Gold-iridium bifunctional electrocatalyst for oxygen reduction and oxygen evolution reactions

Carbon supported gold-iridium composite(Au Ir/C) was synthesized by a facile one-step process and was investigated as the bifunctional catalyst for oxygen reduction reaction(ORR) and oxygen evolution reaction(OER). The physical properties of the Au Ir/C composite were characterized by transmission electron microscopy(TEM), X-ray diffraction(XRD) and X-ray photoelectron spectroscopy(XPS). Although the Au and Ir in the Au Ir/C did not form alloy, it is clear that the introduction of Ir decreases the average Au particle size to 4.2 nm compared to that in the Au/C(10.1 nm). By systematical analysis on chemical state of metal surface via XPS and the electrochemical results, it was found that the Au surface for the Au/C can be activated by potential cycling from 0.12 V to 1.72 V, resulting in the increased surface roughness of Au,thus improving the ORR activity. By the same potential cycling, the Ir surface of the Ir/C was irreversibly oxidized, leading to degraded ORR activity but uninfluenced OER activity. For the Au Ir/C, Ir protects Au against being oxidized due to the lower electronegativity of Ir. Combining the advantages of Au and Ir in catalyzing ORR and OER, the Au Ir/C catalyst displays an enhanced catalytic activity to the ORR and a comparable OER activity. In the 50-cycle accelerated aging test for the ORR and OER, the Au Ir/C displayed a satisfied stability, suggesting that the Au Ir/C catalyst is a potential bifunctional catalyst for the oxygen electrode.     

Silver triangular nanoplates as electrocatalyst for oxygen reduction reaction

Triangular Ag nanoplates with large and small sizes were successfully synthesized for oxygen electroreduction. From the results of the x-ray diffraction analysis, it was concluded that Ag nanoplates of small size are the crystals that are essentially composed of (111) planes. The data provided by electrochemical measurement and the Koutecky–Levich equation showed that the electron numbers involved in the oxygen reduction reaction of small and large Ag nanoplates are 3.27 and 3.16, respectively. Small Ag nanoplates exhibit maximum activity towards the oxygen reduction reaction.     

Double-template synthesis of platinum nanomaterials for oxygen reduction

Microchimica Acta - A new Hg(II)-imprinted thiol-functionalized silica gel sorbent was synthesized by a surface imprinting technique for selective solid-phase extraction of Hg(II). Compared to a...     

A readily-prepared, convergent, oxygen reduction electrocatalyst

Monomeric cobalt(II) tetraphenylporphyrin immobilized in high concentrations within vapour-phase polymerized polypyrrole deposited on an ITO electrode catalyzes the 4-electron reduction of dioxygen to water, a reaction requiring concerted action by two separate catalytic groups.     

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.     

Niobium oxide-supported platinum ultra-low amount electrocatalysts for oxygen reduction

We demonstrate a new approach to synthesizing high-activity electrocatalysts for the O(2) reduction reaction with ultra low Pt content. The synthesis involves placing a small amount of Pt, the equivalent of a monolayer, on carbon-supported niobium oxide nanoparticles (NbO(2) or Nb(2)O(5)). Rotating disk electrode measurements show that the Pt/NbO(2)/C electrocatalyst has three times higher Pt mass activity for the O(2) reduction reaction than a commercial Pt/C electrocatalyst. The observed high activity of the Pt deposit is attributed to the reduced OH adsorption caused by lateral repulsion between PtOH and oxide surface species. The new electrocatalyst also exhibits improved stability against Pt dissolution under a potential cycling regime (30,000 cycles from 0.6 V to 1.1 V). These findings demonstrate that niobium-oxide (NbO(2)) nanoparticles can be adequate supports for Pt and facilitate further reducing the noble metal content in electrocatalysts for the oxygen reduction reaction.     

Microwave-assisted synthesis of sulfur-doped graphene supported PdW nanoparticles as a high performance electrocatalyst for the oxygen reduction reaction

Sulfur-doped graphene (SG) is synthesized by a simple microwave irradiation method and PdW nanoparticles are grown in situ on SG. The electrocatalyst shows excellent activity for the oxygen reduction reaction (ORR) in alkaline solution and the reaction kinetics investigation shows that PdW-SG follows a four-electron transfer process in ORR, which is much better than Pd-SG or Pd-G. The improved catalytic performance may result from the changes in the electronic structure when Pd alloys with W as well as the strong interactions between the PdW nanoparticles and SG.     

采用解离的氢原子作为还原剂制备高氧还原电催化性能的Pd核@Pt壳纳米结构

质子交换膜燃料电池(PEMFC)作为一种清洁、高效的能源转化装置,已经备受学术界与产业界的关注.然而,高活性、高稳定性与低成本的铂基阴极氧还原(ORR)电催化剂的缺乏,严重限制PEMFC的大规模商业化应用.为提高贵金属铂的电催化性能,核壳纳米结构的研究受到广范关注.然而,核壳纳米结构的制备过程通常需要采用有机前驱体、表面活性剂与较高的反应温度,导致大多核壳结构制备方法的大规模应用受到限制.我们在室温下无表面活性剂与高沸点溶剂的参与下,通过钯表面吸附的解离的氢原子来还原K2PtCl4,得到Pd核@Pt壳纳米结构.通过改变加入K2PtCl4的量,可以成功控制壳的厚度;通过透射电子显微镜(TEM)观察得知,我们制备了铂壳厚度分别为0.45,0.75,0.9 nm的核壳结构.Pd核@Pt壳纳米结构的良好的纳米晶体结构与外延生长模式,通过高分辨透射电子显微镜(HRTEM)与能量色散谱仪(EDS)得到证实.同时,所制备Pd核@Pt壳样品的核壳结构通过高角环形暗场-扫描透射-元素分布(HAADF-STEM-EDX)表征方法,得到证实.X射线粉末衍射(XRD)表征证实,样品Pd核@Pt壳并无单独的Pd或Pt衍射峰出现,而是表现出良好的同种晶相结构;相对于单质Pt,样品中Pd核的存在导致Pd核@Pt壳核壳结构表现出一定程度的晶格紧缩.X射线光电子能谱(XPS)表明,钯核的存在导致铂壳的电子结合能增大,并且当铂壳厚度增大到一定程度后,核壳结构引起的电子效应维持不变.通过XPS分峰拟合可知,Pd核@Pt壳结构中零价态的铂含量均在80%以上,并且零价态的铂含量随着铂壳层厚度的增大而增大.采用电感耦合等离子体(ICP)与XPS,发现铂的表面富集现象,并且铂表面富集现象随着铂壳层厚度的增大而增大.在半电池中,经过循环伏安扫描活化,Pd核@Pt壳表现出明显的铂的氢吸附与脱附特征峰,再次证明了铂壳层的成功包覆.Pd核@Pt壳纳米颗粒表现出优于Pt/C(JM)的面积比活性、质量比活性及电化学稳定性.核壳结构的良好的ORR电催化性能,来源于催化剂表面含氧物种吸附强度的减弱;上述现象归因于钯核与铂壳之间的电子效应与晶格应力效应.此处简易、清洁的核壳结构制备方法也可以用来在温和条件下制备Ni核@Pt壳等核壳结构.     

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.     

High performance electrocatalyst: Pt-Cu hollow nanocrystals

Pt-Cu hollow nanocrystals with excellent electrocatalytic activities were produced by a one-pot synthesis method. The catalytic activities of these nanocrystals toward methanol electro-oxidation were studied by cyclic voltammetry (CV). The Pt-Cu hollow nanocrystals exhibited higher catalytic activity for methanol oxidation than commercial Pt black and Pt/C.     

Manganese vanadium oxide hollow microspheres: a novel electrocatalyst for oxygen reduction reaction

Journal of Solid State Electrochemistry - The development of nonprecious catalysts with high electrocatalytic activities for the oxygen reduction reaction (ORR) has attracted considerable...     

Self-supported bimodal-pore structured nitrogen-doped carbon fiber aerogel as electrocatalyst for oxygen reduction reaction

Self-supported 3-dimensional (3D) nitrogen-doped bimodal-pore structured carbon fiber aerogel is synthesized via a facile carbonization process using prawn shells as the raw material. The fabricated N-doped carbon fiber aerogel possesses micro- and meso-porous pores with an N doping level of 5.9% and a high surface area of 526 m² g^− 1. As an electrocatalyst, the resultant N-doped carbon fiber aerogel exhibits superior electrocatalytic activity towards oxygen reduction reaction (ORR) with a more positive ORR onset-potential, better stability and high resistance to crossover effect compared to the commercial Pt/C electrocatalyst.     

Pd-Co-Mo electrocatalyst for the oxygen reduction reaction in proton exchange membrane fuel cells

The catalytic activity of carbon supported Pd-Co-Mo for the oxygen reduction reaction (ORR) in a single cell proton exchange membrane fuel cell (PEMFC) has been investigated at 60 degrees C and compared with data from commercial Pt catalyst and our previously reported Pd-Co-Au and Pd-Ti catalysts. The Pd-Co-Mo catalyst with a Pd:Co:Mo atomic ratio of 70:20:10 exhibits slightly higher catalytic activity like the Pd-Co-Au catalyst than the commercial Pt catalyst, but with excellent chemical stability unlike the Pd-Co-Au catalyst. The Pd-Co-Mo catalyst also exhibits better tolerance to methanol poisoning than Pt. Investigation of the catalytic activity of the Pd-Co-Mo system with varying composition and heat treatment temperature reveals that a Pd:Co:Mo atomic ratio of 70:20:10 with a heat treatment temperature of 500 degrees C exhibits the highest catalytic activity. Although the degree of alloying increases with increasing temperature from 500 to 900 degrees C as indicated by the X-ray diffraction data, the catalytic activity decreases due to an increase in particle size and a decrease in surface area.     

Enhanced activity of gold-supported cobalt oxide for the electrochemical evolution of oxygen

Scanning electron microscopy, linear sweep voltammetry, chronoamperometry, and in situ surface-enhanced Raman spectroscopy were used to investigate the electrochemical oxygen evolution reaction (OER) occurring on cobalt oxide films deposited on Au and other metal substrates. All experiments were carried out in 0.1 M KOH. A remarkable finding is that the turnover frequency for the OER exhibited by ～0.4 ML of cobalt oxide deposited on Au is 40 times higher than that of bulk cobalt oxide. The activity of small amounts of cobalt oxide deposited on Pt, Pd, Cu, and Co decreased monotonically in the order Au > Pt > Pd > Cu > Co, paralleling the decreasing electronegativity of the substrate metal. Another notable finding is that the OER turnover frequency for ～0.4 ML of cobalt oxide deposited on Au is nearly three times higher than that for bulk Ir. Raman spectroscopy revealed that the as-deposited cobalt oxide is present as Co(3)O(4) but undergoes progressive oxidation to CoO(OH) with increasing anodic potential. The higher OER activity of cobalt oxide deposited on Au is attributed to an increase in fraction of the Co sites present as Co(IV) cations, a state of cobalt believed to be essential for OER to occur. A hypothesis for how Co(IV) cations contribute to OER is proposed and discussed.     

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.     

Pt nanoparticle netlike-assembly as highly durable and highly active electrocatalyst for oxygen reduction reaction

A Pt nanoparticle netlike-assembly (Pt-NNA) synthesized through a facile hydrothermal method, with high specific surface area and large overall size, exhibits much higher durability and 2.9 times higher mass activity for oxygen reduction reaction than commercial Pt black catalyst.