Oxygen reduction activity of carbon-supported Pt-M (M = V, Ni, Cr, Co, and Fe) alloys prepared by nanocapsule method

Monodispersed Pt and Pt-M (M = V, Cr, Fe, Co, and Ni) alloy nanoparticles supported on carbon black (denoted as Pt/CB and Pt-M/CB) were prepared by the simultaneous reduction of platinum acetylacetonate and the second metal acetylacetonate within nanocapsules formed in diphenyl ether in the presence of carbon black. For the Pt/CBs, the average Pt diameters measured by scanning transmission electron microscopy (STEM) or X-ray diffraction (XRD) ranged from 2.0 to 2.5 nm, regardless of the catalyst-loading level from 10 to 55 wt % on CB. The alloy composition was found to be well-controlled to the projected value among the supported particles. The activities for the oxygen reduction reaction (ORR) at Nafion-coated catalysts in O2-saturated 0.1 M HClO4 solution were evaluated by using a channel flow electrode (CFE) cell at 30 degrees C. The area-specific ORR activities at Pt-M/CB were found to be 1.3 to 1.8 times higher than that at Pt/CB. The ORR activity increased in the order Pt/CB < Pt-Ni/CB < Pt-Fe/CB < Pt-Co/CB < Pt-V/CB < Pt-Cr/CB.     

Steady-state dc and impedance investigations of H2/O2 alkaline membrane fuel cells with commercial Pt/C, Ag/C, and Au/C cathodes

The performances of H(2)/O(2) metal-cation-free alkaline anion-exchange membrane (AAEM) fuel cells operated with commercially available Au/C and Ag/C cathodes are reported for the first time. Of major significance, the power density obtained with 4 mg cm(-2) Ag/C (60% mass) cathodes was comparable to that obtained with 0.5 mg cm(-2) Pt/C (20% mass) electrodes, whereas the performance when using the same Ag/C cathode in a Nafion-based acidic membrane electrode assembly (MEA) was poor. These initial studies demonstrate that the oxygen reduction electrokinetics are improved when operating Pt/C cathodes at high pH in AAEM-based fuel cells as compared with operation at low pH (in Nafion-based proton-exchange membrane fuel cells). The results of in situ alternating current impedance spectroscopy were core to the assignment of the source of the limited performances of the AAEM-based fuel cells as being the limited supply of water molecules to the cathode reaction sites. Minimizing the thickness of the AAEM improved the performances by facilitating back-transport of water molecules from the anode (where they are generated) to the cathode. The urgent need for development of electrode architectures that are specifically designed for use in AAEM-based fuel cells is highlighted.     

Poly(vinyl alcohol) separators improve the coulombic efficiency of activated carbon cathodes in microbial fuel cells

High-performance microbial fuel cell (MFC) air cathodes were constructed using a combination of inexpensive materials for the oxygen reduction cathode catalyst and the electrode separator. A poly(vinyl alcohol) (PVA)-based electrode separator enabled high coulombic efficiencies (CEs) in MFCs with activated carbon (AC) cathodes without significantly decreasing power output. MFCs with AC cathodes and PVA separators had CEs (43%–89%) about twice those of AC cathodes lacking a separator (17%–55%) or cathodes made with platinum supported on carbon catalyst (Pt/C) and carbon cloth (CE of 20%–50%). Similar maximum power densities were observed for AC-cathode MFCs with (840 ± 42 mW/m²) or without (860 ± 10 mW/m²) the PVA separator after 18 cycles (36 days). Compared to MFCs with Pt-based cathodes, the cost of the AC-based cathodes with PVA separators was substantially reduced. These results demonstrated that AC-based cathodes with PVA separators are an inexpensive alternative to expensive Pt-based cathodes for construction of larger-scale MFC reactors.     

Electrocatalytic activity of porous nanostructured Fe/Pt-Fe electrode for methanol electrooxidation in alkaline media

An electrochemical approach to fabricate a nanostructured Fe/Pt-Fe catalyst through electrodepo-sition followed by galvanic replacement is presented. An Fe/Pt-Fe nanostructured electrode was prepared by deposition of Fe-Zn onto a Fe electrode surface, followed by replacement of the Zn by Pt at open-circuit potential in a Pt-containing alkaline solution. Scanning electron microscopy and energy-dispersive X-ray techniques reveal that the Fe/Pt-Fe electrode is porous and contains Pt. The electrocatalytic activity of the Fe/Pt-Fe electrode for oxidation of methanol was examined by cyclic voltammetry and chronoamperometry. The electrooxidation current on the Fe/Pt-Fe catalyst is much higher than that on flat Pt and smooth Fe catalysts. The onset potential and peak potential on the Fe/Pt-Fe catalyst are more negative than those on flat Pt and smooth Fe electrodes for methanol electrooxidation. All results show that this nanostructured Fe/Pt-Fe electrode is very attractive for integrated fuel cell applications in alkaline media.     

Lead dioxide as an alternative catalyst to platinum in microbial fuel cells

Lead dioxide (PbO₂) was compared to platinum (Pt) as a cathode catalyst in a double-cell microbial fuel cell (MFC) utilizing glucose as a substrate in the anode chamber. Four types of cathodes were tested in this study including two PbO₂ cathodes fabricated using a titanium base with butanol or Nafion^® binders and PbO₂ paste, one Pt/carbon cathode fabricated using a titanium base with a carbon–Pt paste, and a commercially available Pt/carbon cathode made from carbon paper with Pt on one side. The power density and polarization curves were compared for each cathode and cost estimates were calculated. Results indicate the PbO₂ cathodes produced between 2 and 4× more power than the Pt cathodes. Furthermore, the PbO₂ cathodes produced between 2 and 17× more power per initial fabrication or purchase cost than the Pt cathodes. This study suggests that cathode designs that incorporate PbO₂ instead of Pt could possibly improve the feasibility of scaling up MFC designs for real world applications by improving power generation and lowering production cost.     

多孔纳米结构Fe/Pt-Fe电极对碱性介质中甲醇电氧化的催化活性（英文）

An electrochemical approach to fabricate a nanostructured Fe/Pt-Fe catalyst through electrodeposition followed by galvanic replacement is presented. An Fe/Pt-Fe nanostructured electrode was prepared by deposition of Fe-Zn onto a Fe electrode surface, followed by replacement of the Zn by Pt at open-circuit potential in a Pt-containing alkaline solution. Scanning electron microscopy and energy-dispersive X-ray techniques reveal that the Fe/Pt-Fe electrode is porous and contains Pt. The electrocatalytic activity of the Fe/Pt-Fe electrode for oxidation of methanol was examined by cyclic voltammetry and chronoamperometry. The electrooxidation current on the Fe/Pt-Fe catalyst is much higher than that on flat Pt and smooth Fe catalysts. The onset potential and peak potential on the Fe/Pt-Fe catalyst are more negative than those on flat Pt and smooth Fe electrodes for methanol electrooxidation. All results show that this nanostructured Fe/Pt-Fe electrode is very attractive for integrated fuel cell applications in alkaline media.     

碱性条件下Pt-M(Ni,Fe,Mo)/C电催化氧化甲醇的性能对比研究

采用溶胶法制备了碳载Pt-M(M为Ni, Fe, Mo)电催化剂, 并用TEM和XRD技术表征活性物微观结构, 实验结果表明, Pt基合金微粒在碳黑表面分布均匀, 粒径约为2~4 nm. 用循环伏安法测定催化剂在不同碱性条件下的活性, 研究结果表明, 不同掺杂元素催化剂的活性大小顺序为Pt75Ni25/C>Pt75Fe25/C>Pt50Mo50/C, 掺杂Ni可明显地促进纳米Pt的催化活性, Pt75Ni25/C在1.0 mol/L NaOH+1.0 mol/L CH3OH溶液中的峰电流密度可以达到726.9 mA/mg.     

Synthesis of Non-precious N-doped Mesoporous Fe3O4/CoO@NC Materials towards Efficient Oxygen Reduction Reaction for Microbial Fuel Cells

N-doped transition metal oxides are strategic materials towards the efficient oxygen reduction reaction (ORR) of microbial fuel cells (MFCs). Non-precious N-doped Fe₃O₄/CoO@NC−T (T represents carbonization temperature) catalysts are prepared by an efficient two-step strategy for ORR. Fe₃O₄/CoO@NC-750 exhibits the best performance with an efficient four-electron transfer pathway. The optimal power density of MFCs by using Fe₃O₄/CoO@NC-750 as the cathode catalyst (1243.4 mW ⋅ m⁻²) is superior to that of the MFCs with commercial Pt/C catalyst (1080 mW ⋅ m⁻²), which shows an outstanding activity towards ORR. No significant decrease in output voltage results over 70 days, which shows an excellent electrochemical stability.     

Characterization of Fe/N-doped graphene as air-cathode catalyst in microbial fuel cells

This work proposed a simple and efficient approach for synthesis of durable and efficient non-precious metal oxygen reduction reaction(ORR) electro-catalysts in MFCs. The rod-like carbon nanotubes(CNTs)were formed on the Fe–N/SLG sheets after a carbonization process. The maximum power density of1210 ± 23 m W·m~(-2) obtained with Fe–N/SLG catalyst in an MFC was 10.7% higher than that of Pt/C catalyst(1080 ± 20 mW ·m~(-2)) under the same condition. The results of RDE test show that the ORR electron transfer number of Fe–N/SLG was 3.91 ± 0.02, which suggested that ORR catalysis proceeds through a four-electron pathway. The whole time of the synthesis of electro-catalysts is about 10 h, making the research take a solid step in the MFC expansion due to its low-cost, high efficiency and favorable electrochemical performance. Besides, we compared the electrochemical properties of catalysts using SLG, high conductivity graphene(HCG, a kind of multilayer graphene) and high activity graphene(HAG, a kind of GO) under the same conditions, providing a solution for optimal selection of cathode catalyst in MFCs.The morphology, crystalline structure, elemental composition and ORR activity of these three kinds of Fe–N/C catalysts were characterized. Their ORR activities were compared with commercial Pt/C catalyst.It demonstrates that this kind of Fe–N/SLG can be a type of promising highly efficient catalyst and could enhance ORR performance of MFCs.     

氧化铁对铂在碱性介质中催化氧化甲醇的促进作用

Pt催化剂是电催化领域用途最为广泛的贵金属催化剂.Pt资源稀缺,价格昂贵,同时它的物理化学特性又决定了其在多种催化反应中难以被替代.在质子交换膜燃料电池的小分子醇类电氧化过程中,难免存在Pt的毒化现象,其催化性能有待进一步提升.因此,围绕着Pt催化剂纳米结构的设计、抗毒性及反应机理的探索一直是电催化研究面临的重要课题.目前,已被广泛认可的提高Pt催化性能的方法之一是引入第二种金属,通过金属间协同效应(双功能机理)、张力效应或电子效应等对Pt的催化行为进行改性.对于由双/多金属组成的纳米结构催化剂,无论是协同效应还是电子效应,催化活性的提高都需要金属间有丰富的接触界面和恰当的邻近状态.通过调变两组元的种类、原子比和接触状态等可以实现对金属-金属界面的调控,进而调变催化剂性能.除金属助剂外,金属氧化物对Pt催化剂的助催化作用也引起广泛关注.由于金属氧化物与Pt之间的密切接触作用,氧化物的形貌特点对Pt的催化性能可产生重要影响.到目前为止,有关催化剂形貌效应的研究主要集中于贵金属纳米颗粒上(Pt,Au,Pd等),但关于金属氧化物载体/助剂的形貌对贵金属催化性能影响的研究尚不多.具有明确形貌的金属氧化物载体/助剂,暴露的晶面不同,表面原子的配位状态也不同,从而造成与之密切接触的Pt的性质发生改变.因此,金属氧化物的表面性质以及Pt-金属氧化物的界面性质将对电催化性能产生重要影响,深入阐释贵金属-金属氧化物的表/界面性质以及建立有效的构效关系,对设计和制备高效电催化剂具有一定的指导意义.为了提高Pt基催化剂活性、抗CO中毒能力以及稳定性,本文采用共沉淀法和水热法分别制备了纳米棒和六边形纳米片状的Fe2O3作为Pt催化剂的助剂,考察了助剂形貌对Pt催化剂在碱性介质中催化氧化甲醇的促进作用.通过X射线衍射、扫描电子显微镜、透射电子显微镜、X射线光电子能谱以及电化学技术对催化剂进行了表征.结果显示,Fe2O3的存在能显著提高Pt催化剂在碱性介质中对甲醇氧化的电催化性能,而且以Fe2O3纳米棒为助剂制备的Pt-Fe2O3/C-R催化剂催化活性以及稳定性比Fe2O3纳米片为助剂制备的Pt-Fe2O3/C-P催化剂更高.这种促进效应可能与助剂Fe2O3的形态有关.Pt-Fe2O3/C-R催化剂中Pt的质量比活性为5.32 A/mgPt,本征活性为162.7 A/m2Pt,分别是Pt-Fe2O3/C-P催化剂的1.67和2.04倍,是商业PtRu/C样品的4.19和6.16倍.协同效应和电子效应是Pt催化性能提升的主要原因.此外,Pt-Fe2O3/C-R样品中高价态Pt的含量较高,可能也是加速甲醇氧化反应动力学的原因之一.高价态的Pt可能会增强甲醇分子在Pt表面的吸附强度,促进Pt上甲醇氧化反应初始步.这些发现不仅可对甲醇电催化氧化机理有了更深的理解,而且对设计和制备高性能甲醇氧化电催化剂也具有一定的指导意义.     

Comparative characteristics of cathodes with different catalytic systems in hydrogen–oxygen and hydrogen–air fuel cells with proton-conducting polymer electrolyte

The characteristics of low-temperature hydrogen–oxygen (air) fuel cell (FC) with cathodes based on the 50 wt % PtCoCr/C and 40 wt % Pt/CNT catalysts synthesized on XC72 carbon black and carbon nanotubes (CNT) are compared with the characteristics of commercial monoplatinum systems 9100 60 wt % Pt/C and 13100 70% Pt/C HiSPEC. It is shown that the synthesized catalysts exhibit a high mass activity, which is not lower than that of commercial Pt/C catalysts, a high selectivity with respect to the oxygen reduction to water, and a significantly higher stability. The characteristics of PtCoCr/C and Pt/CNT were confirmed by testing in the hydrogen—oxygen FCs. However, when air was used at the cathode, especially in the absence of excessive pressure, a voltage of FC with the cathode based on PtCoCr/XC72 is lower as compared with the commercial systems. Probably, this is associated with the transport limitations in the structure of trimetallic catalyst synthesized on XC72 carbon black due to the absence of mesopores. This drawback was eliminated to a large extent by raising the volume of mesopores as a result of application of mixed support (XC72 + CNT) and the use of only CNT for the synthesis of the monoplatinum catalyst. However, this did not eliminate another drawback, namely, a low platinum utilization coefficient in the cathode active layer as compared with that measured under the model conditions in the 0.5 M Н₂SO₄ solution. Therefore, further research is required to improve the structure of the catalytic systems, which are synthesized both on carbon black and nanotubes, while maintaining their high stability and selectivity.     

Carbon/titanium oxide supported bimetallic platinum/iridium nanocomposites as bifunctional electrocatalysts for lithium-air batteries

Platinum (Pt) and iridium (Ir) catalysts are well known to strongly enhance the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) kinetics, respectively. Pt–Ir-based bimetallic compounds along with carbon-supported titanium oxides (C–TiO₂) have been synthesized for the application as electrocatalysts in lithium oxygen batteries. Transition metal oxide-based bimetallic nanocomposites (Pt–Ir/C–TiO₂) were prepared by an incipient wetness impregnation technique. The as-prepared electrocatalysts were composed of a well-dispersed homogenous alloy of nanoparticles as confirmed by X-ray diffraction patterns and Fourier transform scanning electron microscopy analyses. The electrochemical characterizations reveal that the Pt–Ir/C–TiO₂ electrocatalysts were bifunctional with high activity for both ORR and OER. When applied as an air cathode catalyst in lithium-air batteries, the electrocatalyst improved the battery performance in terms of capacity, reversibility, and cycle life compared to that of cathodes without any catalysts.     

Pt基合金氧还原催化剂设计的密度泛函理论计算研究

本文提出以合金形成能、Pt表面偏析能和氧原子吸附能作为依据筛选具有高活性和高稳定性的表面富Pt氧还原合金催化剂. 利用DFT计算对Pt与各种过渡金属形成的合金的热力学、表面化学和电子性质进行了系统研究,在此基础上预测Pt-V,Pt-Fe,Pt-Co,Pt-Ni,Pt-Cu,Pt-Zn,Pt-Mo,Pt-W等合金可能具有好的氧还原催化活性和稳定性. 所预期的大部分催化剂已有文献研究结果支持. 另外,Pt-Zn和Pt-Mo体系目前报道尚不多,值得进一步的细致研究.     

炭黑负载Pt-Fe双金属催化剂对甲醇的电催化氧化性能

采用浸渍还原法制备了炭黑负载Pt及Pt-Fe双金属催化剂,通过X光衍射、扫描电镜及X射线光电子能谱对催化剂进行了表征.利用循环伏安法和计时电流法研究了溶液pH值和Pt/Fe原子比对Pt-Fe/C催化剂的甲醇电催化氧化活性与稳定性的影响.结果显示,当溶液pH值为9.0,Pt/Fe原子比为1∶1时,所得Pt-Fe/C催化剂对甲醇的电催化氧化活性与稳定性明显优于Pt/C催化剂.Fe的引入不仅提高了Pt粒子的分散与电化学活性表面积,而且有利于富Pt表面的形成,从而提高了Pt的有效利用率与催化性能.     

Fe对Pt-Fe/C催化剂电催化氧还原反应活性的影响

制备了用作直接甲醇燃料电池的碳载Pt-Fe(Pt-Fe/C)阴极催化剂, X射线能量色散谱(EDX)、X射线衍射谱和电化学测量的结果表明, 在Pt-Fe/C催化剂中, Fe以3种形式存在. 质量分数大约为20％的Fe进入Pt的晶格, 形成Pt-Fe合金, 质量分数大约为80％的Fe没有进入Pt的晶格而以Fe和Fe2O3的形式单独存在. 该催化剂经酸处理后, 非合金化Fe和Fe2O3被溶解, 而使Pt-Fe/C催化剂的电化学活性比表面积要比未经酸处理前的增加约30％左右, 导致Pt-Fe/C催化剂对氧还原的电催化活性优于未经酸处理前的Pt-Fe/C催化剂. 研究结果表明, Pt-Fe/C催化剂的电化学活性比表面积对氧还原的电催化活性起重要的作用, 另外, 只有与Pt形成合金的Fe能提高Pt对氧还原的电催化活性, 而非合金化的Fe对Pt催化剂对氧还原的电催化活性基本没有影响.     

电解煤浆制氢阳极的制备及电催化活性研究

将钛片进行预处理, 用处理后的钛片作为电极基体, 然后用循环伏安法在钛基体上沉积制备了Pt/Ti, Pt-Ru/Ti, Pt-Ir/Ti, Pt-Ru-Ir/Ti催化电极, 通过扫描电镜(SEM)、X射线衍射(XRD)、电子能谱(EDS)以及等离子发射光谱(ICP)等方法对所制备电极进行了表征, 包括电极表面形貌、组分的沉积状态、催化层成分组成以及电极寿命等; 在煤浆电解过程中, 采用两电极体系, 对所制备电极的电催化活性进行了测试. 结果表明: 所制备的电极催化活性都高于同面积的铂片电极, 含有Ru, Ir的二元催化电极的活性好于镀铂催化电极. 在一定范围内, 随着Ru元素比例增大, 电极活性增强, 而Ir元素含量过大, 电极活性反而稍微降低, 所以Pt-Ir(1∶0.5)/Ti, Pt-Ru(1∶5)/Ti两电极的催化活性相对较好. 本文所制备的三元催化电极的催化活性低于二元催化电极. Pt-Ru/Ti电极催化活性最好, 相同条件下具有最大的电解电流, H₂的电解效率可达95%以上.     

Potential‐Cycling Synthesis of Single Platinum Atoms for Efficient Hydrogen Evolution in Neutral Media

Single‐atom catalysts (SACs) have exhibited high activities for the hydrogen evolution reaction (HER) electrocatalysis in acidic or alkaline media, when they are used with binders on cathodes. However, to date, no SACs have been reported for the HER electrocatalysis in neutral media. We demonstrate a potential‐cycling method to synthesize a catalyst comprising single Pt atoms on CoP‐based nanotube arrays supported by a Ni foam, termed PtSA‐NT‐NF. This binder‐free catalyst is centimeter‐scale and scalable. It is directly used as HER cathodes, whose performances at low and high current densities in phosphate buffer solutions (pH 7.2) are comparable to and better than, respectively, those of commercial Pt/C. The Pt mass activity of PtSA‐NT‐NF is 4 times of that of Pt/C, and its electrocatalytic stability is also better than that of Pt/C. This work provides a large‐scale production strategy for binder‐free Pt SAC electrodes for efficient HER in neutral media.     

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).     

Impact of modified electrodes on boosting power density of microbial fuel cell for effective domestic wastewater treatment:A case study of Tehran

Utilizing microbial fuel cells (MFCs) is a promising technology for energy-efficient domestic wastewater treatment, but it still faces practical barriers such as low power generation. In this study, the LaMnO₃ perovskite-type oxide nanoparticles and nickel oxide/carbon nanotube/polyaniline (NCP) nanocomposite (the cathode and anode catalysts, respectively) have been prepared and used to enhance power density of MFC. The prepared La-based perovskite oxide catalysts were characterized by X-ray diffraction (XRD) and scanning electron microscopies (SEM). The electrocatalytic properties of the prepared catalysts were investigated through cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) and Tafel plot at ambient temperature. Results show the exchange current densities of LaMnO₃/carbon cloth cathode and NCP nanocomposite/carbon cloth anode were 1.68 and 7 times more compared to carbon cloth cathode, respectively. In comparison to the bare carbon cloth anode, the MFC with the modified electrodes shows 11 times more enhancement in power density output which according to electrochemical results, it can be due to the enhancement of the electron transfer capability. These cathodic and anodic catalysts were examined in batch and semi-continuous modes to provide conditions close to industrial conditions. This study suggests that utilizing these low cost catalysts has promising potential for wastewater treatment in MFC with high power generation and good COD removal efficiency.     

石墨烯基杂化材料在微生物燃料电池电极中的应用

微生物燃料电池（MFC）是利用生物催化剂将污水有机物中的化学能直接转化为电能的技术,因其功率密度和能量转化效率低,电极制作成本高,限制了其大规模实际应用。因此如何提高电极的催化性能并降低电极制作成本成为MFC的研究重点方向。由于石墨烯基杂化材料具有良好的导电性和催化特性,因此石墨烯基杂化材料成为在MFC电极应用中的热点之一。本文综述了近年来MFC石墨烯基杂化电极材料的最新研究进展,重点讨论了改性石墨烯电极、金属及非金属/石墨烯杂化电极、金属氧化物/石墨烯杂化电极、聚合物/石墨烯杂化电极和石墨烯凝胶电极的设计思路和制备方法及其催化性能,着重分析了石墨烯基阳极和阴极杂化材料对MFC产电性能的影响。最后对石墨烯基杂化材料在MFC应用中存在的问题及研究前景进行了总结和展望。