Catalytic Properties of TiO<Subscript>2</Subscript>/Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> Nanoparticles in Plasma Chemical Treatment

We proposed here a new process coupling dielectric barrier discharge (DBD) plasma with magnetic photocatalytic material nanoparticles for improving yield in DBD degradation of methyl orange (MO). TiO₂ doped Fe₃O₄ (TiO₂/Fe₃O₄) was prepared by the sol-gel method and used as a new type of magnetic photocatalyst in DBD system. It was found that the introduction of TiO₂/Fe₃O₄ in DBD system could effectively make use of the energy generated in DBD process and improve hydroxyl radical contributed by the main surface Fenton reaction, photocatalytic reaction and catalytic decomposition of dissolved ozone. Most part of MO (88%) was degraded during 30 min at peak voltage of 13 kV and TiO₂/Fe₃O₄ load of 100 mg/L, with a rate constant of 0.0731 min^?1 and a degradation yield of 7.23 g/(kW h). The coupled system showed higher degradation efficiency for MO removal.     

Degradation of 2-Nitrophenol by Dielectric Barrier Discharge System: The Influence of Carbon Doped TiO<Subscript>2</Subscript> Photocatalyst Supported on Stainless Steel Mesh

This study investigated the degradation of 2-nitrophenol (2-NP) in aqueous solution by dielectric barrier discharge (DBD) system alone and its combination with supported TiO₂ photocatalysts. The TiO₂ photocatalyst supported on a stainless steel mesh was synthesised using sol–gel solution of 8% polyacrylonitrile (PAN)/dimethylformamide/TiCl₄ followed by pyrolysis in the furnace under N₂ atmosphere at temperatures of 300, 350, or 400 °C for 3 h holding time. The supported catalysts were characterized for their morphologies, functional groups, crystallinity, surface areas and elemental chemical states by high resolution scanning electron microscope (HRSEM), Fourier transform infrared, X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET) surface area, and X-ray photoelectron spectroscopy. The influence of solution pH on the degradation of 2-NP was investigated. The residual concentration of 2-NP and the intermediate compounds were quantified and identified using high-performance liquid chromatography coupled with mass spectrometry (HPLC–MS). The concentration of the dissolved ozone, hydrogen peroxide and hydroxyl radicals generated by the DBD in the presence or absence of a catalyst was monitored using ultraviolet–visible spectroscopy and photoluminescence spectroscopy. The HRSEM, HRTEM, XRD and BET analysis revealed that the optimal thermal conditions to obtain well supported uniformly grown, highly active crystalline TiO₂ catalysts with high specific surface area was 350 °C at a 3 h holding time in N₂ atmosphere with a flow rate of 20 mL/min. The supporting procedure simultaneously carbon doped the photocatalyst. The DBD system alone without catalysts successfully mineralised 58.6% of 2-NP within 60 min while combined DBD/supported TiO₂ nanocrystals achieved 77.5% mineralisation within the same treatment time. The increase in mineralisation rate was attributed to the existence of a synergistic effect between the DBD system and the supported catalysts. 2-NP degradation proceeded via hydroxylation, nitration and denitration using DBD alone and combined DBD/Supported TiO₂ photocatalyst. Catechol, hydroquinone, hydroxyl-1,4-benzoquinone, 2-nitrohydroquinone, and 2,4-dinitrophenol were identified as major intermediate products. The order of production of free reactive species by DBD alone and combined DBD with supported photocatalyst was OH° > H₂O₂ > O₃.The results showed that the combined system was more than effective than DBD alone for the degradation of the 2-NP in aqueous solution.     

Simultaneous removal of NO and SO<Subscript>2</Subscript> in a plasma reactor packed with TiO<Subscript>2</Subscript>-coated glass beads

We analyzed the dielectric pellet bed discharge-photocatalyst hybrid process for NO and SO₂ removal. A cylindrical-wire type discharge reactor was packed with glass beads as dielectric pellets and the plasmas were generated by dielectric pellet bed discharge. The TiO₂ photocatalysts were coated onto the glass beads by the dip-coating method and were activated by the light from discharge. Experiments were carried out for three cases: NO removal only, SO₂ removal only, and simultaneous NO and SO₂ removal. As the voltage applied to the plasma reactor increased, or as the residence time increased, the NO and SO₂ removal efficiencies increased. With increasing initial NO and SO₂ concentrations, the NO and SO₂ removal efficiencies decrease. The removal efficiencies for simultaneous NO and SO₂ removal are lower than those for NO only or SO₂ only.     

Microstructure of SiO<Subscript>2</Subscript>/TiO<Subscript>2</Subscript> hybrid electrospun nanofibers and their application in dye degradation

SiO₂/TiO₂ hybrid nanofibers were prepared by electrospinning and applied for photocatalytic degradation of methylene blue (MB). The phase structure, specific surface area, and surface morphologies of the SiO₂/TiO₂ hybrid nanofibers were characterized through thermogravimetry (TG), X-ray diffraction (XRD) analysis, Brunauer–Emmett–Teller (BET) analysis, scanning electron microscopy (SEM), etc. XRD measurements indicated that doping of silica into TiO₂ nanofibers can delay the phase transition from anatase to rutile and decrease the grain size. SEM and BET characterization proved that silica doping can remarkably enhance the porosity of the SiO₂/TiO₂ hybrid nanofibers. The MB adsorption capacity and photocatalytic activity of the SiO₂/TiO₂ hybrid nanofibers were distinguished experimentally. It was found that, although increased silica doping content could enhance the MB adsorption capacity, the intrinsic photocatalytic activity gradually dropped. The SiO₂ (10 %)/TiO₂ composite nanofibers exhibited the highest MB degradation rate, being superior to SiO₂ (20 %)/TiO₂ or pure TiO₂.     

Comparative Actions of NiO and TiO<Subscript>2</Subscript> Catalysts on the Destruction of Phenol and its Derivatives in a Dielectric Barrier Discharge

This study examined processes of decomposing phenol and its derivatives (resorcin, pyrocatechol and hydroquinone) in aqueous solutions under the action of an atmospheric pressure oxygen dielectric barrier discharge in the presence or absence of catalysts in the plasma zone. Two types of catalysts were tested, NiO and TiO₂. It was found that both materials exhibited catalytic properties. The action of NiO accelerated the step of phenol destruction while the action of TiO₂ catalyst resulted in a more preferable composition of decomposition products and provided a higher degree of carboxylic acid conversion into carbon dioxide than the NiO catalyst.     

Influence of Plasma Treatments on the Hemocompatibility of PET and PET + TiO<Subscript>2</Subscript> Films

A dielectric barrier discharge (DBD) in helium was used to ameliorate the interface between the blood and the surface of polymeric implants: polyethylene terephthalate (PET) and PET with titanium oxide (PET + TiO₂). A higher crystallinity degree was found for the DBD treated samples. The wettability of polymers was improved after the treatment. The chemical composition, analyzed by infrared spectroscopy was preserved during the DBD treatment. The surface modifications have been correlated with polymers hemocompatibility. Concerning the polymer surface–blood interaction, the treatment induced a decrease of the interfacial tension between the blood components and the treated surfaces. The in vitro tests of hemocompatibility showed no perturbation in the blood composition when the polymer samples are present in the blood volume. An interesting result is related to the whole blood clotting time that shows a dramatic increase on the treated surfaces. Moreover, the coagulation kinetics on the treated surfaces is modified.     

Nafion/TiO<Subscript>2</Subscript> hybrid membrane fabricated via hydrothermal method for vanadium redox battery

To improve the performance of Nafion membrane as a separator in vanadium redox battery (VRB) system, a Nafion/TiO₂ hybrid membrane was fabricated by a hydrothermal method. The primary properties of this hybrid membrane were measured and compared with the Nafion membrane. The Nafion/TiO₂ hybrid membrane has a dramatic reduction in crossover of vanadium ions compared with the Nafion membrane. The results of scanning electron microscope, energy dispersive X-ray spectroscopy, and X-ray diffraction of the hybrid membrane revealed that the TiO₂ phase was formed in the bulk of the prepared membrane. Cell tests identified that the VRB with the Nafion/TiO₂ hybrid membrane presented a higher coulombic efficiency (CE) and energy efficiency (EE), and a lower self-discharge rate compared with that of the Nafion system. The CE and EE of the VRB with the hybrid membrane were 88.8% and 71.5% at 60 mA cm⁻², respectively, while those of the VRB with Nafion membrane were 86.3% and 69.7% at the same current density. Furthermore, cycling tests indicated that the Nafion/TiO₂ hybrid membrane can be applied in VRB system.     

Dielectric properties and I-V characteristics of (Pb<Subscript>0.4</Subscript>Sr<Subscript>0.6</Subscript>)TiO<Subscript>3</Subscript> thin films improved by TiO<Subscript>2</Subscript> buffer layers

A TiO₂ thin buffer layer was introduced between the (Pb_0.4Sr_0.6)TiO₃ (PST) film and the Pt/Ti/SiO₂/Si substrate in an attempt to improve their electrical properties. Both TiO₂ and PST layers were prepared by a chemical solution deposition method. It was found that the TiO₂ buffer layer increased the (100)/(001) preferred orientation of PST and decreased the surface roughness of the films, leading to an enhancement in electrical properties including an increase in dielectric constant and in its tunability by DC voltage, as well as a decrease in dielectric loss and leakage current density. At an optimized thickness of the TiO₂ buffer layer deposited using 0.02 mol/l TiO₂ sol, the 330-nm-thick PST films had a dielectric constant, loss and tunability of 1126, 0.044 and 60.7% at 10 kHz, respectively, while the leakage current density was 1.95 × 10⁻⁶ A/cm² at 100 kV/cm.     

Fabrication and characterization of TiO<Subscript>2</Subscript>–SiO<Subscript>2</Subscript> composite nanoparticles and polyurethane/(TiO<Subscript>2</Subscript>–SiO<Subscript>2</Subscript>) nanocomposite films

TiO₂–SiO₂ composite nanoparticles were prepared by a sol–gel process. To obtain the assembly of TiO₂–SiO₂ composite nanoparticles, different molar ratios of Ti/Si were investigated. Polyurethane (PU)/(TiO₂–SiO₂) hybrid films were synthesized using the “grafting from” technique by incorporation of modified TiO₂–SiO₂ composite nanoparticles building blocks into PU matrix. Firstly, 3-aminopropyltriethysilane was employed to encapsulate TiO₂–SiO₂ composite nanoparticles’ surface. Secondly, the PU shell was tethered to the TiO₂–SiO₂ core surface via surface functionalized reaction. The particle size of TiO₂–SiO₂ composite sol was performed on dynamic light scattering, and the microstructure was characterized by X-ray diffraction and Fourier transform infrared. Thermogravimetric analysis and transmission electron microscopy (TEM) employed to study the hybrid films. The average particle size of the TiO₂–SiO₂ composite particles is about 38 nm when the molar ratio of Ti/Si reaches to1:1. The TEM image indicates that TiO₂–SiO₂ composite nanoparticles are well dispersed in the PU matrix.     

Synthesis and characterization of radiation sensitive TiO<Subscript>2</Subscript>/monazite photocatalyst

A TiO₂/monazite photocatalyst was prepared by embedding TiO₂ nanoparticles into a monazite substrate surface. TiCl₄ hydrolysis/citric acid chelating procedure under acidic conditions were used to synthesize the nanophase TiO₂ particles. The anatase TiO₂/monazite photocatalyst surface area, morphology, crystalline and elemental concentrations were characterized using Brunauer-Emmett-Teller (BET) method, scanning electron microscopy (SEM), X-ray diffraction (XRD), and inductively coupled plasma-atomic emission spectrometry (ICP-AES). Monazite contains a large amount of Ce-, La-, Nd- and Th-PO₄ compounds; it has been known as a natural mineral material with minor radioactivity. TiO₂-CeO₂ composite is a kind of radiation sensitive photocatalyst in which the radiations of thorium nuclides give energy to trigger TiO₂ and cerium ions which play an energy absorber with charge separator. The result showed that methylene blue and phenol were spontaneously photocatalytic decomposed by TiO₂/monazite composite even in a dark environment. A synergistic effect was also examined with applied exterior UV or ⁶⁰Co irradiation. A hybrid mechanism is proposed; according by the radioluminescence (RL) from excited Ce ion by γ-radiation soliciting CeO₂/TiO₂ heterojunction (HJ). This seems to be a possible mechanism to explain this self-activated photo-catalytic behavior.     

Chitosan-modified TiO<Subscript>2</Subscript> as photocatalyst for ethanol reforming under visible light

This work reports the reforming of bio-ethanol on chitosan–TiO₂ hybrid photocatalysts at ambient temperature. The influence of chitosan composition on the photocatalytic performance of chitosan–TiO₂ hybrid was studied. The hybrids were characterized by CHN elemental analysis, nitrogen adsorption–desorption isotherms, thermogravimetric analysis, diffuse reflectance spectroscopy, X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The results showed that the preparation variables used for the incorporation of chitosan on TiO₂ promoted changes in the morphology, superficial area, crystal size and porosity of the photocatalyst, affecting the band gap of this semiconductor and consequently the reactivity of the chitosan–TiO₂ hybrids. The catalysts were evaluated for hydrogen production from ethanol under visible light. It was demonstrated that the calcination temperature of 623 K and a chitosan content of 20% were the most appropriate preparation conditions and the resulting product displays a pore size of 1.9 nm, crystal size of 11.3 nm, BET area of 178 m² g^?1 and band gap of 2.92 eV. The calcination temperature of 623 K and incorporation of 20% of chitosan obtained the same results in the conversion rate of hydrogen in comparison to the pure TiO₂ P25.     

Synthesis,Characterization and Photocatalytic Application of TiO<Subscript>2</Subscript>/SnO<Subscript>2</Subscript> Nanocomposite Obtained Under Non-thermal Plasma Condition at Atmospheric Pressure

A plasma-assisted synthesis of TiO₂/SnO₂ nanocomposite is described. In this approach, a precursor containing a mixture of [TiCl₃ and SnCl₂] exposed to electric discharge was oxidized by plasma-generated reactive species (HO^·/H₂O = 2.85 eV/SHE). SnO₂ microstructures with a diameter of 10–40 µm were coated by thin layers TiO₂ nanorods with mean diameter of 6–8 nm. The obtained TiO₂/SnO₂ nanocomposite was characterized by transmission and scanning electron microscopy, X-ray diffraction and Fourier transform infrared. TiO₂/SnO₂ nanocomposite was found to be a promising new material for the photocatalytic discoloration of aqueous Remazol Brilliant Blue-R dye under daylight and UVA light sources, due to the combined effects of large specific surface area and heterojunction which efficiently separates the electron–hole pairs delaying the charge recombination. The leaching test indicated that the nanocomposite is stable easily reusable.     

Electrospun Li<Subscript>4</Subscript>Ti<Subscript>5</Subscript>O<Subscript>12</Subscript>/Li<Subscript>2</Subscript>TiO<Subscript>3</Subscript> composite nanofibers for enhanced high-rate lithium ion batteries

Li₄Ti₅O₁₂/Li₂TiO₃ composite nanofibers with the mean diameter of ca. 60 nm have been synthesized via facile electrospinning. When the molar ratio of Li to Ti is 4.8:5, the Li₄Ti₅O₁₂/Li₂TiO₃ composite nanofibers exhibit initial discharge capacity of 216.07 mAh g^?1 at 0.1 C, rate capability of 151 mAh g^?1 after being cycled at 20 C, and cycling stability of 122.93 mAh g^?1 after 1000 cycles at 20 C. Compared with pure Li₄Ti₅O₁₂ nanofibers and Li₂TiO₃ nanofibers, Li₄Ti₅O₁₂/Li₂TiO₃ composite nanofibers show better performance when used as anode materials for lithium ion batteries. The enhanced electrochemical performances are explained by the incorporation of appropriate Li₂TiO₃ which could strengthen the structure stability of the hosted materials and has fast Li⁺-conductor characteristics, and the nanostructure of nanofibers which could offer high specific area between the active materials and electrolyte and shorten diffusion paths for ionic transport and electronic conduction. Our new findings provide an effective synthetic way to produce high-performance Li₄Ti₅O₁₂ anodes for lithium rechargeable batteries.     

TiO<Subscript>2</Subscript> nanofibers embedding single crystalline TiO<Subscript>2</Subscript> nanowires

Epitaxially grown titanium dioxide (TiO₂) nanofibers embedding single crystalline TiO₂ nanowires (NWs) were successfully fabricated by electropinning poly(vinyl pyrrolidone)/ethanol solutions mixed with hydrothermally synthesized TiO₂ NWs and titanium isopropoxide precursors and subsequently calcinating the electrospun nanofibers. Utilizing scanning electron microscopy (SEM) and transmission electron microscopy (TEM), the morphologies of TiO₂ NWs and nanofibers were investigated. High resolution TEM (HR-TEM) and selected area electron diffraction (SAED) allowed us to indentify the fact that, during the calcination process under the optimized condition, titanium isopropoxide precursors were epitaxially crystallized on the surface of single crystalline TiO₂ NWs. Based on the X-ray diffraction (XRD) experiments, it was also realized that the crystalline structure of hydrothermally synthesized TiO₂ NWs and epitaxially crystallized TiO₂ nanofibers is anatase and that TiO₂ composite nanofibers embedding TiO₂ NWs exhibited a higher crystallinity than the pristine TiO₂ nanofibers. Additionally, ultraviolet visible (UV–Vis) spectra of nanofibers indicated that optical properties of TiO₂ nanofibers can be tuned by introducing the single crystalline TiO₂ NWs.     

Charge separation by tetrahexahedron-SrTiO<Subscript>3</Subscript>/TiO<Subscript>2</Subscript> heterojunction as an efficient photocatalyst

Charge separation plays a key role in the conversion of solar energy into chemical energy for use in the redox reaction and as well as in the photocatalytic activity. In this study, SrTiO₃ particles with different morphologies including irregular, tetrahexahedron, and cube were synthesized by an in situ solvothermal method. The photocatalytic activity of the synthesized nanoparticles was investigated in the photocatalytic decomposition of methylene blue under UV light irradiation. Tetrahexahedron SrTiO₃ particles exhibited high decomposition activity (70 %), which is about two times higher than those of the irregular and cubic SrTiO₃ particles. The high decomposition activity of tetrahexahedron SrTiO₃ particles could be attributed to the improvement of charge separation achieved on different crystal facets. To reach a good charge separation, tetrahexahedron SrTiO₃/TiO₂ coupled nanoparticles were fabricated by impregnation method. Results showed that coupling tetrahexahedron SrTiO₃ with TiO₂ could produce efficient charge separation between tetrahexahedron SrTiO₃ and TiO₂ due to their matched band edges. In order to achieve better charge separation, the tetrahexahedron SrTiO₃/90 %TiO₂ sample was calcined at different temperatures in the 450–750 °C range. Tetrahexahedron SrTiO₃/90 %TiO₂ coupled nanoparticles calcined at 650 °C show high photocatalytic activity compared with other samples. The prepared samples were characterized by using various techniques such as X-ray diffraction, scanning electron microscopy, photoluminescence emission spectra, and UV–Vis diffuse reflectance spectroscopy.     

Synthesis of Mixed-Phase TiO<Subscript>2</Subscript> Nanopowders Using Atmospheric Pressure Plasma Jet Driven by Dual-Frequency Power Sources

Mixed-phase TiO₂ nanopowders with different ratios of anatase and rutile have been successfully synthesized using atmospheric pressure plasma jet driven by dual-frequency power sources. The crystal structures of the TiO₂ nanopowders were characterized by X-ray diffraction, SAED, HRTEM, and Raman shift spectroscopy. These results indicated that samples possessed anatase and rutile structure, in addition, the crystallinity of the TiO₂ nanopowders increased and the chlorine contamination decreased with discharge RF power increasing. The photocatalytic activity of the TiO₂ nanopowders was evaluated by decomposition methylene blue solution. The TiO₂ nanopowders which were produced at the discharge RF power of 110 W had the highest photocatalytic activity. Optical emission spectroscopy (OES) was used to detect various excited species in the plasma jet. The results indicate that the various RF power significantly changes the intensities of emission lines (Ar, Ar⁺, Ti, Ti⁺, Ti²⁺, Ti³⁺ and O), which results in the TiO₂ nanopowders a mixture of anatase and rutile phases. The nonequilibrium chemical composition could be formed in one step without anneal. It may have potential applications for synthesizing nanosized particles of high crystallinity by reactive nonthermal plasma processing.     

Assessment of operating parameters for photocatalytic degradation of a textile dye by Fe<Subscript>2</Subscript>O<Subscript>3</Subscript>/TiO<Subscript>2</Subscript>/clinoptilolite nanocatalyst using Taguchi experimental design

In the current study, a nanophotocatalyst doped with of TiO₂ and Fe₂O₃ nanoparticles supported on Iranian clinoptilolite was synthesized and characterized by XRD, XRF, SEM, and EDX analyses. The results suggested the successful loading of TiO₂ and Fe₂O₃ nanoparticles onto the surface of clinoptilolite. The SEM images confirmed the average size of nanoparticles deposited on zeolite, which was about 20–40 nm. Furthermore, application of the synthesized photocatalyst in photocatalytic degradation of Acid Black 172 dye was studied using the Taguchi method and the chosen parameters were as follows: pH (2–7), dye concentration (50–200 mg/l), irradiation time (30–120 min), and catalyst dosage (0.5–1.5 g/l). The results indicate that dye concentration, pH, and irradiation time are respectively the most effective factors in these experiments while with the minimum dosage of the catalyst (0.5 g/l), up to 90 % removal efficiency could be achieved. The optimum value for each parameter was pH = 2, dye concentration = 50 mg/l, catalyst dosage = 1 g/l and irradiation time = 60 min, and the dye removal efficiency reached up to 100 % at these optimal conditions. Furthermore, after five-times recycling and reusing the catalyst, the efficiency of the photocatalytic degradation was reduced from 91.5 to 65.9 %, which is still an acceptable value.     

Enhancement of visible-light photocatalytic activity of Cu-doped TiO<Subscript>2</Subscript> nanoparticles

Bare TiO₂ and Cu-doped TiO₂ nanoparticles with different nominal doping amounts of Cu ranging from of 0.5 to 5.0 mol% were synthesized using the modified sol–gel method. The samples were physically characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, Brunauer–Emmett–Teller-specific surface area, UV–Vis diffuse reflectance spectroscopy, zeta potential, X-ray photoelectron spectroscopy, inductively coupled plasma, and photoluminescence techniques. The Cu-doped TiO₂ exhibited good photocatalytic activity in mineralization of oxalic acid and formic acid under visible light irradiation. Photomineralization of oxalic and formic acids under visible light irradiation revealed greatly enhanced photoactivity exhibited by the 2.0 mol% Cu-doped TiO₂ photocatalyst compared to bare TiO₂ . The enhanced photocatalytic performance arises from copper ion doping in the TiO₂ structure, leading to an extended photoresponsive range, enhanced photogenerated charge separation, and transportation efficiency.     

DSC investigation of nanocrystalline TiO<Subscript>2</Subscript> powder

The aim of the article is to investigate the influence of particle size on titanium dioxide phase transformations. Nanocrystalline titanium dioxide powder was obtained through a hydrothermal procedure in an aqueous media at high pressure (in the range 25–100 atm) and low temperature (≤200 °C). The as-prepared samples were characterized with respect to their composition by ICP (inductive coupled plasma), structure and morphology by XRD (X-ray diffraction), and TEM (transmission electron microscopy), thermal behavior by TG (thermogravimetry) coupled with DSC (differential scanning calorimetry). Thermal behavior of nanostructured TiO₂ was compared with three commercial TiO₂ samples. The sequence of brookite–anatase–rutile phase transformation in TiO₂ samples was investigated. The heat capacity of anatase and rutile in a large temperature range are reported.     

Low-temperature NO<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> Selective Reduction by Hydrocarbons on H-Mordenite Catalysts in Dielectric Barrier Discharge Plasma

Toward achieving selective catalytic reduction of NO _x by hydrocarbons at low temperatures (especially lower than 200 °C), C₂H₂ selective reduction of NO _x was explored on H-mordenite (H-MOR) catalysts in dielectric barrier discharge (DBD) plasma. This work reported significant synergistic effects of DBD plasmas and H-MOR catalysts for C₂H₂ selective reduction of NO _x at low temperatures (100–200 °C ) and across a wide range of O₂ content (0–15%). At 100 °C, NO _x conversions were 3.3, 11.6 and 66.7% for the plasma alone, catalyst alone and in-plasma catalysis (IPC) cases (with a reactant gas mixture of 500 ppm NO, 500 ppm C₂H₂, 10% O₂ in N₂, GHSV = 12,000 h⁻¹ and input energy density of 125 J L ⁻¹), respectively. At 200 °C, NO _x conversions were 3.8, 54.0 and 91.4% for the above three cases, respectively. Also, strong signals of hydrogen cyanide (HCN) byproduct were observed in the catalyst alone system by an on-line mass spectrometer. By contrast, almost no HCN was detected in the IPC system.