Advanced 3D ordered electrodes for PEMFC applications: From structural features and fabrication methods to the controllable design of catalyst layers

The catalyst layers(CLs) electrode is the key component of the membrane electrode assembly(MEA) in proton exchange membrane fuel cells(PEMFCs). Conventional electrodes for PEMFCs are composed of carbon-supported, ionomer, and Pt nanoparticles, all immersed together and sprayed with a micron-level thickness of CLs. They have a performance trade-off where increasing the Pt loading leads to higher performance of abundant triple-phase boundary areas but increases the electrode cost. Major challenges must be overcome before realizing its wide commercialization. Literature research revealed that it is impossible to achieve performance and durability targets with only high-performance catalysts, so the controllable design of CLs architecture in MEAs for PEMFCs must now be the top priority to meet industry goals. From this perspective, a 3D ordered electrode circumvents this issue with a support-free architecture and ultrathin thickness while reducing noble metal Pt loadings. Herein, we discuss the motivation in-depth and summarize the necessary CLs structural features for designing ultralow Pt loading electrodes. Critical issues that remain in progress for 3D ordered CLs must be studied and characterized. Furthermore, approaches for 3D ordered CLs architecture electrode development, involving material design, structure optimization, preparation technology, and characterization techniques, are summarized and are expected to be next-generation CLs for PEMFCs. Finally, the review concludes with perspectives on possible research directions of CL architecture to address the significant challenges in the future.

Pt掺杂对Ti/SnO_(2)-Sb-Nd纳米球状电极性能的影响

采用一步水热法成功制备出不同Pt掺杂量下Ti/SnO_(2)-Sb-Nd-Pt纳米球状电极,通过SEM、XRD和XPS表征电极表面的形貌、结构和化学组成,LSV、CV和加速寿命(ALT)测试电极的电化学性能和稳定性,并通过降解硝基苯(NB)能力验证电极催化活性。结果表明,Pt掺杂不会改变电极的SnO_(2)晶型结构,适量Pt掺杂可以使电极表面涂层更加均匀致密,提高电极稳定性,但降低了涂层中吸附氧含量,使得电极催化活性降低。掺杂1.5%Pt后,电极ALT由28.0 min延长至78.2 h,虽然NB去除率由96.53%降至80.61%,但在电极实际使用寿命内,NB理论降解总量由62.6 mg/cm^(2)增至8 754.1 mg/cm^(2)。显示了该电极具有良好的应用潜力,为开发高效、稳定的电极材料提供了参考。

Ti-Pt周期调制梯度材料的制备及准等熵加载特性

基于波阻抗梯度材料的准等熵加载技术是掌握材料动态响应特性的重要技术手段,对于提升材料服役性能至关重要。采用电子束蒸发镀膜技术成功制备出Ti-Pt周期调制梯度材料,通过对周期层内双组分(Ti和Pt单层)厚度的调控,实现了波阻抗的宏观梯度变化。梯度材料实测总厚度与理论设计总厚度的误差仅为1.67%,并且实测平均硬度及弹性模量分别为2.8和99.8 GPa。材料内部层界面清晰,物相分析未发现金属合金相。利用一级轻气炮驱动TiPt周期调制梯度材料加载5μm厚Al靶,在Al靶内产生冲击-准等熵加载波形。数值模拟结果与实验曲线在上升趋势上吻合良好,5μm厚Al靶处的粒子速度、应力和应变率曲线的准等熵段存在较大起伏,应变率曲线在正负值间持续振荡,并且振幅较大。应力云图显示周期调制梯度材料在加载过程中会形成多个波系的追赶、叠加、整合。数值模拟结果显示,当靶材厚度为60μm时,波系完成整合,转变为连续的压缩波。结合数值模拟结果开展了60μm厚Al靶的轻气炮加载实验,粒子速度曲线和应力曲线的准等熵段转变为平滑的加载波形,应变率曲线准等熵段振幅显著减小,实现了良好的准等熵加载效果。研究结果表明,周期调制梯度材料与靶材厚度需进行匹配设计,研究结果可为新型周期调制梯度结构的应用提供指导。

Role of Bridge-bonded Formate in Formic Acid Dehydration to CO at Pt Electrode： Electrochemial in-situ Infrared Spectroscopic Study

Formic acid （HCOOH） decomposition at Pt film electrode has been studied by electrochem- ical in situ FTIR spectroscopy under attenuated-total-reflection configuration, in order to clarify whether bridge-bonded formate （HCOOD） is the reactive intermediate for COad for-mation from HCOOH molecules. When switching from HCOOH-free solution to HCOOH- containing solution at constant potential （E=0.4 V vs. RHE）, we found that immediately upon solution switch COad formation rate is the highest, while surface coverage of formate is zero, then after COad formation rate decreases, while formate coverage reaches a steady state coverage quickly within ca. 1 s. Potential step experiment from E=0.75 V to 0.35 V, reveals that formate band intensity drops immediately right after the potential step, while the COad signal develops slowly with time. Both facts indicate that formate is not the reactive intermediate for formic acid dehydration to CO.

Preparation and Optimization of Porous Membrane Electrodes via Gradient Coating in Hydrogen Fuel Cell

Fuel cells are considered to be one of the ideal alternatives to traditional fossil energy conversion devices.Membrane electrodes are the core components in the hydrogen fuel cells.Our work reported the synthesis of the Pt/C catalysts with different Pt loading,and by changing the Nafion content,hot pressing temperature and hot pressing pressure,the catalyst coated membrane(CCM)spraying process was optimized.Moreover,the three-dimensional structure model of the single battery membrane electrode was studied quantitatively,and the porous membrane electrode with gradient distribution was fabricated under optimized processing conditions,with excellent electrical performance.

Electrochemical oxidation of Rhodamine B with cerium and sodium dodecyl benzene sulfonate co-modified Ti/Pb0_(2)electrodes:Preparation,characterization,optimization,application

Regulation of the electronic structure and interface property becomes a major strategy in the preparation of electrocatalyst.This paper reports the synthesis of cerium(Ce)and sodium dodecyl benzene sulfonate(SDBS)comodified Ti/PbO_(2)electrodes(Ti/PbO2CeSDBS).Ce and SDBS could greatly change the electronic structure and interface property of PbO2.Ti/PbO_(2)CeSDBS exhibited excellent electrocatalytic activity and stability in Rhodamine B(RhB)electrocatalytic oxidation reaction.The improved electrocatalytic activity associates with the synergistic effect of electronic and interface factors.In the electrochemical degradation of RhB,the removal efficiencies of RhB and COD are about 0.880 and 0.694 respectively after the electrolysis of 220 min with Ti/PbO_(2)Ce4SDBS40,which are higher than the contrast Ti/PbO_(2)electrodes.In the meantime,the accelerated lifetime of Ti/PbO_(2)Ce4SDBS40 is more than 6.2 times than that of Ti/PbO_(2).

Electrochemical oxidation of ammonia-containing wastewater using Ti/RuO_2-Pt electrode

The electrochemical oxidation degradation processes for artificial and actual wastewater containing ammonia were carried out with a Ti/RuO2-Pt anode and a Ti plate cathode. We studied the effects of different current densities, space sizes between the two electrodes, and amounts of added NaCl on ammonia-containing wastewater treatm.ent. It was shown that, after a 30-min treatment under the optimal conditions, which were a current density of 20 mA/cm2, a space size between the two electrodes of I cm, and an added amount of 0.5 g/L of NaC1, the COD concentration in municipal wastewater was 40 mg/L, a removal rate of 90%; and the NH3-N concentration was 7 mg/L, a removal rate of 88.3%. The effluent of municipal wastewater qualified for Class A of the Discharge Standard of Pollutants for Municipal Wastewater Treatment Plant （GB 18918-2002）.

Electrocatalytic performance of Pt/Ru/Sn/W fullerene electrode for methanol oxidation in direct methanol fuel cell

In this work,fullerene was modified by platinum,ruthenium,tin and tungsten nanoparticles.The material was characterized by XRD,ICP-OES and TEM micrograph.The average nanoparticle size on fullerene was 5-8 nm.The application of this material was investigated as a catalyst for methanol oxidation in direct methanol fuel cell.A glassy carbon electrode was modified by Pt/Ru/Sn/W fullerene and electrocatalytic activity of the electrode toward methanol oxidation in basic medium has been demonstrated and investigated using cyclic voltammetry.The catalyst showed good reactivity for methanol oxidation.

Electrically enhanced photodegradation of an azodye(Acid Orange II) using a Pt/TiO_2 film electrode irradiating with an UV lamp

A photoelectrochemical process in the degradation of an azodye (Acid Orange II) on a Pt/TiO 2 film electrode was investigated. By using the glass device and the voltage stabilized source of direct current, decolorization ratios higher than 78% were observed during a period of 5h. Comparing this value with the sum of the decolorization ratios obtained by a sole application of electrochemical(lower than 3%) and photochemical(about 23%) procedures, a significant synergic effect between both processes was observed. The effects of adscititious voltage and pH value on the decolorization ratios were obvious while the effect of the amount of aeration was minor.

Restructuring of well-defined Pt-based electrode surfaces under mild electrochemical conditions

Since the 1980s,single-crystal Pt electrodes with well-defined surface structures have been deemed stable under mild electrochemical conditions(e.g.,in the potential region of electric double layers,underpotential deposition of hydrogen,or mild hydrogen evolution/OH adsorption)and have served as model electrodes for unraveling the structure-performance relation in electrocatalysis.With the advancement of in situ electrochemical microscopy/spectroscopy techniques,subtle surface restructuring under mild electrochemical conditions has been achieved in the last decade.Surface restructuring can considerably modify electrocatalytic properties by generating/destroying highly active sites,thereby interfering with the deduction of the structure-performance relation.In this review,we summarize recent progress in the restructuring of well-defined Pt(-based)electrode surfaces under mild electrochemical conditions.The importance of the meticulous structural characterization of Pt electrodes before,during,and after electrochemical measurements is demonstrated using CO adsorption/oxidation,hydrogen adsorption/evolution,and oxygen reduction as examples.The implications of present findings for correctly identifying the reaction mechanisms and kinetics of other electrocatalytic systems are also briefly discussed.

Ion-Conductive-Polymer-Film Actuators with Pt Electrodes Selectively Grown using Non-Electrolyzed Plating

Organic soft actuators are of special interest in many fields including intravascular neurosurgery. Ion conductive polymer film （ICPF） actuators have been one of the strong candidates. The ICPF investigated here was a cation-exchange membrane （Nation 117, Du Pont）. When a voltage is given between the metal eIectrodes of an ICPF actuator, the ICPF actuator bends in the water due to the motion of Li＋ cations with associated water. In order to increase the freedom of the deformation of the ICPF actuator, structures of independent electrode pairs were proposed. The electrodes were selectively deposited by non-electrokvzed plating including the Pt [（NH3）6]^4＋ deposition process in a [Pt（NH3）6]Cl4 solution and the reduction process in a NaBH4 solution. Here, an elastomer adhesive tape with a fine electrode patterns was used performances were reported in detail. as a mask. The actuators processing conditions and their actuator

Preparation and electrocatalytic property of Au-Pt/SnO_2/GC composite electrode

Au-Pt/SnO2/GC composite electrode was prepared by self-assembling Au-Pt nanoparticles on SnO2 film, which was deposited on actived glassy carbon （GC）. Atomic force microscopy （AFM） and scanning electron microscopy （SEM） images revealed that dense and uniform Au-Pt particles with 25-nm diameter were dispersed on SnO2 film. X-ray photoelectron spectroscopy （XPS） results proved that there was an interaction between Au-Pt nanoparticles and SnO2 support. Electrochemical experiments showed that Au-Pt/SnOz/GC composite electrode had a good electrocatalytic activity to the oxidation of methanol

An Unusually High Sensitivity of Pt-black pH Electrode

The potentials of Pt-black electrode using a copper conducting wire instead of the salt bridge in acid and alkaline solutions without the use of H2 evolution reactions were measured. There were three nonlinear portions in the calibration curve. Unusually, the potential slopes at pH 3-5 and 8-10 indicated 200 mV and 70 mV per pH, respectively. Such high sensitivity for pH slope, more than 4 times of usual 59 mV per pH, may be credited to the special properties of the Pt-black surface. SEM （scanning electronical microscopy） was applied to characterize the surface of the Pt-black electrode. Its working mechanism is well explained in the theory of capacitance potentials rather than Nernst＇s redox potentials.

Pt-N-TiO_(2)纳米管电极的制备及其表征

采用光化学沉积法与等离子体法制备Pt-N-TiO_(2)纳米管电极,SEM、EDS以及XRD等表征手段表明TiO_(2)纳米管管径约为90 nm,Pt纳米颗粒均匀负载至纳米管管口且未改变TiO_(2)纳米管结构。UV-Vis-DRS表明Pt-N-TiO_(2)纳米管光吸收性能在可见光区相比掺Pt前提高明显。CV、EIS电化学性能分析表明Pt-N-TiO_(2)纳米管表面电荷转移加快,具有更好的导电性能和氧化性能。通过降解目标染料甲基紫分析Pt-N-TiO_(2)纳米管的光电催化性能,在初始浓度10 mg/L,pH=3,外加偏压25 V,Pt负载浓度为1 g/L,甲基紫60 min降解率93.64%,降解过程符合一级动力学反应方程。

Electrochemical oxidation of aniline by a novel Ti/TiO_xH_y/Sb-SnO_2 electrode

Electrochemical oxidation of aniline in aqueous solution was investigated over a novel Ti/TiOxHy/Sb-SnO2 electrode prepared by the electrodeposition method.Scanning electron microscopy,X-ray diffraction,and electrochemical measurements were used to characterize its morphology,crystal structure,and electrochemical properties.Removal of aniline by the Ti/TiOxHy/Sb-SnO2electrode was investigated by ultraviolet-Visible spectroscopy and chemical oxygen demand（COD）analysis under different conditions,including current densities,initial concentrations of aniline,pH values,concentrations of chloride ions,and types of reactor.It was found that a higher current density,a lower initial concentration of aniline,an acidic solution,the presence of chloride ions（0.2wt%NaCl）,and a three-dimensional（3D） reactor promoted the removal efficiency of aniline.Electrochemical degradation of aniline followed pseudo-first-order kinetics.The aniline（200 mL of 100mg·L-（-1）） and COD removal efficiencies reached 100%and 73.5%,respectively,at a current density of 20 mA·cm-（-2）,pH of 7.0,and supporting electrolyte of 0.5 wt%Na2SO4 after 2 h electrolysis in a 3D reactor.These results show that aniline can be significantly removed on the Ti/TiOxHy/Sb-SnO2electrode,which provides an efficient way for elimination of aniline from aqueous solution.

Effect of Sb dopant amount on the structure and electrocatalytic capability of Ti/Sb-SnO_2 electrodes in the oxidation of 4-chlorophenol

Ti/Sb-SnO2 anodes were prepared by thermal decomposition to examine the influence of the amount of Sb dopant on the structure and electrocatalytic capability of the electrodes in the oxidation of 4-chlorophenol. The physicochemical properties of the Sb-SnO2 coating were markedly influenced by different amounts of Sb dopant. The electrodes, which contained 5% Sb dopant in the coating, presented a much more homogenous surface and much smaller mud-cracks, compared with Ti/Sb-SnO2 electrodes containing 10% or 15% Sb dopant, which exibited larger mud cracks and pores on the surface. However, the main microstructure remained unchanged with the addition of the Sb dopant. No new crystal phase was observed by X-ray diffraction （XRD）. The electrochemical oxidation of 4-chlorophenol on the Ti/SnO2 electrode with 5% Sb dopant was inclined to electrochemical combustion; while for those containing more Sb dopant, intermediate species were accumulated. The electrodes with 5% Sb dopant showed the highest efficiency in the bulk electrolysis of 4-chlorophenol at a current density of 20 mA/cm^2 for 180 min; and the removal rates of 4-chlorophenol and COD were 51.0% and 48.9%, respectively.

Ti基镶嵌金刚石颗粒掺硼金刚石电极及其性能

利用粉末压片机在Ti片表面镶嵌金刚石颗粒,以此为衬底,通过热丝化学气相沉积技术沉积掺硼金刚石(boron-doped diamond, BDD)薄膜,制备新型Ti基镶嵌金刚石颗粒BDD (Ti/D/BDD)电极,并制备Ti基BDD (Ti/BDD)电极作为对比。采用扫描电子显微镜、拉曼光谱仪和电化学工作站表征电极的形貌、B掺杂水平和电化学性能,利用紫外可见分光光度计测试电极模拟废水降解的效果。结果表明:沉积时间相同时,Ti/D/BDD电极比Ti/BDD电极具有更大的电化学活性面积,更低的薄膜阻抗,使得电极对酸性橙G表现出更高的降解速率,更低的降解能耗。沉积10 h时,Ti/D/BDD电极具有最高的双电层电容(1.87 mF),最低的薄膜电阻(0.4?);降解120 min后,Ti/D/BDD电极的色度移除率比Ti/BDD电极最高可提升53.1%,同时能耗降低14.2%。

Preparation and application of pharmaceutical wastewater treatment by praseodymium doped SnO_2/Ti electrocatalytic electrode

Praseodymium was selected as a promoter for SnO2/Ti electrode to improve the electrocatalytic performance by electrodeposition in pharmaceutical wastewater treatment; the micrograph and the structure were characterized by SEM and XRD. Mixture uniform design was used in the optimization of the electrolytic conditions; mathematical model was established according to the rate of wiping COD off, which revealed the relationship between the current intensity, time of electrolysis, the amount of doped Pr, and the ratio of area （SnOJTi：Al）. On the basis of the analysis of the empirical model, the optimized parameters had been obtained; the rate of wiping COD off was up to 94.9%, it decreased from 392 to 20 mg/L. Experimental results showed that the electrocatalytic performance of the electrode doped with Pr was superior for the treatment of pharmaceutical wastewater.

Enhancing Capacitance Performance of Ti3C2Tx MXene as Electrode Materials of Supercapacitor: From Controlled Preparation to Composite Structure Construction

Ti3C2Tx,a novel two-dimensional layer material,is widely used as electrode materials of supercapacitor due to its good metal conductivity,redox reaction active surface,and so on.However,there are many challenges to be addressed which impede Ti3C2Tx obtaining the ideal specific capacitance,such as restacking,re-crushing,and oxidation of titanium.Recently,many advances have been proposed to enhance capacitance performance of Ti3C2Tx.In this review,recent strategies for improving specific capacitance are summarized and compared,for example,film formation,surface modification,and composite method.Furthermore,in order to comprehend the mechanism of those efforts,this review analyzes the energy storage performance in different electrolytes and influencing factors.This review is expected to predict redouble research direction of Ti3C2Tx materials in supercapacitors.

Surface Modification Process by Electrical Discharge Machining with Ti Powder Green Compact Electrode

This paper describes a new method of surface modification by Electrical Discharge Machining (EDM). By using ordinary EDM machine tool and kerosene fluid, a hard ceramic layer can be created on the workpiece surface with Ti or other compressed powder electrode in a certain condition. This new revolutionary method is called Electrical Discharge Coating (EDC). The process of EDC begins with electrode wear during EDM,then a kind of hard carbide is created through the thermal and chemical reaction between the worn electrode material and the carbon particle decomposed from kerosene fluid under high temperature. The carbide is piled up on a workpiece quickly and becomes a hard layer of ceramic about 20 μm in several minutes. This paper studies the principle and process of EDC systemically by using Ti powder green compact electrode. In order to obtain a layer of compact ceramic film, it is very important to select proper electric pulse parameters, such as pulse width, pulse interval, peak current. Meantime, the electrode materials and its forming mode will effect the machining surface quality greatly. This paper presents a series of experiment results to study the EDC process by adopt different technology parameters. Experiments and analyses show that a compact TiC ceramic layer can be created on the surface of metal workpiece. The hardness of ceramic layer is more 3 times higher than the base body, and the hardness changes gradiently from surface to base body. The method will have a great future because many materials can be easily added to the electrode and then be coated on the workpiece surface. Gearing the parameters ceramic can be created with different thickness. The switch between deposition and removal process is carried out easily by changing the polarity, thus the gear to the thickness and shape of the composite ceramic layer is carried out easily. This kind of composite ceramic layer will be used to deal with the surface of the cutting tools or molds possibly, in order to lengthen their life. It also can be found wide application in the fields of surface repairing and strengthening of the ship or aircraft.