Electrocatalytic mechanism and kinetics of SOMs oxidation on ordered PtPb and PtBi intermetallic compounds: DEMS and FTIRS study

The electrocatalytic activities and mechanisms of PtPb and PtBi ordered intermetallic phases towards formic acid, formaldehyde and methanol oxidation have been studied by DEMS and FTIRS, and the results compared to those for a pure polycrystalline platinum electrode. While PtPb exhibits an enhanced electrocatalytic activity for the oxidation of all three organic molecules when compared to a Pt electrode, PtBi exhibits an enhanced catalytic activity towards formic acid and formaldehyde oxidation, but not methanol. FTIRS data indicate that adsorbed CO does not form on PtPb or PtBi intermetallic compounds during the oxidation of formic acid, formaldehyde and methanol, and therefore their oxidation on both PtPb and PtBi intermetallic compounds proceeds via a non-CO(ads) pathway. Quantitative DEMS measurements indicate that only CO(2) was detected as a final product during formic acid oxidation on Pt, PtPb and PtBi electrodes. At a smooth polycrystalline platinum electrode, the oxidation of formaldehyde and methanol produces mainly intermediates (formaldehyde and formic acid), while CO(2) is a minor product. In contrast, CO(2) is the major product for formaldehyde and methanol oxidation at a PtPb electrode. The high current efficiency of CO(2) formation for methanol and formaldehyde oxidation at a PtPb electrode can be ascribed to the complete dehydrogenation of formaldehyde and formic acid due to electronic effects. The low onset potential, high current density and high CO(2) yield make PtPb one of the most promising electrocatalysts for fuel cell applications using small organic molecules as fuels.     

Electrocatalytic activity of ordered intermetallic phases for fuel cell applications

The electrocatalytic activities of a wide range of ordered intermetallic phases toward a variety of potential fuels have been studied, and results have been compared to those of a pure polycrystalline platinum (Pt(pc)) electrode. A significant number of the ordered intermetallic phases exhibited enhanced electrocatalytic activity when compared to that of Pt, in terms of both oxidation onset potential and current density. The PtBi, PtIn, and PtPb ordered intermetallic phases appeared to be the most promising electrocatalysts tested thus far for fuel cell applications. PtPb, in particular, showed an onset potential that was 100 mV less positive and a peak current density approximately 40 times higher than those observed for Pt in the case of methanol oxidation. The ability to control the geometric and electronic structures of the electrocatalytic material by using ordered intermetallic phases has been shown to be a promising direction of inquiry in the search for superior electrocatalysts for fuel cell applications.     

Enhanced activity for ethanol electrooxidation on Pt–MgO/C catalysts

MgO promoted Pt/C electrocatalysts were rapidly prepared by intermittent microwave heating method and characterized using different techniques. Electrooxidation of ethanol on MgO promoted Pt/C catalysts in alkaline media was studied. Such electrocatalysts are superior to pure Pt electrocatalysts. The influence of the amount of MgO in the catalysts on catalytic activity for ethanol oxidation was tested. The electrode with a weight ratio of Pt to MgO of 4:1 showed the highest electrocatalytic activity for ethanol oxidation. The presence of MgO in the electrocatalysts improved the kinetic processes, giving the exchange current density for ethanol oxidation of 1.8 × 10⁻⁵ A cm⁻² on Pt–MgO/C instead of 3.3 × 10⁻⁷ A cm⁻² on Pt/C.     

Synthesis, characterization, and electrocatalytic activity of PtPb nanoparticles prepared by two synthetic approaches

Intermetallic PtPb nanoparticles have been synthesized by two solution-phase reduction methods. In the first (PtPb-B), Pt and Pb salts were reduced by sodium borohydride in methanol at room temperature. In the second (PtPb-N), metal-organic Pt and Pb precursors were reduced by sodium naphthalide in diglyme at 135 degrees C. Both methods produced small agglomerated nanoparticles of the ordered intermetallic PtPb (mean crystal domain size <15 nm) which were characterized by pXRD, SEM, UHV-STEM, BET, EDX, and electron diffraction. The electrocatalytic activity of PtPb nanoparticles produced by both methods toward formic acid and methanol oxidation was investigated and compared to Pt and PtRu. Both PtPb-B and PtPb-N nanoparticles exhibited enhanced electrocatalytic activity compared to commercially available Pt black and PtRu nanoparticles. For formic acid oxidation, the PtPb nanoparticles exhibited considerably lower onset potentials and higher current densities than Pt or PtRu. For methanol oxidation, the PtPb nanoparticles had onset potentials slightly positive of PtRu but exhibited higher current densities at potentials about 100 mV positive of onset. The general applicability of these methods for the synthesis of nanoparticles of ordered intermetallic phases is discussed.     

Synergistic Hybrid Catalyst for Ethanol Detection: Enhanced Performance of Platinum Palladium Bimetallic Nanoparticles Decorated Graphene on Glassy Carbon Electrode

The present study highlights the first time use of hybrid synergy electrocatalysis to design a cost effective, non-enzymatic ethanol sensor. The nanohybrid has been synthesized by decorating platinum palladium bimetallic nanoparticles (Pt?PdNPs) on graphene nanosheets (G/Pt?PdNPs). Field emission scanning electron microscopy, energy dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, electrochemical measurements and UV-Vis spectrophotometry have been used to characterize the nanocomposite. An ethanol oxidation current of 332 μA was obtained with the use of G/Pt?PdNPs modified glassy carbon electrode (GCE) that is 167 times higher than that of bare GCE in cyclic voltammetry studies with a potential scan rate of 50 mV/s in 0.1 M NaOH as the supporting electrolyte. Chronoamperometry studies have shown a distinct increase in the current for increasing concentration of ethanol with a wide range of linearity extending from 5 mM to 3 M and a detection limit of 1 mM with the use of G/Pt?PdNPs. Quantum mechanical modeling using density functional theory was used to arrive at the minimization energies of G/Pd, G/Pt and G/Pt?Pd in the presence and absence of ethanol. The improved catalytic activity of G/Pt?PdNPs nanocomposite for ethanol detection is on account of the cooperative effects of Pt and PdNPs, coupled with the high conducting nature of graphene.     

Nitrogen‐Doped Carbon Nanosheets with Size‐Defined Mesopores as Highly Efficient Metal‐Free Catalyst for the Oxygen Reduction Reaction

Nitrogen‐doped carbon nanosheets (NDCN) with size‐defined mesopores are reported as highly efficient metal‐free catalyst for the oxygen reduction reaction (ORR). A uniform and tunable mesoporous structure of NDCN is prepared using a templating approach. Such controlled mesoporous structure in the NDCN exerts an essential influence on the electrocatalytic performance in both alkaline and acidic media for the ORR. The NDCN catalyst with a pore diameter of 22 nm exhibits a more positive ORR onset potential than that of Pt/C (?0.01 V vs. ?0.02 V) and a high diffusion‐limited current approaching that of Pt/C (5.45 vs. 5.78 mA cm^?2) in alkaline medium. Moreover, the catalyst shows pronounced electrocatalytic activity and long‐term stability towards the ORR under acidic conditions. The unique planar mesoporous shells of the NDCN provide exposed highly electroactive and stable catalytic sites, which boost the electrocatalytic activity of metal‐free NDCN catalyst.     

MoS2 Nanosheets Supported on 3D Graphene Aerogel as a Highly Efficient Catalyst for Hydrogen Evolution

The development of efficient catalysts for electrochemical hydrogen evolution is essential for energy conversion technologies. Molybdenum disulfide (MoS₂) has emerged as a promising electrocatalyst for hydrogen evolution reaction, and its performance greatly depends on its exposed edge sites and conductivity. Layered MoS₂ nanosheets supported on a 3D graphene aerogel network (GA‐MoS₂) exhibit significant catalytic activity in hydrogen evolution. The GA‐MoS₂ composite displays a unique 3D architecture with large active surface areas, leading to high catalytic performance with low overpotential, high current density, and good stability.     

Enhanced catalytic activity of Ru through N modification toward alkaline hydrogen electrocatalysis

Exploring highly efficient electrocatalysts and understanding the reaction mechanisms for hydrogen electrocatalysis,including hydrogen oxidation reaction （HOR） and hydrogen evolution reaction （HER） in alkaline media are conducive to the conversion of hydrogen energy.Herein,we reported a new strategy to boost the HER/HOR performances of ruthenium （Ru） nanoparticles through nitrogen （N） modification.The obtained N-Ru/C exhibit remarkable catalytic performance,with normalized HOR exchange current d...     

Facile and Large-Scale Fabrication of Sub-3 nm PtNi Nanoparticles Supported on Porous Carbon Sheet: A Bifunctional Material for the Hydrogen Evolution Reaction and Hydrogenation

Facile and large-scale preparation of materials with uniform distributions of ultrafine particles for catalysis is a challenging task, and it is even more difficult to obtain catalysts that excel in both the hydrogen evolution reaction (HER) and hydrogenation, which are the corresponding merging and splitting procedures of hydrogen, respectively. Herein, the fabrication of ultrafine bimetallic PtNi nanoparticles embedded in carbon nanosheets (CNS) by means of in situ self-polymerization and annealing is reported. This bifunctional catalyst shows excellent performance in the hydrogen evolution reaction (HER) and the hydrogenation of p-nitrophenol. Remarkably PtNi bimetallic catalyst with low metal loading (PtNi₂@CNS-600, 0.074 wt % Pt) exhibited outstanding HER activity with an overpotential as low as 68 mV at a current density of 10 mA cm⁻² with a platinum loading of only 0.612 μg_Pt cm⁻² and Tafel slope of 35.27 mV dec⁻¹ in a 0.5 m aqueous solution of H₂SO₄, which is comparable to that of the 20 % Pt/C catalyst (31 mV dec⁻¹). Moreover, it also shows superior long-term electrochemical durability for at least 30 h with negligible degradation compared with 20 % Pt/C. In addition, the material with increased loading (mPtNi₂@CNS-600, 2.88 % Pt) showed robust catalytic activity for hydrogenation of p-nitrophenol at ambient pressure and temperature. The catalytic activity towards hydrogen splitting is a circumstantial evidence that agrees with the Volmer–Tafel reaction path in the HER.     

Sonochemical synthesis of graphene oxide supported Pt–Pd alloy nanocrystals as efficient electrocatalysts for methanol oxidation

Pt–Pd bimetallic nanoparticles supported on graphene oxide (GO) nanosheets were prepared by a sonochemical reduction method in the presence of polyethylene glycol as a stabilizing agent. The synthetic method allowed for a fine tuning of the particle composition without significant changes in their size and degree of aggregation. Detailed characterization of GO-supported Pt–Pd catalysts was carried out by transmission electron microscopy (TEM), AFM, XPS, and electrochemical techniques. Uniform deposition of Pt–Pd nanoparticles with an average diameter of 3 nm was achieved on graphene nanosheets using a novel dual-frequency sonication approach. GO-supported bimetallic catalyst showed significant electrocatalytic activity for methanol oxidation. The influence of different molar compositions of Pt and Pd (1:1, 2:1, and 3:1) on the methanol oxidation efficiency was also evaluated. Among the different Pt/Pd ratios, the 1:1 ratio material showed the lowest onset potential and generated the highest peak current density. The effect of catalyst loading on carbon paper (working electrode) was also studied. Increasing the catalyst loading beyond a certain amount lowered the catalytic activity due to the aggregation of metal particle-loaded GO nanosheets.     

Platinum/mesoporous WO3 as a carbon-free electrocatalyst with enhanced electrochemical activity for methanol oxidation

A new type of carbon-free electrode catalyst, Pt/mesoporous WO3 composite, has been prepared and its electrochemical activity for methanol oxidation has been investigated. The mesoporous tungsten trioxide support was synthesized by a replicating route and the mesoporous composties with Pt loaded were characterized by using X-ray diffraction (XRD), nitrogen sorption, field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDS) techniques. Cyclic voltammetry (CV), line scan voltammetry (LSV) and chronoamperometry (CA) were adopted to characterize the electrochemical activities of the composites. The mesoporous WO3 showed high surface area, ordered pore structure, and nanosized wall thickness of about 6-7 nm. When a certain amount of Pt nanoparticles were dispersed in the pore structure of mesoporous WO3, the resultant mesostructured Pt/WO3 composites exhibit high electro-catalytic activity toward methanol oxidation. The overall electro-catalytic activities of 20 wt % Pt/WO3 composites are significantly higher than that of commercial 20 wt % Pt/C catalyst and are comparable to the 20 wt % PtRu/C catalyst in the potential region of 0.5-0.7 V. The enhanced electro-catalytic activity is attributed to be resulted from the assistant catalytic effect and the mesoporous structure of WO3 supports.     

Advanced Catalytic Performance of Au–Pt Double‐Walled Nanotubes and Their Fabrication through Galvanic Replacement Reaction

Bimetallic tubular nanostructures have been the focus of intensive research as they have very interesting potential applications in various fields including catalysis and electronics. In this paper, we demonstrate a facile method for the fabrication of Au–Pt double‐walled nanotubes (Au–Pt DWNTs). The DWNTs are fabricated through the galvanic displacement reaction between Ag nanowires and various metal ions, and the Au–Pt DWNT catalysts exhibit high active catalytic performances toward both methanol electro‐oxidation and 4‐nitrophenol (4‐NP) reduction. First, they have a high electrochemically active surface area of 61.66 m² g^?1, which is close to the value of commercial Pt/C catalysts (64.76 m² g^?1), and the peak current density of Au–Pt DWNTs in methanol oxidation is recorded as 138.25 mA mg^?1, whereas those of Pt nanotubes, Au/Pt nanotubes (simple mixture), and commercial Pt/C are 24.12, 40.95, and120.65 mA mg^?1, respectively. The Au–Pt DWNTs show a markedly enhanced electrocatalytic activity for methanol oxidation compared with the other three catalysts. They also show an excellent catalytic performance in comparison with common Au nanotubes for 4‐nitrophenol (4‐NP) reduction. The attractive performance exhibited by these prepared Au–Pt DWNTs can be attributed to their unique structures, which make them promising candidates as high‐performance catalysts.     

Excavated Cubic Platinum–Tin Alloy Nanocrystals Constructed from Ultrathin Nanosheets with Enhanced Electrocatalytic Activity

Excavated polyhedral noble‐metal materials that were built by the orderly assembly of ultrathin nanosheets have both large surface areas and well‐defined facets, and therefore could be promising candidates for diverse important applications. In this work, excavated cubic Pt–Sn alloy nanocrystals (NCs) with {110} facets were constructed from twelve nanosheets by a simple co‐reduction method with the assistance of the surface regulator polyvinylpyrrolidone. The specific surface area of the excavated cubic Pt–Sn NCs is comparable to that of commercial Pt black despite their larger particle size. The excavated cubic Pt–Sn NCs exhibited superior electrocatalytic activity in terms of both the specific area current density and the mass current density towards methanol oxidation.     

“卡房”结构LDHs负载Pt纳米催化剂用于乙醇电催化氧化

乙醇电催化氧化是直接乙醇燃料电池(DEFCs)的核心反应,而DEFCs的阳极电催化剂是提升乙醇转化效率的关键。Pt作为最稳定、最有效的催化剂之一,仍面临着成本高、容易被乙醇氧化产生的中间产物毒化等问题。选择合适的载体实现Pt的高度、均匀、稳定分散,不仅可以提高其抗中毒能力和催化活性,而且还可以减少Pt用量降低成本。本文采用两步电化学沉积法合成了层状双金属氢氧化物(LDHs)纳米阵列负载Pt纳米催化剂(Pt/LDHs/NF),具有“卡房”结构的LDHs增强了Pt纳米粒子的分散,有助于实现高效的乙醇电催化氧化性能。制备的Pt/NiFe-LDH/NF在碱性环境下对乙醇表现出最优的电催化氧化活性,峰值电流密度达到171.99mA·cm^-2。这可为今后设计和制备均匀、稳定分散的Pt基催化剂用于乙醇电催化氧化提供借鉴。     

复合材料NiOx-ZSM-5的制备及微生物电解池催化析氢性能

在Na₂O-TPABr-Al₂O₃-SiO₂-H₂O溶胶体系中加入碳球, 采用水热晶化法合成ZSM-5分子筛载体, 负载镍盐制备复合材料NiO_x-ZSM-5. 利用X射线衍射(XRD)、 扫描电子显微镜(SEM)、 透射电子显微镜(TEM)、 X射线光电子能谱(XPS)、 氮气吸附-脱附和电化学测试等手段对样品进行表征, 利用微生物电解池(MEC)评价其催化析氢性能. 结果表明, 在碳球作用下ZSM-5分子筛为纳米粒子聚集的椭球形貌, 介孔比表面积和介孔孔容明显增加. 浸渍焙烧后的黑色斑点NiO_x覆盖在晶隙形成的介孔表面和分子筛的表面. 相比于纯NiO, 镍盐浸渍量为40%的复合材料中多价态镍氧的吸收峰向高结合能方向移动, 多价态镍、 铝原子和氧空位活性位数量明显 增多, 显著提高了复合材料的电催化活性, 使其具有较高电流密度(8.45 mA/cm²)和较低起始析氢过电位 (151 mV), 优于NiO电极. 在MEC运行周期内, 复合材料的平均析氢电流密度为(28.64±7.4) A/m², 总产气量为(52.67±1.64) mL, H₂纯度为(89.07±0.06)%, 略高于商用Pt/C电极[(89.05±0.05)%], 产氢效率(0.571 m³?m^-3?d^-1)和库仑效率[(76.7±5.4)%]与Pt/C阴极相近, 表明复合材料是一种低成本和高效率的析氢材料.     

Ultrathin Palladium Nanomesh for Electrocatalysis

An ordered mesh of palladium with a thickness of about 3 nm was synthesized by a solution‐based oxidative etching. The ultrathin palladium nanomeshes have an interconnected two‐dimensional network of densely arrayed, ultrathin quasi‐nanoribbons that form ordered open holes. The unique mesoporous structure and high specific surface area make these ultrathin Pd nanomeshes display superior catalytic performance for ethanol electrooxidation (mass activity of 5.40 Am g^?1 and specific activity of 7.09 mA cm^?2 at 0.8 V vs. RHE). Furthermore, the regular mesh structure can be applied to support other noble metals, such as platinum, which exhibits extremely high hydrogen evolution reaction (HER) activity and durability.     

Polyvinylpyrrolidone‐Coordinated Single‐Site Platinum Catalyst Exhibits High Activity for Hydrogen Evolution Reaction

The essence of developing a Pt‐based single‐atom catalyst (SAC) for hydrogen evolution reaction (HER) is the preparation of well‐defined and stable single Pt sites with desired electrocatalytic efficacy. Herein, we report a facile approach to generate uniformly dispersed Pt sites with outstanding HER performance via a photochemical reduction method using polyvinylpyrrolidone (PVP) molecules as the key additive to significantly simplify the synthesis and enhance the catalytic performance. The as‐prepared catalyst displays remarkable kinetic activities (20 times higher current density than the commercially available Pt/C) with excellent stability (76.3 % of its initial activity after 5000 cycles) for HER. EXAFS measurements and DFT calculations demonstrate a synergetic effect, where the PVP ligands and the support together modulate the electronic structure of the Pt atoms, which optimize the hydrogen adsorption energy, resulting in a considerably improved HER activity.     

石墨烯纳米片担载Pt-Pd双金属纳米球作为甲醇氧化的电催化剂(英文)

利用简便的无表面活性剂的方法合成了石墨烯担载的Pt-Pd双金属纳米球.首先由Na2PdCl4与氧化石墨烯发生氧化还原反应生成Pd晶种,然后诱导Pt纳米粒子的生长,得到Pt-Pd双金属纳米球.采用扫描电子显微镜、透射电子显微镜和X射线粉末衍射仪表征了合成的Pt-Pd/GR催化剂的结构,并测定了其作为甲醇氧化电催化剂的性能.结果表明,Pt-Pd/GR催化剂对甲醇氧化反应表现出高催化活性和稳定性,甲醇氧化电流密度为51.8mA·cm-2.     

碳纤维基PtPb阳极催化剂的制备及其电催化性能

以静电纺丝技术与烧结工艺相结合的方式制备了碳纤维基PtPb纳米催化剂,并采用X射线衍射（XRD）、红外光谱（FT-IR）、扫描电镜（SEM）等分析测试手段对其进行了表征。结果表明,在预氧化温度为300 ℃、碳化温度为800 ℃的条件下,所制备的PtPb阳极纳米催化剂结晶程度好、比表面积大,粒径约为3.05 nm,催化活性颗粒均匀分散在多孔碳纤维骨架上。采用循环伏安法（CV）及交流阻抗（EIS）评价了该催化剂对乙醇氧化反应的电催化性能。结果表明,最大峰电流密度达到125 mA/cm²,电荷转移电阻相较于700 ℃下降了近60%。     

PtTe/C催化剂的制备及其对乙醇的电催化氧化性能

采用无机溶胶法制备了用于乙醇燃料电池的PtTe/C催化剂;利用X射线衍射仪分析了催化剂的结构,采用循环伏安法和电化学阻抗法测试了PtTe/C催化剂对乙醇的电催化氧化性能.结果表明,与商业Pt/C催化剂相比,PtTe/C催化剂对乙醇的催化氧化效率明显较高,可使乙醇氧化峰电流密度提高27%,且具有更高的抗CO中毒能力.