Glycol Reduction Research Articles

Electromagnetic Wave Absorption Performance on Fe3O4 Polycrystalline Synthesized by the Synergy Reduction of Ethylene Glycol and Diethylene Glycol

Fe3O4 nanoparticles were synthesized by hydrothermal method with the synergy reduction of ethylene glycol (MEG) and diethylene glycol (DEG). The purity, grain size, magnetism and the microwave absorption performances of the samples can be controlled by the concentration of DEG in the precursor solution. Under the optimized condition of synthesis, the product is of highly crystallized cubic Fe3O4 and the crystallite size of Fe3O4 is about 44-60 nm with the saturation magnetization about 96 emu/g. The Fe3O4 paraffin composites exhibit excellent microwave absorption properties at the frequency range of 1-18 GHz, which are attributed to the electron transition resonance, natural resonance and polarization of Fe3O4. The minimum reflection loss of Fe3O4 synthesized under the MEG and DEG content of 3.58 mol/l and 2.10 mol/l, respectively, can reach -42 dB at a thickness of 2.1 mm. And the effective absorption bandwidth of the samples can reach 3.9 GHz (7.3~11.2 GHz) at the thickness of 2.5 mm. The result demonst...

Electro-oxidation of alcohols using carbon supported gold, palladium catalysts in alkaline media

Mono and binary Pd-Au based catalysts were synthesized using the NaBH4 assisted ethylene glycol reduction method. The catalysts were supported on Vulcan XC 72 carbon black and denoted as Pd/C, Au/C, Pd(Au/C) and Pd-Au/C co-reduction. Pd:Au composition was maintained at 1:2 ratio. XRD profiles confirmed the face centered cubic crystal structure of Pd and Au. The average particle size for Pd/C, Au/C, Pd(Au/C) and Pd-Au/C co-reduction is 5 ±0.6 nm, 22 ±0.7 nm, 17 ±0.4 nm and 6 ±0.2 nm, respectively. The catalysts showed activity towards the oxidation of alcohols (methanol, ethanol, ethylene glycol and glycerol) in alkaline media. Cyclic voltammograms indicated that methanol and ethanol oxidation were more favoured on Pd/C than on Au/C catalysts. It was also noticed that the incorporation of Pd on Au, that is on Pd(Au/C) and Pd-Au/C co-reduction, enhances the onset potential for the oxidation of ethylene glycol and glycerol. When comparing all alcohols studied, it was observed that the maximum current density for the oxidation of ethylene glycol was highest for all catalysts at 54.4, 41.4, 39.8 and 12.1 mA/cm2 on Pd-Au/C co-reduction, Au/C, Pd(Au/C) and Pd/C, respectively. Pd-Au/C co-reduction showed better ADAFC performance under passive conditions as compared to Pd(Au/C) with glycerol and ethylene glycol at 8.34 and 8.46 mW/cm2 respectively, and 0.5 mgPd/cm2. Pd-Au/C cored is a more stable and poisoning tolerant catalyst for ethylene glycol and glycerol oxidation.

Solvothermal Reduction of Graphite Oxide Using Alcohols

In the present work, we use either ethanol or ethylene glycol as reducing agents through the solvothermal method for graphite oxide reduction. A sulfuric acid treatment before the reduction process was also applied to evaluate its influence on the epoxy group ring-opening reaction. Reduced graphene oxide (RGO) samples were obtained with morphology like crumpled sheets. X-ray diffraction analyses (XRD) showed that the RGO produced via ethylene glycol (EG) reduction followed by treatment with sulfuric acid (RGOEGH) presented the largest d-spacing (0.4114 nm). For reduction with ethanol (RGOEt), the d-spacing value was 0.3883 nm. Infrared spectroscopy (FTIR) results indicated that RGOEt exhibited very low-intensity bands related to oxygenated functional groups, suggesting a high reduction degree, while the sample reduced with EG contained oxygen group bands in the spectrum that disappeared when H2SO4 pretreatment was performed. Thermal gravimetric analyses (TGA) results showed that the samples present high stability and confirmed the reduction process. Moreover, the synthesized RGO sheets were comparable to those produced via more expensive and toxic methodologies.

Investigation of electrocatalytic activity and stability of Pt@f-VC catalyst prepared by in-situ synthesis for Methanol electrooxidation

The acidified, functionalized carbon black supported Pt nanocatalyst (Pt@f-VC) was prepared by the modified ethylene glycol reduction method. The functionalized carbon black serves as a stabilizer to prevent agglomeration of the platinum nanoparticles and ensures that Pt NPs have superficially greater dispersion. The prepared nanoparticles have been characterized by Transmission Electron Microscopy (TEM), X-ray Photoelectron Spectroscopy (XPS), X-ray Diffraction (XRD), Raman Spectroscopy (RS) etc. XRD and TEM results showed that Pt NPs have uniform distribution on functionalized carbon support and the average particle sizes of Pt NPs were measured as 3.5 nm. Methanol electrooxidation reaction results showed that Pt@f-VC catalyst has higher catalytic activity and surface area than Pt@VC and commercial available Pt/C (Pt E-TEK).

Ionic Conductivity Measurements-A Powerful Tool for Monitoring Polyol Reduction Reactions.

The reduction of metal precursors during the polyol synthesis of metal nanoparticles was monitored by ex situ ionic conductivity measurements. Using commonly used platinum precursors (K2PtCl6, H2PtCl6, and K2PtCl4) as well as iridium and ruthenium precursors (IrCl3 and RuCl3), we demonstrate that their reduction in ethylene glycol at elevated temperatures is accompanied by a predictable change in ionic conductivity, enabling a precise quantification of the onset temperature for their reduction. This method also allows detecting the onset temperature for the further reaction of ethylene glycol with HCl produced by the reduction of chloride-containing metal precursors (at ≈120 °C). On the basis of these findings, we show that the conversion of the metal precursor to reduced metal atoms/clusters can be precisely quantified, if the reaction occurs below 120 °C, which also enables a distinction between the stages of metal particle nucleation and growth. The latter is demonstrated by the reduction of H2PtCl6 in ethylene glycol, comparing ionic conductivity measurements with transmission electron microscopy analysis. In summary, ionic conductivity measurements are a simple and straightforward tool to quantify the reduction kinetics of commonly used metal precursors in the polyol synthesis.

Enhancing the photoresponse and photocatalytic properties of TiO2 by controllably tuning defects across {101} facets

Introducing defects into semiconductors with well-controlled exposed facets offers an effective route for the development of photocatalytic materials with greatly improved properties. Here, we report a facile ethylene glycol reduction procedure to make anatase titanium dioxide (TiO2) with different concentrations of exposed {001} and {101} facets, leading to different surficial defects. TiO2 with increased concentrations of {101} facets shows a 5-fold improvement in photocurrent generation as well as improved photocatalytic activity towards water splitting under visible light irradiation. The improved activity is ascribed to the oxygen vacancies as well as the variable surface chemical states, which collectively induce a slower recombination rate of photo-induced electron-hole pairs. This work also highlights a feasible strategy to obtain the defective TiO2 and explore the synergistic effect of surface defects and different concentrations of exposed {001} and {101} facets for photocurrent and photocatalytic properties under visible light irradiation.

Nitrogen-doped carbon black supported Pd nanoparticles as an effective catalyst for formic acid electro-oxidation reaction

Pd nanoparticles supported on nitrogen doped carbon black (Vulcan XC-72R) with two different levels of doping were prepared by the microwave-assisted ethylene glycol reduction process and used as catalyst for the formic acid electro-oxidation (FAEO). The results indicate that the different nitrogen doping contents in Pd/N-C catalysts have a significant effect on the performance of FAEO. A higher N content facilitates the uniform dispersion of Pd nanoparticles on carbon black with narrow particle size distribution. Furthermore, the electrochemical results show that the catalyst with a higher N-doping content possesses a higher catalytic activity and a long-term stability for FAEO. The peak current density of the Pd/N-C (high) catalyst is 1.27 and 2.31 times that of the Pd/N-C (low) and homemade Pd/C-H catalyst. The present paper may provide a simple method for preparation of high-performance anode catalyst for direct formic acid fuel cells (DFAFCs).

Graphitic Carbon Nitride Supported Ultrafine Pd and Pd-Cu Catalysts: Enhanced Reactivity, Selectivity, and Longevity for Nitrite and Nitrate Hydrogenation.

Novel Pd-based catalysts (i.e., Pd and Pd-Cu) supported on graphitic carbon nitride (g-C3N4) were prepared for nitrite and nitrate hydrogenation. The catalysts prepared by ethylene glycol reduction exhibited ultrafine Pd and Pd-Cu nanoparticles (∼2 nm), and they showed high reactivity, high selectivity toward nitrogen gas over byproduct ammonium, and excellent stability over multiple reaction cycles. The unique nitrogen-abundant surface, porous structure, and hydrophilic nature of g-C3N4 facilitates metal nanoparticle dispersion, mass transfer of reactants, and nitrogen coupling for nitrogen gas production to improve catalytic performance.

Synthesis of Pt-Ni-Fe/CNT/CP nanocomposite as an electrocatalytic electrode for PEM fuel cell cathode

In order to use carbon nanotube (CNT)-supported catalyst as fuel cell electrodes, Pt-Ni-Fe/CNT/carbon paper (CP) electrode was prepared using an ethylene glycol reduction method. CNTs were directly synthesized on Ni-impregnated carbon paper, plain carbon cloth, and Teflonized carbon cloth using chemical vapor deposition. FESEM and TEM images and thermogravimetric analysis indicated that in situ CNT on carbon paper (ICNT/CP) possesses more appropriate structural quality and stronger adhesion to the substrate than other substrates. The contact angle analysis demonstrated that the degree of ICNT/CP surface hydrophobicity encountered a 24% increase in comparison to CP and promoted to superhydrophobicity from hydrophobicity. The polarization curves and electrochemical impedance spectroscopy results of the loaded Pt-Ni-Fe on in situ and ex situ CNT/CP illustrated that the power density increased and charge transfer resistance reduced compared to commercial Pt/C loaded on CP. The results can be attributed to the outstanding properties of CNTs and high catalytic activity of triple catalysts causing alloying of Pt with Ni and Fe, which makes them a proper candidate to be used as cathode electrodes in proton exchange membrane fuel cells.

Heterostructures in carbon-doped tungsten nitride and its effect on electrocatalytic properties for methanol oxidation

The hexagonal carbon-doped tungsten nitride nanoparticles (WC|N) have been derived from the cubic WN by inducing carbon atoms to WN lattices via a controlled carbonization method. The heterostructures discrepancy in WC|N catalysts involving constitutions of crystal phases and concentration of carbon and nitrogen could be effectively adjusted by simply changing carbonization time, and then had a great impact on the electrocatalytic behaviors of WC|N. Porous morphology of WC|N catalysts was also inherited from tungsten nitrides to provide the large surface area. The ternary Pt/WC|N catalysts were fabricated by an ethylene glycol reduction method with microwave-assisted heating. The intimate contact and intensive interaction between Pt and WC|N catalyst were verified. Impressively, the Pt/WC|N hybrid exhibited superior electrocatalytic activity for methanol oxidation and improved CO anti-poisoning capacity which higher than that of commercial Pt/C catalyst. The catalytic activity was enhanced due to the large amount of distortion which was induced during the diffusion of C into WN lattice and resultant phase transformation. Samples which were carbonized for 120min displayed the outstanding catalytic activity among all the materials even from the different tungsten sources suggest that the extent of distortion in catalyst is the crucial factor for the catalyst activity in electrochemistry reaction.

Purification of poly(vinylpyrrolidone) stabilized platinum nanoparticles by hemodialyzer

This study demonstrates an efficient, economic and rapid technique to purify organic polymer, poly(vinylpyrrolidone) (PVP) stabilized platinum (Pt:PVP) nanoparticles (NPs) hydrosols using a hemodialyzer as an ultrafiltration membrane having average pore diameter 1.8 nm. For this, Pt:PVP of two different diameters- dTEM1.5±0.5nm and dTEM8.7±0.9nm were synthesized by high temperature ethylene glycol reduction method. The Pt:PVP of both diameters were successfully purified from the impurities produced as byproduct (Na+, OH−, Cl− or oxidized ethylene glycol derivatives) without any loss of Pt, confirmed by inductively coupled plasma optical emission spectrometry (ICP-OES) measurements of the ultrafiltrates. Transmission electron microscopy (TEM), powder X-ray diffraction (XRD) patterns and UV–visible absorption spectra measurements revealed that size and morphology of prepared Pt NPs were unaffected by the purifying process. It was observed that at constant transmembrane pressure (TMP) (10 psi) and flow rate (1.2 L/min), the purifying efficacy of the hemodialyzer was better than the commercially available membranes specially made for NPs purification. Additionally, hemodialyzer was at least 10 times reusable without any significant fouling after washing with EtOHH2O mixture.

Electron transfer dependent catalysis of Pt on N-doped carbon nanotubes: Effects of synthesis method on metal-support interaction

The influence of catalyst synthesis strategy, including ethylene glycol (EG) reduction, sodium borohydride reduction and impregnation-H2-reduction, on the metal-support-interaction of Pt on nitrogen-doped carbon nanotubes (Pt/NCNTs) was systematically investigated and summarized. The catalytic performances were explored in the electro-oxidation reactions of glycerol, formic acid and CO, and the hydrolysis of ammonia borane (AB). Through X-ray photoelectron spectroscopy (XPS), density functional theory calculations and CO stripping technique, it was revealed that the synthesis methods drastically affected the electronic property of Pt nanoparticles (NPs). Pt NPs preferentially interacted with graphitic nitrogen in EG reduction method due to the electron donating property of graphitic nitrogen, while preferentially interacted with pyridinic nitrogen and defects in the impregnation-H2-reduction method due to the vacancies containing NP favoring the charged metal ion adsorption. The catalytic activity strongly depended on the electronic property of Pt NPs, which can be ascribed by the binding energy of Pt4f7/2(0) from XPS. The higher catalytic activity was obtained over electron-enriched Pt NPs for the electro-oxidation reactions. On the other hand, electron-deficient Pt NPs had better intrinsic activity in AB hydrolysis. The results herein suggested that appropriate synthesis method should be rationally applied to maximize the activities of Pt for targeting reactions benefited from electron-enriched or electron-deficient metal NPs.

Hollow porous carbon nanofibers as novel support for platinum-based oxygen reduction reaction electrocatalysts

The design and construction of reliable oxygen reduction reaction (ORR) electrocatalysts with high activity and durability are crucial issues in proton exchange membrane fuel cells (PEMFCs). In this article, the coaxial electrospinning method was employed for fabrication of a new-type hollow porous carbon nanofibers (HPCNF). The HPCNF was employed as the material to deposit platinum (Pt) catalyst (Pt/HPCNF) via the simple ethylene glycol reduction method, meanwhile, Pt supported on carbon nanotubes (Pt/CNT) and on commercial carbon blacks (Vulcan XC-72R) (Pt/Vulcan) were also synthesized by the same method as comparisons. The Pt nanoparticles were deposited evenly on the surface of the HPCNF as well as the cross-section, while partial aggregation can be observed on the Vulcan and CNT. The electrochemical properties were detected in detail by cyclic voltammetry (CV) as well as linear sweep voltammetry (LSV). Finally, the suitable carbonization temperature was demonstrated as 1000 °C. The Pt/HPCNF-1000 exhibited excellent electrochemical active surface (ECSA) when compared with the Pt/CNT and Pt/Vulcan, even the same as the JM20. Moreover, the mass activity (at 0.8 V) of Pt/HPCNF-1000 shows approximately 1.9 times higher mass activity than that of Pt/Vulcan, 1.3 times higher than that of JM20 and relatively close to that of the Pt/CNT. When comes to the specific activity, the Pt/HPCNF-1000 shows the highest value. More importantly, the durability of the Pt/HPCNF-1000 was the best among all the catalysts after ADT test, Pt/HPCNF-1000 showed only 57 mV loss in the half-wave potential; meanwhile, the commercial JM20 exhibited about 98 mV decrease in half-wave potential; whereas, Pt/CNT demonstrated a significant half-wave potential decrease about 165 mV. These results indicated that the novel hollow porous carbon nanofibers may be a promising substitute for traditional carbon support for the oxygen reduction reaction of PEMFCs.

CO oxidation and oxygen reduction activity of bimetallic Sn–Pt electrocatalysts on carbon: effect of the microstructure and the exclusive formation of the Pt3Sn alloy

Alloy-type Sn–Pt/C electrocatalysts with the desired Pt/Sn = 3.0 ratio have been prepared by controlled surface reactions using home-made 20 wt% Pt/C (20Pt/C) catalysts with different Pt dispersion. Reaction conditions were found for the preparation of highly dispersed 20Pt/C catalysts by a modified NaBH4-assisted ethylene glycol reduction method using ethanol as a solvent. It has been demonstrated that the increase of the heating time in ethanol up to 2 h results in decreasing dispersion of Pt. Upon using highly dispersed 20Pt/C catalyst, the exclusive incorporation of Sn onto the Pt sites was achieved resulting in the exclusive formation of the Pt–Sn alloy phase. According to in situ XPS studies, the pre-treatment of the air exposed catalyst in H2 even at 170 °C resulted in the complete reduction of the ionic tin to Sn0, suggesting alloy formation. In contrast, the catalyst with lower Pt dispersion cannot be completely reduced even at 350 °C, as 10% of tin still remains in the form of Sn4+ surface species. The electrocatalytic performance of both Sn-20Pt/C catalysts in the CO electrooxidation and the oxygen reduction reaction is superior to that of the parent 20Pt/C catalysts. Our data obtained for the oxygen reduction indicate that the small size of the bimetallic nanoparticles in the highly dispersed Sn-20Pt/C catalyst, along with their optimal surface composition, result in increased activity compared to the catalyst with lower dispersion.

Pt/Fe/NiO on CNT/CP substrate as a possible electrode of nano chip devices

In the present work, PtFeNiO/CNT/CP electrode was prepared with ethylene glycol reduction process. Growth of interconnected CNTs on the CP surface, surface morphology and degree of hydrophobicity were studied with Field emission scanning electron microscopy, Energy dispersive spectroscopy, Transmission electron microscopy, Thermal gravimetric analysis and Contact angle techniques. Polarization, P–I (power density–current density) curves and Electrochemical impedance spectroscopy analysis (determined by Half cell testing) were applied to investigation of electrochemical properties of the prepared electrodes. The results indicated that the improvement of performance and reduction of charge transfer resistance PtFeNiO/CNT/CP compared to PtFeNiO/CP, CNT/CP, CP and commercial catalyst Pt/C (10 wt%) loaded on CP, can be attributed to strong adhesion of in-situ CNTs to the CP, lower agglomeration of CNTs, outstanding electrical and thermal conductivity of CNT along with high catalytic activity of triple catalyst. These results make them promising candidates for the future of nano chip devices.

Microwave-Assisted Synthesis of Monophase and Low-Platinum PtRu Alloy Nanoparticles and the Catalytic Performance Towards Methanol Oxidation

In this work, low-platinum PtRu/C alloy nanoparticles have been synthesized by microwave assisted ethylene glycol reduction as electrochemical catalysts toward methanol oxidation reaction (MOR). Their Ru content dependence of phase composition was comparatively discussed with the phase diagram of bulk PtRu catalysts, their catalytic performance to MOR was also studied and co-related with the physicochemical characteristics. The results reveal that PtRu alloy nanoparticles have wider monophase range than the bulk PtRu alloys, and the hcp-structured catalyst exhibits better MOR activity and durability than the catalyst with fcc structure.

Composition dependent activity of Fe1−xPtx decorated ZnCdS nanocrystals for photocatalytic hydrogen evolution

In this work, ZnCdS nanoparticles (NPs) were decorated with FePt alloy, forming nanocomposites via ethylene glycol reduction method. The photocatalytic H2 production of the Fe1−xPtx–ZnCdS NPs was studied by changing the composition and weight percentage of Fe1−xPtx alloy in the nanocomposites under visible light (λ ≥ 420 nm) irradiation. The results showed that the hydrogen production rate of Fe1−xPtx–ZnCdS NPs had a significant enhancement over the pure ZnCdS (740 μmol g−1 h−1). The activity of the nanocomposites was dependent on the composition of Fe1−xPtx alloy and the highest hydrogen production rate of 2265 μmol g−1 h−1 was achieved by the 0.5 wt% Fe0.3Pt0.7–ZnCdS nanocomposites, which was even better than that of 0.5 wt% Pt–ZnCdS (1626 μmol g−1 h−1) under the same condition. This study highlights the significance of Pt base alloys as new cocatalysts for the development of novel composite photocatalysts.

A Facile Diethylene Glycol Reduction Method for the Synthesis of Ultrafine Pd/C Electrocatalyst with High Electrocatalytic Activity for Methanol Oxidation

AbstractThe high‐quality carbon supported Pd nanoparticles (Pd/C) composites have wide applications in catalysis. In this work, we demonstrate an efficient diethylene glycol (DEG) reduction method for the synthesis of a Pd/C catalyst with high dispersion and small particle size. During the synthesis, no surfactants and halogen ions are introduced in the reaction system, and DEG efficiently acts as solvent and reducing agent, which results in a “clean” Pd surface. Meanwhile, compared to the classic ethylene glycol (EG) reduction method, the present DEG reduction method can produce the high‐quality Pd/C composites. As a result, the as‐prepared Pd/C electrocatalyst exhibits a large electrochemical active surface area and good electrocatalytic performance for the methanol oxidation reaction in an alkaline media, due to the high dispersion and small particle size. This result indicates the as‐prepared Pd/C electrocatalyst has potential applications in alkaline direct methanol fuel cells.

Platinum Nanoparticles on Interconnected Ni3P/Carbon Nanotube–Carbon Nanofiber Hybrid Supports with Enhanced Catalytic Activity for Fuel Cells

AbstractA new class of hybrid support is prepared by chemical vapor deposition of acetylene yielding carbon nanofibers (CNFs) on electrolessly plated Ni3P on carbon nanotubes (Ni3P/CNT). The as‐prepared Ni3P/CNT–CNF hybrid is used to support platinum nanoparticles, produced by the microwave‐assisted ethylene glycol reduction method, as an electrocatalyst (Pt/Ni3P/CNT–CNF). The as‐prepared Ni3P/CNT–CNF hybrid and Pt/Ni3P/CNT–CNF catalyst are characterized by SEM, TEM, XRD, and thermogravimetric analysis. Electrochemical evaluations of the electrocatalyst are performed for methanol oxidation and oxygen reduction reactions. The electrochemical active surface area of Pt/Ni3P/CNT–CNF, evaluated both by hydrogen adsorption cyclic voltammetry (CV; 95 m2 g−1) and CO anodic stripping CV (106 m2 g−1), is higher than that of a Pt/CNT benchmark. Electrochemical evaluation of methanol oxidation and oxygen reduction reactions indicate that as‐prepared Pt/Ni3P/CNT–CNF shows enhanced activity relative to that of commercial Pt/C‐JM and Pt/CNT. The superior performance of as‐prepared Pt/Ni3P/CNT–CNF is mostly attributed to the improved electron transfer and facilitated mass transport originating from the tailor‐made Ni3P/CNT–CNF hybrid support.

Nafion functionalized carbon nanohorns as catalyst support for proton exchange membrane fuel cells

Carbon nanohorns (CNHs) are synthesized by DC arc-discharge method in helium atmosphere. The synthesized CNHs are heat treated and then functionalized with Nafion. Platinum is reduced onto Nafion functionalized CNHs through ethylene glycol reduction method. Pt/Nafion-CNHs catalysts are prepared by varying deposition times from 1 to 7h. Detailed characterization of CNHs and the catalyst is performed using scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy, X-ray diffraction (XRD) and thermo gravimetric analysis (TGA). Membrane electrode assemblies are prepared by decal method and electrode performance is analyzed using hydrogen pumping technique. SEM and TGA analysis of soot indicates relatively high level purity of CNHs. TEM and XRD analysis of catalyst with 6h deposition time reveals that Pt nanoparticles are uniformly deposited on multiwall CNHs surface with particle size of 3–4nm. Hydrogen pumping studies reveals that Nafion functionalized CNHs act as good catalyst support without hindering electron transfer at electrodes. Hence, these graphitic carbon supports have potential application for high power density applications.