Quartz Tube Research Articles

Oxidation of cobalt as investigated by x-ray photoelectron spectroscopy

Thin films of cobalt (about 20 nm) were deposited on a silicon ⟨100⟩ substrate. The deposition was carried out using the e-beam technique. The films were oxidized under two different conditions: in vacuum and in a quartz tube furnace. The elemental cobalt and the two oxidized samples were characterized by the technique of x-ray photoelectron spectroscopy. Magnesium Kα radiation (1253.6 eV) was used as the source of the x-ray excitation. The spectral data in the cobalt 2p, 2s, 3s, 3p, Auger LMM regions, oxygen 1s region, and carbon 1s regions were recorded under a high resolution mode. The sample oxidized in vacuum showed features distinct from that oxidized in the quartz tube furnace. The data will serve as a comparison for the cobalt oxides formed under different processing conditions.

Computational modeling of a surfatron mode microwave plasma in NH3/N2 for remote radical generation in a silicon native oxide cleaning process

Plasma-produced NxHy radicals facilitate the removal of native oxide layers in a semiconductor wafer surface. A remote microwave excited plasma with a NH3–N2 feed gas is used commonly to produce the active radicals. We perform a three-dimensional modeling of a microwave excited plasma operating in a surfatron mode. The device consists of a rectangular waveguide intersecting a quartz tube through which the feed gas flows. We discuss the propagation of a polarized 2.45 GHz microwave from the waveguide into the quartz tube where power is deposited into the plasma. The plasma–wave interaction is found to be highly three dimensional, with a propagating surface mode of the wave established along the dielectric tube plasma interface. Significant heating occurs on the side of the tube that directly faces the incident wave. As the flow carries the plasma-produced species down the tube, species radial profiles become increasingly diffusion controlled and axisymmetric. The dominant radicals that exit the tube are H2 and NH2, with nearly complete conversion of the feed gases to product species. The gas temperature rises above this inlet feed gas temperature and increases with increasing wave power. However, the gas temperature increase is not consequential to the overall radical yield from the plasma. The parametric study with changing pressure and input power illustrates the role of specific chemical reactions in the overall remote plasma process.

Improved continuous measurement system for atmospheric total peroxy and total organic nitrate under the high NOx condition.

We improved the thermal dissociation cavity attenuated phase shift spectroscopy (TD-CAPS) instrument to measure atmospheric total peroxy nitrates (PNs) and organic nitrates (ONs) continuously under the condition of high NOx. In TD-CAPS, PNs and ONs are dissociated in heated quartz tubes to form NO2, and the NO2 concentration is measured by cavity attenuated phase shift spectroscopy (CAPS). The original TD-CAPS system overestimates PN and ON concentrations in the presence of high NO concentrations. Our laboratory experiments and numerical simulations showed that the main cause of the overestimation was NO oxidation to NO2 by peroxy radicals generated in the heated quartz tubes. In the improved system, NO was converted to NO2 by adding excess O3 after the quartz tubes so that CAPS detected NOx (NO and NO2) instead of NO2. The uncertainty of the improved system was less than 20% with ∼15 parts per billion by volume (ppbv) NO and ∼80ppbv NO2. The estimated detection limit (3σ) was 0.018ppbv with an integration time of 2minin the presence of 64ppbv NO2. The improved system was tested for measurement of PNs and ONs in an urban area, and the results indicated that interference from NO was successfully suppressed.

Synthesis of millimetre-scale HZSM-5 single crystals by secondary hydrothermal treatment

Millimetre-scale HZSM-5 single crystals were successfully synthesized by a two-step hydrothermal method. In the first step, millimetre-sized silicalite-1 single crystals were prepared by hydrothermal synthesis using quartz tube as siliceous source. In the second step, framework Al atoms were inserted into the single crystals of silicalite-1 by another hydrothermal treatment involving NaAlO2 as aluminium source. Through the characterizations of power and single crystal X-ray diffraction, optical microscope, ICP, 27Al MAS NMR, 29Si MAS NMR, and n-propylamine temperature-programmed decomposition (NPA-TPD), it was confirmed framework Al atoms with uniform spatial distribution can be inserted into giant single crystals of silicalite-1 with no obvious effects on the crystal structure, size and morphology. Such giant HZSM-5 single crystals are a promise candidate for the probe adsorption investigations, which can be applied in the measurement of framework Al spatial distribution. The strategy of insertion of aluminium or other heteroatoms of pure siliceous zeolite through secondary hydrothermal method provides a possible route to prepare giant single crystals that is difficult to synthesize directly.

Development of an Ir/TiO2 catalytic coating for plasma assisted hydrogenation of CO2 to CH4

The hydrogenation of CO2 to methane over a 20 wt% Ir/TiO2 catalytic coating has been investigated in a tubular dielectric barrier discharge (DBD) reactor. The 1.2 µm Ir/TiO2 coating was deposited onto the inner wall of a quartz tube by a combustion-evaporation method from a mixture containing a Ti precursor and a colloidal suspension of Ir nanoparticles (2 nm). The catalyst was characterised by XRD, SEM, TEM/EDS and CO chemisorption. The Ir(0) state in the as-synthesised film was confirmed by XPS. The CH4 conversion increased by 1.5 times, as compared to an empty tube. A maximum CO2 conversion rate of 2.1 μmol s−1 was achieved at a fuel production efficiency of 3.5%. Surface reactions onto the catalyst surface are responsible for enhancement of reaction rate. The results presented in this work open up new possibilities in plasma-catalysis, whereby efficient reactions can be carried out over small volumes of catalyst.

On the formation of ammonia from the thermal decomposition of hydroxylammonium nitrate vapor

The ionic liquid hydroxylammonium nitrate (HAN) is a promising propellant for various types of spacecraft propulsion systems. With respect to combustion and plasma-based electric propulsion, the thermal decomposition of HAN into gas phase species provides a convenient feed gas supply. While the decomposition of HAN in the liquid phase has been extensively studied, little is known about the decomposition chemistry of HAN vapor interacting with heated surfaces. The ability to decompose HAN vapor on a reactive surface could provide a means to control the feed gas composition and enhance the performance of spacecraft propulsion systems.In this initial qualitative study, HAN was vaporized and thermally decomposed using porous 316-stainless-steel and quartz disks under vacuum conditions. Decomposition products with low vapor pressures would condense on an in-line quartz tube which was subsequently collected and analyzed with Raman spectroscopy, NMR spectroscopy, and FT-IR spectroscopy. At temperatures above 440 K the 316-stainless-steel system produced significant quantities of ammonia which reacted with vaporized nitric acid to form ammonium nitrate. Temperatures below 440 K yielded partial HAN decomposition which resulted in a binary mixture of HAN and ammonium nitrate. The degree to which HAN was consumed was determined by analysis of the 1008 cm−1N-OH asymmetric Raman band of HAN and the 1049 cm−1 symmetric stretching Raman band of the nitrate ion, NO3−. The quartz system yielded significantly different results with no ammonium nitrate detected at temperatures above 440 K. Reformed HAN was the primary product detected at lower temperatures. The difference in reported measurements and visual observations highlights the distinct differences in HAN vapor decomposition chemistry from the two materials examined.

Synthesis, structural, optical and electrical properties of CuxSbySz powders

The family of chalcogenides appears as promising candidates to act as absorbers in alternative solar cells in order to reduce the dependence on fossil fuels. The five absorber materials, CuSbS2, Cu3SbS3, Cu3SbS4, Cu12Sb4S13 and Cu14Sb4S13, were synthesized by the direct fusion of the elements inside evacuated quartz tubes. The resulting ingots were characterized electrically by the hot probe method and by direct resistance measurement. These ingots were then ground in order to obtain very fine powders. Also their pellets were characterized by X-Ray Diffraction, Raman spectroscopy, optical and electrical analysis. The X-Ray diffraction and Raman spectroscopy results confirmed the material's purity. Their band gap energies were determined by the Kubelka-Munk model, and found to be ranging between 1.24 and 1.47 eV. The five materials have P-type conductivities.

Crystal structure and thermoelectric properties of bulk polycrystalline (SbxBi1-x)2Se3 alloys

Samples of (SbxBi1-x)2Se3 compounds were synthesized from pure elements via simple melting in evacuated quartz tubes. Internal crystal structure, distribution of constituent elements and surface morphology were examined by X-ray diffraction analysis, energy dispersive x-ray spectroscopy and scanning electron microscope, respectively. Over a temperature range of 300–480 K, electrical and thermoelectrical properties were investigated. The electrical conductivity showed semi-metallic behavior against temperature increasing till a certain point, thereafter, exhibited semiconducting trend. A significant increase was observed due to Sb-doping. Seebeck coefficient exhibited notable increase as temperature increases, reaching its maximum. However, a serious decrease was observed with further temperature increasing. The most Sb-doped compound (Sb0.1Bi0.9)2Se3 showed a maximum power factor of 13.29 μW cm−1 K−2 at 373 K. Temperature dependence of the thermoelectric figure of merit ZT was studied, showing that the values increase with temperature increasing and then decrease. For the pristine Bi2Se3 compound, at room temperature, ZT increased from 0.014 to 0.68 at 363 K and then decreased again to 0.13 at 473 K. Doping with Sb at x = 0.1 resulted in remarkable increase in the ZT values over the entire temperature range. The improvement in electrical conductivity and the power factor are responsible for the greatly enhanced ZT throughout the whole temperature range. The maximum ZT was found at 0.87 for (Sb0.1Bi0.9)2Se3 at 373 K.

Comparison of radiant intensity in aqueous media using experimental and numerical simulation techniques.

Accurately modelling the propagation of radiant intensity in aqueous environments poses significant challenges for both academia and industry, due to complex interactions like absorption, scattering, and reflection. This study aims to improve the accuracy of optical modeling in water-based systems by comparing experimental data with numerical simulation techniques, addressing the need for more reliable simulation methods in multiple applications like treatment of water and environmental monitoring.Implementation has been done by analyzing how the method compares with the discrete ordinate method, radiometry, and actinometry. The study further quantifies the effect of the photoreactor quartz tube on measured intensity for multiple wavelengths. Losses in light intensity are estimated to be 10 ± 0.5% for FX-1 265 source. In contrast, the simulation in a water medium showed an increase of up to 64% in the light intensity delivered to the central part of the tube due to internal reflections and scattering. Model predictions from ray tracing successfully compared with the Discrete Ordinate Method (DOM) and experimental data (within ± 6%), ensuring the accurate design of complex systems for water disinfection. The data from simulations is seen to tackle challenges faced in complex radiation modeling and demonstrates that the method can be utilized as a useful tool for optimization and prediction.

Diffusion flame, heated quartz tube or dielectric barrier discharge? Comparing the resistance of hydride atomizers towards interferences with detection by atomic absorption spectrometry

The resistance of three types of hydride atomizers towards interferences from other hydride forming elements and mercury was comprehensively investigated. Four hydride forming elements (Pb, Bi, Se and Te) were used as model analytes while seven hydride forming elements and mercury were investigated as potential interferents. The atomizers studied were based on a diffusion flame - DF, an externally heated quartz tube (multi)atomizer - (MM)QTA as well as a dielectric barrier discharge plasma - DBD. The performance of even two designs of DBD atomizers was compared. The first configuration (REF-SIN) was realized by a DBD chamber with glued electrodes coupled to a power supply source with sinusoidal modulation of high voltage. The second configuration of the DBD atomizer (SE-SW) comprised of a DBD chamber with the sputtered electrodes powered by a square-wave modulated high voltage source. The DF atomizer was found to be the most robust towards atomization interferences. However, its sensitivity was 30 to 50 times lower compared to (MM)QTA and DBD based atomizers due to its short optical path. The DBD atomizer in REF-SIN arrangement can compete very well with (MM)QTA atomizer in terms of resistence to interferences as well as sensitivity. The resistence of DBD atomizer in SE-SW configuration towards atomization interferences is slightly worse compared to (MM)QTA and DBD in REF-SIN design.

Measurement of the main neutral species densities and temperatures in iodine plasmas using optical absorption techniques

Iodine is a promising propellant for future plasma thrusters used in space propulsion. It is therefore important to understand the basic physics and chemistry of low-pressure iodine plasmas. In the present work, optical absorption methods are used to measure the densities of iodine molecules, I2, and iodine atoms, I, the translational temperature of the atoms and the dissociation fraction. The plasma is generated in a long quartz tube by a capacitively coupled RF discharge, and the pressure is varied between a few Pa and a few tens of Pa. The translational temperature of the atom vapour increases both with RF power and with pressure and reaches 1000 K at 50 W and 25 Pa. The molecules appear to be efficiently dissociated, with a dissociation fraction found above 65%, on average along the line-of-sight, at 120 W and 5 Pa. The population of the upper, 2P1/2∘ , fine-structure level of the atomic ground term is found to be negligible, which confirms the existence of a high quenching rate, due to collisions with molecules and/or atoms. These measurements can be helpful for chemistry models of iodine plasmas.

Thermal reflux to synthesise C3N4 nanostructures with high yield and enhanced photocatalytic activity in hydrogen evolution.

Graphitic carbon nitride (g-C3N4) is an attractive photocatalyst and a thermal reflux method was used to significantly increase the yield of g-C3N4 nanostructures and enhance their photocatalytic activity for H2 production. When raw material was placed in an inclined quartz tube with the bottom in the high temperature zone and the top in the low temperature zone, the vapor of the raw material was condensed from the top and refluxed to the bottom to then participate in the reaction again. This method can significantly improve the yield of g-C3N4 with an increase of 28.2%. When used as the photocatalyst in water splitting, these g-C3N4 nanostructures exhibit excellent activity with an H2 production of 2102 μmol h-1 g-1 under visible irradiation, which is 43.2% higher than the sample prepared by a traditional thermal polymerization method. This method is also promising to use for the synthesis of similar two-dimensional nanostructures for effective H2 production.

Applicability of quartz tube digestion for the determination of highly siderophile and volatile chalcophile element abundances with Os isotopic compositions using ICP-MS/MS and N-TIMS

Applicability of quartz tube digestion for the determination of highly siderophile and volatile chalcophile element abundances with Os isotopic compositions using ICP-MS/MS and N-TIMS

Электрохимические сенсоры на основе сеток из однослойных углеродных нанотрубок для вольтамперометрического определения аскорбиновой кислоты

Modern highly sensitive and selective sensors are able to determine biologically active substances, which makes this direction one of the most popular areas of analytical chemistry. The study featured the electrochemical properties of new fiber materials based on single-wall carbon nanotubes with prospects of using them in the voltammetry of ascorbic acid. 
 The authors developed a new technology to synthesize films from disordered single-wall carbon nanotubes by chemical vapor deposition. Fibers were produced from a solvent by wet-pulling of single-wall carbon nanotubes networks. Thin films of randomly oriented single-wall carbon nanotube bundles were deposited downstream of a floating aerosol CVD reactor, which included a high temperature furnace with a quartz tube. The synthesis of the single-wall carbon nanotube samples was performed at 825°C. Ethanol served as carbon source while ferrocene was used as catalyst precursor. The single-wall carbon nanotubes were collected on a nitrocellulose filter in the form of films with transmittances of 10% in the middle of the visible wavelength (550 nm). The method was optimized to involve air annealing at 300–320°C and a treatment with strong inorganic acids, i.e., HCl, HNO3 + H2SO4. The voltammetric curves recording included background electrolyte, scan rate, and preconditioning. These parameters were selected experimentally to obtain the maximal sensor response to ascorbic acid content. The anodic peak of ascorbic acid in the phosphate buffer electrolyte (pH 6.86) was observed at a potential of +0.2 V. The current and peak area of ascorbic acid oxidation depended neither on the time nor on the conditioning potential of the sensor. The linear dependences of these parameters on the concentration of ascorbic acid stayed within 50–500 μmol/L (8.8–90 mg/L) at a scan rate of 0.1 mV/s. The single-wall carbon nanotube microsensor had a length of 0.5 cm and an average width of 400 μm. Its sensitivity was two times as high as that of a disk glassy carbon electrode with a diameter of 5 mm. 
 The experimental sensors proved effective in determining ascorbic acid in food products, pharmaceuticals, and biological fluids.

Evaluation of inactivation of bacterial indicators in real drinking water using UVC-LED

Bacterial contamination of drinking water sources is a serious problem. Here, we investigated the inactivation of bacterial indicators, namely total heterotrophic bacteria, total and fecal coliform in real drinking water using UVC-LED devices. Real drinking water samples collected every fortnight for a year from five different sampling sites showed significant prevalence of bacterial indicators. Each device was made up of 9 UVC-LED chips arranged in a line on a heat sink, covered with quartz tube, and submersible in water. A UVC-LED chip had an emission maximum, wall plug efficiency, and radiant power of around 276 nm, 0.018, and 10–12 mW, respectively. Inactivation was performed with 4 UVC-LED devices placed in series in a rectangular stainless-steel chamber with 1.2 L effective volume. With 30 LPH flow rate, and corresponding energy dosage of about 10.8 mJ/cm2, all bacterial indicators (initial load about 103 CFU/100 mL) were inactivated, as required by regulatory bodies. Notably, dark repair of bacterial indicators was not significant (<1 %) up to 24 h of storage in clean opaque (dark) vessel, whereas slight photo repair of bacterial indicators was observed (<10 %). Electrical energy (EE3) for complete inactivation and cost for water disinfection were determined to be about 1.397 kWh/m3 and ₹ 9.03 (€ 0.09 or $ 0.10), respectively. The estimated cost is affordable in developing countries. The study may be a referral to develop applications of UVC-LED irradiation for point-of-use drinking water disinfection and useful for resource-poor communities challenged with bacterial contaminated drinking water.

Analysis of Concentrated Solar Energy Storage in Packed Beds with Multiple Heat Sources and an Optical Quartz Tube

Analysis of Concentrated Solar Energy Storage in Packed Beds with Multiple Heat Sources and an Optical Quartz Tube

Effect of overheating-induced minor addition on Zr-based metallic glasses

Melt treatment is well known to have an important influence on the properties of metallic glasses (MGs). However, for the MGs quenched from different melt temperatures with a quartz tube, the underlying physical origin responsible for the variation of properties remains poorly understood. In the present work, we systematically studied the influence of melt treatment on the thermal properties of a Zr50Cu36Al14 glass-forming alloy and unveiled the microscopic origins. Specifically, we quenched the melt at different temperatures ranging from 1.1T l to 1.5T l (T l is the liquidus temperature) to obtain melt-spun MG ribbons and investigated the variation of thermal properties of the MGs upon heating. We found that glass transition temperature, T g, increases by as much as 36 K, and the supercooled liquid region disappears in the curve of differential scanning calorimetry when the melt is quenched at a high temperature up to 1.5T l. The careful chemical analyses indicate that the change in glass transition behavior originates from the incorporation of oxygen and silicon in the molten alloys. The incorporated oxygen and silicon can both enhance the interactions between atoms, which renders the cooperative rearrangements of atoms difficult, and thus enhances the kinetic stability of the MGs.

(Invited) Proton Surface Exchange Kinetics and Stability of Thin-Film Triple Conducting Oxides for Protonic Ceramic Electrolysis Cells

Protonic ceramic electrolysis cells (PCECs) have been attracting attention due to their ability to operate in the intermediate temperature (300 - 500 ˚C) sweet-spot. These temperatures enable fast kinetics, inexpensive materials (no precious metals; stainless interconnects), and lower operating voltage for producing green hydrogen, without the accelerated degradation that may be observed at higher temperatures. The steam electrodes often support triple conduction and thereby host the proton exchange / oxygen evolution process at the surface, where steam is split. Steam electrode materials development is at a relatively early stage, with open questions around the relationships among bulk composition, evolving surface chemistry, kinetic quantities, and degradation mechanisms. We are investigating the proton exchange surface coefficient (k) and its evolution over time on model thin film electrodes in order to ultimately develop highly active and long-term stable steam electrodes for PCECs.ABO3 perovskites with Ba on the A-site and nominally multivalent ions on the B-site are candidates for steam electrodes given the varied compositions in this class that can transport oxide ions, protons, and electronic species, and the lowering of hydration enthalpies by the basicity introduced by Ba. However, very few measurements of k exist for these materials, and the evolution of surface chemistry and thus k is poorly understood.In this work, we fabricated and compared two perovskite triple conducting oxides by growing geometrically well-defined films of Ba(Pr,Y)O3-x (BPY) and Ba(Co,Fe,Zr,Y)O3-x (BCFZY) with pulsed laser deposition. We examined the proton surface exchange coefficients (k-values) using simultaneous in-situ optical transmission relaxation and electrical conductivity relaxation measurements upon switching pH2O at a temperature of 400 ˚C, and continued these switches as a function of time to assess stability. To our knowledge, this is the first use of an optical transmission method to probe elevated temperature steam splitting kinetics, and we interpret the optical (and electrical) changes as indicative of redox during the hydrogenation process. The k-values of BPY thin films were approximately ten times higher than those of the BCFZY thin films, and BPY also retained higher k-values over time. The bulk and surface chemical compositions of BPY and BCFZY thin films before and after relaxation measurements were compared using Rutherford backscattering spectrometry, angle-resolved X-ray photoelectron spectroscopy, and scanning transmission electron microscopy with spectroscopy. Pronounced Ba enrichment and Si contamination (from the quartz tube) were evident at the surface of BPY by both S/TEM-EDS and XPS, whereas for BCFZY these surface chemical features were only detectable by XPS and absent in S/TEM-EDS. Implications for materials design of steam electrodes will be discussed, considering efficiency and lifetime.

A Disposable Sensor for Rapid Histamine Detection in Fish Using Molecularly Imprinted Carbon Paste Electrode

Introduction: Histamine (HM), a toxic compound, is produced due to an enzymatic reaction when histidine (HS)-rich red fish such as tunas and other fish and their processed products are improperly stored, e.g., leaving them at room temperature. With the increasing popularity of raw fish consumption, HM analysis is mandatory for these fish in various countries. However, the conventional immunoassay method is time-consuming, costly, and technically demanding, burdening wholesalers heavily.Molecularly Imprinted Polymers-based materials are attractive materials for sensor fabrication due to their high selectivity, stability, and ease of production. In this study, we attempted to develop a Molecularly Imprinted Polymer grafted Carbon Paste (MIP-CP) for histamine sensing. Experimental Methods First, a radical polymerization initiator was fixed on the surface of graphite particles [1]. Next, histamine dihydrochloride, itaconic acid, and ethylene glycol dimethacrylate (EDMA) were dissolved in a mixture of distilled water and dimethylformamide to prepare a polymerization solution. The polymerization solution and initiator-fixed graphite were placed in a quartz tube and irradiated with a xenon lamp for 1 hr. HM was extracted and removed using acetic acid. MIP-CP was prepared by mixing MIP-grafted graphite and silicon oil containing ferrocene in a 7:3 weight ratio. Non-imprinted polymer (NIP)-CP was also prepared using the same procedure, except that HM was not added.Differential pulse voltammetry (DPV) was performed with electrodes packed with the obtained MIP-CPs on a disposable chip [2]. The performance of the HM sensor was evaluated based on the relationship between the oxidation current of ferrocene and HM concentration. (Measurement range 0 μg/mL~100 μg/mL) Experimental results The dependence of the oxidation current density on HM concentration at the NIP and MIP electrodes was confirmed (0.0085 μA-mL/μg, R²=0.9357). The increase in current density with increasing HM concentration at the MIP-CP electrode was more than three times greater than at the NIP-CP electrode. This confirmed that MIP-CP exhibited current changes corresponding to the interaction between HM and HM-imprinted sites. Furthermore, the current increased linearly with increasing HM concentration from 0-100 µg/mL. This dynamic range includes 50 µg/mL, which is considered the lower limit of acceptable Hm concentration in fish meat.However, the current value was constant for HS concentration at 0.75 µA over the range of 40-100 µg/mL and below. Therefore, the sensor is saturated with HS at concentrations above 40 µg/mL, and histidine interference can be excluded by subtracting 0.75 µA from the current value obtained when measuring the fish meat sample. Conclusion We successfully developed a reagentless, disposable histamine sensor using MIP-CP, which provides a rapid, reliable, and cost-effective method for histamine detection in fish.

Oxysulfide-Based Photocatalyst Sheet Modified with Silica Layer for Z-Scheme Overall Water Splitting at Atmospheric Pressure

Photocatalytic water splitting using particulate photocatalysts is considered as an ideal route to produce economically cheap renewable, and transportable H2 utilizing sunlight [1]. Photocatalyst sheets are directly scalable and have recently gained interest because a benchmark STH conversion efficiency of 1.0% was achieved at near ambient pressure using the one composed of Rh, La-codoped SrTiO3 and Mo-doped BiVO4 (BVO:Mo) as the H2- and O2- evolution photocatalysts (HEP and OEP), respectively. However, such systems absorb only a little portion of the sunlight due to the weak visible light absorption of the doped SrTiO3 [2]. To utilize longer wavelength visible light, our group has recently studied photocatalyst sheets composed of Ga-doped La5Ti2Cu0.9Ag0.1O7S5 (LTCA:Ga) (HEP) and BVO:Mo (OEP) with Au as conducting layer. The combination of LTCA:Ga/Au/BVO:Mo modified with Rh/Cr2O3 and CoO x as reduction and oxidation cocatalysts, respectively, achieved an STH efficiency of 0.4% under reduced pressure, but this was far lower than the oxide-based sheet system and the activity was decreased sharply against background pressure [3]. Considering intense visible light absorption of LTCA (λabs ~ 700 nm) and the associated maximum theoretical energy conversion efficiency for this combination, improvements in the net STH efficiency and activation under atmospheric pressure is highly indispensable.In this study, LTCA photocatalysts with different dopants were applied to the sheet system in combination with hydrothermally synthesized BVO:Mo and the resulting sheets were modified with CoO x /Cr2O3/Rh cocatalysts in an attempt to upgrade the water splitting activity. Moreover, surface modification onto LTCA-based photocatalyst sheets with a thin amorphous TiO2 and SiO2 layer were evaluated at elevated pressure and high temperature.Doped LTCA were synthesized by a conventional solid-state reaction in sealed evacuated quartz tubes similar to previous studies [3]. Precursors were blended inside a glove box. BVO:Mo (Mo 0.1 mol%) was synthesized by a hydrothermal method [4]. Photocatalyst sheet was fabricated by the particle transfer method [3]. SiO2 and TiO2 layers functioning as molecular sieves were deposited onto the cocatalyst-modified sheet from titanium tetraisopropoxide (TTIP) or tetraethyl orthosilicate (TEOS) by photo-decomposition and hydrolysis method, respectively, to prevent backward reactions at elevated pressure [5]. Photocatalytic water splitting reaction was carried out at different temperatures and pressures using a closed gas circulation system.Rh cocatalyst was first adsorbed and photo-deposited onto the doped LTCA/Au/BVO:Mo(h) sheet [3]. Gas evolution rates were significantly enhanced upon deposition of Cr2O3 layer as the oxygen reduction reaction (ORR), a backward reaction, was majorly suppressed promoted by uncovered Rh surface under the measured condition. Photocatalyst sheet composed of doped LTCA/Au/BVO:Mo(h) with optimal dopant amounts and cocatalysts loadings showed the H2 and O2 evolution rates of 110 and 54 µmol/h, respectively, under visible light irradiation and yielded an STH of 0.67% at 4 kPa and temperature 301 K [6]. The water splitting activity was improved by 1.6 times under reduced pressure compared to the previously studied LTCAGa/Au/BVO:Mo. However, this activity was highly sensitive against background pressure as nearly 90% reduced upon increasing pressure from 2 to 90 kPa owing to the predominating ORR occurring on LTCA and exposed Au surface. To suppress this backward reaction, TiO2 layer was coated to suppress ORR but the sheet failed to work at a temperature higher than 318 K due to the condensation of such layer. However, SiO2 layer coated sheet effectively suppressed ORR backward reaction and stably work under hot water and elevated pressure [6]. Consequently, under optimized condition SiO2 deposited sheet achieved an STH of 0.4% at 90 kPa at temperature 333 K.Doped LTCA materials were applied to the photocatalyst sheet systems as HEP along with BVO:Mo and Au layer as OEP and conductive layer, respectively, for Z-scheme pure water splitting under visible light. This combination achieved an STH of 0.67% at reduced pressure. This STH is considered as one of the highest values recorded for OWS systems involving non-oxide photocatalysts. The activity of the photocatalyst sheet was found negatively dependent onto background pressure due to the ORR on LTCA and Au layer. Surface modifications with SiO2 layer activated the sheet under atmospheric pressure. These findings will contribute to the improvement in the STH for other systems under realistic condition where OWS is likely to be conducted at an ambient pressure. References Nandy et al. Chem. Sci. 2021, 12, 9866-9884.Wang et al. Nat. Mater. 2016, 15, 611-615.Chen et al. ACS Catal. 2023, 13, 3285-3294.Li et al. Energy Environ. Sci., 2014, 7, 1369-1376.Pan et al. Angew. Chem. Int. Ed. 2015, 54, 2955-2959.Nandy et al. Joule, 2023, under revision.