Comparative study of hydrogen peroxide electro-generation on gas-diffusion electrodes in undivided and membrane cells

The generation of hydrogen peroxide by means of the cathodic reduction of oxygen at gas-diffusion electrodes with a near 100% current efficiency was achieved in concentrations sufficient for the mineralization of refractory organics in Fenton treatment. A decrease in current efficiency over time at high temperatures and high current densities was observed. The polarization study carried out in potentiostatic, potentiodynamic and galvanostatic modes in 0.5 M Na₂SO₄ solution at pH 3 showed that the destruction of hydrogen peroxide at the cathode of the electrochemical reactor, as well as its chemical decomposition in the bulk solution, takes place at a significantly lower rate than the oxidation of H₂O₂ at the Ti–IrO₂ anode. Preparative electrolysis in the membrane reactor showed much higher current efficiencies for H₂O₂ electro-generation in comparison with tests carried out in an undivided cell. The performance of different proton-exchange membrane in this process was studied and a membrane cell with a heterogeneous MK-40 type PEM was found to be suitable. An optimized cell design, the appropriate selection of electrodes, supporting electrolytes, and a membrane resulted in a lower voltage in the membrane cell in comparison with the undivided cell.     

Influence of surfactants on the electroreduction of oxygen to hydrogen peroxide in acid and alkaline electrolytes

The effect of surfactants on the electroreduction of O₂ to H₂O₂ was investigated by cyclic voltammetry and batch electrolysis on vitreous carbon electrodes. The electrolytes were either 0.1 M Na₂CO₃ or 0.1 M H₂SO₄ at 295 K, under 0.1 MPa O₂. Electrode kinetics and mass transport parameters showed the influence of surfactants on the O₂ electroreduction mechanism. The cationic surfactant (Aliquat 336^®, tricaprylmethylammonium chloride), at mM levels, increased the standard rate constant of O₂ electroreduction to H₂O₂ 15 times in Na₂CO₃ and 1900 times in H₂SO₄, to 1.8 × 10^–6 m s^–1 and 9.9 × 10^–10 m s^–1, respectively. This effect on the reaction rate might be due to an increase of the surface pH, induced by the Aliquat 336^® surface film. The nonionic (Triton X-100) and anionic (sodium dodecyl sulfate) surfactants retarded the O₂ electroreduction, presumably by forming surface structures, which blocked the access of O₂ to the electrode. Ten hour batch electrosynthesis experiments performed at 300 A m^–2 superficial current density, 0.1 MPa O₂, 300 K, on reticulated vitreous carbon (30 ppi), showed that compared to the values obtained in the absence of surfactant, mM concentrations of Aliquat 336^® increased the current efficiency for peroxide from 12% to 61% (0.31 M H₂O₂) in 0.1 M Na₂CO₃ and from 14% to 55% (0.26 M H₂O₂) in 0.1 M H₂SO₄, respectively.     

Electrosynthesis of hydrogen peroxide by partial reduction of oxygen in alkaline media. Part II: Wall-jet ring disc electrode for electroreduction of dissolved oxygen on graphite and glassy carbon

A wall-jet ring disc electrode was constructed by adapting a wall-jet flow through electrochemical cell. Commercially available spectral graphite and glassy carbon were used as working disc electrodes and the ring electrode was made of stainless steel. The efficiency and rate constants, measured in a planar parallel flow hydrodynamic regime, indicated the partial electroreduction of dissolved oxygen as a quasi-reversible two-electron process for both electrode materials tested.     

Preparation and electrochemical property of three-phase gas-diffusion oxygen electrodes for metal air battery

Three-phase gas-diffusion oxygen electrodes for metal air battery were prepared and characterized. Nano-structured γ-MnO₂ catalysts were synthesized by solid state redox reaction of two compounds, Mn(CH₃COO)₂·4H₂O and C₂H₂O₄·2H₂O. Their crystal phase, morphologies and particle size were characterized by XRD, TEM, respectively. The electrochemical property of three-phase gas-diffusion oxygen electrodes composed of nano-structured γ-MnO₂ catalysts for oxygen reduction was examined by using the linear polarization method in a neutral solution. Besides, the surface morphologies of the catalytic layer of three-phase gas-diffusion oxygen electrodes were also investigated by SEM. Experimental results revealed that these kinds of three-phase gas-diffusion oxygen electrodes have excellent electrochemical performance. The optimal proportion of nano-structured γ-MnO₂ catalysts in the catalytic layer was 60 wt.%. Three-phase gas-diffusion oxygen electrodes composed with nano-structured γ-MnO₂ catalysts appear to be a highly possible candidate for applications in neutral solution metal air battery.     

A hydrogen peroxide sensor based on electrochemically roughened silver electrodes

Silver (Ag) electrodes were roughened by electrochemical oxidation-reduction cycles (ORC) in a KCl solution. The roughened Ag electrode exhibited a powerful electrocatalytic activity for the reduction of hydrogen peroxide (H₂O₂). Atomic force microscopy and electrochemical experiments confirmed that the electrocatalytic ability mainly resulted from the Ag nanoparticles produced in the process of ORC on the roughened Ag electrode. The electrochemical behaviors of the roughened Ag electrodes toward the reduction of H₂O₂ and the factors related to that reduction were investigated in detail.     

氢氧直接合成过氧化氢贵金属催化剂的研究

采用浸渍法制备了一系列负载型钯催化剂，用于催化氢气和氧气直接合成过氧化氢的反应。分别考察了钯负载节、溶剂、载体预处理对反应的影响；结合XPS分析推断了催化剂活性组分价态。结果发现钯最佳负载量为1．88％（质量分数）；氢气在溶剂中的溶解度越大其反应转化率也越高，其中甲醇和丙酮都是良好的溶剂；载体经过卤化铵预处理可大幅度地提高催化剂的选择性；金属态钯为具有催化活性的价态。     

Improved performances of electrodes based on Cu-loaded copper hexacyanoferrate for hydrogen peroxide detection

Copper hexacyanoferrate thin films were potentiodynamically deposited on glassy carbon electrodes and employed for the chronoamperometric detection of hydrogen peroxide at 0.0 V vs. SCE. A new experimental procedure based on the intercalation of copper ions inside the structure of the films led to sensors with improved performances. The modified electrode displayed an increased sensitivity to hydrogen peroxide detection together with a wider linear response range and a lower detection limit. Furthermore, even if the electrode response decreased with use, the initial activity could be restored by performing a new intercalation procedure.     

用氢氧的非平衡等离子体直接合成过氧化氢

引言 过氧化氢是一种多用途绿色氧化剂,目前主要用蒽醌法生产.蒽醌法虽然技术成熟,但过程复杂,装置投资大,生产成本高,且对环境有污染.因此,近年来国外对于以氢气和氧气为原料,直接合成过氧化氢的新方法研究十分重视[1-3].     

Catalytic epoxidation with electrochemically in situ generated hydrogen peroxide

The epoxidation of allyl alcohol with in situ generated hydrogen peroxide was performed in an electrochemical cell with a trickle-bed electrode, composed of carbon black, graphite, PTFE and titanium silicalite-1 (TS-1) as heterogeneous epoxidation catalyst. Mass transport in interaction with the catalytic activity limits the epoxidation rate. The conversion of allyl alcohol increases with increase in the content of epoxidation catalyst in the electrode. In contrast, the specific reaction rate decreases due to the reduced accessibility of active sites in the catalyst.     

Kinetic characterization of Prussian Blue-modified graphite electrodes for amperometric detection of hydrogen peroxide

Prussian Blue-modified graphite electrodes (G/PB) with electrocatalytic activity toward H₂O₂ reduction were obtained by PB potentiostatic electrodeposition from a mixture containing 2.5 mm FeCl₃ + 2.5 mm K₃[Fe(CN)₆] + 0.1 m KCl + 0.1 m HCl. From cyclic voltammetric measurements, performed in KCl aqueous solutions of different concentrations (5 × 10⁻²–1 m), the rate constant for the heterogeneous electron transfer (k _s) was estimated by using the Laviron treatment. The highest k_s value (10.7 s⁻¹) was found for 1 m KCl solution. The differences between the electrochemical parameters of the voltammetric response, as well as the shift of the formal potential, observed in the presence of Cl⁻ and NO₃⁻ compared to those observed in the presence of SO₄²⁻ ions, points to the involvement of anions in the redox reactions of PB. The G/PB electrodes showed a good electrochemical stability proved by a low deactivation rate constant (0.8 × 10⁻¹² mol cm² s⁻¹). The electrocatalytic efficiency, estimated as the ratio , was found to be 3.6 (at an applied potential of 0 mV vs. SCE; Γ = 5 × 10⁻⁸ mol cm⁻²) for a H₂O₂ concentration of 5 mm, thus indicating G/PB electrodes as possible H₂O₂ sensors.     

反应介质对氢氧直接合成过氧化氢的影响研究

以超声浸渍法制备的PdO／γ-Al2O3-U为催化剂,考察不同无机酸、不同硫酸浓度对氢氧直接合成过氧化氢的影响。结果表明：酸性介质有利于氢氧直接合成过氧化氢,当反应介质为H2SO4溶液时,氢氧直接合成过氧化氢收率好于其他,其最佳浓度为0．35mol／L。     

惰性气体对氢氧等离子体直接合成过氧化氢的影响

在H₂/O₂体系中添加惰性气体(Ar、He、N₂)进行常压介质阻挡放电,合成了H₂O₂水溶液。系统研究了不同惰性气体对体系击穿电压及H₂O₂合成能效的影响。结果表明,添加气体对击穿电压、O₂转化率、H₂O₂选择性、H₂O₂收率及能量效率能产生较大影响。其中Ar的引入不仅降低了击穿电压,还提高了合成H₂O₂的能量效率;当Ar添加量为56.6 ml·min^-1时,击穿电压由11.8 kV降为10.2 kV;合成H₂O₂的能量效率提高51%,由3.45 g·(kW·h)^-1提高至5.20 g·(kW·h)^-1(以100%H₂O₂计)。发射光谱表征发现,在H₂-O₂-Ar放电体系中存在以亚稳态为末态的辐射Ar(696.5、794.8、811.5 nm),表明亚稳态Ar物种的潘宁电离作用可能是降低击穿电压的主要因素。由示波器测量的放电电流波形图可知,Ar的加入增大了体系电子密度,使得相同功率下O₂转化速率大幅提高,从而使合成H₂O₂能量效率显著提高。     

Macrokinetic analysis of polarisation characteristics of gas-diffusion electrodes in contact with liquid electrolytes, Part II: Oxygen reduction as example for a higher order reaction

Classical partial oxidation processes often suffer from low selectivities. Promising alternatives are electrochemical processes where the oxidation takes place at a packed-bed anode while an oxygen-consuming gas–liquid membrane is used as cathode. As a basis for the reliable design of such a process, the performance of oxygen-consuming gas-diffusion electrodes (GDE) is investigated experimentally and is analysed based on a rigorous model accounting for the reaction microkinetics and all relevant mass and charge transport phenomena. The results indicate that oxygen is transported in the gas-filled pores by Knudsen diffusion and that the cathodic oxygen reduction follows a parallel reaction scheme forming hydrogen peroxide at the carbon black support and water at the applied platinum catalyst particles.     

过氧化氢稳定度简易分析方法

国内外过氧化氢标准给出的过氧化氢稳定度的分析方法分析操作时间长达几个小时至十几个小时,对生产过程中工艺指标分析和用户使用分析带来不便,尤其是在需要大量和全面监控产品质量的情况下,更需加大人力和物力上的投入。介绍了一种快速分析过氧化氢稳定度的方法,利用测量过氧化氢在一定温度和时间下分解所放出的氧气体积量来计算出与国家标准条件相当的稳定度的大小。经过工厂和有关单位的实际应用,证明此方法可满足生产单位、应用单位和科研单位的需求。利用该方法可在1.5 h内得到分析结果,从而更加快速地指导生产。     

双氧水装置的化学清洗技术

对福州一化化学品有限公司双氧水装置新、旧系统投产前的清洗实例表明,该法对蒽醌法生产过氧化氢的装置进行清洗,可满足双氧水生产的要求。介绍了双氧水的生产流程、清洗原理和工艺。     

Epoxidation of propylene and direct synthesis of hydrogen peroxide by hydrogen and oxygen

The autoreduction of palladium–platinum-containing titanium silicalite leads to an effective catalyst for the epoxidation of propylene to propylene oxide by O₂ in the presence of H₂. The one-pot reaction is favoured compared to the two-step reaction path.     

Synthesis of hydrogen peroxide in microbial fuel cell

BACKGROUND: Hydrogen peroxide (H₂O₂) is an important chemical product, and this study investigated its synthesis at the cathode of a microbial fuel cell (MFC) system using spectrographically pure graphite (SPG) rods as cathode electrode. RESULTS: Electrochemical methods showed that oxygen reduction reaction (ORR) on SPG mainly followed the two‐electron pathway yielding H₂O₂, while, the optimal condition for H₂O₂ production was in 0.1 mol L^?1 Na₂SO₄ electrolyte. When SPG was used as the cathodic electrode in the MFC system, H₂O₂ concentration reached 78.85 mg L^?1 after 12 h operation with an external resistance of 20 Ω (H₂O₂ production rate was 6.57 mg L^?1 h^?1). Coulombic efficiency, current efficiency and COD conversion efficiency were 12.26%, 69.47% and 8.51%, respectively. Repeated experiments proved this system had a stable operating performance. CONCLUSIONS: H₂O₂ was synthesized at the cathode of an MFC, and this study provides a proof‐of‐concept demonstration to realize the process of synthesizing H₂O₂ with wastewater. Copyright © 2010 Society of Chemical Industry     

蒽醌法双氧水钯催化剂的制备及工业应用

以铝溶胶、丙烯酸-丙烯酰胺共聚物（AC-1）、六亚甲基四胺为原料,采用油柱成型法制备氧化铝球形颗粒,并使用浸渍法得到Pd/Al2O3催化剂,用于2-乙基蒽醌催化加氢反应。使用N2吸附、XRD、TEM、CO脉冲滴定等手段对催化剂进行表征,考察了添加AC-1对催化剂结构的影响。结果表明,加入AC-1不改变催化剂的晶体结构,但会增加比表面积和孔径,同时使催化剂表面Pd颗粒的尺寸减小,Pd的分散度增大。催化剂在实验室反应器中的活性由12.5 g/L增加至14.5g/L,在过氧化氢产能为10kg/天的模型实验装置和7000吨/年的工业生产装置中时空产率分别提升77%和70.0%,在过氧化氢产能为20万吨/年的工业生产装置中,时空产率可达8.35 kg 过氧化氢/(kg 催化剂•d),显著高于现有工业用催化剂（ 6.14 kg 过氧化氢/(kg 催化剂•d)）。     

氢氧直接合成过氧化氢用催化剂的研究进展

过氧化氢（H₂O₂）是一种高效的绿色氧化剂,广泛应用于化学品合成、印染纺织、污水处理等领域。近年来,氢氧直接合成过氧化氢作为一种简单、环保、原子效率高的合成方法,成为一大研究热点。本文系统性地介绍了近年来氢氧直接合成过氧化氢催化剂的催化反应机理,负载金属的不同结构和性质对直接合成过氧化氢的催化性能与作用机理,重点讨论了与催化剂载体相关的载体结构、载体酸性、载体添加物、载体与金属相互作用等方面对反应活性和选择性的影响。最后对比了近年来直接合成过氧化氢用催化剂的催化性能,认为合成高选择性、高产率的催化剂仍是未来直接合成过氧化氢工业化应用的发展方向。