared. All experiments are performed with two sets of samples: state-of-the-art samples that are composed of a binder, a conductive additive, and an active material and polished samples for single-particle analysis. Near-edge X-ray absorption fine structure spectroscopy shows that ionic Ni2+ reacts to give Ni3+ when charging and forms covalent bonds with its oxygen neighbors. A Ni2+/Ni3+ gradient across the particles balances out with the increasing state of charge, as verified by ESM. Therefore, the results also provide an important view that improves the mechanistic understanding of ESM in electrode materials. Finally, the interplay between the electronic and ionic conductivities and the crystallinities of NCM622 cathodes is elaborated and discussed.

In English

By the method of density functional theory with exchange-correlation functional B3LYP and basis set 3‑21G (d), the structural and energy characteristics have been considered of the molecular models of SnO2 nanoclusters of different size and composition with the number of Sn atoms from 1 to 10. Incompletely coordinated surface tin atoms were terminated by hydroxyl groups. It has been shown that the Sn–O bond length in nanoclusters does not depend on the cluster size and on the coordination number of Sn atoms, but is determined by the coordination type of neighboring oxygen atoms. Namely, the bond length Sn–O(3) (@ 2.10 Å) is greater than that of Sn–O (2) (@ 1.98 Å). The calculated values of Sn–O (3) bond lengths agree well with the experimental ones for crystalline SnO 2 samples (2.05 Å). The theoretically calculated width of the energy gap decreases naturally with increasing cluster size (from 6.14 to 3.46 eV) and approaches the experimental value of the band gap of the SnO 2 crystal (3.6 eV). The principle of additivity was used to analyze the energy characteristics of the considered models and to estimate the corresponding values for a cassiterite crystal. According to this principle, a molecular model can be represented as a set of atoms or atomic groups of several types that differ in the coordination environment and, therefore, make different contributions to the total energy of the system. The calculated value of the atomization energy for SnO2 is 1661 kJ/mol and corresponds satisfactorily to the experimentally measured specific atomization energy of crystalline SnO2 (1381 kJ/mol). It has been shown that a satisfactory reproduction of the experimental characteristics of crystalline tin dioxide is possible when using clusters containing at least 10 state atoms, for example, (SnO2)10×14H2O.

IR-Spectroscopic Study of Complex Formation of Nitrogen Oxides (NO, N2O) with Cationic Forms of Zeolites and the Reactivity of Adsorbed Species in CO and CH4 Oxidation.

The formation of complexes and disproportionation of nitrogen oxides (NO, N2O) on cationic forms of LTA, FAU, and MOR zeolites was investigated by diffuse-reflectance IR spectroscopy. N2O is adsorbed on the samples under study in the molecular form and the frequencies of the first overtone of the stretching vibrations ν10–2 and the combination bands of the stretching vibrations with other vibrational modes for N2O complexes with cationic sites in zeolites (ν30–1 + ν10–1, ν10–1 + δ0–2) are more significantly influenced by the nature of the zeolite. The presence of several IR bands in the region of 2400–2600 cm−1 (the ν10–1 + δ0–2 transitions) for different zeolite types was explained by the availability of different localization sites for cations in these zeolites. The frequencies in this region also depend on the nature of the cation (its charge and radius). The data can be explained by the specific geometry of the N2O complex formed, presumably two-point adsorption of N2O on a cation and a neighboring oxygen atom of the framework. Adsorption of CO or CH4 on the samples with preliminarily adsorbed N2O at 20–180 °C does not result in any oxidation of these molecules. NO+ and N2O3 species formed by disproportionation of NO are capable of oxidizing CO and CH4 molecules to CO2, whereas NOx is reduced simultaneously to N2 or N2O. The peculiarities in the behavior of cationic forms of different zeolites with respect to adsorbed nitrogen oxides determined by different density and localization of cations have been established.

Harnessing Intramolecular Chalcogen-Chalcogen Bonding in Merocyanines for Utilization in High-Efficiency Photon-to-Current Conversion Optoelectronics.

A novel series of donor (D)-π-acceptor (A) merocyanine molecules harnessed with intramolecular chalcogen bonding (ChaB) is designed, synthesized, and characterized. ChaB comprises periodic chalcogen atoms, S, Se, and Te, and a neighboring oxygen atom of a carbonyl moiety. Compared to the D-π-A merocyanine dye with nontraditional intramolecular hydrogen bonding, the novel molecules with an intramolecular ChaB exhibit remarkably smaller absorption spectral widths and higher absorption coefficients attributed to their cyanine-like characteristics approaching the resonance parameter (c2) ∼0.5; furthermore, they exhibit better thermal stabilities and electrical charge-carrier transport properties in films. These novel D-π-A merocyanines harnessed with intramolecular ChaB networks are successfully utilized in high-performance color-selective organic photon-to-current conversion optoelectronic devices with excellent thermal stabilities. This study reports that the unique intramolecular ChaB plays an essential role in locking the molecular conformation of merocyanine molecules and enhancing the optical, thermal, and optoelectronic properties of high-performance and high-efficiency organic photon-to-current conversion devices.

Bayesian sparse modeling of extended x-ray absorption fine structure to determine interstitial oxygen positions in yttrium oxyhydride epitaxial thin film

This article presents a Bayesian sparse modeling method to analyze extended x-ray absorption fine structure (EXAFS) data with basis functions built on two-body signals. This method does not require any structural model and allows us to evaluate regression coefficients proportional to the radial distribution functions of the respective elements and their errors and is very effective for analysis of EXAFS with weak absorption intensity and severe signal-to-noise ratios. As an application example, we used it to analyze the EXAFS of an yttrium oxyhydride (YOxHy) epitaxial thin film. These EXAFS data show weak absorption intensity and a severe signal-to-noise ratio due to the small amount of x-ray absorption in the thin film sample. However, this approach revealed that the radial distance ratio of the second neighbor yttrium to the first neighbor oxygen coincides with that of a tetrahedral configuration. This result demonstrates that the interstitial oxygen position is tetrahedral in the YOxHy thin film.

Hydrogen Bonds Dominate Brønsted Acid Sites in Zeolite SSZ-42: A Classification of Their Diversity.

The zeolite catalyst SSZ‐42 shows a remarkable high abundance (≈80 %) of hydrogen‐bonded Brønsted acid sites (BAS), which are deshielded from the 1H chemical shift of unperturbed BAS at typically 4 ppm. This is due to their interaction with neighboring oxygen atoms in the zeolite framework when oxygen alignments are suitable. The classification and diversity of hydrogen bonding is assessed by DFT calculations, showing that oval‐shaped 6‐rings and 5‐rings allow for a stronger hydrogen bond to oxygen atoms on the opposite ring side, yielding higher experimental chemical shifts (δ (1H)=6.4 ppm), than circular 6‐rings (δ(1H)=5.2 ppm). Cage‐like structures and intra‐tetrahedral interactions can also form hydrogen bonds. The alignment of oxygen atoms is expected to impact their role in the stabilization of intermediates in catalytic reactions, such as surface alkoxy groups and possibly transition states.

Effect of a long-term exposure of anatase TiO2 powder doped with surface-located Sb3+ ions to UV radiation on its photocatalytic activity

Ultraviolet photocatalytic experiments on the kinetics of decolorization of methyl orange and the 121 Sb Mössbauer characterization of the title catalyst were performed. The stereochemically active electronic lone pair of Sb 3+ was found to completely deactivate the neighboring oxygen vacancy as a recombination center towards the photogenerated electrons and holes.

Formation of a macrocycle from di-chloro-dimethyl-silane and a pyridoxalimine Schiff base ligand.

The reaction of di-chloro-dimethyl-silane with a polydentate Schiff base ligand derived from pyridoxal and 2-ethano-lamine yielded the macrocyclic silicon compound (8E,22E)-4,4,12,18,18,26-hexa-methyl-3,5,17,19-tetra-oxa-8,13,22,27-tetra-aza-4,18-disilatri-cyclo-[22.4.0.010,15]octa-cosa-1(24),8,10,12,14,22,25,27-octa-ene-11,25-diol, C24H36N4O6Si2. The asymmetric unit contains the half macrocycle with an intra-molecular O-H⋯N hydrogen bond between the imine nitro-gen atom and a neighbouring oxygen atom. The crystal structure is dominated by C-H⋯O and C-H⋯π inter-actions, which form a high ordered mol-ecular network.

Structure of silver molybdate glasses by X-ray and neutron diffraction

• (Ag 2 O) x (MoO 3 ) 1-x glasses of 0.2 ≤ x ≤ 0.4 cover the possible compositional range. • The Mo-O coordination numbers N MoO decrease from 5.4 to 4.2 with increasing x . • The strong decrease of N MoO corresponds to a large ratio of non-bridging oxygen/Ag + of ∼2.3. • The sharp Mo-O peak at 0.177 nm is followed by a broad distance distribution (≤0.25 nm). • The bond lengths in MoO 6 indicate that the Mo sites are displaced to octahedral edges. The structure of (Ag 2 O) x (MoO 3 ) 1-x glasses of 0.2 ≤ x ≤ 0.4 is studied by combining X-ray and neutron diffraction which allows separating the Mo-O and Ag-O distances up to r ≤ 0.25 nm. The total Mo-O coordination numbers decrease from 5.4 to 4.2 with increasing x . This strong decrease and the excessive formation of non-bridging oxygen (NBO) require each other. A fixed ratio NBO/O add = 4.6 is a good approximation. Oxygen O add is added with the network-modifier oxide. The distributions of Mo-O distances show a sharp peak at 0.177 nm of three oxygen neighbors that is followed of a broad distribution with one to three more oxygens. Mixtures of MoO 6 , MoO 5 , and MoO 4 are used to model the distance distributions. Their strong broadening is caused by the second-order Jahn-Teller effects in the MoO 6 octahedra with out-of-center displacements of the Mo sites preferably to edges.

Structural, Spectroscopic, Antiferromagnetic and in vitro antiproliferative studies of copper (II) pyrophosphate complex against Human breast cancer cell lines

• Structural studies. • Antiferromagnetic interactions. • Human breast cancer cell lines. • Cytotoxicity studies. In purpose to search for compounds of biological interest, we have succeeded in synthesizing a copper complex with polypyridine ligands. The architecture of the compound consists of O, N-donor entities, the pyrophosphate anion HP 2 O 7 3− and the two heterocyclic molecules, 1,10-phenanthroline and 2,2′-bipyridine. X-ray diffraction study proves that our compound crystallizes in a monoclinic cell of space group P2 1 /n. The atomic arrangement can be described by the aggregation of [(C 10 H 8 N 2 )(C 12 H 10 N 2 )Cu 2 (H 2 O) 2 (HP 2 O 7 )] + cation, which contributes to the macrocyclic compound-complex. The second sphere of the cationic complex is localized the anion ClO 4 − to complete the neutrality. Magnetic studies show an antiferromagnetic coupling exchange between metal copper ions which mediated throw neighboring oxygen atom belonging from the pyrophosphate anion. The biological antiproliferative activity of the sample shows a relatively high cytotoxicity IC50 respectively toward MCF-7 breast cancer cell lines.

Superconductivity in the three-band model of cuprates: nodal direction characteristics and influence of intersite interactions

The three-band Emery model is applied to study the selected principal features of the d-wave superconducting phase in the copper-based compounds. The electron–electron correlations are taken into account by the use of the diagrammatic expansion of the Guztwiller wave function (DE-GWF method). The nodal Fermi velocity, Fermi momentum, and effective mass are all determined in the paired state and show relatively good agreement with the available experimental data, as well as with the corresponding single-band calculations. Additionally, the influence of the next-nearest neighbor oxygen–oxygen hopping and intersite Coulomb repulsion terms on the superconducting phase is analyzed.

Insights into the Mechanism of Methanol Steam Reforming Tandem Reaction over CeO2 Supported Single-Site Catalysts.

We demonstrated how the special synergy between a noble metal single site and neighboring oxygen vacancies provides an "ensemble reaction pool" for high hydrogen generation efficiency and carbon dioxide (CO2) selectivity of a tandem reaction: methanol steam reforming. Specifically, the hydrogen generation rate over single site Ru1/CeO2 catalyst is up to 9360 mol H2 per mol Ru per hour (579 mLH2gRu-1s-1) with 99.5% CO2 selectivity. Reaction mechanism study showed that the integration of metal single site and O vacancies facilitated the tandem reaction, which consisted of methanol dehydrogenation, water dissociation, and the subsequent water gas shift (WGS) reaction. In addition, the strength of CO adsorption and the reaction activation energy difference between methanol dehydrogenation and WGS reaction play an important role in determining the activity and CO2 selectivity. Our study paves the way for the further rational design of single site catalysts at the atomic scale. Furthermore, the development of such highly efficient and selective hydrogen evolution systems promises to deliver highly desirable economic and ecological benefits.