变压加载对直接甲醇燃料电池阳极性能的影响（英文）

为评价直接甲醇燃料电池(DMFC)阳极的稳定性,利用扫描电化学显微镜和常规电化学技术,研究了变压加载过程中DMFC阳极性能的变化。结果表明,在探针扫描过程中,经不同电压加载后的DMFC阳极表面的扫描电流呈相似的锯齿状分布。当阳极加载2h,随加载电位升高,扫描峰电流的数量减少,对应峰电流的数值则先增大再减小,表明阳极的催化活性处于不均匀分布状态且随加载时间延长和加载电位升高而逐渐降低。在不同加载电位下,随加载时间延长,循环伏安曲线上的正向和反向电流峰先负移再正移,但抗CO性能持续降低。DMFC阳极在0.6V下分别加载16h和72h后,催化剂粒径由3.4nm分别增大到3.6nm和4.4nm。在0.8V下加载72h后,Pt/Ru重量比由2.0增加到3.9。变压加载使催化活性的不均匀分布加剧催化剂粒径长大,Ru流失加快,从而导致阳极催化性能衰减。     

变压加载对直接甲醇燃料电池阳极性能的影响（英文）北大核心CSCD

为评价直接甲醇燃料电池(DMFC)阳极的稳定性,利用扫描电化学显微镜和常规电化学技术,研究了变压加载过程中DMFC阳极性能的变化。结果表明,在探针扫描过程中,经不同电压加载后的DMFC阳极表面的扫描电流呈相似的锯齿状分布。当阳极加载2h,随加载电位升高,扫描峰电流的数量减少,对应峰电流的数值则先增大再减小,表明阳极的催化活性处于不均匀分布状态且随加载时间延长和加载电位升高而逐渐降低。在不同加载电位下,随加载时间延长,循环伏安曲线上的正向和反向电流峰先负移再正移,但抗CO性能持续降低。DMFC阳极在0.6V下分别加载16h和72h后,催化剂粒径由3.4nm分别增大到3.6nm和4.4nm。在0.8V下加载72h后,Pt/Ru重量比由2.0增加到3.9。变压加载使催化活性的不均匀分布加剧催化剂粒径长大,Ru流失加快,从而导致阳极催化性能衰减。     

变压加载对直接甲醇燃料电池阳极性能的影响（英文）

为评价直接甲醇燃料电池(DMFC)阳极的稳定性,利用扫描电化学显微镜和常规电化学技术,研究了变压加载过程中DMFC阳极性能的变化。结果表明,在探针扫描过程中,经不同电压加载后的DMFC阳极表面的扫描电流呈相似的锯齿状分布。当阳极加载2h,随加载电位升高,扫描峰电流的数量减少,对应峰电流的数值则先增大再减小,表明阳极的催化活性处于不均匀分布状态且随加载时间延长和加载电位升高而逐渐降低。在不同加载电位下,随加载时间延长,循环伏安曲线上的正向和反向电流峰先负移再正移,但抗CO性能持续降低。DMFC阳极在0.6V下分别加载16h和72h后,催化剂粒径由3.4nm分别增大到3.6nm和4.4nm。在0.8V下加载72h后,Pt/Ru重量比由2.0增加到3.9。变压加载使催化活性的不均匀分布加剧催化剂粒径长大,Ru流失加快,从而导致阳极催化性能衰减。     

碳载PtSn催化剂上乙醇电氧化的原位时间分辨红外光谱研究

采用调变的多元醇法制备了高分散碳载PtSn催化剂(PtSn/C),XRD测试结果表明金属粒子的平均粒径为2.2 nm,略小于Pt/C催化剂,而晶格参数相对增大。通过电化学原位时间分辨红外光谱研究了乙醇在PtSn/C催化剂上的吸附和氧化过程,表明线性吸附态CO(CO_L)是主要的乙醇解离吸附物种,导致催化剂中毒,阻止反应继续进行;当电位增大到0.3 V时,出现了乙醛和乙酸的红外吸收峰,作为乙醇解离吸附的竞争反应,乙醛和乙酸的生成有效抑制了催化剂中毒,随着电位的增大和时间的延长,生成乙酸的选择性增大;电位进一步增大至0.4 V时有微弱CO₂吸收峰出现,是乙醇电氧化的最终产物,主要来自于CO_L的氧化消耗。根据实验结果讨论了PtSn/C催化剂上乙醇的电催化氧化机理。     

胶体金纳米颗粒的表面等离子体发射特性

利用电化学方法制备出粒径为20-80 nm的胶体金纳米颗粒。研究其荧光发射光谱特性,在485nm处观察到表面自由电子集体激发导致的表面等离子体共振发射峰,其位置不随激励光波长的变化而移动。当激励光波长为485 nm时,观察到最强的发射峰。在240和640 nm处,还观察到倍频发射峰和3/4分频发射峰。增加金纳米颗粒粒径,观察到发射谱的峰值增大而发射峰的位置只有很小的红移。     

用微米级LaNi5为催化剂生长的碳管的ESR谱研究

用微米级LaNi₅合金粉末为催化剂, 以乙炔为原料, 采用化学气相沉积(CVD)法合成了多壁碳纳米管. 在100~290 K温度下测量了41 μm≤d≤150 μm粒径催化剂制备的不同直径分布的碳纳米管的电子自旋共振（ESR）谱,研究了测量温度、微米级催化剂粒径及制备过程的氢气氛对生成的碳纳米管的ESR谱线型、g因子、线宽的影响. 发现碳纳米管的g因子随其直径的增大而增大,分别为2.040 0（催化剂粒径41 μm≤d≤50 μm, 碳纳米管的直径分布为10 nm到20 nm）和2.089 8（催化剂粒径100 μm≤d≤150 μm,碳纳米管的直径分布为70 nm到120 nm）. 发现小管径纳米管的ESR谱图有一个峰, 而大管径纳米管的ESR谱图有两个峰A和B, 且随测量温度的升高, 峰B强度增大.     

磁场对碳纸上磁电沉积的AuPt颗粒性能的影响

AuPt纳米颗粒是一种催化锂空气电池空气电极上氧气还原反应和氧气析出反应的双功能催化剂．在电沉积制备AuPt颗粒的过程中施加了磁场,恒电流沉积条件下,随着磁场强度的增加,AuPt催化剂颗粒的粒径从1 μm减小到200 nm,同时催化活性增大．垂直于电场方向的磁场有助于提高AuPt/C空气电极的催化能力．使用脉冲电沉积,结晶粒径可减小至约100 nm．通过调节电场和磁场参数,可原位制备具有不同形貌、不同组成和催化性能的AuPt催化剂．     

柔性ITO衬底电化学沉积制备Cu/Cu2O薄膜

研究了使用电化学沉积法于碱性条件下在柔性ITO衬底上制备Cu/Cu₂O薄膜的方法。循环伏安曲线表明Cu₂O与Cu的阴极峰分别位于-500 mV(vs Ag/AgCl)和-800 mV(vs Ag/AgCl)附近。利用循环伏安法考察了生长温度和电解液pH值等对Cu₂O与Cu阴极峰电位的影响,阴极峰随生长温度的升高以及pH值的降低而略向阳极移动,沉积电流也随之相应增大。与弱酸性条件相比,上述两个阴极峰随pH值升高而移动的程度明显减小,这可能与碱性条件下C₃H₆O电离程度增大以及C₃H₆O根作为配体的过量程度有关。通过X射线衍射光谱和扫描电子显微镜的表征证实,在所研究的生长温度区间和pH值内可利用电化学沉积法在柔性ITO衬底上制备Cu/Cu₂O纳米混晶薄膜。在相同的生长温度和pH条件下,电化学沉积电位对样品表面形貌和晶体性质具有较大影响。     

表面合金电催化剂上甲酸氧化的原位FTIR反射光谱研究

运用原位红外反射光谱(FTIRS)和电化学循环伏安法(CV)研究了甲酸在三种不同电极上的电催化特性。结果表明甲酸在碳载铂电极(Pt/GC)上的电催化氧化机理与本体铂电极(Pt)相类似,即可以通过活性中间体或毒性中间体氧化至CO_2。Pt/GC对甲酸的氧化比Pt具有更高的电催化活性。Pt/GC表面以Sb吸附原子修饰的电极(Sb-Pt/GC)上,甲酸氧化的起始电位(E;)提前至-0.10V,氧化电流峰电位(Ep)提前至0.34V,氧化峰电流(jp)值增加了7.28倍,半峰宽(FWHM)为0.30V。同样,Surface al-loy/GC电极上,E_I为-0.12V,E_p为0.32V和j_p为7.25mA·cm~(-2),相对Pt/GC分别负移了0.22,0.02V和增大了8.15倍,半峰宽(FWHM)为0.5V。表明Sb-Pt/GC和Surface alloy/GC电极不仅能够有效地抑制毒性中间体CO的生成,而且还可以显著地提高其对活性中间体的氧化的电催化活性。     

PtRhSn/GN催化剂上甲醇电催化氧化的原位红外光谱研究

通过多元醇还原法制备了石墨烯(GN)负载的Pt及Pt基多元催化剂:Pt/GN,PtRh/GN,PtSn/GN,PtRhSn/GN。循环伏安研究表明,Rh的加入提升了Pt基催化剂的甲醇电催化氧化活性,而Sn的加入明显降低了甲醇在Pt基催化剂上的过电位,起始氧化电位负移106mV。电化学原位红外光谱研究进一步表明,Rh和Sn的加入使得Pt基催化剂对甲醇氧化的起始氧化电位负移;Rh的加入使得CO谱峰强度增大,而Sn的加入明显降低了CO谱峰强度。三元催化剂PtRhSn/GN很好的综合了Rh和Sn的电子效应及协同效应特点,相比于Pt/GN催化剂,起始氧化电位负移60mV,且活性达到其1.57倍。     

Progress in Developments of Inorganic Nanocatalysts for Application in Direct Methanol Fuel Cells

Significant progress has been made in the last few years toward synthesizing highly dispersible inorganic catalysts for application in the electrodes of direct methanol fuel cells. In addition, research toward achieving an efficient catalyst supporting matrix has also attracted much attention in recent years. Carbon black- (Vulcan XC-72) supported Platinum and Platinum-Ruthenium catalysts have for long served as the conventional choice as the cathode and the anode catalyst materials, respectively. Oxygen reduction reaction at the cathode and methanol oxidation reaction at the anode occur simultaneously during the operation of a direct methanol fuel cell. However, inefficiencies in these reactions result in a generation of mixed potential. This, in turn, gives rise to reduced cell voltage, increased oxygen stoichiometric ratio, and generation of additional water that is responsible for water flooding in the cathode chamber. In addition, the lack of long-term stability of Pt-Ru anode catalyst, coupled with the tendency of Ru to cross through the polymer electrolyte membrane and eventually get deposited on the cathode, is also a serious drawback. Another source of potential concern is the fact that the natural resource of Pt and the rare earth metal Ru is very limited, and has been predicted to become exhausted very soon. To overcome these problems, new catalyst systems with high methanol tolerance and higher catalytic activity than Pt need to be developed. In addition, the catalyst-supporting matrix is also witnessing a change from traditionally used carbon powder to transition metal carbides and other high-performance materials. This article surveys the recent literature based on the advancements made in the field of highly dispersible inorganic catalysts for application in direct methanol fuel cells, as well as the progress made in the area of catalyst-supporting matrices.     

Binary-surfactant (Brij 35 + Tween 20) assisted preparation of highly dispersed Pt nanoparticles on carbon

Pt nanoparticles supported on Vulcan XC-72R, synthesized by a surfactant-stabilized colloidal method, exhibited excellent properties as anode catalyst for low-temperature fuel cell. The Pt/C catalyst prepared with binary-surfactant (Brij 35 + Tween 20) at 10 times CMC had an average particle size of 2.8 nm with quite a narrow distribution between 2 and 4 nm. Our preparation method resulted in complete reduction of Pt and full loading of Pt nanoparticles on the carbon. The home-made Pt/C catalyst showed higher EAS and better catalytic activity than a commercial Pt/C catalyst. The method used in this study provided an easy and reproducible procedure for the preparation of Pt nanoparticles supported on carbon.     

室温合成非晶三硫化钼析氢催化剂的性能调制以及其在串联制氢器件中的应用

高催化活性、低成本、良好工艺兼容性以及高稳定性的析氢催化剂是实现一体化光电化学水解制氢器件的关键, 然而传统的贵金属催化剂由于储量稀缺、成本高昂而严重限制了光电化学水解制氢器件的产业化进程. 本文在室温下通过湿法化学合成法制备了高催化活性、成本低廉以及工艺兼容性好的非金属非晶三硫化钼析氢催化剂, 并研究了不同催化剂滴涂量对其催化活性以及串联制氢器件制氢性能的影响. 结果表明, 存在最优化非晶三硫化钼催化剂滴涂量以获得最佳催化活性(10 mA/cm²电流密度对应电势达260 mV vs. RHE(可逆氢电极), 塔菲尔斜率达68 mV/dec), 其粗糙表面以及多孔结构可获得更大的电化学接触面积以促进析氢反应. 进一步将其作为光阴极应用于串联制氢器件, 可有效降低过电势损失和提高光生电流密度输出, 与光阳极结合有望提高制氢效率.     

Ultrathin Fe‐N‐C Nanosheets Coordinated Fe‐Doped CoNi Alloy Nanoparticles for Electrochemical Water Splitting

The development of highly active and cost‐effective catalyst materials toward electrochemical water splitting is of great importance for converting and storing the intermittent solar energy in the form of hydrogen. Herein, for the first time, an ultrathin Fe and N‐co‐doped carbon nanosheet encapsulated Fe‐doped CoNi alloy nanoparticle (FeCoNi@FeNC) composite is obtained and applied as a bifunctional catalyst for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). This catalyst exhibits prominent catalytic performances for both HER and OER, which only requires overpotentials of 102 and 330 mV, respectively, to reach a current density of 10 mA cm^?2 in alkaline media. The high catalytic activity is intrinsically associated with the presence of Fe in both nanosheets and nanoparticles, which has triggered the occurrence of coordinative effects between Fe‐N‐C and FeCoNi that are beneficial for HER and OER, as revealed by electrochemical techniques. In an overall water splitting electrolyzer, FeCoNi@FeNC is employed as both the cathode and anode catalysts, achieving 12 mA cm^?2 at 1.63 V for a duration of more than 12 h.     

Nanosized IrO<Subscript>2</Subscript> electrocatalysts for oxygen evolution reaction in an SPE electrolyzer

Nanosized IrO₂ electrocatalysts (d ~ 7–9 nm) with specific surface area up to 100 m² g⁻¹ were synthesized and characterized for the oxygen evolution reaction in a solid polymer electrolyte (SPE) electrolyzer. The catalysts were prepared by a colloidal method in aqueous solution and a subsequent thermal treatment. An iridium hydroxide hydrate precursor was obtained at ~100 °C, which was, successively, calcined at different temperatures from 200 to 500 °C. The physico-chemical characterization was carried out by X-ray diffraction (XRD), thermogravimetry–differential scanning calorimetry (TG–DSC) and transmission electron microscopy (TEM). IrO₂ catalysts were sprayed onto a Nafion 115 membrane up to a loading of 3 mg cm⁻². A Pt catalyst was used at the cathode compartment with a loading of 0.6 mg cm⁻². The electrochemical activity for water electrolysis of the membrane-electrode assemblies (MEAs) was investigated in a single cell SPE electrolyzer by steady-state polarization curves, impedance spectroscopy and chrono-amperometric measurements. A maximum current density of 1.3 A cm⁻² was obtained at 1.8 V and 80 °C for the IrO₂ catalyst calcined at 400 °C for 1 h. A stable performance was recorded in single cell for this anode catalyst at 80 °C. The suitable catalytic activity and stability of the most performing catalyst were interpreted in terms of proper combination between nanostructure and suitable morphology.     

Electrostatic spraying of membrane electrode for proton exchange membrane fuel cell

In order to improve the performance of proton exchange membrane fuel cell (PEMFC), the optimization of electrostatic spraying of membrane electrode was conducted. The influence of the spraying voltage on morphology, elemental composition of catalyst layer, and performance of the PEMFC were investigated. The results show that increasing spraying voltage could reduce agglomeration of the carbon-supported platinum particles, leading to more uniform pore distribution. High voltage did not accelerate oxidation of platinum catalyst. A high electrochemical active surface area of 26.18 m²/g_pt was obtained when the platinum-carbon catalyst layer was deposited in cone jet mode. With further increasing spraying voltage, the total ohmic resistance and catalytic activity were changed slightly, whereas the charge transfer resistance was increased. Using the optimized electrostatic spraying parameters (injection rate = 100 μL min⁻¹, spraying voltage = 8.5 kV, and working distance = 12 mm), a peak power density of 1.408 W cm⁻² was obtained with an output voltage of 0.451 V.     

Electrochemical promotion of propane oxidation over Pd, Ir, and Ru catalyst-electrodes deposited on YSZ

The effect of electrochemical promotion of catalysis was investigated for the oxidation of propane using Pd, Ir, and Ru catalyst-electrodes sputter-deposited on YSZ disks in the temperature range of 250–450 °C. Electrophobic type behavior was observed, i.e., the catalytic reaction rate was found to increase with catalyst potential. The observed rate changes under polarization were strongly non-Faradaic and exceeded under anodic potential application the electrocatalytic rate of O^2? supply to the catalyst surface, I/2F, by up to a factor of 250 for Pd, 125 for Ir, and 15 for Ru catalyst-electrodes.     

Effect of ultrasonic power on the structure of activated carbon and the activities of Ru/AC catalyst

Ruthenium-based materials are the second-generation catalysts for ammonia synthesis. Ruthenium is less inhibited by ammonia, less sensitive to poisons, and more active than the traditional iron-based catalyst. The relatively high cost of Ru compared to that of iron requires a high dispersion of the metal on a suitable support. Carbon-supported Ru catalysts with promoters have been reported to be active for ammonia synthesis. The ultrasonic technique has been proven to be beneficial to the preparation of supported catalysts. In this paper, the effects of ultrasonic treatment on the surface texture, oxygen groups of activated carbon (AC) as well as ruthenium dispersion were investigated by the employments of N(2) physisorption, TPD-MS and CO chemisorption respectively. It have been shown that ash content in AC can be effectively eliminated by ultrasonic pretreatment, at the same time, the BET surface area and total pore volume are reduced, and the amount of the decomposable surface oxygen groups are decreased. Furthermore the ash content decrease and the mesopore surface area increase with the ultrasonic power increasing. The activities of a series of barium-potassium-promoted Ru/AC catalysts for ammonia synthesis were tested at 10,000 h(-1), 10.0 MPa and 400 degrees C. The results show that the activities of Ru/AC catalysts which were prepared by ultrasonic treatment are greatly increased, and the optimum pretreatment power is 100 W. The ash content of this carbon support is decreased from 1.39% to 1.15%. As a result, the catalytic activity is improved from 65.3 to 83.8 mmol g(-1) h(-1).     

Complexed sol-gel synthesis of improved Pt-Ru-Os-based anode electro-catalysts for direct methanol fuel cells

A high specific surface area (SSA) Pt-Ru-Os-based anode catalyst synthesized by a novel complexed sol-gel (CSG) process shows better catalytic activity in comparison to pure equi-atomic compositions of Pt-Ru anode catalysts synthesized by similar sol-gel processes. A homogeneous amorphous gel was successfully synthesized by complexing platinum(II) acetylacetonate, ruthenium(III) acetylacetonate and osmium(III) chloride with tetramethylammonium hydroxide (TMAH) used as a complexing agent. Phase-pure Pt(Ru,Os) and Pt(Ru) solid solutions possessing high specific surface area (∼110-120 m²/g) were successfully synthesized by controlled removal of carbonaceous species present in the as-prepared precursor generated from the CSG process. This has been successfully achieved by precise thermal treatments of the precursor using controlled oxidizing atmospheres. Results indicate that the nano-crystalline Pt(Ru,Os) solid solution of nominal composition 50 at%-Pt-40 at% Ru-10 at% Os possesses good chemical homogeneity, and reveals excellent catalytic activity, thus demonstrating the potential of the novel CSG process for synthesizing high-performance Pt-Ru-Os-based catalysts for direct methanol fuel cells.     

Electrochemical characterization of platinum-based anode catalysts for membraneless fuel cells

In the present work, carbon-supported Pt–Sn, Pt–Ru, and Pt–Sn–Ru electrocatalysts with different atomic ratios were prepared by alcohol-reduction method to study the electro-oxidation of ethanol in membraneless fuel cells. The synthesized electrocatalysts were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), and X-ray diffraction (XRD) analyses. The prepared catalysts had similar particle morphology, and their particle sizes were 2–5 nm. The electrocatalytic activities were characterized by cyclic voltammetry (CV) and chronoamperometry (CA). The electrochemical results obtained at room temperature showed that the addition of Sn and Ru to the pure Pt electrocatalyst significantly improved its performance in ethanol electro-oxidation. The onset potential for ethanol electro-oxidation was 0.2 V vs. Ag/AgCl, in the case of the ternary Pt–Sn–Ru/C catalysts, which was lower than that obtained for the pure Pt catalyst (0.4 V vs. Ag/AgCl). During the experiments performed on single membraneless fuel cells, Pt ? Sn ? Ru/C (70:10:20) performed better among all the catalysts prepared with power density of 36 mW/cm². The better performance of ternary Pt–Sn–Ru/C catalysts may be due to the formation of a ternary alloy and the smaller particle size.