The MOF/GO-based derivatives with Co@CoO core-shell structure supported on the N-doped graphene as electrocatalyst for oxygen reduction reaction

The development of nonprecious catalyst for oxygen reduction reaction (ORR) is important for the commercialization of the alkaline fuel cells (AFCs). Herein, we prepared a kind of Co-based nanoparticles (NPs) with a core-shell (Co@CoO) structure supported on the N-doped graphene (Co@CoO/NG) as an efficient ORR catalyst via simply pyrolyzing the ZIF-67 anchored on the synthesized graphene oxide (GO). The catalytic activity for ORR of the obtained Co@CoO/NG is comparable with the state-of-art Pt/C catalyst in terms of the onset and half-wave potential in the alkaline solution. In addition, the Co@CoO/NG exhibited an excellent ORR durability and antimethanol activity compared to the commercial Pt/C. This research would provide a simple strategy to prepare the high-performance nonprecious metal-based catalysts for AFCs.     

Bio‐inspired iron/sulfur/graphene nanocomposite and its use in the catalysis of the oxygen reduction reaction at room temperature in alkaline media on a glassy carbon electrode

This work demonstrates the performance of a bio‐inspired iron/sulfur/graphene nanocomposite as a non‐platinum electrocatalyst for the oxygen reduction reaction (ORR) in an alkaline medium. The catalyst shows the most positive ORR onset potential (1.1 V vs. RHE) according to its unique structure in the alkaline medium (KOH solution, pH = 13) at low temperature (T = 298 K). The catalyst is evaluated by the rotating‐disk electrode (RDE) method under various rotating speeds (0–2,000 rpm) in the potential range ?0.02–1.18 V vs. a rechargeable hydrogen electrode (RHE). The number of transferred electrons, as one of the most important parameters, is almost constant over a wide range of potentials (0.1–0.8 V), which indicates a more efficient four‐electron pathway from O₂ to H₂O on the FePc‐S‐Gr surface. The mean size of catalyst centers are in the nanoscale (<10 nm). The estimated Tafel slope in the appropriate range is about ?110 mV per decade at low current density, and E_1/2 of FePc‐S‐Gr displays a negative shift of only 7.1 mV after 10,000 cycles.     

Synthesis of dual-doped non-precious metal electrocatalysts and their electrocatalytic activity for oxygen reduction reaction

The pyrolyzed carbon supported ferrum polypyrrole(Fe-N/C) catalysts are synthesized with or without selected dopants, p-toluenesulfonic acid(TsOH), by a facile thermal annealing approach at desired temperature for optimizing their activity for the oxygen reduction reaction(ORR) in O2-saturated 0.1 mol/L KOH solution. The electrochemical techniques such as cyclic voltammetry(CV) and rotating disk electrode(RDE) are employed with the Koutecky-Levich theory to quantitatively obtain the ORR kinetic constants and the reaction mechanisms. It is found that catalysts doped with TsOH show significantly improved ORR activity relative to the TsOH-free one. The average electron transfer numbers for the catalyzed ORR are determined to be 3.899 and 3.098, respectively, for the catalysts with and without TsOH-doping. The heat-treatment is found to be a necessary step for catalyst activity improvement, and the catalyst pyrolyzed at 600℃ gives the best ORR activity. An onset potential and the potential at the current density of-1.5 mA/cm2 for TsOH-doped catalyst after pyrolysis are 30 mV and 170 mV, which are more positive than those without pyrolized. Furthermore, the catalyst doped with TsOH shows higher tolerance to methanol compared with commercial Pt/C catalyst in 0.1 mol/L KOH. To understand this TsOH doping and pyrolyzed effect, X-ray diffraction(XRD), scanning electron microscope(SEM) and X-ray photoelectron spectroscopy(XPS) are used to characterize these catalysts in terms of their structure and composition. XPS results indicate that the pyrrolic-N groups are the most active sites, a finding that is supported by the correspondence between changes in pyridinic-N content and ORR activity that occur with changing temperature. Sulfur species are also structurally bound to carbon in the forms of C–Sn–C, an additional beneficial factor for the ORR.     

Synthesis of dual-doped non-precious metal electrocatalysts and their electrocatalytic activity for oxygen reduction reaction

The pyrolyzed carbon supported ferrum polypyrrole(Fe-N/C) catalysts are synthesized with or without selected dopants, p-toluenesulfonic acid(TsOH), by a facile thermal annealing approach at desired temperature for optimizing their activity for the oxygen reduction reaction(ORR) in O2-saturated 0.1 mol/L KOH solution. The electrochemical techniques such as cyclic voltammetry(CV) and rotating disk electrode(RDE) are employed with the Koutecky-Levich theory to quantitatively obtain the ORR kinetic constants and the reaction mechanisms. It is found that catalysts doped with TsOH show significantly improved ORR activity relative to the TsOH-free one. The average electron transfer numbers for the catalyzed ORR are determined to be 3.899 and 3.098, respectively, for the catalysts with and without TsOH-doping. The heat-treatment is found to be a necessary step for catalyst activity improvement, and the catalyst pyrolyzed at 600℃ gives the best ORR activity. An onset potential and the potential at the current density of-1.5 mA/cm2 for TsOH-doped catalyst after pyrolysis are 30 mV and 170 mV, which are more positive than those without pyrolized. Furthermore, the catalyst doped with TsOH shows higher tolerance to methanol compared with commercial Pt/C catalyst in 0.1 mol/L KOH. To understand this TsOH doping and pyrolyzed effect, X-ray diffraction(XRD), scanning electron microscope(SEM) and X-ray photoelectron spectroscopy(XPS) are used to characterize these catalysts in terms of their structure and composition. XPS results indicate that the pyrrolic-N groups are the most active sites, a finding that is supported by the correspondence between changes in pyridinic-N content and ORR activity that occur with changing temperature. Sulfur species are also structurally bound to carbon in the forms of C–Sn–C, an additional beneficial factor for the ORR.     

片状碳载金属纳米颗粒复合物的制备及其氧还原电活性

将双氰胺、蔗糖与酞菁铁(钴)的混合物通过简单热解法,制备出Co/C-N、Fe/C-N和Fe-Co/C-N纳米复合物。随后利用热还原法,将少量铂沉积于Co/C-N上得到片状碳负载的Co-Pt纳米颗粒Co-Pt/C-N。对样品进行了详细表征,并研究了其在全域pH范围内(酸性、中性与碱性溶液)中的氧还原反应(ORR)活性。结果表明,Co/C-N具有比Fe/C-N和Fe-Co/C-N更高的ORR起始电位和半波电位,并且在碱性和中性溶液中,Co/C-N表现出比Pt/C更强的ORR电活性;在酸性溶液中,铂负载量(质量分数)8.1%的Co-Pt/C-N表现出与Pt/C相近的ORR起始与半波电位。催化剂优异的电活性主要归因于片状碳形成的三维结构、金属纳米颗粒的均匀分布以及丰富的吡啶氮。     

Synthesis and characterization of iron‐ and nitrogen‐functionalized graphene catalysts for oxygen reduction reaction

Iron‐ and nitrogen‐functionalized graphene (Fe‐N‐G), as well as iron‐ and nitrogen‐functionalized oxidized graphene (Fe‐N‐Gox) catalysts were synthesized as non‐noble metal electrocatalysts for oxygen reduction reaction (ORR). The physical properties of the resultant catalysts were characterized using nitrogen adsorption measurements, X‐ray diffraction, Raman and X‐ray photoelectron spectroscopies and transmission electron microscopy. Subsequently, ORR activities of the catalysts were determined electrochemically using a conventional three‐electrode cell via cyclic voltammetry with a rotating disc electrode, the results of which indicated that the synthesized catalysts had a marked electrocatalytic activity towards ORR in acid media. Among the synthesized catalysts, that functionalized using 2,4,6‐tris(2‐pyridyl)‐1,3,5‐triazine as nitrogen source had the highest electrocatalytic activity with the highest onset potential (0.98 V/SHE) and limiting current density (5.12 mA cm⁻²). The findings are particularly important to determine a non‐precious metal catalyst for ORR activity in fuel cells.     

Pt单层修饰Pd/C氧还原催化剂

分别利用液相热解法和浸渍还原法制备了碳载钯纳米催化剂（Pd/C）,并研究了其对氧还原反应的电催化活性。与浸渍还原法相比,液相热解法得到的Pd/C催化剂虽然粒径较大,但表现出较好的氧还原反应（ORR）活性和稳定性.在所制备的Pd/C催化剂基础上,通过置换欠电势沉积的Cu原子单层,获得了Pt单层修饰的Pd/C催化剂,其ORR活性较Pd/C催化剂有显著提高,且与纯Pt/C催化剂接近,而其耐久性则较纯Pt/C催化剂有显著提升,显示出Pt单层催化剂的潜在优势.     

应用于氧还原反应的石墨烯-无定形碳核壳结构复合材料载铂催化剂(英文)

采用氯化法制备石墨烯-无定型碳复合材料(GNS@a-C),并用作质子交换膜燃料电池(PEMFC)氧还原反应Pt催化剂的载体.结果显示,所制Pt/GNS@a-C催化剂与传统商业催化剂Pt/C相比,有较好的活性和较高的稳定性:质量活性(0.121 A/mg)几乎是Pt/C(0.064 A/mg)的两倍.更重要的是,该新型催化剂加速4000圈后其电化学活性面积保留了最初的51%,与Pt/C的33%相比,前者有更好的电化学稳定性,显示它在PEMFC中将具有较好的应用潜力.     

Fe/N/C氧还原催化剂的热稳定性及活性位结构

研制高活性的Fe/N/C氧还原催化剂对于降低燃料电池成本、实现商业化应用有重要意义. 为了实现Fe/N/C催化剂的理性设计,需要深入研究其活性位结构. 本文我们发展一种研究活性位结构的新策略,即以预先合成好的聚间苯二胺基Fe/N/C催化剂(PmPDA-FeNx/C)为起始物,对其在1000~1500 ^oC高温下再次进行热处理并使其失活,通过关联催化剂热处理前后的结构变化与氧还原催化性能来揭示活性位结构. 实验结果表明,随着热处理温度升高,活性中心结构被破坏,铁原子析出团聚并形成纳米颗粒,氮元素挥发损失,导致催化剂失活. XPS分析显示,低结合能含氮物种的含量与催化剂的ORR活性呈良好的正相关性,表明活性中心很可能是由吡啶N和Fe-N物种构成的.     

Hollow Spheres of Iron Carbide Nanoparticles Encased in Graphitic Layers as Oxygen Reduction Catalysts

Nonprecious metal catalysts for the oxygen reduction reaction are the ultimate materials and the foremost subject for low‐temperature fuel cells. A novel type of catalysts prepared by high‐pressure pyrolysis is reported. The catalyst is featured by hollow spherical morphologies consisting of uniform iron carbide (Fe₃C) nanoparticles encased by graphitic layers, with little surface nitrogen or metallic functionalities. In acidic media the outer graphitic layers stabilize the carbide nanoparticles without depriving them of their catalytic activity towards the oxygen reduction reaction (ORR). As a result the catalyst is highly active and stable in both acid and alkaline electrolytes. The synthetic approach, the carbide‐based catalyst, the structure of the catalysts, and the proposed mechanism open new avenues for the development of ORR catalysts.     

掺氮介孔炭作为双功能材料用于氧还原与超级电容器

以壳聚糖为含氮碳源,正硅酸乙酯为软模板,硝酸镍为催化剂,通过简单的低温水热法及后续炭化,成功合成出掺氮介孔炭材料（NMC-1）.NMC-1含有多孔结构以及氮氧等杂原子,能提高其电催化性能、双电层电容与赝电容.由于NMC-1在碱液中表现出显著的催化氧还原反应活性和具有较高的超级电容器比电容（在0.2A/g时为252F/g）及好的循环稳定性,因此,它有可能作为一种可再生、环保的双功能材料同时应用于燃料电池与超级电容器领域.     

溶剂热法制备磷掺杂碳纳米管作为氧气还原和氧气析出反应双功能电催化剂的研究

对氧气还原(ORR)和氧气析出(OER)反应都具有催化活性的双功能催化剂在金属-空气电池中起着关键作用.本文通过溶剂热反应,一步原位合成了磷掺杂碳纳米管(P-CNT).旋转环盘电极测试表明磷掺杂能够明显提高碳纳米管的催化活性,P-CNT在碱性电解质中对ORR和OER都具有优异的催化活性.P-CNT对ORR的催化还原为近4电子反应,可与商业催化剂Pt/C(20 wt%)相比;而其对OER的催化活性则高于Pt/C(20 wt%).此外,P-CNT的长期稳定性优于Pt/C(20 wt%).P-CNT对ORR和OER的高催化活性和稳定性主要归因于磷对碳的掺杂以及磷与碳间强的化学键合.     

以金属有机骨架为前驱体的高活性氧还原非贵金属催化剂制备

The development of a non‐precious metal electrocatalyst (NPME) with a performance superior to commercial Pt/C for the oxygen reduction reaction (ORR) is important for the commercialization of fuel cells. We report the synthesis of a NPME by heat‐treating Co‐based metal organic frameworks (ZIF‐67) with a small average size of 44 nm. The electrocatalyst pyrolyzed at 600 °C showed the best performance and the performance was enhanced when it was supported on BP 2000. The resulting electrocatalyst was composed of 10 nm Co nanoparticles coated by 3–12 layers of N doped graphite layers which as a whole was embedded in a carbon matrix. The ORR performance of the electrocatalyst was tested by rotating disk electrode tests in O2‐saturated 0.1 mol/L KOH under ambient conditions. The electrocatalyst (1.0 mg/cm2) showed an onset potential of 1.017 V (vs. RHE) and a half‐wave potential of 0.857 V (vs. RHE), which showed it was as good as the commer‐cial Pt/C (20μgPt/cm2). Furthermore, the electrocatalyst possessed much better stability and re‐sistance to methanol crossover than Pt/C.     

RuxCoySez纳米簇合物对阴极氧还原反应的催化性能

以Ru3（CO）12、Co4（CO）12和Se为原料,采用低温回流技术在1,6-己二醇中合成了RuxCoySez纳米簇合物.利用SEM和XRD测试表征了催化剂的微观形貌和相结构,催化剂粉末以六方结构的Rux簇为主相,同时形成无定形相,呈现高度均匀聚集的纳米颗粒.利用旋转圆盘电极研究了催化剂对氧还原反应电催化活性.在0.5molL-1H2SO4溶液中,RuxCoySez催化剂对氧还原的催化活性和电化学稳定性明显高于RuxSey,开路电位达到0.91V（vs.NHE）.     

酞菁钴催化剂载体表面含氮官能团对其在燃料电池中氧还原性能的影响

以酞菁钴为催化剂,纳米碳管为载体,分别通过超声法和四氢呋喃法混合分散,并在氮气氛围高温热处理制备了两种酞菁钴催化剂.热重分析（TGA）结果显示超声法制备的酞菁钴催化剂（CoPc-CNT-S）含钴的质量分数为8.1 wt%,四氢呋喃混合法制备的酞菁钴催化剂（CoPc-CNT-R）含钴的质量分数为7.0 wt%.X射线光电子谱（XPS）结果显示CoPc-CNT-R催化剂的含氮量是CoPc-CNT-S催化剂的两倍多,且两种催化剂含氮官能团的种类及比例不同.相比较而言,CoPc-CNT-S表面有更多的吡咯型氮.将两种催化剂应用于混合酸碱燃料电池中发现：CoPc-CNT-S对电催化氧还原有较高的活性和稳定性,将CoPc-CNT-S作为燃料电池的阴极催化剂分别工作5 h和15 h后,电荷转移电阻相对CoPc-CNT-R为阴极催化剂时均较低.原因可能是相近比例的吡啶型N和吡咯型N的协同作用有利于电催化氧还原.     

SO2-tolerant Pt-MoO3/C catalyst for oxygen reduction reaction

A Pt-MoO3/C catalyst,aimed to eliminate the harmful effect of sulfur dioxide（SCb） on the performance of Pt nanoparticles（NPs） for catalysis of oxygen reduction reaction（ORR） in proton exchange membrane fuel cells（PEMFC）,is developed and characterized by TEM,XRD and XPS.The results reveal that Pt-MoO3/C catalyst exhibits not only a higher catalytic activity,but also a better SO2 poisoning resistance and a better recovery performance than the commercial Pt/C catalyst does.     

Facile oxygen reduction on a three-dimensionally ordered macroporous graphitic C3N4/carbon composite electrocatalyst

Honeycomb catalysis: a facile oxygen reduction reaction has been observed on a graphitic C(3)N(4)/carbon catalyst with three-dimensional interconnected macropores (see picture with SiO(2) template). This material not only shows catalytic activity that is comparable to that of commercial Pt/C, but also has much higher organic-fuel tolerance and long-term stability.     

Recent advances in carbon-based electrocatalysts for oxygen reduction reaction

Fuel cells are one of the most promising clean energy devices to substitute for fossil fuel in the future to alleviate energy crisis and environmental pollution.As the key reaction on the cathode in the fuel cells,oxygen reduction reaction(ORR) still requires efficient noble metal catalysts such as the comme rcial Pt/C to boost the reaction for its sluggish kinetics.Therefore,it is critical to design earth-abundant carbonbased catalysts with high efficiency and long-term stability to replace the...