Methanol Catalyst Research Articles

Nitrogen-doped carbide-derived carbon/carbon nanotube composites as cathode catalysts for anion exchange membrane fuel cell application

Nitrogen-doped carbide-derived carbon/carbon nanotube (CDC/CNT) composites were prepared and employed for the first time as a cathode electrocatalyst for the anion exchange membrane fuel cell (AEMFC). The CDC/CNT composites were doped with nitrogen using high temperature pyrolysis in the presence of different nitrogen precursors. In the rotating disk electrode measurements all N-CDC/CNT catalysts showed good electrocatalytic activity for oxygen reduction reaction (ORR) in alkaline solution with the half-wave potential (E1/2) around –0.25 V vs SCE. Moreover, the materials showed high tolerance to methanol and excellent stability after 10,000 potential cycles with a negative shift in E1/2 of 10 and 14 mV, respectively. In AEMFC testing employing hexamethyl-p-terphenyl poly(benzimidazolium) (HMT-PMBI) anion exchange membrane, N-CDC/CNT as a cathode catalyst exhibited very good performance with the peak power density of 310 mW cm–2. It can be concluded that the N-CDC/CNT composites are promising cathode catalysts for AEMFCs and alkaline direct methanol fuel cells.

Polyaniline supported g-C3N4 quantum dots surpass benchmark Pt/C: Development of morphologically engineered g-C3N4 catalysts towards “metal-free” methanol electro-oxidation

In spite of being one of the most promising energy conversion devices, the state of the art in the efficient application of direct methanol fuel cell is far from being optimal mostly because of its heavy reliance on expensive Pt anode that suffers from easy CO poisoning. Here, in this work for the first time in literature, we have explored the catalytic efficacy and improved mass activity of morphologically engineered metal-free graphitic carbon nitride towards methanol oxidation. The 2D nano-sheets, 1D nano-rods, and 0D quantum dots of graphitic carbon nitride are successfully prepared from bulk by a thermo-chemical etching process. The materials are thoroughly characterized with the help of X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, field emission scanning electron microscopy, transmission electron microscopy, luminescence study and are studied for methanol oxidation reaction in basic condition with the help of cyclic voltammetry. Among the three different dimensional g-C3N4 materials, the quantum dots show higher methanol oxidation activity due to its abundant edges in nano morphology and maximum atomic percentages of active site of pyridinic N. The 0D g-C3N4 when supported on conducting polyaniline, not only shows higher electrocatalytic methanol oxidation activity than the commercial Pt/C but also demonstrates excellent CO tolerance to be a suitable and applicable metal-free anode catalyst in direct methanol fuel cell applications. The electrostatic interaction between 0D g-C3N4 and conducting polyaniline (PANI) fibres may have improved the electrical conductivity and methanol adsorption of CNQD-PANI electrocatalyst and also played a role in oxidizing the adsorbed CO to upsurge the CO tolerance.

Enhanced reaction lifetime of a bifunctional catalyst for methanol to olefins by combining formaldehyde decomposition on CeO2

A new bifunctional catalyst comprising of CeO2 and SSZ-13 physical mixture was developed, and its lifetime for the methanol to olefins (MTO) reaction was significantly enhanced. Formaldehyde adsorbed on ceria forms formate species, which decomposes to CO or CO2. The formaldehyde decomposition by CeO2 suppressed deposition of the inactive coke species formed (tetramethylnaphthalene), and improved the lifetime of SSZ-13 for MTO catalysis by 4-fold. The morphology of CeO2 has also an impact on the catalytic properties of the physical mixture catalyst, and the solid mixture of rod-like CeO2 and SSZ-13 showed the most extended stability.

Enhanced Methanol Electro‐Oxidation Activity of Pt/rGO Electrocatalyst Promoted by NbC/Mo2C Phases

AbstractDirect methanol fuel cells are attractive power conversion devices for portable and stationary applications. Many electrocatalysts have been explored for fuel cell applications but there is scope to design newer and more efficient electrocatalytic materials. For this purpose we have synthesized Mo2C and bimetallic NbC‐Mo2C carbide phases by carbothermic reduction process. The carbide catalysts are characterized by various analytical techniques. The carbide samples are higly porous and their surface areas are of the order of 630 m2 g−1. Usually Pt is the state‐of‐the‐art anode catalyst in direct methanol fuel cells. Here, Nb‐Mo2C and 10 wt% Pt nanoparticles are deposited on reduced graphene oxide support to obtain Pt/Nb‐Mo2C‐rGO. This material shows highest mass activity of 836.4 mA mgPt−1 when compared to 10 wt% Pt/Mo2C‐rGO and bare 20 wt% Pt/rGO catalysts. Notably, electrochemical tests show that the 10 wt% Pt/Nb‐Mo2C‐rGO catalyst exhibits lower onset potential, large electrochemical surface area, higher activity, and stability for methanol electro‐oxidation in acidic solution compared to the Pt/Mo2C‐rGO and Pt/rGO catalysts. The activty enhancement is atributed to the defective nature of the interface between Pt, Nb‐Mo2C and rGO. It is found that Nb‐Mo2C not only alleviates CO poisoning of Pt nanoparticles, but also generates oxygen containing species at lower potentials. This process helps scavenging the intermediate species such as COads on Pt surfaces and regenerates the active Pt sites for routine alcohol oxidation reaction. The chronopotentiometry and chronoamperometry studies also show that Pt/Nb‐Mo2C‐rGO exhibits lower alcohol oxidation overpotential and longer polarization time/stability compared to Pt/Mo2C‐rGO and bare Pt/rGO catalysts.

Synthesis gas conversion over Cu and Ca modified model Mo6S8 catalysts: A systematic theoretical investigation

We present a combined density functional theory (DFT) and microkinetic modeling study of synthesis gas conversion on Cu and Ca modified Mo6S8 catalysts to value-added products. Our results show that CO∗ + H∗ → HCO∗ + (H) → H2CO∗ + (H) → H3CO∗ + (H) → CH3OH∗ → CH3OH (g) is an optimal pathway on the Ca–Mo6S8 surface. With the combination of Energetic span model (ESM) and binding energy analysis, we conclude that Ca–Mo6S8 is a promising catalyst for formaldehyde and methanol from synthesis gas conversion. Meanwhile, the most energetically favorable outcome on the Cu–Mo6S8 surface is the production of ethanol. Microkinetics simulations are carried out on the basis of the first-principles data, which predict the synthesis gas conversion rate and the product distribution. This study demonstrates that introducing metal Cu or Ca into Mo6S8 will design high-performance catalysts with synergistic interactions for tuning selectivity.

Ultra-small platinum nanoparticles deposited graphene supported on 3D framework as self-supported catalyst for methanol oxidation

The development of anodic catalysts for direct methanol fuel cell applications has recently been concerned in both academy and energy industries. In this study, we successfully developed an efficient electrocatalyst based on ultra-small platinum nanoparticles (Pt NPs) deposited reduced graphene oxide (rGO) supported by a three-dimensional (3D) framework. The catalyst was directly used as a self-supported and binder-free electrode for electrocatalytically catalyzing methanol oxidation (MOR). The achieved results showed the enhanced catalytic behavior of Pt-rGO/3DF towards MOR along with an excellent stability, superior to another electrode catalyst based on commercial Pt-C product. Our findings implied that growth of the Pt NPs on rGO nanosheets supported by a three-dimensional (3D) foam could impressively increase the catalytic performance of the resulting catalyst material towards MOR in alkaline environment. This study may open a novel and efficient option for creating highly catalytic hybrid towards MOR in fuel cell applications.

Enhanced Activity of Cu/ZnO/C Catalysts Prepared by Cold Plasma for CO2 Hydrogenation to Methanol

An activated carbon-supported Cu/ZnO catalyst for CO2 hydrogenation to methanol has been prepared by the facile plasma decomposition of a Cu–Zn precursor at moderate temperature. The Cu/ZnO/C catalyst prepared by cold plasma featured smaller size and higher dispersion than that prepared by traditional calcination. The low operation temperature plays an important role in this. The catalysts are characterized using a multitechnique approach. X-ray photoelectron spectroscopy results indicate that cold plasma can introduce specific O-containing groups on the carbon surface. It also facilitates the dispersion of active components and H spillover. H2 temperature-programmed reduction profiles and transmission electron microscopy images show that the interaction between Cu, ZnO, and carbon in the Cu/ZnO/C catalyst prepared by cold plasma was stronger than that in the catalyst prepared by calcination. The properties are beneficial to the CO2 hydrogenation reaction. The catalytic performance of the catalysts was tested in a fixed-bed reactor. The Cu/ZnO/C catalyst prepared by cold plasma showed an obvious increase in CO2 conversion, methanol selectivity, and productivity in the catalytic evaluation of catalysts. Moreover, it obtained a remarkable space-time yield of 92.5 gmethanol·kgcat–1·h–1 at 260 °C that is approximately 1.5 times that of Cu/ZnO/C prepared by calcination.

Modeling, Analysis and Optimization for the Biodiesel Production Process from Waste Cooking Oil

The present study proposed a rigorous model using detailed kinetics reaction for the alkali transesterification of waste cooking oil with methanol and Alkali Catalyst (NaOH). Aspen Plus software is used. The results showed that the rigorousness of the model helps in predicting more realism and accurate result. The effect of different parameters on the process like temperature, pressure, residence time, methanol to oil ratio, and catalyst (NaOH) weight percentage were studied. All the studied parameters have significant effect on the process performance except pressure. Optimization of the process also carried out to find the best conditions for maximum profit and maximum production. The optimization results showed that the reaction temperature decreased from 60 to 45 ° C, the reaction time decreased from 60 to 49 minutes, the molar ratio of methanol/oil increased from 6:1 to 7.2:1 mole ratio and the catalytic concentration decreased from 1 to 0.25 wt%.

Fabrication of Pt3Ni catalysts on polypyrrole-modified electrochemically exfoliated graphene with exceptional electrocatalytic performance for methanol and ethanol oxidation

Electrochemically exfoliated graphene is deemed as a good catalyst support owing to less functional groups and defects on its surface. However, its inert surface is not conducive to the in-situ growth of catalysts. In this work, electrochemically exfoliated graphene is modified by polypyrrole to increase the surface active sites for growing catalyst nanoparticles. Moreover, to reduce the consumption of rare Pt metal as well as raise its electrocatalytic activity, Pt3Ni alloy catalysts are prepared on its surface. It is worth mentioning that polypyrrole not only serves as a linker to immobilize and disperse Pt3Ni nanoparticle on EEG, but also promotes the poison tolerance of Pt3Ni catalysts by donating electrons. Therefore, the electrocatalytic performance of Pt3Ni catalysts for methanol and ethanol oxidation are highly improved after polypyrrole modification. The optimum ratio of Pt to Ni in Pt–Ni alloy is also studied and the results show that Pt3Ni catalysts exhibit better electrocatalytic performance than other PtxNi alloys (x = 1, 2, 4). The novel strategy that using polypyrrole to modify electrochemically exfoliated graphene may advance the application of electrochemically exfoliated graphene as a new generation catalyst support.

Silicon carbide encapsulated graphite nanocomposites supported Pt nanoparticles as high-performance catalyst for methanol and ethanol oxidation reaction

Silicon carbide encapsulated graphite (SiC/EG) nanocomposites prepared by carbothermal reduction method were used as Pt nanoparticles (NPs) supports for effective methanol and ethanol electrooxidation. Pt NPs with a mean diameter of 2.3 ± 0.4 nm have been uniformly deposited on SiC/EG by electrodeposition method. The Pt/SiC/EG catalyst showed larger electrochemical active surface area (ECSA), higher electrocatalytic activity and durability, better poison tolerance toward methanol and ethanol oxidation than commercial Pt/C catalyst. This outstanding electrocatalytic performance of Pt/SiC/EG was attributed not only to the small size and uniform distribution of Pt NPs, but also to the high corrosion resistance and the porous network structure of SiC/EG support. These results suggest that SiC/EG is a promising catalyst support for electrocatalysts in fuel cells.

Synthesis and antiproliferative activity of new hybrids bearing neocryptolepine, acridine and α-aminophosphonate scaffolds

Synthesis of novel α-aminophosphonate hybrids 8a–f was accomplished by the reaction of 11-phenoxy-4-formylneocryptolepine 3, aminoalkylamino acridines 6a–f and diphenyl phosphite 7 in the presence of lithium perchlorate as Lewis acid catalyst in methanol. The starting aldehyde 3 was obtained by reaction of 11-chloroneocryptolpine 1 with 4-hydroxybenzaldehyde 2 in the presence of potassium carbonate in DMF, whereas 9-aminoalkylamino acridines 6a–f were synthesized by reaction of 9-chloroacridine 4 with appropriate diamines 5a–f. The structure of all synthesized hybrids was confirmed by spectroscopic methods and showed spectra in consistence with the expected structures. The antiproliferative activity of all synthesized hybrids was evaluated against HCT-116, MCF-7, HepG2 and A549 human cancer cell lines. The screened results proved that most of the reported compounds are potent, especially hybrid 8a, which displayed the highest activity against MCF-7, HepG2 and A549 cancer cell lines with IC50 8.2, 23.1 and 19.4 µM, respectively. This activity is significantly higher than the standard drug doxorubicin. Moreover, hybrid 8f showed most potent activity against HCT-116 cancer cell line with IC50 2.4 µM higher than the reference drug doxorubicin (IC50:10.90 µM).

Passive Direct Methanol–Hydrogen Peroxide Fuel Cell with Reduced Graphene Oxide–Supported Prussian Blue as Catalyst

Herein, a reduced graphene oxide–supported Prussian Blue (rGO‐PB) composite as the cathode catalyst for a passive direct methanol–hydrogen peroxide fuel cell (DMHPFC) is used. Unlike the conventional passive direct methanol fuel cell (DMFC) with a cathodic catalyst of noble metal platinum (Pt), the new fuel cell uses hydrogen peroxide as the oxidant. This nonnoble metal catalyst has a low cost, high catalytic activity, and high conductivity due to its 3D conductive network. The fuel cell has a theoretical voltage of 1.76 V (higher than 1.21 V related to the traditional DMFC) and can be used in an oxygen‐free environment. Results show that the cell shows good performance with a peak power density of 20.5 mW cm−2 at a higher temperature of 85 °C. The polarization and impedance curves indicate that as the temperature increases, the cell performance improves continuously with the decrease in mass transfer resistance. The discharging tests show a stable cell performance under continuous operation. The cell voltage has an instant response to the change in the current output.

A One-Pot Method to Prepare Rice-Shaped TiO2 /C/Ni Composite Catalyst for Methanol Oxidation Reaction

TiO2/C/Ni composite is synthesized by carbonizing Ti-EG-Ni polymer under reductive atmosphere. The as-prepared materials were characterized using XRD, SEM, EDS, HRTEM, and Raman IR. The electrocatalytic activity of methanol oxidation reaction was carried out in an alkaline medium. The as-synthesised TiO2/C/Ni-500 composite possesses a unique rice-shaped structure with a homogenous dispersion of Ni and TiO2 nanoparticles in the carbon matrix. This composite exhibits superior electro-catalytic performance for methanol oxidation (at 45 mA cm−2) with excellent stability and a very low onset potential (0.35 V) in alkaline solution. The enhanced electrochemical activity and stability can be attributed to the synergetic effect in the TiO2/C/Ni composite. This work opens a new technique to develop non-noble metal catalysts for direct methanol fuel cells.

Highly efficient methanol oxidation on durable PtxIr/MWCNT catalysts for direct methanol fuel cell applications

Development of highly active and durable Pt based anode materials with higher utilization of Pt is quite crucial towards the commercial viability of direct methanol fuel cells (DMFCs). Herein, multi-walled carbon nanotube supported PtxIr nanostructures (PtxIr/MWCNT) are successfully prepared by one-pot wet chemical reduction without any surfactants. The role of Ir content and its bi-functional mechanism on kinetics of methanol oxidation reaction (MOR) was studied. The MOR on PtxIr/MWCNT follows Langmuir-Hinshelwood mechanism by successive oxidative removal of CO. The co-existence of IrO2 plays a vital role as catalytic promotor. Amongst, Pt2Ir/MWCNT shows enhanced electrocatalytic activity (mass activity (MA), 933.3 mA/mgPt) and durability (13.8% loss of MA after 5000 potential cycles) thru the well-balanced electronic and bi-functional effects. This study implies that the optimized composition of Pt2Ir/MWCNT exhibits efficient methanol oxidation and could be a potential catalyst for direct methanol fuel cells.

Microwave synthesis of MWCNT-supported PtRuNi catalysts and their electrocatalytic activity for direct methanol fuel cells

Multi-walled carbon nanotube (MWCNT)-supported PtRuNi catalysts were synthesized using a microwave heating process. The particle sizes and structures of the catalysts were analyzed using X-ray diffraction and transmission electron microscopy (TEM). The electrocatalytic activities of the catalysts for methanol electrooxidation were evaluated by cyclic voltammetry, chronoamperometry, and impedance spectroscopy. The TEM results revealed that the MWCNT-supported PtRuNi catalyst synthesized via microwave heating for 10 min showed a uniform distribution of nanoparticles with an average size of about 5 nm. The catalyst showed an electrochemically active surface area of 62.2 m2 g−1 and a mass activity of 148.64 mA gpt−1. A decrease in the microwave heating time increased the dispersion and reduced the size of the PtRuNi nanoparticles. Moreover, the improved performance of the catalysts can be attributed to their high proton and electronic conductivity due to nickel hydroxides. Nickel hydroxides produced on the surface of metallic Ni in the Pt lattice contribute to the catalytic activity of PtNi catalysts in direct methanol fuel cells.

Enhanced methanol electro-oxidation activity of electrochemically exfoliated graphene-Pt through polyaniline modification

Pt and Pt-based catalysts are deemed as the popular anode catalysts for direct methanol fuel cells due to their high electrocatalytic activity for methanol oxidation. The structure of the catalyst support is critical to the electrocatalytic performance of the catalysts. In this work, a kind of high-quality graphene (electrochemically exfoliated graphene) with the intact surface is exploited as the catalyst support instead of the popularly used reduced graphene oxide. Pt nanoparticles are successfully synthesized on electrochemically exfoliated graphene and exhibit better methanol electro-oxidation activity than those on reduced graphene oxide. To further raise the electrocatalytic performance of Pt catalysts, the substrate surface is modified by conductive polyaniline. It is found that the interaction of electrochemically exfoliated graphene with polyaniline is much different from the interaction of reduced graphene oxide with polyaniline. The intact surface structure of electrochemically exfoliated graphene is favorable for the combination with polyaniline by π-π interactions, which releases more N species for the growth of Pt nanoparticles. The synergistic interaction of Pt and N species can facilitate the dispersion of Pt nanocrystals as well as the electron transport through Pt-based hybrids, thereby further promoting the electrocatalytic properties of Pt catalysts for methanol oxidation.

Tuning Pt-skinned PtAg nanotubes in nanoscales to efficiently modify electronic structure for boosting performance of methanol electrooxidation

The modification of electronic structure can significantly affect electrocatalytic activity. An architecture art of Pt-skinned PtAg bimetallic nanotubes is successfully synthesized, delivering much higher catalytic activity and better stability toward methanol electrooxidation than PtAg bimetallic nanoparticles and commercial Pt/C catalysts. Theoretical studies reveal that the Pt skin on PtAg bimetallic nanotubes prominently optimize the electronic structure of Pt to greatly enhance the dissociative adsorption of methanol while increasing CO poisoning resistance for fast electrode kinetics, high catalytic current density and stability. This work offers a low Pt loading but highly active anode catalyst for direct methanol fuel cells, demonstrating that rationally tuning the electronic structure by well-controlling surface morphology in nanoscales could open new opportunities to greatly improve the electrocatalytic properties.

Correction: Cu2O template synthesis of high-performance PtCu alloy yolk–shell cube catalysts for direct methanol fuel cells

Correction for 'Cu2O template synthesis of high-performance PtCu alloy yolk-shell cube catalysts for direct methanol fuel cells' by Sheng-Hua Ye et al., Chem. Commun., 2014, 50, 12337-12340, DOI: 10.1039/C4CC04108A.

Hydrogen in methanol catalysts by neutron imaging.

Although of pivotal importance in heterogeneous hydrogenation reactions, the amount of hydrogen on catalysts during reactions is seldom known. We demonstrate the use of neutron imaging to follow and quantify hydrogen containing species in Cu/ZnO catalysts operando during methanol synthesis. The steady-state measurements reveal that the amount of hydrogen containing intermediates is related to the reaction yields of CO and methanol, as expected from simple considerations of the likely reaction mechanism. The time-resolved measurements indicate that these intermediates, despite indispensable within the course of the reaction, slow down the overall reaction steps. Hydrogen-deuterium exchange experiments indicate that hydrogen reduction of Cu/ZnO nano-composites modifies the catalyst in such a way that at operating temperatures, hydrogen is dynamically absorbed in the ZnO-nanoparticles. This explains the extraordinary good catalysis of copper if supported on ZnO by its ability to act as a hydrogen reservoir supplying hydrogen to the surface covered by CO2, intermediates, and products during catalysis.

Supercritical methanol depolymerization and hydrodeoxygenation of pyrolytic lignin over reduced copper porous metal oxides

Supercritical methanol depolymerization and hydrodeoxygenation (SCM-DHDO) is a process to produce fuel from biomass with supercritical methanol and CuMgAlOx catalyst.