Synthesis of Mesoporous Carbon from Okara and Application as Electrocatalyst Support

Carbon materials derived from biomass are economical and simple. Here, a okara‐derived carbon (ODC) was prepared by carbonized cheap and abundant okara at 800 °C in N₂ atmosphere. A high degree of graphitization, mesoporous structure and large specific surface area of ODC were proved by Raman spectroscopy, nitrogen adsorption–desorption isotherms, X‐ray diffraction, Fourier transform infrared spectra and scanning electron microscope. The ODC can be used as support of platinum nanoparticles, and the catalytic performance for methanol electro‐oxidation of its was measured by cyclic voltammetry and CO stripping voltammetry. The results showed that Pt/ODC catalyst had higher electrocatalytic activity and the resistance to poisoning ability toward methanol electrooxidation than the Pt/C catalyst prepared under the same conditions.     

Niobium Dioxide Facilitating Methanol Electrooxidation on Pt/C Catalyst by Synergistic Effect

In this work, Pt nanoparticles are deposited on NbO₂‐modified carbon composites and evaluated as promising direct methanol fuel cell (DMFC) electrocatalysts. Transmission electron microscopy (TEM) and X‐ray diffraction (XRD) indicate that Pt nanoparticles (about 2.5 nm) are uniformly dispersed on NbO₂‐modified carbon composites. Electrochemical measurements show that the mass activity toward methanol electrooxidation on Pt/NbO₂‐C is as high as 3.0 times that of conventional Pt/C. Meanwhile, the onset potential of CO oxidation is negatively shifted by about 46 mV as compared with that of Pt/C, which means that the synergistic effect between NbO₂ and Pt facilitates the feasible removal of poisoning intermediate CO during methanol electrooxidation. X‐ray photoelectron spectroscopy (XPS) characterizations reveal the electron transfer from Nb to Pt, which suppress the poisoning CO adsorption on Pt nanoparticles and facilitate methanol electrooxidation. NbO₂ nanoparticles facilitate methanol electrooxidation on Pt/C catalyst by synergistic effect and electronic effect, which represents a step in the right direction for the development of excellent fuel cell anode electrocatalysts.     

载体制备工艺对Pt/CA催化剂甲醇氧化催化性能的影响

比较研究了炭气凝胶(CA)的制备工艺条件对其表面微观结构及以其为载体的催化剂Pt/CA甲醇氧化催化活性的影响.结果表明,常压干燥制得的CA表面以微孔为主,而超临界CO2干燥制得的CA表面主要以中孔为主,而且比表面积、表面孔容和平均孔径更大;超临界CO2干燥比常压干燥更适合制备高活性甲醇氧化Pt/CA催化剂的载体材料;CA制备过程中催化剂Na2CO3的用量(常用R/C表示,其中R代表制备CA的原料间苯二酚,C代表制备CA的催化剂Na2CO3)为200至1000的范围内,R/C的增大会引起超临界CO2干燥制得CA的表面平均孔径随之增加,R/C为300时制得的CA具有最大的BET比表面积和表面孔容,以其为载体制得的催化剂具有最好的甲醇氧化催化性能.     

Electrocatalytic activity of Pt/C catalysts for methanol electrooxidation promoted by molybdovanadophosphoric acid

A Pt/C catalyst modified by the Keggin-structure molybdovanadophosphoric acid (PMV) is prepared by cyclic voltammetry and the modified Pt/C catalyst is studied for methanol electrooxidation. The results show that the PMV modified Pt/C catalyst has increased the electron transfer coefficient of the rate-determining step and diminished the adsorption of CO on Pt/C catalysts. Significant improvements in the catalytic activity and stability for methanol electrooxidation are observed, and it indicates that the PMV combined with Pt/C catalyst can be considered as a good electrocatalyst material for potential application in direct methanol fuel cells.     

Au/C catalyst prepared by polyvinyl alcohol protection method for direct alcohol alkaline exchange membrane fuel cell application

An Au/C catalyst was prepared by means of the polyvinyl alcohol-protected Au sol method. Highly dispersed Au nanoparticles with an average particle size of around 3.7 nm were obtained as confirmed by transmission electron microscopy. The cyclic voltammogram of Au/C was similar to that of a bulk Au electrode, but a small shift of Au oxide reduction and oxidation potential peaks were observed. The electrooxidation of methanol, ethanol, ethylene glycol, and glycerol on the Au/C catalyst in an alkaline solution was analyzed. Using a cyclic voltammogram, the maximum current density toward alcohol electrooxidation was found to decrease in the order of glycerol > ethylene glycol > ethanol, while methanol was not oxidized. Compared with PtRu/C, the maximum current densities obtained from the Au/C catalyst for ethylene glycol and glycerol electrooxidation were increased by 1.6 and 3.3 times, respectively. The reaction heavily progressed through a C–C bond dissociation path. It was found that main product of glycerol electrooxidation was formic acid, which accounted for more than 60 % of the total product. Using chronoamperometry, the Au/C catalyst showed much better stability than that of PtRu/C for the reaction without C–C bond dissociation and better stability for the reaction with C–C bond dissociation.     

Effect of pH Value on Performance of PtRu/C Catalyst Prepared by Microwave‐Assisted Polyol Process for Methanol Electrooxidation

PtRu/C catalysts with different mean particle sizes have been synthesised by microwave‐assisted polyol process at various pH values and characterised by transmission electron microscopy (TEM), energy dispersive analysis of X‐ray (EDAX) and X‐ray diffraction (XRD). Their electrochemical performances have been tested by cyclic voltammetry, amperomeric i–t, and CO‐stripping techniques. The effects of pH values on performances of the PtRu/C catalysts have been mainly investigated. It has been found that the particle size, composition and catalytic activity of the PtRu/C catalyst are very sensitive to the pH value of reducing solution, and the PtRu/C catalyst prepared at the pH value of 8 exhibits the better performance for methanol electrooxidation than the other samples. The size of the nanoparticles decreases as the pH value increases from 0.2 to 10 with the largest size of 4.4 nm and the smallest one of 2.1 nm. The two metal elements distribute uniformly in the catalyst and their metal loadings are similar to the theoretical value.     

Methanol-tolerant PdPt/C alloy catalyst for oxygen electro-reduction reaction

A carbon-supported Pd-based PdPt catalyst (PdPt/C) with a small amount of Pt was prepared by borohydride reduction method and its activity in the oxygen electro-reduction reaction (ORR) was investigated in acidic conditions both with and without methanol. For comparison, carbon-supported Pt (Pt/C) and Pd (Pd/C) catalysts were prepared and the ORR activities were compared. Results revealed that the PdPt/C catalyst showed slightly lower ORR activity in terms of onset potential of oxygen reduction than Pt/C catalyst in 0.1M HClO₄. However, PdPt/C catalyst exhibited enhanced activity toward selective ORR with methanol-tolerant characteristics in 0.1M HClO₄ in the presence of methanol. The PdPt/C catalyst prepared here is suitable for use as a cathodic electrocatalyst in direct alcohol fuel cells after addition of small amount of expensive Pt metal.     

碱性条件下甲醇阳极氧化碳载催化剂的性能

用化学还原法制备了碳载镍、银、金三种金属单质催化剂,并研究其对甲醇电催化氧化的活性.用X射线衍射光谱(XRD)、X光电子能谱(XPS)表征催化剂的晶相结构、表面组成及价态形式.XRD测试表明均得到了纯度较高的金属单质,催化剂粒径大小在5～11 nm之间,颗粒分布均匀.用循环伏安法测定了不同催化剂对甲醇的电催化氧化的活性...     

Pd-Co/CNT复合催化剂的制备及甲醇电氧化性能

以Pd Cl₂和Co(NO₃)₂为原料，采用分步乙二醇还原法制备了多壁碳纳米管负载Pd-Co复合纳米催化剂Pd-Co/CNT。利用TEM、XRD和XPS对催化剂的结构进行了表征，考察了其甲醇电氧化性能。结果显示，Co的引入使Pd催化剂的分散性得到改善，其电化学表面积可达39.7 m²/g。循环伏安测试表明，当Pd∶Co物质的量比为1∶0.2时，Pd-Co/CNT的甲醇氧化峰电流密度约为Pd/CNT的2.7倍。计时电流结果表明，Co的添加使催化剂的活性衰减比例由Pd/CNT的63.8%降至54.2%，显示出较强的抗中毒能力。Pd-Co复合催化剂性能的改善归因于Pd与Co之间的协同相互作用。     

Carbon-coated Ni-Co alloy catalysts: preparation and performance for in-situ aqueous phase hydrodeoxygenation of methyl palmitate to hydrocarbons using methanol as the hydrogen donor

Carbon-coated Ni, Co and Ni-Co alloy catalysts were prepared by the carbonization of the metal doped resorcinol-formaldehyde resins synthesized by the one-pot extended Stöber method. It was found that the introduction of Co remarkably reduced the carbon microsphere size. The metallic Ni, Co, and Ni-Co alloy particles (mainly 10–12 nm) were uniformly distributed in carbon microspheres. A charge transfer from Ni to Co appeared in the Ni-Co alloy. Compared with those of metallic Ni and Co, the d-band center of the Ni-Co alloy shifted away from and toward the Fermi level, respectively. In the in-situ aqueous phase hydrodeoxygenation of methyl palmitate with methanol as the hydrogen donor at 330 °C, the decarbonylation/decarboxylation pathway dominated on all catalysts. The Ni-Co@C catalysts gave higher activity than the Ni@C and Co@C catalysts, and the yields of n-pentadecane and n-C₆–n-C₁₆ reached 71.6% and 92.6%, respectively. The excellent performance of Ni-Co@C is attributed to the electronic interactions between Ni and Co and the small carbon microspheres. Due to the confinement effect of carbon, the metal particles showed high resistance to sintering under harsh hydrothermal conditions. Catalyst deactivation is due to the carbonaceous deposition, and the regeneration with CO₂ recovered the catalyst reactivity.     

Electrooxidation of methanol on Pt microparticles dispersed on SnO2 thin films

In this work, we have prepared electrodes through the electrodeposition of platinum micro particles on SnO₂ thin films in order to verify the application of this system as a catalyst for the electrooxidation of methanol. The oxide films were prepared through the method of polymeric precursor decomposition and calcinated at 550 °C. The employed oxides have proved to be a good matrix for the dispersion of platinum particles since they present high roughness. The maximum electrooxidation current was attained for a platinum content of approximately 600 μg cm⁻². The chronoamperometric results showed that the current values obtained for the electrooxidation of methanol were up to 10 times higher than the current values obtained with platinized platinum under the same conditions. The possible mechanisms that lead to this enhancement were discussed.     

Methanol electro-oxidation on mesocarbon microbead supported Pt catalysts

Mesocarbon microbeads (MCMB) as Pt catalyst supports were characterized by X-ray electron diffraction, thermal field emission scanning electron microscope and electrochemical analysis. MCMB with different pretreatment were used as the catalyst supports. The XRD patterns show the existence of Pt and the micrograph of SEM shows Pt is absorbed uniformly on the surface of MCMB particles and the platinum grain size is ca. 3-5 nm. The effect of the pretreatment of the support on the catalyst performance of methanol electrooxidation was studied. Electrochemical analysis shows that MCMB are excellent candidates to be used as the support of catalyst for methanol electrochemical oxidation. The catalyst with MCMB boiled in KOH for 1 h as support exhibits a high catalytic activity during the electrooxidation of methanol.     

Synthesis, characterization and catalytic activity of an ultrafine Pd/C catalyst for formic acid electrooxidation

An ultrafine Pd/C catalyst with a uniformly sized and highly dispersed nanostructure was synthesized by an improved liquid phase reduction method; in this process, a complexone (trans-1,2-diaminocyclohexane-N,N,N′,N′-tetraacetic acid, C_yDTA) was used as an alternative stabilizer for the first time. Physicochemical characterizations indicated that the resulting Pd nanoparticles possessed ideal structural characteristics, including an average diameter of 2.1 nm, narrow size distribution ranging from 0.5 to 4.0 nm, no visible agglomerations, and no residual C_yDTA. Electrochemical tests showed that the catalytic activity of the obtained Pd/C catalyst for formic acid electrooxidation was 2.2 times greater than that of Pd/C catalyst prepared in the absence of C_yDTA. This improvement in the electrocatalytic performance was attributed to the uniformly sized and highly dispersed nanostructure, which provided a larger overall electrochemical active surface area.     

The effect of plasma pre-treatment of carbon used as a Pt catalyst support for methanol electrooxidation

Vulcan XC-72 carbon black for use as a catalyst support was treated in three different plasma atmospheres, H₂, Ar and O₂. The results showed that the microstructure and surface functional groups were significantly changed after plasma treatment. Pt/C catalysts were prepared by chemical reduction of H₂PtCl₆ with HCHO and those with untreated and plasma treated carbon black supports were characterized and tested for methanol electrooxidation. TEM showed that the platinum nanoparticles on H₂ and Ar plasma treated carbon were uniform and well distributed. Those on untreated carbon were uniform in most regions but coalesced in others. On O₂ plasma treated carbon agglomeration of the platinum nanoparticles was significant. XRD showed that the catalysts were composed of face-centered cubic Pt nanoparticles and XPS showed that they were metallic with no oxides present. Cyclic voltammetry and chronoamperometry were used to study methanol electrooxidation on the Pt/C catalysts in a solution of 0.5 M H₂SO₄ + 0.5 M CH₃OH, and showed that the catalytic activity those using H₂ and Ar plasma treated carbon was higher than for the untreated one. Catalysts supported by O₂ plasma treated carbon showed no catalytic activity. The treatment atmosphere of carbon therefore had a large effect on the catalyst performance, with the H₂ plasma being the best.     

甲醇在不同方法制备的碳载Pt-TiO_2催化剂上的电催化氧化

采用TiO2溶胶法,在不同条件下制备了碳载Pt-TiO2催化剂.通过循环伏安法(CV),计时电流法(CA)对碳载Pt-TiO2催化剂在甲醇上的电氧化特性进行了研究.结果表明不同条件制备的催化剂对甲醇的电催化氧化的催化活性不同.其中加入聚乙二醇所制得的Pt-TiO2/C催化剂对甲醇的氧化具有最佳的电催化活性和稳定性.     

Pd-Ag/C在硼氢化钠电氧化反应中的电化学行为

采用化学还原法制备了不同原子比的Pd-Ag/C催化剂。通过X射线衍射（XRD）表征了催化剂的晶体结构,并运用循环伏安、计时电流等电化学方法研究了其对硼氢化钠电氧化反应的催化活性。结果表明：适量Ag的掺杂不仅可以提高催化剂的催化活性,而且使得硼氢化钠电氧化反应过程中的转移电子数增加,其中Pd₇₅Ag₂₅/C的催化活性和转移电子数均为最高。     

Porous-microelectrode study on Pt/C catalysts for methanol electrooxidation

We have developed a porous-microelectrode (PME) to investigate the electroactivity of catalyst particles for proton exchange membrane fuel cells. The cavity at the tip of the PME was filled with Pt/C catalysts prepared by impregnation method. Cyclic voltammograms (CVs) recorded in 1 N H₂SO₄ aqueous solution revealed that the active area of the stacked catalysts exist not only at the surface but also inside of the stack. For methanol electrooxidation, 30 wt.% Pt/C exhibited the highest electroactivity, whereas the 50 wt.% Pt/C showed extremely small current. The small current is considered as a result of a small active-surface area. Methanol oxidation peak potential shifted toward cathodic direction as Pt-loading decreased, which agrees well with the Pt-oxide formation potential. The activation energy for methanol oxidation was assessed to be 44±3 kJ mol⁻¹ for all Pt/C catalysts and Pt-disc electrode.     

Effects of ozone treatment of carbon support on Pt-Ru/C catalysts performance for direct methanol fuel cell

This research is aimed to increase the activity and utilization of Pt-Ru alloy catalysts and thus to lower the catalyst loading in anodes for methanol electrooxidation. The Pt-Ru/C catalysts were prepared by chemical reduction. The support of Vulcan XC-72 carbon black was pretreated by ozone at different temperatures for different times. The specific surface area of the samples was evaluated by the standard BET method. The surface concentrations of oxygen were determined by XPS. The results showed that the surface concentrations of oxygen on the carbon were first decreased and then increased with pretreating times, and the specific surface area of the carbon was decreased with pretreating times at the same temperature. The specific surface area was increased with increasing temperature, and the surface concentration of oxygen was first decreased and then increased with increasing temperature for the same pretreating time. Pt-Ru/C catalysts supported by untreated and O₃ treated carbon black were characterized and tested for methanol electrooxidation. X-ray diffraction (XRD) was used to characterize the influence of carbon treated with ozone on Pt-Ru/C catalysts. It was found that the catalysts were composed only of f.c.c. Pt-Ru alloy particles without metallic Ru or Ru oxide. Cyclic voltammetry (CV) and Tafel curves were used for methanol electrooxidation on Pt-Ru/C catalysts in a solution of 0.5 mol/L CH₃OH and 0.5 mol/L H₂SO₄, showing that the catalytic activity of Pt-Ru/C catalysts supported by ozone treated carbon was higher than that by the untreated one. The ozone treatment time and temperature, which affect the performance of Pt-Ru/C catalysts, were discussed. Electrochemical measurements showed that the catalysts supported by the carbon after ozone treatment for 6 min at 140 °C had the best performance.     

Carbon-supported Pt(Cu) electrocatalysts for methanol oxidation prepared by Cu electroless deposition and its galvanic replacement by Pt

Bimetallic Pt–Cu carbon-supported catalysts (Pt(Cu)/C) were prepared by electroless deposition of Cu on a high surface area carbon powder support, followed by its partial exchange for Pt; the latter was achieved by a galvanic replacement process involving treatment of the Cu/C precursor with a chloroplatinate solution. X-ray diffraction characterization of the Pt(Cu)/C material showed the formation of Pt-rich Pt–Cu alloys. X-ray photoelectron spectroscopy revealed that the outer layers are mainly composed of Pt and residual Cu oxides, while metallic Cu is recessed into the core of the particles. Repetitive cyclic voltammetry in deaerated acid solutions in the potential range between hydrogen and oxygen evolution resulted in steady-state characteristics similar to those of pure Pt, indicating the removal of residual Cu compounds from the surface (due to electrochemical treatment) and the formation of a compact Pt outer shell. The electrocatalytic activity of the thus prepared Pt(Cu)/C material toward methanol oxidation was compared to that of a commercial Pt/C catalyst as well as of similar Pt(Cu)/C catalysts formed by simple Cu chemical reduction. The Pt(Cu)/C catalyst prepared using Cu electroless plating showed more pronounced intrinsic catalytic activity toward methanol oxidation than its counterparts and a similar mass activity when compared to the commercial catalyst. The observed trends were interpreted by interplay between mere surface area effects and modification of Pt electrocatalytic performance in the presence of Cu, both with respect to methanol oxidation and poisonous CO removal.     

炭载体前处理对Pt-Ru/C催化剂性能影响

为研究水蒸气处理后热处理对炭黑表面特性的影响,提高DMFC阳极催化剂的催化活性,利用先水蒸气处理后热处理的Vnlcan XC-72炭黑为载体制备Pt-Ru/C催化剂,与水蒸气处理的和未经处理的炭载体制备Pt-Ru/C催化剂的性能进行比较.采用XPS和BET测试了处理后的炭粉表面的含氧浓度和比表面,结果表明：水蒸气处理后,炭载体比表面积增大,含氧浓度降低;水蒸气处理后热处理,炭载体比表面积进一步减小,含氧浓度增加.用XRD对催化剂的结构进行了表征,结果表明：水蒸气处理后热处理的炭黑为载体制备Pt-Ru/C催化剂结晶状态良好,催化剂颗粒较小.在0.5mol/L CH3OH和0.5mol/L H2SO4混合溶液中,利用玻炭电极测试了循环伏安曲线和阶跃电位曲线,结果表明：用先水蒸气处理后热处理的炭粉为载体制备的催化剂比仅水蒸气处理和未经处理的炭粉为载体制备的催化剂的活性最高.