Search

α-pinene is the most abundant monoterpene that represents an important family of volatile organic compounds. Molecular identification of key transient compounds during the α-pinene ozonolysis has been proven to be a challenging experimental target because of a large number of intermediates and products involved. Here we exploit the recently developed hybrid instruments that integrate aerosol mass spectrometry with a vacuum ultraviolet free-electron laser to study the α-pinene ozonolysis. The experiments of α-pinene ozonolysis are performed in an indoor smog chamber, with reactor having a volume of 2 m3 which is made of fluorinated ethylene propylene film. Distinct mass spectral peaks provide direct experimental signatures of previously unseen compounds produced from the reaction of α-pinene with O3. With the aid of quantum chemical calculations, plausible mechanisms for the formation of these new compounds are proposed. These findings provide crucial information on fundamental understanding of the initial steps of α-pinene oxidation and the subsequent processes of new particle formation.

State-to-state photodissociation of CO2(v2 = 0 and 1) at 157 nm via the O(1D) + CO(X1Σ+) channel was studied by using the sliced velocity map imaging technique.

Structural characterization of neutral water clusters is crucial to understanding the structures and properties of water, but it has been proven to be a challenging experimental target due to the difficulty in size selection. Here, we report the size-specific infrared spectra of confinement-free neutral water nonamer (H

The band gap state of TiO2, which is dominated by Ti3+ 3d character, is of great relevance to light absorption, electron trapping, charge recombination, and conduction band structure. Despite the importance, the explanation of the excitation from this state is controversial. To this end, the electronic structures of TiO2(110) and TiO2(011)-(2 × 1) have been systematically measured with two-photon photoemission spectroscopy. The results reveal the anisotropic nature of the electronic structure in rutile TiO2 at seemingly equivalent directions of [110] and [110], the long axes of the TiO6 blocking unit. Although the resonant energy of these two d-d transitions is identical, the energy levels are systematically shifted by 0.1 eV. We propose this anisotropy originates from the broken symmetry of the rutile TiO2 crystals caused by the surface. The proposed asymmetry-caused electronic structure anisotropy could be generalized to other similar materials and may affect associated catalytic properties. This work provides an important benchmark for related calculations.

A slow and clean fluorine atom beam source is one of the essential components for the low-collision energy scattering experiment involving fluorine atom. In this work, we describe a simple but effective photolysis fluorine atom beam source based on ultraviolet laser photolysis, the performance of which was demonstrated by high-resolution time-of-flight spectra from the reactive scattering of F+HD. This beam source paved the way for studies of low energy collisions with fluorine atoms.

Methanol has long been used as a hole scavenger in photocatalysis to improve charge separation. Although the prototypical methanol/TiO2(110) system shows salient adsorption-state-dependent photoact...

Neutral titanium-metal carbonyl complexes with the chemical formula Ti(CO)n (n = 4-7) are produced in the gas phase by the reactions of titanium atoms with carbon monoxide in a pulsed laser vaporization-supersonic expansion source. Their infrared absorption spectra in the carbonyl stretching frequency region are measured by infrared plus vacuum ultraviolet (IR+VUV) two-color ionization spectroscopy based on a tunable VUV free electron laser. Infrared spectroscopy in conjunction with quantum chemical calculations confirm that all of these complexes have unexpected titanium ketenylidene OTiCCO(CO)n-2 structures. Bonding analysis indicates that the OTiCCO core structure can be described by the bonding interactions between a TiO+ cation in the doublet ground state and a doublet ground state of CCO-. The results reveal that the C-O bond breaking and C-C bond formation proceed efficiently in the reactions between laser-vaporized titanium atoms and carbon monoxide.

It has long been predicted that oscillatory behavior exists in reactivity as a function of collision energy for heavy-light-heavy (HLH) chemical reactions in which a light atom is transferred between two heavy atoms or groups of atoms, but direct observation of such a behavior in bimolecular reactions remains a challenge. Here we report a joint theoretical and crossed-molecular-beam study on the Cl + CH4 → HCl + CH3 reaction. A distinctive peak at a collision energy of 0.15 eV for the CH3(v = 0) product was experimentally detected in the backward scattering direction. Detailed quantum-dynamics calculations on a highly accurate potential energy surface revealed that this feature originates from the reactivity oscillation in this HLH polyatomic reaction. We anticipate that such reactivity oscillations exist in many HLH reactions involving polyatomic reagents.

We utilize methanol (CH3OH) photolysis as a probe to identify the photoactivity of rutile (R)-TiO2(100) using the temperature-programmed desorption (TPD) method. Experimental results show that part...

The reaction of chlorine atom Cl(2P) (Cl(2P3/2) and Cl∗(2P1/2)) with D2 was investigated at collision energy from 4.5 kcal/mol to 6.5 kcal/mol with a high-resolution crossed molecular beam apparatus using the technique of D-atom Rydberg tagging detection. The contribution from the spin-orbit excited reaction Cl∗(2P1/2)+D2, which is prohibited by Born-Oppenheimer (BO) approximation, was observed. Collision-energy dependence of differential cross sections (DCSs) near the backward scattering direction was measured. The BO-forbidden reaction Cl∗+D2 was found to be dominant at lower collision energy. As collision energy increases, reactivity of BO-allowed reaction Cl+D2 increases much faster than that of BO-forbidden reaction and becomes dominant at higher collision energy. Our experiment indicates that the additional energy of spin-orbit excitation in Cl∗ facilitates BO-forbidden reaction to pass through the barrier at lower collision energy, while BO approximation is still valid at collision energy near and above the reaction barrier. This tendency of reactivity of Cl/Cl∗+D2 is similar to the isotopic reaction of Cl/Cl∗+H2.

A neutral boron carbonyl complex B

With the dramatically increasing deployment of intelligent devices, the Internet of Things (IoT) has attracted more attention and developed rapidly. It effectively collects and shares data from the surrounding environment to achieve better IoT services. For data sharing, the publish-subscribe (PS) paradigm provides a loosely coupled and scalable communication model. However, due to the loosely coupled nature, it is vulnerable to many attacks, resulting in some security threats to the IoT system, but it cannot provide the basic security mechanisms such as authentication and confidentiality to ensure the data security. Thus, in order to protect the system security and users’ privacy, this paper presents a secure blockchain-based privacy-preserving access control scheme for the PS system, which adopt the fully homomorphic encryption (FHE) to ensure the confidentiality of the publishing events and leverage the ledger to store the large volume of data events and access crossdomain information. Finally, we analyze the correctness and security of our scheme; moreover, we deploy our proposed prototype system on two computers and evaluate its performance. The experimental results show that our PS system can efficiently achieve the equilibrium between the system cost and the security requirement.

The band gap state of TiO

Vibrationally excited reaction of Cl + D2 (v = 1, j = 0) → DCl + D was investigated by a high-resolution crossed beam experiment, with D2 molecules in the vibrationally excited state prepared by th...

Photodissociation dynamics of DNCO + hν → D + NCO at photolysis wavelengths between 200 and 235 nm have been studied using the D-atom Rydberg tagging time-of-flight technique. Product translational energy distributions and angular distributions have been determined. Nearly statistical distribution of the product translational energy with nearly isotropic angular distribution was observed at 210–235 nm, which may come from the predissociation pathway of internal conversion from S1 to S0 state followed by decomposition on S0 surface. At shorter photolysis wavelengths, in addition to the statistical distribution, another feature with anisotropic angular distribution appears at high translational energy region, which can be attributed to direct dissociation on S1 surface. Compared with HNCO, the direct dissociation pathway for DNCO photodissociation opens at higher excitation energy. According to our assignment of the NCO internal energy distribution, dominantly bending and a little stretching excited NCO was produced via both dissociation pathways.

We report a real-space imaging of formaldehyde (HCHO) adsorption on a TiO2(110) surface probed by high-resolution scanning tunnelling microscopy (STM). Density functional theory calculations (DFT) ...

From the interplay of high-resolution scanning tunneling microscopy and density functional theory calculations, we have successfully obtained small-sized nanoporous graphene via a hierarchical reac...

Reaction of methanol (CH3OH) on metal surfaces has received lots of concerns because of its potential application in hydrogen (H2) production and fuel cells. In this work, we have studied the decom...

The water octamer, with its cubic structure consisting of six four-membered rings, presents an excellent system in which to unravel the cooperative interactions driven by subtle changes in the hydrogen-bonding topology. Although many distinct structures are calculated to exist, it has not been possible to extract the structural information encoded in their vibrational spectra because this requires size-selectivity of the neutral clusters with sufficient resolution to identify the contributions of the different isomeric forms. Here we report the size-specific infrared spectra of the isolated cold, neutral water octamer using a scheme based on threshold photoionization using a tunable vacuum ultraviolet free electron laser. A plethora of sharp vibrational bands features are observed for the first time. Theoretical analysis of these patterns reveals the coexistence of five cubic isomers, including two with chirality. The relative energies of these structures are found to reflect topology-dependent, delocalized multi-center hydrogen-bonding interactions. These results demonstrate that even with a common structural motif, the degree of cooperativity among the hydrogen-bonding network creates a hierarchy of distinct species. The implications of these results on possible metastable forms of ice are considered.

Significance Spectroscopic investigation of neutral water clusters is critical in understanding the structures and properties of condensed-phase water. Because of the difficulty for size selection of neutral clusters in general, infrared spectroscopic study of structural evolution of confinement-free, neutral water clusters has been a grand challenge. In this work, we exploit recently developed, hybrid instruments that integrate infrared spectroscopy with a tunable vacuum ultraviolet free-electron laser to capture structural evolution of water clusters. Striking spectral change in the OH stretch region is observed from water tetramer to penta- and hexamer, due to appearance of three-dimensional hydrogen-bonding networks. The technique has the potential to obtain the infrared spectra of size-selected neutral clusters and to access their rich structural landscape.

We have built a high-energy, narrow-bandwidth, nanosecond light source for efficient preparation of vibrationally excited molecules in a molecular beam. It consists of an injection-seeded optical parametric oscillator and two optical parametric amplifiers. Pumped by the second harmonic of a commercial injection-seeded Nd:YAG laser, it can generate pulse energies up to 377 mJ at 655 nm with a bandwidth smaller than 200 MHz. Its stability is excellent, with a standard deviation of pulse energy of 5.2 mJ and a wavelength stability of 0.001 cm

The reaction dynamics of the fluorine atom with vibrationally excited D2(v=1, j=0) was investigated using the crossed beam method. The scheme of stimulated Raman pumping was employed for preparation of vibrationally excited D2 molecules. Contribution from the reaction of spin-orbit excited F*(2P1/2) with vibrationally excited D2 was not found. Reaction of spin-orbit ground F(2P3/2) with vibrationally excited D2 was measured and DF products populated in v′=2, 3, 4, 5 were observed. Compared with the vibrationally ground reaction, DF products from the vibrationally excited reaction of F(2P3/2)+D2(v=1, j=0) are rotationally “hotter”. Differential cross sections at four collision energies, ranging from 0.32 kcal/mol to 2.62 kcal/mol, were obtained. Backward scattering dominates for DF products in all vibrational levels at the lowest collision energy of 0.32 kcal/mol. As the collision energy increases, angular distribution of DF products gradually shifts from backward to sideway. The collision-energy dependence of differential cross section of DF(v′=5) at forward direction was also measured. Forward-scattered signal of DF(v′=5) appears at the collision energy of 1.0 kcal/mol, and becomes dominated at 2.62 kcal/mol.

The ultrafast dynamics of water molecules excited to the two F states is studied by combining two-photon excitation and time-resolved photoelectron imaging techniques. The lifetimes of the F1A1 and F1B1 states of H2O (D2O) were derived to be 1.0±0.3 (1.9±0.4) and 10±3 (30±10) ps, respectively. We propose that the F1A1 state mainly decays through the D state, due to the nonadiabatic coupling between them, while the F1B1 state decays through the F1A1 state via Coriolis interaction.

As an important part of the UPS system, the performance of the battery pack has a direct impact on the reliability, security, and safety of the whole system. Therefore, in recent years, the research on the feasibility of supporting battery selection for UPS system operating environment and performance requirements has been gradually expanded and deepened, to achieve UPS uninterrupted power supply and cost reduction. By comparing the performance of acid-proof exhaust type battery and valve-controlled lead-acid battery, this paper introduces the selection principle of the battery pack and expounds the reason why the UPS power system chooses valve-controlled lead-acid battery. An example is given to illustrate how to calculate battery capacity and its selection and configuration, the influence of environmental temperature and safety factor on the calculation result of battery capacity is discussed, and the optimization method of battery capacity calculation and selection for UPS power supply system is put forward.

The ultrafast decay dynamics of water molecules excited to ′1B1 and ′′1A2 states is studied by combining two-photon excitation and time-resolved photoelectron imaging methods. The lifetime of the ′1B1(000) state of H2O (D2O) is determined to be 1.54 ± 0.1 (22.6 ± 1.6) ps, consistent with a previous high-resolution spectroscopic study. The H2O ′′1A2(000) state decays with a lifetime of 4.1 ± 0.2 ps, while in the D2O ′′1A2(000) state, two independent decay pathways are observed, with time constants of 0.55 ± 0.1 and 13 ± 1 ps, respectively. The former is proposed to be associated with a hitherto undocumented ′′ → pathway, induced by Coriolis interaction.

The adsorption and polymerization of acetaldehyde (CH3CHO) have been investigated on clean and CO pre-covered Co(0001) surfaces using the temperature programmed desorption (TPD) method. On the clean Co(0001) surface, CH3CHO molecules can polymerize to produce paraldehyde with very low efficiency. With pre-dosed CO molecules on Co(0001), the decomposition of CH3CHO is greatly inhibited. When the coverage of pre-dosed CO is0.33 ML, no enhancement of CH3CHO polymerization is observed. However, when the pre-dosed CO coverage is0.33 ML, the polymerization of CH3CHO is significantly enhanced during the TPD process. Further results suggest that CO molecules adsorbed at the bridge/hollow sites may initialize the polymerization by nucleophilic attack of CH3CHO molecules with their O atoms. Moreover, the polymerization product induced by CO molecules is not paraldehyde, but linear polymer chains of CH3CHO at low CH3CHO coverages and probably three dimensional polymer structures at high CH3CHO coverages.

Deuterium kinetic isotope effect (KIE) in the photochemistry of methanol on TiO2(110) has been studied to find the rate-determining step (RDS) and understand the reaction mechanism using two-photon...

Infrared photodissociation spectra of He-buffer-gas-cooled (CO2)3+ were measured at ion trap temperatures of 15, 50, 150, and 280 K. Electronic structure calculations at the mPW2PLYPD/aug-cc-pVDZ l...

We have investigated the photoinduced decomposition of formaldehyde (CH2O) on a rutile TiO2(100)-(1×1) surface at 355 nm using temperature-programmed desorption. Products, formate (HCOO-), methyl radical (CH3·), ethylene (C2H4), and methanol (CH3OH) have been detected. The initial step in the decomposition of CH2O on the rutile TiO2(100)-(1×1) surface is the formation of a dioxymethylene intermediate in which the carbonyl O atom of CH2O is bound to a Ti atom at the five-fold-coordinated Ti4+ (Ti5c) site and its carbonyl C atom bound to a nearby bridge-bonded oxygen (Ob) atom, respectively. During 355 nm irradiation, the dioxymethylene intermediate can transfer an H atom to the Ob atom, thus forming HCOO- directly, which is considered as the main reaction channel. In addition, the dioxymethylene intermediate can also transfer methylene to the Ob row and break the C-O bond, thus leaving the original carbonyl O atom at the Ti5c site. After the transfer of methylene, several pathways to products are available. Thus, we have found that Ob atoms are intimately involved in the photoinduced decomposition of CH2O on the rutile TiO2(100)-(1×1) surface.

Pt-supported TiO2 catalysts have proved to be good catalysts for efficient hydrogen (H2) production from photocatalytic water (H2O) splitting and water–gas shift reactions. However, their origin fo...

We have investigated deuterium (D2) formation from the photolysis of fully deuterated methanol (CD3OD) on the clean and formate (DCOO–) modified rutile (R)-TiO2(110) surfaces at 266 nm using temperature-programmed desorption (TPD) and density functional theory (DFT) methods. Products, D2O and D2, have been detected on both surfaces during the TPD process. About 18.5% of the dissociated D atoms from CD3OD photolysis contribute to D2 formation on the DCOO–-modified R-TiO2(110) surfaces. The value is much higher than that on the clean R-TiO2(110) surfaces, suggesting that surface DCOO– can enhance D2 production from CD3OD photolysis on R-TiO2(110). Further DFT calculation suggests that the BBO-CH-O-Ti5c structure of HCOO– on the surface can largely enhance the BBOv-mediated H2 formation by lowering the barrier of recombinative H2 desorption, leading to efficient H2 production.

The kinetics of the reaction of the simplest Criegee intermediate (CH2OO) with ammonia has been measured under pseudo-first-order conditions with two different experimental methods. We investigated the rate coefficients at 283, 298, 308, and 318 K at a pressure of 50 Torr using an OH laser-induced fluorescence (LIF) method. Weak temperature dependence of the rate coefficient was observed, which is consistent with the theoretical activation energy of -0.53 kcal mol-1 predicted by quantum chemistry calculation at the QCISD(T)/CBS//B3LYP/6-311+G(2d,2p) level. At 298 K, the rate coefficient at 50 Torr from the OH LIF experiment was (5.64 ± 0.56) × 10-14 cm3 molecule-1 s-1 while at 100 Torr we obtained a slightly larger value of (8.1 ± 1.0) × 10-14 cm3 molecule-1 s-1 using the UV transient absorption method. These experimental values are within the theoretical error bars of the present as well as previous theoretical results. Our experimental results confirmed the previous conclusion that ammonia is negligible in the consumption of CH2OO in the atmosphere. We also note that CH2OO may compete with OH in the oxidation of ammonia under certain circumstances, such as at night-time, high altitude and winter time.

The ultrafast excited-state dynamics of 2,5-dimethylpyrrole following excitation at wavelengths in the range of 265.7-216.7 nm is studied using the time-resolved photoelectron imaging method. It is found that excitation at longer wavelengths (265.7-250.2 nm) results in the population of the S1(1πσ*) state, which decays out of the photoionization window in about 90 fs. At shorter pump wavelengths (242.1-216.7 nm), the assignments are less clear-cut. We tentatively assign the initially photoexcited state(s) to the 1π3p Rydberg state(s) which has lifetimes of 159 ± 20, 125 ± 15, 102 ± 10 and 88 ± 10 fs for the pump wavelengths of 242.1, 238.1, 232.6 and 216.7 nm, respectively. Internal conversion to the S1(1πσ*) state represents at most a minor decay channel. The methyl substitution effects on the decay dynamics of the excited states of pyrrole are also discussed. Methyl substitution on the pyrrole ring seems to enhance the direct internal conversion from the 1π3p Rydberg state to the ground state, while methyl substitution on the N atom has less influence and the internal conversion to the S1(πσ*) state represents a main channel.

Cryogenic ion-trap infrared photodissociation spectroscopy combined with a dielectric barrier discharge source was constructed to establish the general trends in the stepwise growth motif of trimethylamine (TMA)n+ complexes. The results showed a strong preference for the formation of a stable charge-shared NN type (TMA)2+ ion core over the proton-transferred CHN type ion core, evidencing that the source condition has a remarkable effect on the kinetic stability of isomers. A maximum of four TMA molecules are located perpendicularly to the NN axis of the charge-shared (TMA)2+ ion core. In the n = 7 and 8 clusters, the subsequent two TMA molecules are located at each end of the NN axis of the (TMA)2+ ion core, completing the first coordination shell. Starting at n = 9, the additional TMA molecules form a second solvation shell, and the cluster spectra show similarities to the solution phase spectrum of aqueous TMA.

Infrared photodissociation spectroscopy was employed to establish the general trends in the stepwise growth motif of cationic dimethylamine (DMA)n+ (n = 4-13) complexes. Electronic structure calculations were performed to identify the structure of the low-lying isomers and to assign the observed spectral features. The results showed the preference of the formation of the proton-transferred (CH3)2NH2+ ion core. The (CH3)2NH2+-[(CH3)2N] ion-radical pair contact and the ion-radical separated pair could coexist at n = 4. The [(CH3)2N] radical is separated from the (CH3)2NH2+ ion core by one DMA molecule at n = 4-6 and by two or more DMA molecules in the larger clusters. This suggests that the (CH3)2NH2+-[(CH3)2N] ion-radical contact pair is not stable in the subsequent radiation-induced processes of DMA, and the [(CH3)2N] radical is released from the charged site in the cationic DMA networks.

We report the preparation of D2 molecules in v=2 level in molecular beam condition. A single longitudinal mode laser system was used for excitation of D2 from (v=0, j=0) to (v=2, j=0) with the scheme of stimulated Raman pumping. An excitation efficiency of 25.2% has been achieved, which was determined by the scheme of resonance-enhanced multiphoton ionization. Dependence of relative excitation efficiency on laser energy has been measured. We found that the increasing rate of excitation efficiency became slower as pulse energy of Stokes laser increase, while the excitation efficiency still increases approximately linearly with pump pulse energies up to 60 mJ. The spectral line shapes of Raman transition was also measured at different laser energies and considerable dynamical Stark effect was observed. A single peak was found on the three dimension surface of relative excitation efficiency, indicating the process occurred in the present study is a process of stimulated Raman pumping instead of stimulated adiabatic Raman passage.

The adsorption and reaction of acetaldehyde on the clean and CO pre-covered Ru(0001) surfaces have been investigated using temperature programmed desorption method. On the clean Ru(0001) surface, the decomposition of acetaldehyde is the main reaction channel, with little polymerization occurring. However, on the CO pre-covered Ru(0001) surface, the decomposition of acetaldehyde is inhibited considerably with increasing CO coverage. Whereas, the polymerization occurs efficiently, especially at high CO coverage (θCO>0.5 ML), which is strongly CO coverage dependent. Combined with previous studies, the well-ordered hexagonal structure of CO layer formed on the Ru(0001) surface at high CO coverage that matches the configuration of paraldehyde is likely to be the origin of this remarkable phenomenon.

Infrared-vacuum ultraviolet (IR-VUV) spectra of neutral trimethylamine dimer were measured in the 2500–3800 cm−1 region. Quantum chemical calculations were performed to identify the structure of the low-lying isomers and to assign the observed spectral features. The bands at 2975 and 2949 cm−1 were assigned to the antisymmetric C–H stretching and the band at 2823 cm−1 to the symmetric C–H stretching, respectively. The 2739 cm−1 band was due to the CH3 bending overtone, which disappeared at low IR laser power of 1 mJ/mm2. The extra band at 2773 cm−1 could be due to Fermi resonance behavior of the light isotopologue, these are often close in energy and can strongly mix through cubic terms in the potential function. Experimental and theoretical results indicate the likely coexistence of multiple structures. The peak widths of IR spectra of neutral trimethylamine dimer are not significantly affected by the structural transformation, allowing the stretching modes to be well resolved.

Methanol/TiO2(110) is a model system in the surface science study of photocatalysis where methanol is taken as a hole capture. However, the highest occupied molecular orbital of adsorbed methanol lies below the valence band maximum of TiO2, preventing the hole transfer. To study the level alignment of this system, electronic structure of methanol covered TiO2(110) surface has been measured by ultraviolet photoelectron spectroscopy and the molecular orbitals of adsorbed methanol have been clearly identified. The results indicate the weak interaction between methanol and TiO2 substrate. The static electronic structure also suggests the mismatch of the energy levels. These static experiments have been performed without band gap excitation which is the prerequisite of a photocatalytic process. Future study of the transient electronic structure using time-resolved UPS has also been discussed.

Low-temperature oxidation of CO, perhaps the most extensively studied reaction in the history of heterogeneous catalysis, is becoming increasingly important in the context of cleaning air and lowering automotive emissions. Here, we have studied low-temperature CO oxidation on Co(0 0 0 1) using temperature programed desorption method. We show that chemisorbed O adlayer on Co(0 0 0 1) does not promote CO 2 formation. However, when a Co 3 O 4 -like surface is formed at 90 K, large amount of CO 2 is produced at 90 K in the presence of weakly bound oxygen species, demonstrating that low-temperature CO oxidation can be rationalized on O 2 -saturated Co 3 O 4 -like oxide surfaces. However, the formation of carbonate species via the CO 2 product and weakly bound oxygen species reduces the yield of low temperature CO 2 . Thus, how to block the formation of carbonate plays a key role in enhancing the low-temperature CO 2 production on the Co 3 O 4 -like oxide surfaces.

The co-adsorption of CO and H 2 O on a Co(0001) surface at 100 K has been systematically studied using temperature programmed desorption (TPD) and density functional theory (DFT) calculations. While the TPD spectra of CO is almost not affected by the presence of H 2 O, the stabilization of H 2 O by co-adsorbed CO is found for the first time in a large coverage range (0.15 ML θ CO θ H2O 2 O is gradually separated into three peaks at 0.6 ML coverage. Those at lower and higher temperatures may be attributed to the repulsive interaction between H 2 O molecules and the attractive interaction between H 2 O and CO molecules, respectively. With increasing the coverage of predosed CO, not only the position of the high temperature peak shifts toward higher temperature (by about 15 K), but the intensity is greatly strengthened until a maximum is achieved when θ CO = 0.36 ML. DFT calculations suggest that the attractive interaction between H 2 O and CO on Co(0001) originates from the formation of intermolecular hydrogen bonds. This work not only provides insights into water gas shift reactions with H 2 O and CO as reactants, but opens new avenues for a volume of catalytic process of technological importance.

We have conducted a series of temperature-programmed desorption (TPD) experiments to study the photoinduced reactions of methanol (CH3OH) on a rutile(R)-TiO2(110) surface with 355 nm light. Products formaldehyde (CH2O) and water (H2O) have been detected. The results clearly show that the photochemistry of CH3OHTi5c is hindered by the coadsorbed multilayer CH3OH or H2O. For multilayer CH3OH adsorption, CH3OH molecules hydrogen-bonded to the bridge bonded oxygen sites inhibit the CH3OHTi5c photochemistry. Combined with previous theoretical studies (Sci. China Chem. 2015, 58, 614–619), CH3OH molecules hydrogen bonded to the BBO sites increase the energy barrier of C–H bond dissociation and decrease the energy barrier of the reverse reaction, resulting in lowering the efficiency of CH3OHTi5c photolysis. As the coverage of CH3OH keeps increasing to multilayer, the efficiency of the CH3OHTi5c photolysis does not decrease any more. However, with the coadsorbed H2O molecules, the efficiency of CH3OHTi5c photolysi...