气体扩散电极参数对阴离子交换膜燃料电池性能的影响

优化了碱性阴离子交换膜燃料电池（AAEMFC）使用的气体扩散电极（GDE）,发现催化层中PTFE含量与催化剂担载量对电池性能与其电化学动力学特征影响很大.采用i-V曲线,开路电压,电池内阻与在线的电化学阻抗谱与动力学分析,评估了所制GDE的电化学性能.在所研究的AAEMFC电极催化层中,PTFE的最佳含量是20%,Pt载量对膜电极三相界面、催化层导电性与催化剂利用率的影响极大.当制备的GDE催化层中Pt/C的Pt载量为1.0mg/cm²,PTFE含量为20%时,AAEMFC的峰电流密度在50^oC达到了213mW/cm².兼顾Pt催化剂的利用率与成本,在没有明显影响电池性能的情况下,Pt的担载量可降至0.5mg/cm².     

Pt掺杂对Mo-Ru-Se簇合物电催化氧还原性能的影响

直接甲醇燃料电池(DMFC)是理想的移动电源,但因金属Pt阴极催化剂的选择性较差,甲醇在阴极产生“混合电位”,导致电池效率降低。抗甲醇氧电还原催化剂可降低“混合电位”,是解决该问题的有效的方法。     

有序化膜电极研究进展

燃料电池的性能方面在近年来有很大提高,但要实现商业化其成本和Pt用量需要进一步的降低. 大量的文献工作证明了有序化膜电极有助于提高电极中催化剂的利用率、降低Pt的用量以及增加反应的三相界面,特别是3M公司制备的纳米薄膜电极（NSTFs）是一种高活性,高稳定性的薄膜状催化层,从而电极稳定性也大幅提高. 此外也有不少工作使用导电性好的碳纳米管阵列,以及稳定性高的金属氧化物阵列等作为这种3D结构催化层中催化剂的有序载体,研究进一步提高Pt基催化剂的活性,降低Pt担载量,构效关系等一些基础性的工作. 但是总体上看,现有的有序化膜电极,均需要进一步改进. 本文评述了目前国内外有序化膜电极的研究现状.     

Current challenges related to the deployment of shape-controlled Pt alloy oxygen reduction reaction nanocatalysts into low Pt-loaded cathode layers of proton exchange membrane fuel cells

The reduction of the amount of platinum used in proton exchange membrane fuel cell cathodes at constant power density helps lower the cell stack cost of fuel cell electric vehicles. Recent screening studies using the thin film rotating disk electrode technique have identified an ever-growing number of Pt-based nanocatalysts with oxygen reduction reaction Pt-mass activities that allow for a substantial projected decrease in the geometric platinum loading at the cathode layer. However, the step from a rotating disk electrode test to a membrane electrode assembly test has proved a formidable task. The deployment of advanced, often shape-controlled dealloyed Pt alloy nanocatalysts in actual cathode layers of proton exchange membrane fuel cells has remained extremely challenging with respect to their actual catalytic activity under hydrogen/oxygen flow, their hydrogen/air performance at high current densities, and their morphological stability under prolonged fuel cell operations. In this review, we discuss some of these challenges, yet also propose possible solutions to understand the challenges and to eventually unfold the full potential of advanced Pt-based alloy oxygen reduction reaction catalysts in fuel cell electrode layers.     

扫帚状氧化铈制备及其对Pt基阳极催化剂催化性能的影响

采用水热合成法,合成了比表面积为175 m~2·g~(-1),孔径在2~4nm范围内的扫帚状CeO_2。通过微波辅助乙二醇还原氯铂酸法制备了Pt-CeO_2/RGO催化剂,探究扫帚状CeO_2的添加对Pt基催化剂电催化性能的影响。利用X射线衍射仪(XRD)、扫描电镜(SEM)、N_2吸附-脱附、X射线光电子能谱(XPS)对所制备的CeO_2及催化剂进行表征。利用电化学工作站对催化剂进行电化学性能测试。结果表明,催化剂中CeO_2保持原有扫帚状,Pt纳米粒子均匀分布于石墨烯载体表面;当m_(RGO)∶m_(CeO2)=1∶2时,添加了扫帚状CeO_2的Pt-CeO_2/RGO催化剂的电催化性能最优,电化学活性表面积为102.83 m~2·g~(-1),对乙醇氧化的峰值电流密度为757.17A·g~(-1),1 000 s的稳态电流密度为108.17 A·g~(-1),对乙醇催化氧化反应的电荷转移电阻最小,活化能最低。     

扫帚状氧化铈制备及其对Pt基阳极催化剂催化性能的影响

采用水热合成法,合成了比表面积为175 m²·g^-1,孔径在2~4nm范围内的扫帚状CeO₂。通过微波辅助乙二醇还原氯铂酸法制备了Pt-CeO₂/RGO催化剂,探究扫帚状CeO₂的添加对Pt基催化剂电催化性能的影响。利用X射线衍射仪（XRD）、扫描电镜（SEM）、N₂吸附-脱附、X射线光电子能谱（XPS）对所制备的CeO₂及催化剂进行表征。利用电化学工作站对催化剂进行电化学性能测试。结果表明,催化剂中CeO₂保持原有扫帚状,Pt纳米粒子均匀分布于石墨烯载体表面;当m_RGO∶m_CeO2=1∶2时,添加了扫帚状CeO₂的Pt-CeO₂/RGO催化剂的电催化性能最优,电化学活性表面积为102.83 m²·g^-1,对乙醇氧化的峰值电流密度为757.17 A·g^-1,1 000 s的稳态电流密度为108.17 A·g^-1,对乙醇催化氧化反应的电荷转移电阻最小,活化能最低。     

Selective hydrogenation of o-chloronitrobenzene (o-CNB) over supported Pt and Pd catalysts obtained by laser vaporization deposition of bulk metals

Carbon nanotubes (CNTs), γ-alumina (γ-Al₂O₃) and silica (SiO₂) supported Pt and Pd catalysts were produced by laser vaporization deposition of respective bulk metals. The catalysts were characterized by inductive coupled plasma emission spectrometer (ICP), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). The catalytic properties of the catalysts were investigated in the liquid phase hydrogenation of o-chloronitrobenzene (o-CNB) to o-chloroaniline (o-CAN) under 333 K and 1.0 MPa hydrogen pressure. The results show that the catalytic properties are greatly affected by the supports. Pt/CNTs catalyst exhibits the best catalytic performance among the Pt-based catalysts, producing o-CAN with 99.6% selectivity at complete conversion. Pd/CNTs catalyst exhibits the best catalytic performance among the Pd-based catalysts, giving o-CAN with 95.2% selectivity at complete conversion. For Pt-based catalysts, geometric effect and the textures and properties of the supports play important roles on catalytic properties. On the other hand, geometric effect, electronic effect and the textures and properties of the supports simultaneously influence the catalytic properties of the Pd-based catalysts. In addition, hydrogenolysis of the C–Cl bond can be well inhibited over all catalysts prepared by laser vaporization deposition.     

不同结构及氮掺杂NiO/rGO氧还原催化剂的制备与性能研究

本文以还原氧化石墨烯（rGO）为载体制备了片状NiO/rGO和球形NiO/N-rGO结构的氧还原催化剂. 通过X-射线衍射（XRD）、Raman（拉曼）测试、X-射线光电子能谱（XPS）、扫描电子显微镜（SEM）和透射电子显微镜（TEM）等方法表征了两种催化剂的结构和形貌. 采用循环伏安法（CV）、Tafel曲线、线性扫描伏安法（LSV）、旋转圆盘电极（RDE）和旋转环盘电极（RRDE）等技术测试研究了两种催化剂的电化学催化氧还原性能. 研究结果表明,球形NiO/N-rGO催化剂催化氧还原的峰电流密度和起始电位（0.89 V vs. RHE）与商业化的Pt/C（20%）催化剂相近. 旋转圆盘电极（RDE）和旋转环盘电极（RRDE）测试证明,在碱性电解液中NiO/rGO和NiO/N-rGO催化的氧还原反应均主要通过4?鄄电子途径反应途径发生,球形NiO/N-rGO催化剂展现出替代Pt/C基催化剂的潜力.     

Carbon black supported PtCu nanoparticles derived from mix-phased Cu precursor for high-performanced oxygen reduction reaction in acid medium

Alloying high-cost Pt with transition metals has been considered as an effective route to synthesize the electrocatalysts with low Pt loading and excellent activity towards oxygen reduction reaction (ORR) under acid solution. The galvanic replacement method, as featured with efficiency and simplicity, is widely reported to produce Pt-based bimetallic alloys and thereby declare the significance of reductive transition metal precursor on the enhancement of ORR performance. Herein, mix-phased Cu−Cu₂O precursor was applied to prepare carbon black supported highly dispersed PtCu alloy nanoparticles (PtCu/C). The proper Cu−Cu₂O ratios can exactly facilitate the generation of small sized PtCu alloy nanoparticles with regulated bimetallic content. Meanwhile, the Cu₂O phase is revealed to benefit the electron transfer from Pt to Cu and thus improve the intrinsic activity of Pt active sites. And the metallic Cu can favor the promotion of electrochemical active surface area. Consequently, the as-prepared PtCu/C behaves impressive ORR activity with half-wave potential of 0.88 V (vs. RHE) and mass activity of 0.49 A cm⁻² mg_Pt⁻¹ at 0.8 V, which is 9.8 times of commercial Pt/C catalysts. Our work will offer helpful advices for the development and regulation of novel Pt-based alloy materials towards diverse electrocatalysis.     

Activity of Pt anode catalyst modified by underpotential deposited Pb in a direct formic acid fuel cell

We characterized the electrocatalytic activity of platinum electrode modified by underpotential deposited lead (PtPb_upd) for a formic acid (HCOOH) oxidation and investigated the influence on the power performance of direct formic acid fuel cells (DFAFC). Based on the electrochemical analysis using cyclic voltammetry and chronoamperometry, PtPb_upd electrode modified by underpotential deposition (UPD) exhibited significantly enhanced catalytic activity for HCOOH oxidation below anodic overpotential of 0.4 V (vs. SCE). Multi-layered PtPb_upd electrode structure of Pt/Pb_upd/Pt resulted in more stable and enhanced performance using 50% reduced loading of anode catalyst. The performance of multi-layered PtPb_upd anode is about 120 mW/cm² at 0.4 V and it also showed a sustainable cell activity of 0.52 V at an application of constant current loading of 110 mA/cm².     

助剂对Ni基催化剂结构及甲烷化性能的影响

本文采用等体积浸渍制备了掺杂不同金属助剂改性的Ni基催化剂,考察了其催化浆态床CO甲烷化的性能。通过XRD、H2-TPR、HR-TEM等表征对催化剂进行了分析,结果表明,掺杂Zr、Co、Ce、Zn、La助剂促进了Ni物种在载体表面的分散,减小了Ni的晶粒尺寸,降低了催化剂的还原温度;掺杂Mg助剂则导致催化剂的还原温度升高。浆态床活性评价结果表明,掺杂Zr、Co、Ce、Zn、La助剂提高了催化剂的甲烷化性能,其中以La助剂的效果最明显,通过对La负载量进一步优化后发现,当La负载量为8%时,催化剂的甲烷化催化性能最优,CO转化率、CH4选择性和时空收率分别达到96.3%、87.1%和179.6 g·kg-1·h-1;掺杂Mg助剂则降低了催化剂的甲烷化活性。     

助剂对Ni基催化剂结构及甲烷化性能的影响

本文采用等体积浸渍制备了掺杂不同金属助剂改性的Ni基催化剂,考察了其催化浆态床CO甲烷化的性能。通过XRD、H₂-TPR、HR-TEM等表征对催化剂进行了分析,结果表明,掺杂Zr、Co、Ce、Zn、La助剂促进了Ni物种在载体表面的分散,减小了Ni的晶粒尺寸,降低了催化剂的还原温度;掺杂Mg助剂则导致催化剂的还原温度升高。浆态床活性评价结果表明,掺杂Zr、Co、Ce、Zn、La助剂提高了催化剂的甲烷化性能,其中以La助剂的效果最明显,通过对La负载量进一步优化后发现,当La负载量为8%时,催化剂的甲烷化催化性能最优,CO转化率、CH₄选择性和时空收率分别达到96.3%、87.1%和179.6g·kg^-1·h^-1;掺杂Mg助剂则降低了催化剂的甲烷化活性。     

Sol–gel preparation and electrochemical properties of La-doped Li4Ti5O12 anode material for lithium-ion battery

A sol–gel method using Ti(OC₄H₉)₄, LiCH₃COO·2H₂O, and La(NO₃)₃·6H₂O as starting materials and ethyl acetoacetate as chelating agent to prepare pure and lanthanum (La)-doped Li₄Ti₅O₁₂ is reported. The structure and morphology of the active materials characterized by powder X-ray diffraction and scanning electron microscopy analysis indicate that doping with a certain amount of La³⁺ does not affect the structure of Li₄Ti₅O₁₂, but can restrain the agglomeration of the particles during heat treatment. The electrochemical properties measured by cyclic voltammetry, electrochemical impedance spectroscopy, and galvanostatic charge–discharge cycling tests show that La-doped Li₄Ti₅O₁₂ presents a much improved electrochemical performance due to a decrease in charge transfer resistance. At current densities of 1 and 5 C, the La-doped Li₄Ti₅O₁₂ exhibits excellent reversible capacities of 156.16 and 150.79 mAh?g^?1, respectively. The excellent rate capability and good cycling performance make La-doped Li₄Ti₅O₁₂ a promising anode material for lithium-ion batteries in energy storage systems.     

铂合金氧还原催化剂:合成、结构和性能

质子交换膜燃料电池是一种将燃料中的化学能直接转化为电能的装置,它具有转化效率高、能量密度高、低温启动、易于操作等优点,因而被认为是最具发展前景的新能源利用方式,在电动汽车、便携电源及分散式电站有着广泛应用.但是,目前质子交换膜燃料电池技术的发展面临着巨大挑战,主要问题包括高成本、低功率密度和低寿命.众所周知,质子交换膜燃料电池中的阴极氧还原反应在酸性条件下是一个复杂的四电子过程,动力学速度缓慢,限制了电池的最终性能.目前大量使用的阴极氧还原催化剂是细小的铂或铂合金纳米颗粒负载在碳载体上,其成本占燃料电池总成本的比例最大.制约燃料电池商业化发展的另一个重要问题是电池寿命低,其中氧还原催化剂的稳定性是决定电池寿命的主要因素.在这样的研究背景下,如何降低催化剂中铂的用量、提高催化剂活性和稳定性显得尤为重要,这也是近年来国内外学者研究的热点.在铂基合金催化剂中,通常采用过渡金属元素作为掺杂元素,由于原子半径不匹配(几何效应)以及电子结构不同(电子效应),合金催化剂表现出优于纯铂催化剂的催化性能.近几年,对于铂基合金催化剂的研究已取得重大进展,以合金组成和结构研究为基础,通过精确控制原子结构、调控表面电子状态以及制备工艺,获得了各种特殊形貌的催化剂,大大提高了催化活性.本文深入综述了近年来铂基合金氧还原催化剂制备、形貌和性能,特别关注了催化剂形貌和催化活性之间的关系.值得注意的是,具有有序原子排列的铂合金催化剂不仅在半电池中表现出优异活性,在实际质子交换膜燃料电池中也显示了很好的活性和稳定性.另一方面,碳载体的形貌及微观结构也对提高催化活性和稳定性起到决定性作用,通过化学手段加强金属纳米颗粒与碳载体之间的相互作用也是提高催化剂稳定性的重要途径.尽管铂基氧还原催化剂在近几年取得了重要进展,但在实际商业化过程中还存在诸多挑战,本文在综述进展的基础上,对铂基催化剂的发展提出了展望.首先,对于氧还原反应机理仍需要深入研究,采用更加精确的理论模型模拟氧还原动力学过程,以获得影响催化活性的关键因素.其次,提高催化剂在膜电极中的催化活性和利用率.目前,氧还原催化剂在半电池测试中性能优异,但是实际燃料电池操作条件下其性能远不能达到要求,这与膜电极、催化剂层及扩散层结构相关.因此,基于不同铂基催化剂的特性,合理设计膜电极组件的结构是将催化剂进行实际应用的基础.最后,催化剂的稳定性仍需进一步提高,尽管目前大部分催化剂在实验室半电池研究中表现了很好的稳定性,但在实际燃料电池中的稳定性研究还不足,而且对催化剂在膜电极中性能衰退机理的研究也非常有限.因此,对于铂基氧还原催化剂的研发仍需要国内外科研工作者不懈的努力.     

Iodinated carbon materials for oxygen reduction reaction in proton exchange membrane fuel cell. Scalable synthesis and electrochemical performances

Doped graphene-based cathode catalysts are considered as promising competitors for ORR, but their power density has been low compared to Pt-based cathodes, mainly due to poor mass-transport properties. A new electrocatalyst for PEMFCs, an iodine doped grahene was prepared, characterized, and tested and the results are presented in this paper. We report a hybrid derived electrocatalyst with increased electrochemical active area and enhanced mass-transport properties. The electrochemical performances of several configurations were tested and compared with a typical Pt/C cathode configuration. As a standalone catalyst, the iodine doped graphene gives a performance with 60% lower than if it is placed between gas diffusion layer and catalyst layer. If it is included as microporous layer, the electrochemical performances of the fuel cell are with 15% bigger in terms of power density than the typical fuel cell with the same Pt/C loading, proving the beneficial effect of the iodine doped graphene for the fuel cell in the ohmic and mass transfer region. Moreover, the hybrid cathode manufactured by commercial Pt/C together with the material with best proprieties, is tested in a H₂-Air fuel cell and a power density of 0.55 W cm⁻² at 0.52 V was obtained, which is superior to that of a commercial Pt-based cathode tested under identical conditions (0.46 W cm⁻²).     

Overview on the selective lean NO x reduction by hydrocarbons over Pt-based catalysts

Selective catalytic reduction of NO _x with hydrocarbons (HC-SCR) has received much attention as one of potential technologies for reducing NO _x emissions under lean-burn conditions. Pt/ZSM-5 prepared by sublimation method and Pt/V/MCM-41 catalysts have been introduced for the wider activity temperature window than those Pt catalysts reported previously. The influence of pre-treatment, oxygen concentration, water and SO₂ on the activities of Pt-based catalysts has been discussed. Combinatorial catalysis, which has been developed recently for discovering the practical HC-SCR catalysts quickly, has been introduced too. Finally, the reaction mechanism of HC-SCR over Pt-based catalysts has been briefly discussed.     

One-step synthesis of Pt nanoparticles/reduced graphene oxide composite with enhanced electrochemical catalytic activity

A one-step electrochemical approach for synthesis of Pt nanoparticles/reduced graphene oxide(Pt/RGO) was demonstrated.Graphene oxide(GO) and chloroplatinic acid were reduced to RGO and Pt nanoparticles(Pt NPs) simultaneously,and Pt/RGO composite was deposited on the fluorine doped SnO 2 glass during the electrochemical reduction.The Pt/RGO composite was characterized by field emission-scanning electron microscopy,Raman spectroscopy and X-ray photoelectron spectroscopy,which confirmed the reduction of GO and chloroplatinic acid and the formation of Pt/RGO composite.In comparison with Pt NPs and RGO electrodes obtained by the same method,results of cyclic voltammetry and electrochemical impedance spectroscopy measurements showed that the composite electrode had higher catalytic activity and charge transfer rate.In addition,the composite electrode had proved to have better performance in DSSCs than the Pt NPs electrode,which showed the potential application in energy conversion.     

Influence of highly efficient PbS counter electrode on photovoltaic performance of CdSe quantum dots-sensitized solar cells

PbS electrode with high catalytic activity to S_n ^2? reduction certificated by the measurements of electrochemical impedance spectroscopy and cyclic voltammetry was prepared by a simple method. The high catalytic activity makes it be a low-cost alternative counter electrode to platinum (Pt) to be used in quantum dots-sensitized solar cells (QDSSCs) based on polysulfide electrolyte. The photovoltaic performance enhancement of the quantum dots (QDs)-sensitized semiconductor thin films due to the PbS counter electrode was evaluated by fabricating QDSSCs based on CdSe QDs-sensitized ZnO (SnO₂) thin film. CdSe QDs-sensitized ZnO thin film has the lower internal total series resistance and electron transmission time, the higher electron lifetime and electron collection efficiency than the CdSe QDs-sensitized SnO₂ thin film. Replacing the Pt counter electrode with the PbS counter electrode leads to more improvement on the short circuit photocurrent density for QDSSC based on the ZnO thin film than the SnO₂ thin film. Therefore, the process to limit the photovoltaic performance of CdSe QDs-sensitized solar cell and the possible way to improve the photovoltaic performance were analyzed.     

Room temperature polymerization of poly(3,4‐ethylenedioxythiophene) as transparent counter electrodes for dye‐sensitized solar cells

Poly(3,4‐ethylenedioxythiophene) (PEDOT) counter electrode is prepared with in situ polymerization of 3,4‐ethylenedioxythiophene on a fluorine‐doped tin oxide over‐layer glass at room temperature. The cyclic voltammetry, electrochemical impedance spectroscopy, and Tafel polarization are measured to evaluate the catalytic activity of PEDOT counter electrode for I₃^?/I^? redox couple. Comparing the data with that of traditional thermal decomposed Pt counter electrode, it is found that PEDOT has higher catalytic activity than that of Pt counterpart. Power conversion efficiency of the dye‐sensitized solar cell (DSC) with PEDOT counter electrode can attain to 7.713%, a little higher than that of the cell with Pt counter electrode (7.300%). Taking the advantage of high transparency of PEDOT counter electrode, an Ag mirror is put on the back side of PEDOT counter electrode of the DSC to reflect light back for power conversion. Power conversion efficiency of the DSC with this special structure can be further enhanced to 8.359%, which mainly stems from the improved short‐circuit current density by the increased irradiated light intensity. Copyright © 2014 John Wiley & Sons, Ltd.     

Composition effects of FePt alloy nanoparticles on the electro-oxidation of formic acid

The catalytic activities of FexPt100-x alloy nanoparticles at different compositions (x=10, 15, 42, 54, 58, and 63) in the electro-oxidation of formic acid have been investigated by using cyclic voltammetry (CV), chronoamperometry, and electrochemical impedance spectroscopy (EIS). It was observed that the electrocatalytic performance was strongly dependent on the FePt particle composition. In chronoamperometric measurements, the alloy particles at x approximately 50 showed the highest steady-state current density among the catalysts under study and maintained the best long-term stability. In addition, on the basis of the anodic peak current density, onset potentials, and the ratios of the anodic peak current density to the cathodic peak current density in CV studies, the catalytic activity for HCOOH oxidation was found to decrease in the order of Fe42Pt58>Fe54Pt46 approximately Fe58Pt42>Fe15Pt85>Fe10Pt90>Fe63Pt37. That is, within the present experimental context, the alloy nanoparticles at x approximately 50 appeared to exhibit the maximum electrocatalytic activity and stability with optimal tolerance to CO poisoning. Consistent responses were also observed in electrochemical impedance spectroscopic measurements. For the alloy nanoparticles that showed excellent tolerance to CO poisoning, the impedance in the Nyquist plots was found to change sign from positive to negative with increasing electrode potential, suggesting that the electron-transfer kinetics evolved from resistive to pseudoinductive and then to inductive characters. However, for the nanoparticles that were heavily poisoned by adsorbed CO species during formic acid oxidation, the impedance was found to be confined to the first quadrant at all electrode potentials. The present work highlights the influence of the molecular composition of Pt-based alloy electrocatalysts on the performance of formic acid electro-oxidation, an important aspect in the design of bimetal electrocatalysts in fuel cell applications.