Study on the Oxidation Enhancement of Formic Acid and Formate Blended Fuel Solution on Pt Catalyst

The effect of [HCOOH]/[HCOONa] ratio on the oxidation activity of HOOH and HCOONa blended fuel solution on Pt nanocatalyst is studied using cyclic voltammetry, chronoamperometry, and Tafel analysis. Five electrolyte solutions with the same total concentrations of HCOOH and HCOONa but different [HCOOH]/[HCOONa] ratios are tested. Blended solutions containing both higher HCOOH and HCOONa concentrations are found to be more active than single HCOOH or HCOONa solution, with the solution containing 0.8 mol dm^–3 HCOONa and 0.2 mol dm^–3 HCOOH exhibiting the best activity. The reasons behind the better performance of the HCOOH and HCOONa blended solutions – such as electric conductivity, pH, concentrations of HCOOH, and HCOONa, ionic strength of the solution, and oxidation mechanism of HCOOH – are investigated. Enhanced oxidation activity of the HCOOH and HCOONa blended solution is observed to be the mutual effect of various reasons, with pH and [HCOO^–] assuming the key roles.     

Synthesis of Pd/C Catalyst by Modified Polyol Process for Formic Acid Electrooxidation

Pd catalyst supported on Vulcan XC‐72 carbon black was prepared by a modified polyol process. Its performance was compared with that of Pd/C catalyst prepared by impregnation reduction method by using NaBH₄ as a reducing agent for formic acid electrooxidation. Their physical characterisations were tested by means of energy dispersive analysis of X‐ray, X‐ray diffraction and transmission electron micrographs. Their activities were presented by cyclic voltammetry and chronoamperometry. The results show that the particle sizes of Pd/C catalysts prepared by modified polyol process and impregnation reduction method are 3.9 and 7.9 nm, respectively. The size dispersion of the former is narrower and more homogeneous than that of the latter. However, both of Pd/C catalysts display the characteristic diffraction peaks of a Pd face‐centred cubic (f.c.c.) crystal structure. The results of electrochemical measurements present that the Pd/C catalyst prepared by modified polyol process has the higher electrocatalytic activity and stability for formic acid electrooxidation in comparison to the Pd/C one by impregnation reduction method due to the particle size effect, and its peak current density of CV and the current of chronoamperometric curve at 1,000 s reach 33.2 and 11.2 mA cm^–2, respectively.     

Effect of pH Value and Temperatures on Performances of Pd/C Catalysts Prepared by Modified Polyol Process for Formic Acid Electrooxidation

The highly active Pd/C catalysts for formic acid electrooxidation have been prepared by a modified polyol process at different pH values of reaction solutions and different reducing temperatures, respectively. Their physical properties have been characterised by energy dispersive analysis of X‐ray, X‐ray diffraction and transmission electron microscopy. Their electrochemical performances for formic acid electrooxidation have been tested by cyclic voltammetry and amperometric i–t curves. The results of physical characterisations show that all the Pd/C catalysts present an excellent face centered cubic crystalline structure. Their particle sizes are decreasing firstly and then increasing with the increasing of the pH values of reaction solutions. The reducing temperatures also markedly affect the Pd particle sizes. And their nanoparticles have narrow size distributions and are highly dispersed on the surface of carbon support, and Pd metal loading in Pd/C catalyst is similar to the theoretical value of 20 wt.%. The results of electrochemical measurements present that the Pd/C catalyst prepared by waterless polyol process at the pH value of 10 and the reducing temperature of 120 °C has the smallest particle size of about 5.6 nm, and exhibits the highest catalytic activity (1172.0 A · g_Pd<?h‐2.85>^–1<?h.8>) and stability for formic acid electrooxidation.     

Evaluation of the Performance of Platinum Nanoparticle–Titanium Oxide Nanotubes as a New Refreshable Electrode for Formic Acid Electro‐oxidation

Platinum nanoparticles (Pt‐NP) are deposited on the surface of titanium oxide nanotubes (TN) by microemulsion method. Highly ordered TN on a pure titanium substrate are successfully fabricated by anodizing of titanium. The morphology and surface analysis of Pt‐NP/TN electrodes were investigated using scanning electron microscopy and X‐ray diffraction spectroscopy, respectively. The electro‐oxidation of formic acid on Pt‐NP/TN electrodes in acidic medium was studied by cyclic voltammetry and chronoamperometry methods. The results showed that the oxidation peak currents on the Pt‐NP/TN electrode for formic acid oxidation are several times larger than a smooth platinum electrode and confirmed the better electro‐catalytic activity and stability of these new electrodes. The photocatalytic properties of titanium oxide make the Pt‐NP/TN electrode reusable after a short UV treatment, and the electro‐oxidation current density of Pt‐NP/TN electrode after UV‐cleaning can be re‐established. So Pt‐NP/TN electrode has a good application potential to fuel cells.     

Direct Formic Acid Fuel Cells with 600 mA cm–2 at 0.4 V and 22 °C

A demonstration of direct formic acid fuel cells (DFAFCs) generating very high power density at ambient temperature is reported. In particular, the performance of the Pd black as an anode catalyst for DFAFCs with different formic acid feed concentrations at different operating temperatures has been evaluated. The Pd black based DFAFCs with dry air and zero backpressure can generate a maximum power density of 248 and 271 mW cm^–2 at 22 °C and 30 °C respectively. The open cell potential is 0.90 V. These results show that DFAFCs are potentially excellent alternative power sources for small portable electronic devices.     

A Sulfophenylated Polysulfone as the DMFC Electrolyte Membrane – an Evaluation of Methanol Permeability and Cell Performance

A sulfophenylated polysulfone (PSU‐sph), carrying 0.8 sulfonic acid units per repeating unit of the polymer, is evaluated as a membrane electrolyte for DMFC applications. The liquid uptake, methanol transport characteristics, electrolyte conductivity, and fuel cell performance are investigated. The methanol transport and DMFC performance results are compared to those of Nafion® 117. The PSU‐sph membrane investigated shows superior qualities with regard to methanol crossover, with a methanol permeability of approximately 25% compared to that of Nafion®. The conductivity was measured to be 15% compared to that of Nafion®. However, this could not fully account for the internal resistance of the cell, implying that the contact resistance between the electrodes and electrolyte is higher when PSU‐sph is used, probably because the electrodes are developed for use with Nafion® membranes. The stability of the PSU‐sph membrane seems promising, with very low degradation observed over a period of 72 hours. It was concluded that although the mass transport properties of the PSU‐sph membrane sample investigated were superior, it could not match the performance of Nafion® 117 in a DMFC application. However, a higher degree of sulfonation may have a significant positive effect on cell performance. The results also showed that a fully intergrated MEA is needed to fully assess new menbrane materials.     

Effective Catalysts for Wet Oxidation Of Formic Acid by Oxygen and Ozone

The catalytic wet-air oxidation and catalytic ozonation of a formic acid solution have been studied at room temperature using more than 20 kinds of catalysts including Pt/C, Pt/Al₂O₃, Pd/Al₂O₃, etc. The most effective catalyst was Pt/Al₂O₃. The apparent activation energies for the catalytic wet-air oxidation and ozonation on Pt/Al₂O₃ were both about 5 kcal/mol. This fact suggests that these reactions on the catalyst were diffusion controlled, and thus, the potential of the catalyst is likely much higher.     

Electrocatalytic Performance of Palladium Dendrites Deposited on Titania Nanotubes for Formic Acid Oxidation

Pd catalyst with dendritic morphology was synthesized on ordered and uniformly distributed titania nanotubes (TNT/Ti), and bare Ti by a simple electrochemical deposition process. The influence of support morphology was studied in relation to Pd deposition and its electro catalytic oxidation of formic acid. The structural property of Pd dendrites was characterized by scanning electron microscopy and X‐ray diffraction. The electrochemical study showed the activity and durability of Pd/TNT/Ti catalyst for formic acid oxidation was enhanced compared to Pd/Ti electro catalyst. The synergetic contribution from TNT/Ti as support for Pd and its enhanced catalytic activity is discussed.     

甲酸废水综合回收利用技术及产业化研究

针对在工业化处理环氧类增塑剂生产工艺废水过程中所遇到的甲酸气体挥发、沉淀剂失效、蒸发器结垢等问题,通过采取增加冷却盘管调节水温40℃以下,添加阳离子度30％-50％的改性聚丙烯酰胺沉淀剂等措施,并改造多效蒸发器结构形成气-液-固三相平衡避免结垢发生,年处理废水6．75万t,回用水6．25万t,减排COD4．6t／a,具有良好的借鉴意义。     

甲酸与六偏磷酸钠生产市场状况及联产新工艺

阐述了甲酸与六偏酸钠的生产及市场状况,着重介绍了甲酸与六偏磷酸钠联产新工艺及生产成本估算.     

Preparation of Platinum‐Poly(O‐dihydroxybenzene) Composite Catalyst and Its Electrocatalytic Activity Toward Methanol and Formic Acid Oxidation

A composite catalyst has been successfully prepared by dispersing Pt nanoparticles on a poly(o‐dihydroxybenzene) (PoDHB) modified glassy carbon (GC) electrode and characterized by SEM, EDX, and electrochemical analysis. Compared with Pt nanoparticles deposited on the bare GC, the Pt/PoDHB/GC exhibits higher catalytic activity and stronger poisoning tolerance for electro‐oxidation of methanol and formic acid. The enhanced performance could be attributed to the increase of electrochemical active surface area (EASA) arisen from the PoDHB modification. Furthermore, performance limiting factors such as platinum loading, polymer mass, H₂SO₄, methanol, and formic acid concentrations have been evaluated for optimizing the electrocatalytic activities.     

Electrocatalytic Oxidation of Formic Acid at Pt Modified Electrodes: Substrate Effect of Unsintered Au Nano‐Structure

A Pt‐modified Au catalyst featured with novel layered structures and ultra‐low Pt loading has been designed and electrochemically fabricated on a glassy carbon (GC) electrode. SEM characterization suggests that as‐formed Pt/Au/GC electrode grows in a Stranski–Krastanov mode, resulting in a nearly ideal layered structure with Au at the inner layer and Pt at the outer layer. The electrocatalytic activity of the synthesized Pt/Au/GC electrode towards formic acid electrooxidation was studied, and comparative experiments with other modified electrodes (i.e., Pt/GC, Pt/Au, and Pt/Pt) were also conducted. As a result, the electrocatalytic activity of the outer‐layered Pt depends significantly on the intrinsic properties of the substrates. The prepared Pt/Au/GC electrode with Au nanoparticles modified GC as the substrate shows remarkable catalytic activity for the formic acid oxidation, much higher than that of its counterparts, Pt/GC, Pt/Au, and Pt/Pt electrodes. Additionally, the measured electrochemical impedance spectra indicate that the charge‐transfer resistance for formic acid electrooxidation on Pt/Au/GC electrode is smaller than that on other Pt modified electrodes.     

ZrC–C and ZrO2–C as Novel Supports of Pd Catalysts for Formic Acid Electrooxidation

The Pd/ZrC–C and Pd/ZrO₂–C catalysts with zirconium compounds ZrC or ZrO₂ and carbon hybrids as novel supports for direct formic acid fuel cell (DFAFC) have been synthesized by microwave‐assisted polyol process. The Pd/ZrC–C and Pd/ZrO₂–C catalysts have been characterized by X‐ray diffraction (XRD), X‐ray photoelectron spectroscopy (XPS), energy dispersive analysis of X‐ray (EDAX), transmission electron microscopy (TEM), and electrochemical measurements. The physical characteristics present that the zirconium compounds ZrC and ZrO₂ may promote the dispersion of Pd nanoparticles. The results of electrochemical tests show that the activity and stability of Pd/ZrC–C and Pd/ZrO₂–C catalysts show higher than that of Pd/C catalyst for formic acid electrooxidation due to anti‐corrosion property of zirconium compounds ZrC, ZrO₂, and metal–support interaction between Pd nanoparticles and ZrC, ZrO₂. The Pd/ZrC–C catalyst displays the best performance among the three catalysts. The peak current density of formic acid electrooxidation on Pd/ZrC–C electrode is nearly 1.63 times of that on Pd/C. The optimal mass ratio of ZrC to XC‐72 carbon is 1:1 in Pd/ZrC–C catalyst with narrower particle size distribution and better dispersion on surface of the mixture support, which exhibits the best activity and stability for formic acid electrooxidation among all the samples.     

Transport Properties,Local Coordination,and Thermal Stability of the Water/Diethylmethylammonium Methanesulfonate Binary System

Ammonium based protic ionic liquids are highlighted for their great potential to sustain proton transport in proton exchange membrane (PEM) fuel cells. Yet, there remain questions concerning the effect of water produced by the fuel cell at the cathode side on the performance of the ionic liquid. In this contribution we report the effect of water on the transport properties and the local coordination in the binary system of the protic ionic liquid diethylmethylammonium methanesulfonate ([DEMA][OMs]) and water, employing ¹H NMR, Raman, and infrared spectroscopy. We observe that the self‐diffusion of cations and anions increases with the water content and that cations and anions diffuse at the same rate at all concentrations investigated. ¹H NMR and vibrational spectroscopy, on the other hand, indicate that added water interacts primarily with the anion and slightly affects the ionicity of the ionic liquid. In addition, by investigating the thermal stability of the binary system we find that although [DEMA][OMs] displays a continuous loss of water upon increasing temperature a fraction of water molecules can be retained even above 120 °C, and that the complete loss of water is immediately followed by decomposition, which is observed to occur at about 185 °C.     

电导率法评定聚环氧琥珀酸对碳酸钙结垢过程的影响

本文采用传统的一步法合成阻垢剂聚环氧琥珀酸（PESA）,并用红外进行表征。电导率法评定PESA的阻垢性能较好。通过改变溶液温度、阻垢剂浓度测定溶液的电导率随时间的变化值,推断PESA影响碳酸钙结垢过程的原因：低温时晶格畸变起主要作用;高温时分散起主要作用,从动力学上影响碳酸钙结垢过程。温度发生变化,PESA影响碳酸钙结垢过程的控制过程发生改变。加晶种时,PESA表面吸附作用显著。PESA的阻垢效果不能用络合效应理论解释。     

Nafion膜内基团与水分子的相互作用

Nafion膜由于其良好的电化学性能被广泛应用,但其溶胀性即膜内水分子的存在和含量的大小对膜的性能产生影响,因为水分子会与膜基团发生作用.在制取几种不同端基的Nafion膜的基础上,应用红外光谱方法比较膜的不同基团对水分子结构对称性的不同影响,从而探讨基团与水分子的作用方式.膜内的阳离子Lewis酸性越强,对-OH的亲和性越强,水分子不对称性越大,其O-H伸缩振动越困难,振动频率越大,强度越强;膜内的阴离子,Lewis碱性越强,水分子O-H伸缩振动越困难,频率越大,基团的这种效应与溶液中氢键的作用相反.     

直接甲醇燃料电池质子交换膜的发展现状

直接甲醇燃料电池(DMFC)是20世纪90年代兴起的第六代燃料电池,以其诸多的优点引起人们的广泛关注和研究。其中聚合物电解质膜是DMFC的关键技术,起着隔离阴阳极、质子传输、绝缘电子的作用。它的作用决定着DMFC的输出功率、电池效率、成本及应用前景。本文介绍了已商品化的全氟磺酸膜(Nafion膜)的结构及性能、以及替代膜的国内外发展现状,指出DMFC用膜的研究是21世纪能源研究的重点。     

Advantages of a Polyimide Membrane Support in Nonhumidified Fluorohydrogenate‐Polymer Composite Membrane Fuel Cells

We have successfully prepared composite membranes consisting of the ionic liquid N‐ethyl‐N‐methylpyrrolidinium fluorohydrogenate and the polymer 2‐hydroxyethylmethacrylate and have secured them on a polyimide (PI) membrane support. The resulting EMPyr(FH)_1.7F–HEMA (9:1 molar ratio) composite possesses ionic conductivity of 75 mS cm⁻¹ at 120 °C when a 16‐µm support is employed, showing improved performance with elevated temperature; this marks a significant difference from devices using conventional polytetrafluoroethylene supports. In the single cell test, a maximum power density of 31 mW cm⁻² is observed at 120 °C. Cross‐sectional SEM images of the corresponding membrane electrode assemblies reveal no significant difference in membrane thickness before and after cell testing, implying that this support does not suffer from membrane softening issues.     

Influence of Methanol Crossover on the Fuel Utilization of Passive Direct Methanol Fuel Cell

The effect of methanol crossover on the fuel utilization of a passive direct methanol fuel cell (DMFC) was reported. The results revealed that the Faradaic efficiency decreased from 46.9 to 17.4% when methanol concentration increased from 1.0 to 8.0 mol L^–1 at the lower current density 11.1 mA cm^–2. However, the Faradaic efficiency increased from 14.7 to 31.3% when methanol concentration increased from 1.0 to 8.0 mol L^–1 at a higher current density of 44.4 mA cm^–2. On the other hand, although the amount of methanol was increased, the Faradaic efficiency did not change, obviously due to the uniform methanol crossover and methanol diffusion at the same methanol concentration and constant current.     

Effect of temperature, oxidant and catalyst loading on the performance of direct formic acid fuel cell

We investigated the effect of temperature, oxidant and catalyst loading on the performance of direct formic acid fuel cell (DFAFC). When oxidant was changed from air to oxygen, the power density was increased to 17.3 mW/ cm² at 25 ‡C. The power density of DFAFC operated with oxygen showed a maximum value of 40.04 mW/cm² with the temperature rise from room temperature to 70 °C. The highest power density of DFAFC using air was observed for Pt-Ru black catalyst with loading of 8 mgPt/cm² at room temperature. At 70 ‡C; however, the performance of catalyst with the loading of 4 mgPt/cm² was higher than that of 8 mgPt/cm². The DFAFC, operated with oxygen and catalyst of 4 mgPt/cm² loading, showed the best performance at all temperature range. The enhancement of cell performance with an increase of catalyst loading is believed to come from an increase of catalyst active sites. However, operated at higher temperature or with oxygen, the cell with higher catalyst loading showed lower performance than expected. It is speculated that the thick catalyst layer inhibits the proton transport.