Adsorption Of O2 Molecules Research Articles

Co2+ Doping and Molecular Adsorption Behavior of Anatase TiO2 (001) Crystal Plane

TiO2 (001) crystal plane exhibits molecular adsorption and photocatalytic activity. The loading capacity of reactive oxygen species present on crystal planes helps in the significant improvement of catalytic activity. The methods of synthesis and conditions of existence significantly affect the molecular adsorption properties of crystal planes, which in turn affects the ability of the system to load reactive oxygen species. Herein, we report the simulation of the molecular adsorption behavior on the TiO2 (001) using the density functional theory technique. The results show that the crystal plane doped with Co2+ produces an oxygen defect and chemisorbs O2 molecules present in the vicinity. Under conditions of adequate O2 concentration, the second O2 molecule is chemisorbed. This significantly improves the ability of the crystal plane to store oxygen. However, the undoped planes adsorb H2O molecules and undergo hydroxylation under the synthesis and processing conditions. The ability to adsorb O2 molecules is poor. The doping of Co2+ increases the electrical conductivity of the crystal plane and the electrical sensitivity of adsorbed O2 molecules, which is beneficial to the further improvement of the catalytic activity of the system. Fourier transform infrared spectroscopy (FTIR), and electrochemical impedance spectroscopy (EIS) techniques were used to confirm these results. The results indicate that the adsorption capacity of O2 present on the TiO2 (001) crystal plane can be changed by Co2+ doping to improve the catalytic activity of the crystal plane.

Strain boosts CO oxidation on Ni single-atom-catalyst supported by defective graphene

In order to realize the sulfur and water resistance and facilitate the CO oxidation reactions, the effects of strain on the adsorption of CO, O2, SO2 and H2O molecules on Ni single-atom-catalyst supported by single-carbon-vacancy graphene (Ni-SG) have been studied based on first principles calculations. It shows that the compressive strain increases the adsorption energies of all above mentioned molecules on Ni-SG, where SO2 is adsorbed more strongly on Ni-SG than CO. However, in the presence of tensile strain, the adsorption energies decreases significantly when the molecules (O2 and SO2) obtain electrons from Ni-SG, while the adsorption energies just slightly decrease when the molecules (CO and H2O) lose electrons to Ni-SG, which finally achieves the preferential adsorption of CO and O2 molecules on Ni-SG by tensile strain. In addition, with tensile strain increasing to 10%, the rate-limited energy barrier along Eley-Rideal (ER) path monotonically increases from 0.77 eV to 0.98 eV, while the rate-limited energy barrier along Langmuir-Hinshelwood (LH) path monotonically decreases from 0.54 eV to 0.44 eV, indicating that the tensile strain can facilitate the LH mechanism while imped the ER mechanism on Ni-SG. The Hirshfeld charge and orbital levels of O2 and CO molecules are modulated by the tensile strain, which plays an important role for the decreasing of energy barriers for CO oxidation. Overall, the tensile strain can enhance the sulfur and water resistance of Ni-SG, as well as boost the CO oxidation reactions.

Surface coordination enhanced visible-light photocatalytic coupling of benzylamine to N-benzylidene benzylamine over the Pd/NH2-MIL-125(Ti) nanosheets

The two-dimensional (2D) Metal Organic Framework (MOF) of NH2-MIL-125(Ti) nanosheets with oxygen vacancies were prepared to construct a multifunctional photocatalyst via surface modification of Pd nanoparticles (Pd/MTNs). The obtained photocatalyst showed the highly efficiency for precisely transformation of benzylamine to N-benzylidene benzylamine under visible light irradiation and 1 atm air pressure at room temperature. With the assistance of theoretical mathematical model, the MTNs loaded 0.5% wt Pd completed the transformation for benzylamine (>99%) precisely to N-Benzylidenebenzylamine (99%). However, the Bulk loaded 0.5% wt Pd exhibits decreased conversion (80.5%) and selectivity (85.9%). AFM, XPS and UV–vis DRS experiments indicated that the open 2D structure of MTNs would contribute to the generation of surface oxygen vacancies (OV) sites and abundant Ti metal sites with underfilling electrons 3d orbit, enhancing the light absorption. In-situ FTIR revealed that these exposed Ti atoms would act as the discriminating sites to specifically adsorb the benzylamine molecules forming chemical coordination bonds -C-N⋯Ti- on interface, polarizing and activating -C-N-bonds in benzylamine. Additionally, series of in-situ EPR and experimental results elucidated that the surface OV sites would act as the functional sites to capture the O2 molecules from air. Furthermore, surface Pd sites would as an active site to accelerate the photo-generated electrons transfer from inside to interface, inducing the activation of adsorbed O2 molecules to O2–. Based on these cooperating function sites in MTNs, a possible catalytic mechanism was discussed in a molecular scale. This work highlights the rational construction of a multifunctional photocatalyst and the synergistic effects of the surface coordination and photocatalysis.

Elucidating the Ambient Stability and Gas Sensing Mechanism of Nickel-Decorated Phosphorene for NO2 Detection: A First-Principles Study.

In the field of layered two-dimensional functional materials, black phosphorus has attracted considerable attention in many applications due to its outstanding electrical properties. It has experimentally shown superior chemical sensing performance for the room temperature detection of NO2, highlighting high sensitivity at a ppb level. Unfortunately, pristine black phosphorus demonstrated an unstable functionality due to the fast degradation of the material when exposed to the ambient atmosphere. In the present work, a deepened investigation by density functional theory was carried out to study how nickel decoration of phosphorene can improve the stability of the material. Further, an insight into the sensing mechanism of nickel-loaded phosphorene toward NO2 was given and compared to pristine phosphorene. This first-principles study proved that, by introducing nickel adatoms, the band gap of the material decreases and the positions of the conduction band minimum and the valence band maximum move toward each other, resulting in a drop in the conduction band minimum under the redox potential of O2/O2–, which may result in a more stable material. Studying the adsorption of O2 molecules on pristine phosphorene, we also proved that all oxygen molecules coming from the surrounding atmosphere react with phosphorus atoms in the layer, resulting in the oxidation of the material forming oxidized phosphorus species (POx). Instead, by introducing nickel adatoms, part of the oxygen from the surrounding atmosphere reacts with nickel atoms, resulting in a decrease of the oxidation rate of the material and in subsequent long-term stability of the device. Finally, possible reaction paths for the detection of NO2 are given by charge transfer analyses, occurring at the surface during the adsorption of oxygen molecules and the interaction with the target gas.

A Library of ROS-Catalytic Metalloenzyme Mimics with Atomic Metal Centers.

MetalN-coordinated centers supported by carbonaceous substrates have emerged as promising artificial metalloenzymes (AMEs) to mimic the biocatalytic effects of their natural counterparts. However, the synthesis of well-defined AMEs that contain different atomic metalN centers but present similar physicochemical and coordination structures remains a substantial challenge. Here, 20 different types of AMEs with similar geometries and well-defined atomic metalN-coordinated centers are synthesized to compare and disclose the catalytic activities, substrate selectivities, kinetics, and reactive oxygen species (ROS) products. Their oxidase (OXD)-, peroxidase (POD)-, and halogen peroxidase (HPO)-mimetic catalytic behaviors are systematically explored. The Fe-AME shows the highest OXD- and HPO-mimetic activities compared to the other AMEs due to its high vmax (0.927× 10-6 m s-1 ) and low Km (1.070× 10-3 m), while the Cu-AME displays the best POD-like performance. Furthermore, theoretical calculation reveals that the ROS-catalytic paths and activities are highly related to the electronic structures of the metal centers. Benefiting from its facile adsorption of H2 O2 molecule and lower energy barrier to generating •O2 - , the Fe-AME displays higher ROS-catalytic performances than the Mn-AME. The engineered AMEs show not only remarkably high ROS-catalytic performances but also provide new guidance toward developing metalN-coordinated biocatalysts for broad application fields.

Computational Design of Gas Sensors Based on V3S4 Monolayer.

Novel magnetic gas sensors are characterized by extremely high efficiency and low energy consumption, therefore, a search for a two-dimensional material suitable for room temperature magnetic gas sensors is a critical task for modern materials scientists. Here, we computationally discovered a novel ultrathin two-dimensional antiferromagnet V3S4, which, in addition to stability and remarkable electronic properties, demonstrates a great potential to be applied in magnetic gas sensing devices. Quantum-mechanical calculations within the DFT + U approach show the antiferromagnetic ground state of V3S4, which exhibits semiconducting electronic properties with a band gap of 0.36 eV. A study of electronic and magnetic response to the adsorption of various gas agents showed pronounced changes in properties with respect to the adsorption of NH3, NO2, O2, and NO molecules on the surface. The calculated energies of adsorption of these molecules were −1.25, −0.91, −0.59, and −0.93 eV, respectively. Obtained results showed the prospective for V3S4 to be used as effective sensing materials to detect NO2 and NO, for their capture, and for catalytic applications in which it is required to lower the dissociation energy of O2, for example, in oxygen reduction reactions. The sensing and reducing of NO2 and NO have great importance for improving environmental protection and sustainable development.

First-principles study on CO oxidation on CuO(111) surface prefers the Eley−Rideal or Langmuir−Hinshelwood pathway

Using the first-principles approach, we investigated the electronic and chemical properties of cupric oxide CuO (110) and CuO (111) and substantiated their catalytic activity toward CO oxidation. It is found that CuO (111) surface is more stable than the CuO (110) surface. We firstly study that adsorption of CO and O2 on perfect, oxygen vacancies and Cu-anchored CuO (111) surface. It is found that adsorption of CO and O2 molecules are chemical. Then we selected the most stable adsorption structure of CO/O2 to investigated the CO oxidation mechanism on different surface, here we choose to study the Langmuir–Hinshelwood (LH) mechanism and Eley–Rideal (ER) mechanism. The results show that perfect and Ovacancy CuO (111) surface is more inclined to LH mechanism, while the Cu-anchored CuO (111) surface is more inclined to ER mechanism. The results show that CuO catalyst is very effective for CO oxidation. Our work provides a deep understanding for the search of economical and reasonable CO oxidation catalysts.

Hydroxylation and molecular adsorption behavior of SnO2 (110) crystal plane

Density functional theory simulates the hydroxylation and molecular adsorption mechanism of H2O molecules on the SnO2 (110) crystal plane. The results show that the crystal plane captures H2O molecules and undergoes hydroxylation, and the crystal plane hydroxylation further chemically adsorb H2O molecules, which is confirmed by Fourier transform infrared spectroscopy. Hydroxylation promotes the adsorption of O2 molecules on the crystal plane by van der Waals forces. O2 molecules are adsorbed by van der Waals forces before and after the crystal plane hydroxylation, which resulted in the decrease and increase of the crystal plane conductivity, respectively. The results are confirmed by electrochemical impedance spectroscopy. At the same time, according to the energy optimization of the adsorption model, the change of the adsorption active site after the crystal plane hydroxylation affects the adsorption energy of the molecules on the crystal plane, which leads to the change of the crystal plane conductivity.

Controllable band structure of ZnO/g-C3N4 aggregation to enhance gas sensing for the dimethylamine detection

Volatile organoamines exist widely in various industrial and commercial products. The chronic and prolonged exposure to amines can compromise human health and cause even the risk of serious illness. Herein, the aggregation of ZnO decorated with g-C3N4 (ZOCN) is synthesized and it can serve as enhanced sensitive sensor for the detection of dimethylamine (DMA). The structure, morphology, composition and band structure of the materials are characterized by various analytical techniques. The results show that, controllable additions of g-C3N4 affect self-assemble of nanoparticles and aggregation structure, even energy band, as confirmed by DFT calculation. Notably, the formed heterojunction is conductive to electron transfer and adsorption of more O2 molecules to form reactive oxygen species, thereby promoting the reaction between oxygen and DMA and leading to high sensitivity to DMA with a detection limit of 920 ppb and about 2.5 times higher sensitivity than pristine ZnO. ZOCN-based sensor shows a high selectivity to DMA, a fast response time (1 s) and a fast recovery time (40 s) to various concentrations of gas phase DMA at low temperatures. Additionally, the sensor exhibits a linear relationship between the response and concentration of DMA vapor in a wide concentration range, a characteristic that is desirable for quantitative analysis in gas sensors.

Influence of Unsaturations on the Organization and Air Reactivity of Triglyceride Monolayers.

The behavior of Langmuir monolayers of saturated and unsaturated C18 triglycerides (TAGs) was studied as two-dimensional (2D) models for paint systems at the air-water interface or transferred onto solid films. The organization of saturated tristearin (C18:0) monolayer was probed thanks to grazing incidence X-ray diffraction: one observes a hexagonal packing of the chains perpendicular to the air-water interface, in contrast to what is described in the literature. Conversely, the mono- and polyunsaturated TAGs (triolein C18:1, trilinolein C18:2, and trilinolenin C18:3) monolayers do not present any organization at the air-water interface but do exhibit peculiar reactivity regarding the air atmosphere. The obtained results derived from the evolution of surface pressure-molecular area isotherms and monolayer compressibility under different atmospheres over time, combined with ultrahigh-vacuum infrared (UHV-FTIR) spectroscopy, showed the adsorption of O2 molecules in the monolayer together with chemical reactions with hydrocarbon chains. The kinetic effect of lead ions, known to be efficient siccative agents in oil paints, was also assessed: the addition of Pb2+ in the subphase induces an increase of the O2 adsorption.

Regulation of Magnetism on Fe- and Ni-Doped Sno2 (110) Surfaces by Oxygen Vacancy and Adsorbed O2 Molecule

Regulation of Magnetism on Fe- and Ni-Doped Sno2 (110) Surfaces by Oxygen Vacancy and Adsorbed O2 Molecule

Lewis base sites of non-oxide supports boost oxygen absorption and activation over supported Pt catalysts.

Formaldehyde (HCHO) oxidation to improve indoor air quality has attracted extensive attention. Designing efficient catalysts for HCHO removal at room temperature still remains challenging. Herein, we report a novel strategy to boost HCHO oxidation by the synergistic effect of Pt nanoparticles and C3N4. The pyridine nitrogen of C3N4 can create Lewis base sites, which function in adsorbing and activating O2 molecules. As the preparation temperature increased, the pyridine nitrogen content increased on the C3N4 surface, leading to a more significant synergistic effect. The mechanism study by in situ DRIFTS indicated that the adsorbed O2 molecules were activated by Pt/C3N4. As a result, the Pt/C3N4-650 has the most outstanding performance for HCHO oxidation at room temperature. HCHO can be completely eliminated with a concentration of 80 ppm at room temperature at a GHSV of 50 000 ml g−1 h−1. This study will provide a new perspective to design efficient HCHO oxidation catalysts.

Achieving acetone efficient deep decomposition by strengthening reactants adsorption and activation over difunctional Au(OH)Kx/hierarchical MFI catalyst

Realizing the simultaneous adsorption and activation of O2 and reactants over supported noble metal catalysts is crucial for the oxidation of organic hydrocarbons. Herein, we report a facile one-step ethylene glycol reduction method to synthesize difunctional Au(OH)Kx sites, which were anchored on a hierarchical hollow MFI support and adopted for acetone decomposition. The alkali ion-associated adjacent surface hydroxyl groups were coordinated with Au nanoparticles, resulting in partially oxidized Au1+ sites with improved dispersion. The results obtained from exclusive ex situ and in situ experiments illustrated that the proper content of K and hydroxyl groups significantly enhanced the adsorption of surface O2 and acetone molecules around the Au sites simultaneously, whereas the excess K species inhibited the catalytic performance by blocking the pore structure and decreasing the acidity of catalysts. The Au(OH)K0.7/h-MFI catalyst exhibited the highest efficiency for acetone oxidation, over which 1500 ppm acetone can be completely oxidized at just 280 °C with an extremely low activation energy of 32.5 kJ mol−1. The carbonate species were detected as the main intermediates during acetone decomposition over the difunctional Au(OH)Kx sites through a Langmuir − Hinshelwood (L − H) mechanism. This finding paves the way for designing and constructing efficient functional active sites for the complete oxidation of hydrocarbons.

Unsaturated NiII Centers Mediated the Coordination Activation of Benzylamine for Enhancing Photocatalytic Activity over Ultrathin Ni MOF-74 Nanosheets.

Creating accessible unsaturated active sites in metal-organic frameworks (MOFs) holds great promise for developing highly efficient catalysts. Herein, ultrathin Ni MOF-74 nanosheets (NMNs) with high-density coordinatively unsaturated NiII centers are prepared as a photocatalyst. The results of in situ ATR-IR, Raman, UV-vis DRS, and XPS suggest that abundant NiII centers can act as the active sites for boosting benzylamine (BA) activation via forming -Ni-NH2- coordination intermediates. The generation of coordination intermediates assists the transfer of photo-generated holes to BA molecules for producing BA cation free radicals, better impelling the breaking of N-H bonds and the photooxidation of BA molecules. The photo-generated electrons further activate O2 molecules to O2•- radicals for triggering the reaction. The experiments reveal that the coordination activation of BA molecules may be a rate-determining step on NMNs rather than the adsorption and activation of O2 molecules. Moreover, NMNs possess a better ability for the separation of photo-generated carriers in comparison with bulk Ni MOF-74 (NMBs). As a result, NMNs achieve a kinetic rate constant of 0.538 h-1 for the photocatalytic oxidative coupling of BA under visible light, about 50 times higher than that of NMBs (0.0011 h-1). Finally, a probable synergetic catalytic mechanism with coordination activation and photocatalysis is discussed on a molecular level. This study not only highlights the importance of coordination activation for heterogeneous photocatalysis but also affords an inspiration for building ultrathin MOF nanosheets.

Plasma-catalytic NO x production in a three-level coupled rotating electrodes air plasma combined with nano-sized TiO2

A novel three-level coupled rotating electrodes air plasma with nano-sized TiO2 photocatalysts is developed for plasma-catalytic NO x production. The effects of plasma catalysis on NO x production with different air flow rates, different N2 fractions and different humidity levels are evaluated. Final results show the exceptional synergistic effect between TiO2 and three-level coupled rotating electrodes air plasma significantly increases the NO x concentration by 68.32% (from 4952 to 8335 ppm) and reduces the energy cost by 40.55% (from 2.91 to 1.73 MJ mol−1) at an air flow rate of 12 l min−1 and relative humidity level of 12%, which beats the ideal thermodynamic energy limit ∼2.5 MJ mol−1 for the thermal gas-phase process. A possible mechanism for enhanced NO x production with TiO2 is discussed: Highly energetic electrons in plasma contribute to the formations of the electron–hole pairs and oxygen vacancy (Vo) on the TiO2 catalyst surface, which may facilitate the dissociative adsorption of O2 molecules to form superoxide radical groups (like O2 −), and H2O molecules to form surface hydroxyl groups (like OH·), and thus, improving energy efficiency.

Reactive adsorption mechanism of O2 onto coal vitrinite during the low temperature oxidation process

Here, incorporating with the experiments of low-temperature oxidation, the adsorption and diffusion of O2 molecules onto macromolecular model of coal vitrinite was simulated via the MD (molecular dynamics) and GCMC (grand canonical monte carlo). The energy variation and the dominated adsorption configuration of O2 were clarified, as well as the RDF (radial distribution function) and the self-diffusion coefficients of various functional groups. The isosteric heat of O2 adsorption lies within 16.40–16.57 kJ/mol, which decreases linearly with the increasing temperature. The GCMC and RDF analysis indicated that the adsorption affinity of various functional groups for O2 follows the order of aromatic > pyrrole > pyridine and the O2 molecules prefer to absorb onto the coal vitrinite at the L orientation (OO bond perpendicular to coal vitrinite plane) for aromatics and at the V orientation (OO bond parallel to coal vitrinite plane) for pyridine rings. The self-diffusion coefficients of O2 molecules are in the order of magnitude of 10−6-10−5 m2/s. Thus, both the adsorption affinity and diffusion ability of O2 molecules differ distinctly among various function groups, providing the energy and materials for the gradual self-activation reaction of spontaneous combustion of coal. The low-temperature oxidation experiments suggest that the oxidation reaction of different structures in the low-temperature oxidation process of coal occurs at different oxidation temperatures, which also proves that the different oxidation activity of structures in coal. The pyrrole, pyridine, and aromatic are dominant adsorption sites for O2 molecules and also serve as the first order reaction zone of coal spontaneous combustion, producing more heat than the locations of the aliphatic chains and oxygen functional groups due to their wide distribution. The simulation and experimental results indicated two functions of the physical adsorption for coal spontaneous combustion. One is to delivery oxygen for oxidation reaction and the other is to release heat as the triggering mechanism of the coal spontaneous combustion.

Effect of Ag doping on SnO2 sensing for detecting H2S: A first-principles study

First-principles calculations were performed to investigate the effect of Ag doping on SnO2 sensing of H2S with oxygen vacancy formation and oxygen species preadsorption. Ag preferentially substituted for Sn5c atoms, and Ag atoms were favorable for the generation of oxygen vacancies at O2c sites on the SnO2 (110) surface. The adsorbed O2 molecules dissociated on the Ag-doped SnO2 surface more easily because of the dopant catalysis, and the resistance of the Oads-preadsorbed Ag-doped SnO2 surface increased because of increased electron transfer from the surface to the Oads species. When exposed to H2S, H2S released more electrons back to the Oads-preadsorbed Ag-doped SnO2 surface, thereby increasing surface conductance. Therefore, Ag doping enhanced SnO2-semiconductors sensing. This study can provide an improved understanding of Ag-enhanced SnO2 sensing, which is helpful for designing SnO2 sensors with high sensitivity and sensing response.

Enhancement of Activity and Development of Low Pt Content Electrocatalysts for Oxygen Reduction Reaction in Acid Media.

Platinum is a main catalyst for the electroreduction of oxygen, a reaction of primary importance to the technology of low-temperature fuel cells. Due to the high cost of platinum, there is a need to significantly lower its loadings at interfaces. However, then O2-reduction often proceeds at a less positive potential, and produces higher amounts of undesirable H2O2-intermediate. Hybrid supports, which utilize metal oxides (e.g., CeO2, WO3, Ta2O5, Nb2O5, and ZrO2), stabilize Pt and carbon nanostructures and diminish their corrosion while exhibiting high activity toward the four-electron (most efficient) reduction in oxygen. Porosity of carbon supports facilitates dispersion and stability of Pt nanoparticles. Alternatively, the Pt-based bi- and multi-metallic catalysts, including PtM alloys or M-core/Pt-shell nanostructures, where M stands for certain transition metals (e.g., Au, Co, Cu, Ni, and Fe), can be considered. The catalytic efficiency depends on geometric (decrease in Pt–Pt bond distances) and electronic (increase in d-electron vacancy in Pt) factors, in addition to possible metal–support interactions and interfacial structural changes affecting adsorption and activation of O2-molecules. Despite the stabilization of carbons, doping with heteroatoms, such as sulfur, nitrogen, phosphorus, and boron results in the formation of catalytically active centers. Thus, the useful catalysts are likely to be multi-component and multi-functional.

Oxygen Adsorption Induced Superconductivity in Ultrathin FeTe Film on SrTiO3(001).

The phenomenon of oxygen incorporation-induced superconductivity in iron telluride (Fe1+yTe, with antiferromagnetic (AFM) orders) is intriguing and quite different from the case of FeSe. Until now, the microscopic origin of the induced superconductivity and the role of oxygen are far from clear. Here, by combining in situ scanning tunneling microscopy/spectroscopy (STM/STS) and X-ray photoemission spectroscopy (XPS) on oxygenated FeTe, we found physically adsorbed O2 molecules crystallized into c (2/3 × 2) structure as an oxygen overlayer at low temperature, which was vital for superconductivity. The O2 overlayer were not epitaxial on the FeTe lattice, which implied weak O2 –FeTe interaction but strong molecular interactions. The energy shift observed in the STS and XPS measurements indicated a hole doping effect from the O2 overlayer to the FeTe layer, leading to a superconducting gap of 4.5 meV opened across the Fermi level. Our direct microscopic probe clarified the role of oxygen on FeTe and emphasized the importance of charge transfer effect to induce superconductivity in iron-chalcogenide thin films.

TiO2/SiO2 Coated 310S Stainless Steel for Hydrogen Peroxide Generation via Photocatalytic Reaction

The photocatalytic reactor was designed by assembling the parts of a photocatalyst, an ultraviolet light source and an air distribution. This prototype reactor was used to generate H2O2 via photocatalytic reaction. TiO2 and TiO2/SiO2 prepared from sol-gel method were coated on 310S stainless steel substrate using dip-coating technique. Rice husk ash was used as the source of SiO2. The major phase of all the pure TiO2 and SiO2 particles was anatase and amorphous, respectively. The surface analysis showed the coated TiO2 and TiO2/SiO2 with an average roughness of 365.391 and 1322.001 nm, respectively, compared with the average thickness of coated TiO2 which was measured to be 2.7325 μm and for TiO2/SiO2, which was 4.7856 m. The results also showed the coating of TiO2/SiO2 was highly porous at the surface compared with pure TiO2. The TiO2/SiO2 show good photocatalytic reaction activity because SiO2 doping on TiO2 increased the adsorption of O2 and H2O molecules towards the photoactive center of TiO2. Thus, the incorporation of SiO2 onto the photocatalyst helped to increase photocatalytic activity. The generation of H2O2 increased with increasing ambient humidity up to 60% RH, but then decreased. This behavior was explained by the effect of water vapor adsorption on the SiO2 surface. The air flowrate enhanced the generation of H2O2, higher air flow rate produced a higher amount of H2O2. H2O2 was generated at the highest concentration of 64 ppmv from the TiO2/SiO2 photocatalyst at ambient humidity of 60% RH and air flowrate 8.20 m/s.