PtRuP nanoparticles supported on mesoporous carbon thin film as highly active anode materials for direct methanol fuel cell

PtRu nanocatalyst supported on mesoporous carbon thin film (TFC) with incorporation of the non-metallic phosphorus is explored as an anodic catalytic material for direct methanol fuel cell (DMFC). The catalyst 20 wt.% PtRuP_0.1/TFC gives a very high current density in the electrochemical oxidation of methanol, which is much enhanced than that of the PtRu/TFC without P loading and two times higher compared to a commercial PtRu/XC-72 catalyst. XPS and EXAFS analysis of the catalysts show that phosphorus helps to reduce the size of PtRu nanoalloy by acting as a surface protecting agent to the nanoparticles and it does not alter the electronic structure of PtRu. The PtRuP nanocatalyst with a particle size of 3 nm was found to have the best reactivity and catalytic stability.     

Decolorization of organic dyes on Pilkington Activ™ photocatalytic glass

The air–solid photocatalytic degradation of organic dye films Acid Blue 9 (AB9) and Reactive Black 5 (RBk5) is studied on Pilkington Activ™ glass. The Activ™ glass comprises of a colorless TiO₂ layer deposited on clear glass. The Activ™ glass is characterized using atomic force microscopy (AFM) and X-ray diffraction (XRD). Using AFM, the TiO₂ average agglomerate particle size is 95 nm, with an apparent TiO₂ thickness of 12 nm. The XRD results indicate the anatase phase of TiO₂, with a calculated crystallite size of 18 nm.

Dyes AB9 and RBk5 are deposited in a liquid film and dried on the Activ™ glass to test for photodecolorization in air, using eight UVA blacklight-blue fluorescent lamps with an average UVA irradiance of 1.4 mW/cm². A novel horizontal coat method is used for dye deposition, minimizing the amount of solution used while forming a fairly uniform dye layer. About 35–75 monolayers of dye are placed on the Activ™ glass, with a covered area of 7–10 cm². Dye degradation is observed visually and via UV–vis spectroscopy.

The kinetics of photodecolorization satisfactorily fit a two-step series reaction model, indicating that the dye degrades to a single colored intermediate compound before reaching its final colorless product(s). Each reaction step follows a simple irreversible first-order reaction rate form. The average k₁ is 0.017 and 0.021 min⁻¹ for AB9 and RBk5, respectively, and the corresponding average k₂ is 2.0 × 10⁻³ and 1.5 × 10⁻³ min⁻¹. Variable light intensity experiments reveal a p = 0.44 ± 0.02 exponent dependency of initial decolorization rate on the UV irradiance. Solar experiments are conducted outdoors with an average temperature, water vapor density, and UVA irradiance of 30.8 °C, 6.4 g water/m³ dry air, and 1.5 mW/cm², respectively. For AB9, the average solar k₁ is 0.041 min⁻¹ and k₂ is 5.7 × 10⁻³ min⁻¹.     

Oxidative conversion of methane to syngas over NiO/MgO solid solution supported on low surface area catalyst carrier

Influence of time-on-stream (0.5–15 h), CH₄/O₂ ratio in feed (1.8–8.0), space velocity (6000–510,000 cm³ g⁻¹ h⁻¹), catalyst particle size (22–70 mesh), and catalyst dilution by inert solid particles (diluent/catalyst weight ratio=4) on the performance at different temperatures (600–900°C) of the NiO/MgO solid solution deposited on SA-5205 [which is a low surface area macroporous silica-alumina catalyst carrier] in the oxidative conversion of methane to syngas (a mixture of CO and H₂) has been investigated. The dependence of conversion and selectivity on the space velocity is strongly influenced by the temperature. Both the conversion and selectivity for H₂ and CO are decreased markedly by increasing the CH₄/O₂ ratio in the feed. The catalyst dilution resulted in a small but significant decrease in both the conversion and selectivity for H₂ and CO. The increase in the catalyst particle size had also a small but significant effect on both the conversion and selectivity in the oxidative conversion process. Both the heat and mass transfer processes seem to play significant roles in the oxidative conversion of methane to syngas at a very low contact time or very high space velocity (5.1×10⁵ cm³ g⁻¹ h⁻¹).     

Combinatorial investigation of Pt–Ru–M as anode electrocatalyst for direct methanol fuel cell

The addition of Au/TiO₂ and zeolites as active components to PtRu/C electrode in DMFC was investigated by using combinatorial high-throughput-screening test. Addition of Au/TiO₂ to PtRu/C electrode, especially in the ratio of PtRu/C: Au/TiO₂ 9:1, 8:2, 7:3, were effective to improve the performance of direct methanol fuel cell. The electrochemical properties of the prepared electrodes were compared using cyclic voltammetry, impedance spectroscopy and a single cell performance test of a direct methanol fuel cell (DMFC). The adsorbed CO on Pt might be easily oxidized on the surface of Au/TiO₂ by interaction between PtRu/C and Au/TiO₂. The addition of the solid acid proton conducting materials (ZSM-5) on PtRu/C anode leads to the high temperature operation. The cell performance was maintained over the cell temperature 120 °C (maximum current density was 200 mA/cm² at 160 °C) by the addition of ZSM-5 as proton conducting materials.     

Effects of electrodeposited Co and Co–P catalysts on the hydrogen generation properties from hydrolysis of alkaline sodium borohydride solution

Co and Co–P catalysts electroplated on Cu in sulfate based solution without or with an addition of H₂PO₂⁻ ions were developed for hydrogen generation from alkaline NaBH₄ solution. The microstructures of the Co and Co–P catalysts and their hydrogen generation properties were analyzed as a function of cathodic current density and plating time during the electrodeposition. An amorphous Co–P electrodeposit with micro-cracks was formed by electroplating in the sulfate based solution containing H₂PO₂⁻ ions. It was found that the amorphous Co–P catalyst formed at 0.01 A/cm² exhibited 18 times higher catalytic activity for hydrolysis of NaBH₄ than did the polycrystalline Co catalyst. The catalytic activity of the electrodeposited Co–P catalyst for hydrolysis of NaBH₄ was found to be a function of both cathodic current density and plating time, that is, parameters determining the concentration of P in the Co–P catalyst. Especially, Co–13 at.% P catalyst electroplated on Cu in the Co–P bath at a cathodic current density of 0.01 A/cm² for 1080 s showed the best hydrogen generation rate of 954 ml/min g-catalyst in 1 wt.% NaOH + 10 wt.% NaBH₄ solution at 30 °C.     

Preparation of highly dispersed PEM fuel cell catalysts using electroless deposition methods

A methodology for the electroless deposition (ED) of PtCl₆²⁻ using dimethylamine borane (DMAB) on a Rh-seeded carbon support has been developed for electrochemical and fuel cell applications. This procedure required seeding the carbon with a Rh-precursor catalyst via wet impregnation prior to the exposure of an aqueous ED bath containing PtCl₆²⁻, DMAB, and sodium citrate (complexing/stabilizing agent). Kinetic parameters that affect the extent and rate of PtCl₆²⁻ deposition include concentrations of PtCl₆²⁻, DMAB, and sodium citrate as well as pH and concentrations of Rh seed sites. A linear relationship between rate and extent of PtCl₆²⁻ deposition and DMAB and Rh concentrations was found while the citrate concentration had little effect on rate and a modest effect on extent. Lastly, extent of PtCl₆²⁻ deposition showed a maximum with respect to pH. Characterization of the Rh-seeded, carbon support by transmission electron microscopy (TEM) shows that the Rh particle diameters remain constant at 33–43 Å as the Rh weight loading increases from 0.4% to 2.2% to 4.4%. Further, after deposition of similar loadings of Pt, TEM analysis shows Pt particle diameters decrease with increasing Rh loading, since equal amounts of Pt were deposited on greater numbers of Rh seed particles. This pattern suggests a shell-core geometry, where Pt is deposited more or less uniformly around a Rh core.     

Influence of the surface area of the support on the activity of gold catalysts for CO oxidation

In the preparation of 1% Au/TiO₂ catalysts supported on either Degussa P-25 or anatase (90 m² g⁻¹) by deposition–precipitation, the gold content passes through a maximum at about the isoelectric point (pH 6), but maximum specific rates occur at pH 8–9 because the Au particle size becomes smaller as the pH is further increased. The gold uptake increases with the surface area of the support (anatase, rutile, P-25) and is complete above 200 m² g⁻¹; adsorption of the gold precursor at pH 9 is shown to be equilibrium-limited. Highest activities are found with supports of 50 m² g⁻¹. Catalysts made with high-area anatase (240 or 305 m² g⁻¹) are least active but show least deactivation.With Au/SnO₂ catalysts, gold uptake does not depend on the area of the support, and is highest at pH 7–8; very active catalysts (T₅₀ = 230–238 K) are obtained using SnO₂ of 47 m² g⁻¹. Storing a catalyst at 258 K for 1 week dramatically improves its stability. Results for Au/CeO₂ and Au/ZrO₂ catalysts confirm that moderate support areas give the most active catalysts, and suggest that surface area is often more important than chemical composition.     

Preparation and characterization of heteropolyacid/mesoporous carbon catalyst for the vapor-phase 2-propanol conversion reaction

H₃PMo₁₂O₄₀ catalyst was chemically immobilized on the surface modified CMK-3 (SM-CMK-3) support as a charge compensating component, by taking advantage of the overall negative charge of [PMo₁₂O₄₀]³⁻. The supported H₃PMo₁₂O₄₀/SM-CMK-3 catalyst was characterized to have high surface area (≈1000 m²/g) and relatively large pore volume (0.83 cm³/g). The H₃PMo₁₂O₄₀/SM-CMK-3 catalyst was applied to the vapor-phase 2-propanol conversion reaction. The H₃PMo₁₂O₄₀/SM-CMK-3 catalyst exhibited higher 2-propanol conversion than the unsupported H₃PMo₁₂O₄₀ and the impregnated H₃PMo₁₂O₄₀ on CMK-3. Furthermore, the PMo₁₂/SM-CMK-3 catalyst showed the enhanced oxidation activity (acetone formation) and the suppressed acid catalytic activity (propylene formation) compared to the other two catalysts. It is believed that [PMo₁₂O₄₀]³⁻ species were chemically and finely immobilized on the SM-CMK-3 support as charge matching species, and thus, the PMo₁₂/SM-CMK-3 catalyst showed an excellent oxidation activity.     

Conversion of syn-gas to lower alkenes over Fe-TiO2-ZnO-K2O catalyst system

Conversion of syn-gas to lower alkenes is studied over a multicomponent catalyst system, Fe-TiO₂-ZnO-K₂O. Various reaction variables affecting the conversion were studied. At H₂:CO=1, 2.5 kg/cm² pressure, 250°C temperature and GHSV=960 h⁻¹, maximum selectivity of 68% to alkenes was obtained at 45% conversion of the feed. The alkenes consist of a mixture of propylene (65%) and ethylene (35%). The catalyst is active even after 200 h of use. The catalyst samples were characterised by BET surface area measurements, TPR and TPD. XRD and ESCA studies reveal the presence of Fe₂O₃ phase in the fresh catalyst. This phase is ably promoted by Zn and K. On reaction with CO+H₂, electron-rich species are formed on catalyst surface, which are the most likely active species. In addition to this, there is an improvement in dispersion of the active phase. These factors may contribute toward better performance of the catalyst in the conversion of syn-gas to lower alkenes.     

Photocatalytic conversion of CH4 and CO2 to oxygenated compounds over Cu/CdS–TiO2/SiO2 catalyst

Coupled semiconductor (CS) Cu/CdS–TiO₂/SiO₂ photocatalyst was prepared using a mutli-step impregnation method. Its optical property was characterized by UV–vis spectra. BET, XRD, Raman and IR were used to study the structure of the photocatalyst. Fine CdS was found dispersed over the surface of anatase TiO₂/SiO₂ substrate. Chemisorption and IR analysis showed methane absorbed in the molecular state interacted weakly with the surface of catalyst, and the interaction of CO₂ with CS produced various forms of absorbed CO₂ species that were primarily present in the form of formate, bidentate and linear absorption species. Photocatalytic direct conversion of CH₄ and CO₂ was performed under the operation conditions: 373 K, 1:1 of CO₂/CH₄, 1 atm, space velocity of 200 h⁻¹ and UV intensity of 20.0 mW/cm². The conversion was 1.47% for CH₄ and 0.74% for CO₂ with a selectivity of acetone up to 92.3%. The reaction mechanisms were proposed based on the experimental observations.     

Combustion synthesis and electrochemical characterisation of Pt–Ru–Ni anode electrocatalyst for PEMFC

The present work studies the synthesis by the combustion method of an anode catalyst for protonic exchange membrane fuel cell (PEMFC) employing two different fuels, that is, urea and sucrose. The unsupported pure solid solution Pt_0.6Ru_0.3Ni_0.1 was selected from a calculated and empirical ternary phase diagram, which was previously studied. Theoretically, this particular composition exhibited single-phase features without the presence of secondary phases as RuO₃ and NiO, regarding the oxygen partial pressure conditions generated during the combustion synthesis. In the X-ray diffraction (XRD) analysis of the nanoparticles synthesized by using two different fuels, a single-phase Pt_0.6Ru_0.3Ni_0.1 alloy was detected. However, the X-ray photoelectron spectroscopy (XPS) studies showed that the nanoparticles prepared could present an onion-shell structure, in the case of the sample synthesized with sucrose as fuel, the external layers are partially constituted by Ni hydroxides, which can exhibit an active role in the hydrogen oxidation reaction. The electrochemical behaviour of this unsupported catalyst was performed by preparing MEAs, which were evaluated using a I–V polarisation curve test. The results obtained indicated that the nanoparticles prepared by sucrose have better performance, 260 mW/cm², than those prepared using urea, 170 mW/cm². These results are discussed in relation with the hydrogen oxidation mechanism. The results obtained reveal combustion synthesis as an appropriate method for preparing PEMFC electrocatalysts, due to its versatility, simplicity and fastness.     

High-loading Pt-alloy catalysts for boosted oxygen reduction reaction performance

To improve performance of membrane electrode assembly (MEA) at large current density region, efficient mass transfer at the cathode is desired, for which a feasible strategy is to lower catalyst layer thickness by constructing high loading Pt-alloy catalysts on carbon. But the high loading may induce unwanted particle aggregation. In this work, H-PtNi/C with 33% (mass) Pt loading on carbon and monodisperse distribution of 3.55?nm PtNi nanoparticles, was prepared by a bimodal-pore route. In electrocatalytic oxygen reduction reaction (ORR), H-PtNi/C displays an activity inferior to the low Pt loading catalyst L-PtNi/C (13.3% (mass)) in the half-cell. While in H₂-O₂ MEA, H-PtNi/C delivers the peak power density of 1.51?W·cm^?2 and the mass transfer limiting current density of 4.4?A·cm^?2, being 21% and 16% higher than those of L-PtNi/C (1.25?W·cm^?2, 3.8?A·cm^?2) respectively, which can be ascribed to enhanced mass transfer brought by the thinner catalyst layer in the former. In addition, the same method can be used to prepare PtFe alloy catalyst with a high-Pt loading of 36% (mass). This work may lead to a range of catalyst materials for the large current density applications, such as fuel cell vehicles.     

Catalysed titanium mesh electrodes for ethylene glycol fuel cells

Electrodes comprising thermally deposited Pt, PtRu and PtRuW on titanium mesh were evaluated for the oxidation of ethylene glycol in acidic electrolyte. The electrodes were characterised using cyclic voltammetry, scanning electron microscopy and X-ray diffraction and the effect of reactant concentration and temperature were examined. Single fuel cell tests employing the titanium mesh anode with the PtRuW catalyst showed better performance than that of the PtRu catalyst. A peak power density of 15 mW cm⁻² was obtained at a temperature of 90 °C with 1.0 M ethylene glycol solution. The performance of the catalysed PtRu mesh electrode was comparable to that of a commercial, alcohol oxidation, PtRu carbon supported catalyst.     

炭化工艺对酚醛树脂基碳分子筛性能的影响

以工业酚醛树脂为碳源,三嵌段聚合物F127为模板剂,制备碳分子筛。采用N_2吸附-脱附对制备的碳分子筛进行表征,研究炭化制备工艺对碳分子筛孔径分布的影响。结果表明,炭化温度、炭化时间和炭化升温速率对碳分子筛孔径分布影响较大。在炭化升温速率为1℃·min~(-1)、炭化温度800℃和炭化时间1 h条件下制备的碳分子筛孔径分布最为集中,BET比表面积716.59 m~2·g~(-1),单点总孔容0.557 75 cm~3·g~(-1),单点吸附微孔孔容0.301 81 cm~3·g~(-1)。     

Ce修饰Na Y分子筛负载PdO纳米晶催化剂用于苯的催化氧化反应

以CeO_2修饰多孔NaY分子筛作为载体,采用高温液相还原法制备纳米晶PdO催化剂,用于低浓度苯催化氧化反应。采用XRD、N2吸附-脱附、透射电镜-能谱(HRTEM-EDS)、H2程序升温还原(H_2-TPR)、O_2程序升温脱附(O_2-TPD)和程序升温表面反应(TPSR)等对载体和催化剂进行表征。结果表明,NaY分子筛结构稳定,比表面积651 m~2·g~(-1)和孔容0. 326 cm~3·g~(-1),纳米晶PdO能够较均匀地分散在NaY载体上,颗粒尺寸约(3～5) nm。加入一定量CeO_2后,Pd O以较小的纳米晶颗粒形式分散在CeO_2周围,活性组分与助剂协同作用促进了催化剂中晶格氧的流动性,明显改善了0. 2%Pd/NaY的氧化性能。0. 2%Pd/8%Ce/NaY表现出最佳催化活性和良好稳定性,250℃可完全催化降解1000×10~(-6)的苯,并且230℃连续反应100 h,催化剂转化率稳定在86%。     

电极对微生物燃料电池同时处理有机废水和含铜重金属废水产电性能的影响

实验以有机废水为阳极底物,以活性污泥中的混合菌为阳极接种微生物,以含铜废水为阴极液,构建双室MFC,探讨电极对MFC同时处理有机废水和含铜重金属废水产电性能的影响.结果表明:MFC对阳极有机废水COD的去除率最高为79.1%,对阴极液中Cu²⁺的去除率最高为95.6%.活性炭/石墨棒电极MFC产电性能最优,开路电压最高为800mV,是石墨棒电极MFC的1.25倍,是活性炭/碳纸电极MFC的1.3倍,是碳纸电极MFC的1.5倍.当电极距离为2cm时,MFC开路电压580mV,内阻为181Ω,产电性能最优.电极表面积为75cm²时,MFC的开路电压470mV,是电极表面积为50cm²的MFC的1.1倍,是电极表面积为30cm²的MFC的2.1倍.当A_An/A_cat=0.4时MFC产能最佳,MFC的开路电压最高为600mV,最大功率密度48.2mW/m².     

多孔纳米碳纤维作为质子交换膜燃料电池微孔层的性能

质子交换膜燃料电池膜电极中的微孔层结构对改善体系的水管理能力,提升膜电极的整体性能发挥重要作用。本文通过静电纺丝和后续热处理的方法制备了多孔纳米碳纤维（PCNF）,并以此构建膜电极的微孔层。与炭黑颗粒作为微孔层呈现出紧密堆积结构不同,由PCNF搭建的微孔层结构疏松呈现三维贯通状。膜电极的发电测试表明,以多孔纳米碳纤维作为微孔层（MPL-PCNF）的膜电极其最大功率密度达70.0mW/cm²,远高于炭黑颗粒为微孔层（MPL-CB）的膜电极（58.1mW/cm²）,而没有微孔层（Ref）结构的膜电极最大功率密度仅为27.7mW/cm²,显示出PCNF作为微孔层材料的明显优势。     

Highly active PtRu catalysts supported on carbon nanotubes prepared by modified impregnation method for methanol electro-oxidation

A simple and rapid synthesis method (denoted as modified impregnation method, MI) for PtRu/CNTs (MI) and PtRu/C (MI) was presented. PtRu/CNTs (MI) and PtRu/C (MI) catalysts were characterized by transmission electron microscopy (TEM) and X-ray diffractometry. It was shown that Pt-Ru particles with small average size (2.7 nm) were uniformly dispersed on carbon supports (carbon nanotubes and carbon black) and displayed the characteristic diffraction peaks of Pt face-centered cubic structure. Cyclic voltammetry and chronoamperometry showed that the Pt-Ru/CNTs (MI) catalyst exhibited better methanol oxidation activities than Pt-Ru/C (MI) catalyst and commercial Pt-Ru/C (E-TEK) catalyst. The single cells with Pt-Ru/CNTs (MI) catalyst exhibited a power density of 61 mW/cm², about 27% higher than those single cells with commercial Pt-Ru/C (E-TEK) catalyst.     

Preparation of three-dimensional ordered macroporous SiCN ceramic using sacrificing template method

Three-dimensional (3D) long range well ordered macroporous SiCN ceramics were prepared by infiltrating sacrificial colloidal silica templates with the low molecular weight preceramic polymer, polysilazane. This was followed by a thermal curing step, pyrolysis at 1250 °C in a N₂ atmosphere, and finally the removal of the templates by etching with dilute HF. The produced macroporous SiCN ceramics showed high BET surface areas (pore volume) in the range 455 m²/g (0.31 cm³/g)–250 m²/g (0.16 cm³/g) with the pore sizes of 98–578 nm, which could be tailored by controlling the sizes of the sacrificial silica spheres in the range 112–650 nm. The sphere-inversed macropores were interconnected by 50 ± 30 nm windows and 3–5 nm mesopores embedded in the porous SiCN ceramic frameworks, which resulted in a trimodal pore size distribution. The surface of the achieved porous SiCN ceramic was then modified by Pt–Ru nanoparticle depositing under mild chemical conditions.     

YSZ thin films deposited by spin-coating for IT-SOFCs

Dense and crack-free yttria stabilized zirconia (YSZ) thin films were fabricated using a spin-coating technique for intermediate temperature solid oxide fuel cells (IT-SOFCs). The film thickness was greatly affected by spinning speed and coating cycles. The morphology of the films was investigated with scanning electron microscope. With cathodes consisting of yttria-stabilized bismuth oxide and sliver, anodes of samaria-doped ceria and nickel, the supported YSZ films were characterized as electrolytes for single cells with humidified hydrogen as fuel and stationary air as oxidant. Open circuit voltage was 1.08 V at 700 °C, close to the theoretical value and power density was 535 mW/cm² at 750 °C and 400 mW/cm² at 700 °C. Impedance analysis indicates that the performances of the SOFCs are determined essentially by the interfacial resistances, suggesting that optimizing the electrode materials are especially important for IT-SOFCs.