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Oxygen vacancy (Ov) as well as Ov migration in metal oxide are of great importance in structural evolution of active center in single-atom catalysts (SACs). Here, the interplay between invasive single Pt atom and native Ov in SA-Pt/rutile TiO2(110) surface, as well as their synergetic effect on water dissociation are investigated by density functional theory (DFT) calculations. We show that importing Pt atom as Pt-ads, Pt2c, Pt5c and Pt6c modes could decelerate the Ov migration effectively, especially in Pt6c mode. Under oxygen-rich conditions, Pt6c substitution could make oxygen Ov formation easier, but migration harder. On Pt6c/Ti1−yO2−x1(110) surface, as a bimetal center, Pt4c-Ti5c concave could not make water dissociation process easier; however, the O2c closed to Pt become a good proton acceptor to make water dissociation on Ti5c-O2c more convenient with the aid of topmost Ti5c.

Oxygen evolution reaction (OER) still suffers from the bottleneck in electrocatalytic water splitting. Herein, in virtue of volcano plots drawn by theoretical calculation, the (001) facet was screened as the superb facet of orthorhombic CoSe2 for OER. Afterwards, CoSe2(001) nanosheets were synthesized and the exposure ratio of (001) facet is controllable with thermodynamics methods effectively. The single-facet CoSe2(001) delivered an overpotential as low as 240 mV at 10 mA·cm−2 in 1 M KOH, which outperformed the bulk (380 mV) as well as other CoSe2-base OER catalysts reported before. Especially, a shorter Co-Co path was observed in CoSe2(001) by X-ray absorption spectroscopy. Further density functional theory (DFT) studies revealed that the reversible compression on the shorter Co-Co path could regulate the electronic structure of active sites during the OER process, and thus the energy barrier of the rate-determining step was reduced by 0.15 eV. This work could inspire more insights on the modification of electronic structure for OER electrocatalysts.

In this manuscript, ruthenium (Ru) nanoparticles functionalized with nitrene ligands through the ruthenium-nitrene (Ru N) π bonds are explored. By synthesizing the nitrene ligands with and without 15N-labelling, Ru N π bonds on Ru nanoparticles are evidenced by experimental and theoretically calculated FTIR spectra. The coordination of nitrene ligands on Ru nanoparticles surface, the interfacial charge delocalization and the impact of nitrene ligands on the catalytic performance of Ru nanoparticles are further characterized by magic-angle spinning solid-state carbon nuclear magnetic resonance spectroscopy (13C NMR) of 13CO-adsorbed Ru nanoparticles, photoluminescence and the hydrogenation of styrene.

The oxidation of hydrocarbons to produce high value-added compounds (ketones or alcohols) using oxygen in air as the only oxidant is an efficient synthetic strategy from both environmental and economic views. Herein, we successfully synthesized cobalt single atom site catalysts (Co SACs) with high metal loading of 23.58 wt.% supported on carbon nitride (CN), which showed excellent catalytic properties for oxidation of ethylbenzene in air. Moreover, Co SACs show a much higher turn-over frequency (19.6 h−1) than other reported non-noble catalysts under the same condition. Comparatively, the as-obtained nanosized or homogenous Co catalysts are inert to this reaction. Co SACs also exhibit high selectivity (97%) and stability (unchanged after five runs) in this reaction. DFT calculations reveal that Co SACs show a low energy barrier in the first elementary step and a high resistance to water, which result in the robust catalytic performance for this reaction.

Oxygen-involved electrochemical reactions are crucial for plenty of energy conversion techniques. Herein, we rationally designed a carbon-based Mn-N2C2 bifunctional electrocatalyst. It exhibits a half-wave potential of 0.915 V versus reversible hydrogen electrode for oxygen reduction reaction (ORR), and the overpotential is 350 mV at 10 mA cm-2 during oxygen evolution reaction (OER) in alkaline condition. Furthermore, by means of operando X-ray absorption fine structure measurements, we reveal that the bond-length-extended Mn2+-N2C2 atomic interface sites act as active centers during the ORR process, while the bond-length-shortened high-valence Mn4+-N2C2 moieties serve as the catalytic sites for OER, which is consistent with the density functional theory results. The atomic and electronic synergistic effects for the isolated Mn sites and the carbon support play a critical role to promote the oxygen-involved catalytic performance, by regulating the reaction free energy of intermediate adsorption. Our results give an atomic interface strategy for nonprecious bifunctional single-atom electrocatalysts.

The regulation of catalytic activity in the oxygen reduction reaction (ORR) is significant to the development of metal–air batteries and other oxygen involving energy conversion devices. Herein, we propose an atomic interface strategy to construct a single atom copper catalyst (denoted as Cu-SA/SNC) which exhibits enhanced ORR activity with a half-wave potential of 0.893 V vs. RHE in alkaline media. Moreover, synchrotron-radiation-based X-ray absorption fine structure (XAFS) investigations together with density functional theory (DFT) calculations reveal that the isolated bond-shrinking low-valence Cu (+1)–N4–C8S2 atomic interface moiety serves as an active site during the ORR process, and the synergistic mechanism between the Cu species and the carbon matrix at the atomic interface plays a critical role in boosting the ORR efficiency, by adjusting the reaction free energy of intermediate adsorption. This atomic interface concept may provide an alternative methodology for the rational design of advanced oxygen electrode materials and new probability to improve their catalytic performance.

Single-atomic-site (SAS) catalysts, a new frontier of catalysts, always show extremely high atom efficiency and unexpected catalytic properties. Herein, a pyrolyzing coordinated polymer (PCP) strategy is developed, which is facile and widely applicable in the synthesis of a series of SAS catalysts including SAS-Fe, SAS-Ni, SAS-Cu, SAS-Zn, SAS-Ru, SAS-Rh, SAS-Pd, SAS-Pt, and SAS-Ir. The as-obtained SAS catalysts can be easily synthesized at gram scale and the metal loading of SAS-Fe catalysts achieves a record value of 30 wt%, which meets the requirement of practical applications. Moreover, it is discovered that SAS-Fe catalysts show unprecedented catalytic performance for epoxidation of styrene using O2 as the only oxidant (yield: 64%; selectivity: 89%), while Fe nanoparticles and ironporphyrin are inactive. This discovery is believed to pave the way for exploiting the unparalleled properties of SAS catalysts and promoting their industrial applications.

Recently, ambient electrochemical N2 fixation has gained great attention. However, the commercial Pt-based electrocatalyst hardly shows its potential in this field. Herein, it is found that the isolated Pt sites anchored on WO3 nanoplates exhibit the optimum electrochemical NH3 yield rate (342.4 µg h-1 mg-1 Pt ) and Faradaic efficiency (31.1%) in 0.1 m K2 SO4 at -0.2 V versus RHE, which are about 11 and 15 times higher than their nanoparticle counterparts, respectively. The mechanistic analysis indicates that N2 conversion to NH3 follows an alternating hydrogenation pathway, and positively charged isolated Pt sites with special Pt-3O structure can favorably chemisorb and activate the N2 . Furthermore, the hydrogen evolution reaction can be greatly suppressed on isolated Pt sites decorated WO3 nanoplates, which guarantees the efficient going-on of nitrogen reduction reaction.

Development of single-site catalysts supported by ultrathin two-dimensional (2D) porous matrix with ultrahigh surface area is highly desired but also challenging. Here we report a cocoon silk chemistry strategy to synthesize isolated metal single-site catalysts embedded in ultrathin 2D porous N-doped carbon nanosheets (M-ISA/CNS, M = Fe, Co, Ni). X-ray absorption fine structure analysis and spherical aberration correction electron microscopy demonstrate an atomic dispersion of metal atoms on N-doped carbon matrix. In particular, the Co-ISA/CNS exhibit ultrahigh specific surface area (2105 m2 g−1) and high activity for C–H bond activation in the direct catalytic oxidation of benzene to phenol with hydrogen peroxide at room temperature, while the Co species in the form of phthalocyanine and metal nanoparticle show a negligible activity. Density functional theory calculations discover that the generated O = Co = O center intermediates on the single Co sites are responsible for the high activity of benzene oxidation to phenol.

The enhanced works of separation for the low adhesive (0 0 0 1)ZnO|(1 1 1)ZrO2 interfacess via Y-doping in ZnO slab were systematically studied using data-mining technique and density functional theory (DFT) study. The lattice constants in 31 types of doped wurtzite Zn0.9375X0.0625O were evaluated from DFT calculations. No linear correlation is found between the lattice constants and atomic radii. A support vector regression (SVR) for the lattice constants of 32 Zn0.9375X0.0625O has been performed. SVR method with leave-one-out cross-validation is used for evaluating the regression models. The correlation coefficient obtained by the models was 0.905. The accuracy of SVR model was higher than those of artificial neural network (ANN) and partial least square (PLS) methods. Zn0.9375Y0.0625O has the largest lattice constants among the investigated systems. In Y-ZnO(0 0 0 1) surface, a significant segregation phenomena occurs. Hence, dopant Y expands the lateral lattice and leaves the Zn-terminal surface intact. For coherent (0 0 0 1)Y-ZnO|(1 1 1)ZrO2 interfaces, Y-doping can enhance the work of separation significantly (∼82%) compared with the undoped (0 0 0 1)ZnO|(1 1 1)ZrO2 interfaces.

In-depth understanding of interfacial adhesive properties is required to access the long-term performance of substrate-film structures. The ZnO|ZrO 2 (or ZnO|YSZ) interfaces are of widely interests in experiments, however, the study on their adhesive strength is rare. Works of separation for (0 0 0 1)ZnO|(1 1 1)ZrO 2 interfaces have been investigated by using density functional calculations. Four coherent interface configurations were calculated to clarify the influence of atom termination and stacking sequence on the interfacial strength. The coherent interface model indicates that the small values for the work of separation are attributed to the large lattice mismatch between two slabs. Among the four configurations, interface model with Zr ZrO2 -O ZrO2 ⋯O ZnO B -Zn ZnO β stacking sequence has the largest work of separation, followed by the model with Zr ZrO2 -O ZrO2 ⋯Zn ZnO β -O ZnO B stacking sequence. We also construct “semicoherent interface” models to investigate the effect of strain. The Zr ZrO2 -O ZrO2 ⋯O ZnO B -Zn ZnO β sequence brings in some direct electrostatically repulsive anion-anion interactions across the interface, which causes significant distortion for the interface, especially on ZnO slab. Based on the “semicoherent interface” model with Zr ZrO2 -O ZrO2 ⋯Zn ZnO β -O ZnO B sequence, we elucidate that the interfacial adhesive strength for (0 0 0 1)ZnO|(1 1 1)ZrO 2 interface is very low.

For guidance for developing Fe/Co-Sn-based anode materials for lithium-ion batteries, the mechanical, thermodynamic and electronic properties of FeSn5 and CoSn5 intermetallic phases under pressures ranging from 0 to 30 GPa have been investigated systematically using first-principles total-energy calculations within the framework of the generalized gradient approximation. The pressure was found to have significant effects on the mechanical, thermodynamic and electronic properties of these compounds. In the selected pressure range, CoSn5 has a more negative formation enthalpy than FeSn5. Based on the calculated elastic constants, the bulk modulus, shear modulus, and Young’s modulus were determined via the Viogt-Reuss-Hill averaging scheme. The variations of specific heats at constant volume for FeSn5 and CoSn5 in a wide pressure (0 - 30 GPa) and temperature (0 - 1000 K) range are also predicted from phonon density of states calculation. The calculated results suggested that both FeSn5 and CoSn5 are mechanically stable at pressure from 0 to 30 GPa. FeSn5 is dynamically stable at pressure up to, 30 GPa, at least, however, CoSn5 is dynamically stable no higher than 15 GPa.

Photoanode material with high efficiency and stability is extensively desirable in photoelectrochemical (PEC) water splitting for green/renewable energy source. Herein, novel heterostructures is constructed via coating rutile TiO2 nanorods with metal organic framework (MOF) materials UiO-66 or UiO-67 (UiO-66@TiO2 and UiO-67@TiO2 ), respectively. The π electrons in the MOF linkers could increase the local electronegativity near the heterojunction interface due to the conjugation effect, thereby enhancing the internal electric field (IEF) at the heterojunction interface. The IEF could drive charge transfer following Z-scheme mechanism in the prepared heterostructures, inducing photogenerated charge separation efficiency increasing as 156% and 253% for the UiO-66@TiO2 and UiO-67@TiO2 , respectively. Correspondingly, the UiO-66@TiO2 and UiO-67@TiO2 enhanced the photocurrent density as approximate two- and threefolds compared with that of pristine TiO2 for PEC water oxidation in universal pH electrolytes. This work demonstrates an effective method of regulating the IEF of heterojunction toward further improved charge separation.

Strain engineering has been a powerful strategy to manipulate the catalytic reaction activity. Here, CO oxidation reaction on Cu2O(1 1 1) surface without and with biaxial strain was investigated with density functional theory. The barriers heights of rate-determining steps (rds) in Mars-van-Krevelen, Langmuir-Hinshelwood and Eley-Rideal mechanism are strain sensitive. Applying strain could tune the performance of CO oxidation on Cu2O(1 1 1) by varying rds barriers heights, while the preferred reaction mechanism would swing between Langmuir-Hinshelwood and Eley-Rideal under particular strain. Furthermore, it is suggested that proper interfacial construction is an effective strategy to introduce suitable strain amplitude to achieve the desired reaction activity.

The effects of invasive single atom Pt on native oxygen vacancy migration in anatase TiO2(1 0 1) surface, as well as their coupling effect on water dissociation are investigated by means of the first-principles calculations based on density functional theory (DFT). Our results show that introducing Pt atom as Pt-ads and Pt5c modes could accelerate the Ov migration effectively. However, the roles of Pt2c and Pt6c are to decelerate the Ov migration. Oxygen-poor condition is beneficial for forming Pt-ads/TiO2-x1(1 0 1) and Pt2c/TiO2-x2(1 0 1), whereas oxygen-rich condition is beneficial for forming Pt5c/Ti1-yO2-x1(1 0 1) and Pt6c/Ti1-yO2-x1(1 0 1). Under their optimal conditions, Pt5c and Pt6c substitutions could make oxygen Ov formation easier, while Pt-adsorption and Pt2c substitution show no effect on Ov formation. The effect of imported Pt atoms mainly applies to the paths where they are involved directly. When Pt substituted either Ti5c or Ti6c, Ov tends to distribute around it and decreases its coordination number to 4 for maintaining a planar coordinated configuration of Pt-O. The adjacent bimetal Pt4c-Ti4c site in Pt6c/TiO2-x(1 0 1) can serve as the active center for water dissociation reaction. These findings can provide a “quasi-dynamic” perspective to understand the catalytic process of single atom supported on metal oxide surfaces.

The mechanical, thermodynamic and electronic properties of FeSn5 and CoSn5 intermetallic phases at zero pressure have been systemically investigated by first-principles calculations using ultrasoft pseudopotential and generalized gradient approximation (GGA). The equilibrium lattice constants of FeSn5 and CoSn5 at zero pressure are in good agreement with the available experimental values. Thermodynamic and mechanical properties of FeSn5 and CoSn5 are predicted by calculating formation enthalpy, phonon density of states and elastic constants, respectively. Formation enthalpies calculation indicates that FeSn5 and CoSn5 are energetically unfavorable compare to FeSn2 and CoSn2. This may be the partial reason why FeSn5 and CoSn5 were hidden in the Fe/Co–Sn phase diagrams previously. FeSn5 and CoSn5 exhibit opposite relative incompressible behavior along a-axis and c-axis. Our results reveal that both FeSn5 and CoSn5 are mechanically and dynamically stable at 0 GPa. The quasi-harmonic model is employed to calculate the temperature dependence of specific heat at constant volume. In addition, the electron density of states and electron density difference are calculated to disclose the underlying electronic structure.

Noble metals play a momentous role in heterogeneous catalysis but still face a huge challenge in selectivity control. Herein, we report isolating contiguous Pt atoms and forming Pt-Zn intermetallic nanoparticles as an effective strategy to optimize the selectivity of Pt catalysts. Contiguous Pt atoms are isolated into single atoms and Pt-Zn intermetallic nanoparticles are formed which are supported on hollow nitrogen-doped carbon nanotubes (PtZn/HNCNT), as confirmed by aberration-corrected high-resolution transmission electron microscopy and X-ray absorption spectrometry measurements. Interestingly, this PtZn/HNCNT catalyst promotes the hydrogenation of 4-nitrophenylacetylene to 4-aminophenylacetylene with a much higher conversion ( > 99%) and selectivity (99%) than the comparison samples with Pt isolated-single-atomic-sites (Pt/HNCNT) and Pt nanoparticles (Pt/CN). Further density functional theory (DFT) calculations disclose that the positive Zn atoms assist the adsorption of nitro group and Pt-Zn intermetallic nanoparticles facilitate the hydrogenation on nitro group kinetically., Noble metals play a momentous role in heterogeneous catalysis but still face a huge challenge in selectivity control. Herein, the authors demonstrate that isolating contiguous Pt atoms and forming Pt-Zn intermetallic nanoparticles is an effective strategy to optimize the selectivity of Pt catalysts.

The hydrosilylation reaction is one of the largest-scale application of homogeneous catalysis and is widely used to enable the commercial manufacture of silicon products. However, considerable issues including disposable platinum consumption, undesired side reactions and unacceptable catalyst residues still remain. Here, we synthesize a heterogeneous partially charged single-atom platinum supported on anatase TiO2 (Pt1δ+/TiO2) catalyst via an electrostatic-induction ion exchange and two-dimensional confinement strategy, which can catalyze hydrosilylation reaction with almost complete conversion and produce exclusive adduct. Density functional theory calculations reveal that unexpected property of Pt1δ+/TiO2 originates from atomic dispersion of active species and unique partially positive charge Ptδ+ electronic structure that conventional nanocatalysts do not possess. The fabrication of single-atom Pt1δ+/TiO2 catalyst accomplishes a reasonable use of Pt through recycling and maximum atom-utilized efficienc...

Tuning the selectivity of metal catalysts is of paramount importance yet a great challenge. A new strategy to effectively control the selectivity of metal catalysts, by tuning the lattice strain, is reported. A certain amount of Co atoms is introduced into Ru catalysts to compress the Ru lattice, as confirmed by aberration-corrected high-resolution transmission electron microscopy (HRTEM) and X-ray absorption fine structure (XAFS) measurements. We discover that the lattice strain of Ru catalysts can greatly affect their selectivity, and Ru with 3 % lattice compression exhibits extremely high catalytic selectivity for hydrogenation of 4-nitrostyrene to 4-aminostyrene compared to pristine Ru (99 % vs. 66 %). Theoretical studies confirm that the optimized lateral compressive strain facilitates hydrogenation of the nitro group but impedes the hydrogenation of the vinyl group. This study provides a new guideline for designing metal catalysts with high selectivity.

Strain regulation has become an important strategy to tune the surface chemistry and optimize the catalytic performance of nanocatalysts. Herein, the construction of atomic-layer IrOx on IrCo nanodendrites with tunable IrO bond length by compressive strain effect for oxygen evolution reaction (OER) in acidic environment is demonstrated. Evidenced from in situ extended X-ray absorption fine structure, it is shown that the compressive strain of the IrOx layer on the IrCo nanodendrites decreases gradually from 2.51% to the unstrained state with atomic layer growth (from ≈2 to ≈9 atomic layers of IrOx ), resulting in the variation of the IrO bond length from shortened 1.94 A to normal 1.99 A. The ≈3 atomic-layer IrOx on IrCo nanodendrites with an IrO bond length of 1.96 A (1.51% strain) exhibits the optimal OER activity compared to the higher-strained (2.51%, ≈2 atomic-layer IrOx ) and unstrained (>6 atomic-layer IrOx ) counterparts, with an overpotential of only 247 mV to achieve a current density of 10 mA cm-2 . Density functional theory calculations reveal that the precisely tuned compressive strain effect balances the adsorbate-substrate interaction and facilitates the rate-determining step to form HOO*, thus assuring the best performance of the three atomic-layer IrOx for OER.