Nanostructured silver catalyzed nickel foam cathode for an aluminum–hydrogen peroxide fuel cell

A nanostructured Ag catalyzed nickel foam cathode for an aluminum–hydrogen peroxide fuel cell was prepared using an electrodeposition technique. SEM images show that Ag nano-islands, about 2–3 μm in length and 100–200 nm in width are aligned on the surface of the Ni foam substrate. The composition of the catalyst layer of the cathode was examined by XRD. Electrochemical performance and stability of the cathode for the reduction of hydrogen peroxide in aluminum–hydrogen peroxide fuel cell were studied.     

Electrocatalytic performance of Pb−Ru pyrochlore prepared by the amorphous citrate precursor method for bifunctional air electrodes

Pb−Ru pyrochlore has been of interest as bifunctional electrocatalyst for an air electrode. An amorphous citrate precursor (ACP) process has been optimized to prepare Pb−Ru pyrochlore powders with high surface areas with consequent improvement of its electrocatalytic performance in an air electrode. The surface area of the final powder is 30 m²/g, which is larger than the value obtained by the conventional hydroxide method. A PTEF-bonded gas diffusion electrode loaded with pyrochlore catalysts prepared by the ACP method showed good bifunctional performance. The electrode loaded with only 10 mg/cm² of pyrochlore powder prepared by ACP showed good bifunctional performance, i.e. 100 mA/cm² for oxygen reduction and 100 mA/cm² for oxygen evolution, at 0.6 and 1.6 V vs. RHE, respectively. This performance compares well to the results from lower-area pyrochlore at much higher loading.     

酞菁催化剂对镍氢电池性能的影响

研究2种酞菁类催化剂——酞菁钴、酞菁铁作为负极添加剂对Ni-MH电池充放电、电池内压及循环性能的影响。结果表明：在负极材料中加入酞菁钴、酞菁铁能够显著提高电池充放电性能,1C充电至额定容量时,电池最高电压分别较对比电池降低25 mV和31 mV;5C放电时,中值电压分别较对比电池高45 mV和51 mV。电池的循环性能得到改善,0.5C循环150次时,分别剩余额定容量的75%和83%;电池安全性得到提高,电池内压显著降低。     

MoS2/硼掺杂石墨烯的电化学析氢和储锂性能

为了研发高效低成本的析氢反应(HER)电催化剂和高性能的电化学储锂电极材料,通过一步水热法制备MoS₂/硼掺杂石墨烯（MoS₂/BG）复合材料. 结果表明,少堆积MoS₂纳米片均匀地分散在硼掺杂石墨烯上,并具有较多的无序结构和扩大的层间距. 作为析氢反应电催化剂,MoS₂/BG复合材料表现出较高的电催化活性和较低的Tafel斜率（46.3 mV/dec）;作为电化学储锂电极材料,MoS₂/BG复合材料表现出优异的电化学储锂性能,可逆比容量为1 205 mA·h/g,并具有稳定的循环性能和显著增强的高倍率特性. MoS₂/BG复合材料电化学性能优异是由于硼掺杂改变石墨烯的电子性质和表面特性,以及无序结构较多的弱堆积MoS₂层均匀地分散在硼掺杂石墨烯表面,增加电催化析氢反应的活性位点和电化学储锂能力,降低电极反应的电子转移阻抗,增强电极反应的动力学性能.     

Non-destructive transmission electron microscopy study of catalyst degradation under electrochemical treatment

A novel, non-destructive transmission electron microscopy technique is introduced, which enables the observation of the identical locations of a catalyst before and after electrochemical treatment (IL-TEM). The significance of this method is exemplified by the analysis of a standard, commercially available carbon supported platinum catalyst. We demonstrate that the observed changes of the catalyst particles are a direct consequence of the applied electrochemical treatment; and that selected catalyst regions are representative for the catalyst as a whole. Different electrochemical treatments were applied in order to discuss the potential of the method for studying processes of catalyst degradation.     

Electrocatalysis by nanocrystalline tungsten carbides and the effects of codeposited silver

The electrocatalytic activity of two nanocrystalline tungsten carbides, WC and W₂C, towards the anodic oxidation of hydrogen in 1.5 M H₂SO₄ at 65 °C is presented. The carbides, which were synthesised by solid-state reduction of W(VI) using carbon, are both electrocatalytic. The WC phase shows greater electrocatalysis than the W₂C phase, and also shows a greater degree of passivity against corrosion in the hot sulphuric acid electrolytes. The effect of codeposited silver is to enhance the electrocatalytic activity of the WC phase, whilst not in itself showing any electrocatalysis.     

Ammonia-treated carbon-supported cobalt tungsten as fuel cell cathode catalyst

The ammonia-treated carbon-supported cobalt tungsten (Co-W/C) was prepared by a reaction employing a temperature program in a stream of NH₃ between 773 and 1073 K. The effects of the NH₃ heat-treatment temperature, Co-W ratio and the preparation method were investigated. The activity of Co-W/C for the oxygen reduction reaction (ORR) was evaluated using a rotating disc electrode and single fuel cell measurements. The Co-W/C prepared by the impregnation method with the same atomic ratio of Co and W, and NH₃ heat treated at 823 K, exhibited the highest ORR activity with an onset potential of 0.74 V (vs. RHE at 5 μA cm⁻²). The XRD and temperature-programmed measurements revealed that the catalyst active species were ascribed to the presence of CoW oxynitride and Co nitride. The catalyst surface was characterized as nitrided metal (accommodation of the N-atom in the host Co-W lattice resulting from a sufficient distance between the Co-W atoms and N) and N-containing carbon (Co surrounded by N-atoms and attached to the C support) by X-ray photoelectron spectroscopy. The Co-W oxynitrides, Co nitride and pyrrolic-type nitrogen of the N-containing carbons are likely responsible for the good ORR activity.     

Cobalt based non-precious electrocatalysts for oxygen reduction reaction in proton exchange membrane fuel cells

Cobalt based non-precious metal catalysts were synthesized using chelation of cobalt (II) by imidazole followed by heat-treatment process and investigated as a promising alternative of platinum (Pt)-based electrocatalysts in proton exchange membrane fuel cells (PEMFCs). Transmission electron microscopy (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) measurements were used to characterize the synthesized CoN_x/C catalysts. The activities of the catalysts towards oxygen reduction reaction (ORR) were investigated by electrochemical measurements and single cell tests, respectively. Optimization of the heat-treatment temperature was also explored. The results indicate that the as-prepared catalyst presents a promising electrochemical activity for the ORR with an approximate four-electron process. The maximum power density obtained in a H₂/O₂ PEMFC is as high as 200 mW cm⁻² with CoN_x/C loading of 2.0 mg cm⁻².     

金属钴卟啉负载炭黑在碱性介质中的性质研究

将合成的四甲氧基苯基钴卟啉(CoTMPP)负载于经过双氧水和硝酸预处理且掺杂了MnOx的炭载体上,作为氧还原电催化剂。采用X射线衍射(XRD)、红外透射光谱(IR)、循环伏安曲线(CV)和Koutevky-Levich关系式评价了电催化剂对氧还原反应的电催化性能。结果表明,在碱性介质中,MnOx的掺杂有利于提高催化剂的催化活性,CoTMPP负载于6 mol/L硝酸处理过的炭载体BP 2000上活性较好,同时发现焙烧的最佳温度是900℃。