Kinetics Of Methanol Oxidation Reaction Research Articles

Pt3Sn0.5Mn0.5 Intermetallic Electrocatalyst with Superior Stability for CO-Resilient Methanol Oxidation.

The sluggish kinetics of methanol oxidation reaction (MOR) and poor long-term durability of catalysts are the main restrictions of the large-scale applications of direct methanol fuel cells (DMFCs). Herein, we demonstrated an inspirational ternary Pt3Sn0.5Mn0.5/DMC intermetallic catalyst that reached 4.78 mA cm-2 and 2.39 A mg-1Pt for methanol oxidation, which were 2.50/2.44 and 5.62/5.31 times that of commercial PtRu/C and Pt/C. After the durability test, Pt3Sn0.5Mn0.5/DMC presented a very low current density attenuation (38.5%), which was significantly lower than those for commercial PtRu/C catalyst (84.2%) and Pt/C (93.1%). Density functional theory (DFT) calculations revealed that the coregulation of Sn and Mn altered the surface electronic structure and endowed Pt3Sn0.5Mn0.5 with selective adsorption of Pt for CO and Sn for OH, which optimized the adsorption strength for intermediates and improved the reaction kinetics of MOR. Beyond offering an advanced electrocatalyst, this study provided a new point of view for the rational design of superior methanol oxidation catalysts for DMFC.

Enhanced methanol electrooxidation by electroactivated Pd/Ni(OH)2/N-rGO catalyst

Direct methanol fuel cells, in which electrocatalytic oxidation of methanol takes place, are one of the most promising technologies for facilitating the shift to renewable energy sources. However, they still suffer from high-catalyst-prices, as well as sluggish kinetics of methanol oxidation reaction (MOR). Therefore, herein, palladium/Nickel(II) hydroxide/nitrogen doped reduced graphene oxide (Pd/Ni(OH)2/N-rGO) hybrid was fabricated via facile two-step solution method and utilized as electrocatalyst for MOR. The in-situ electrochemical activation pre-treatment was proposed to engineer a highly active electrocatalyst. The Pd/Ni(OH)2/N-rGO, which had distinctive structural features along with robust synergistic effects, outperformed the commercial Pd electrocatalyst in terms of catalytic activity towards MOR, with elevated anodic peak current density values. The in-situ electrochemical activation pre-treatment lead to 3.3, 3.0, and 2.0-fold increase in activity of Pd/Ni(OH)2/N-rGO, Pd/N-rGO, and Pd/C, respectively. This research lays the door for a unique technique to manufacture high-performance, low-cost electrocatalysts that might be used in fuel cell technology instead of existing Pd electrocatalysts.

Ultrathin PtRu Nanowires as Efficient and Stable Electrocatalyst for Liquid Fuel Oxidation Reactions

Direct liquid fuel cells (DLFCs) are promising clean energy conversion devices for their high energy density, low environmental pollution, and convenient transportation and storage. However, the commercialization of DLFCs is still limited by the lack of highly active and stable catalysts for the anodic oxidation of liquid fuels. Herein, a new class of ultrathin PtRu nanowires (NWs) with a diameter of 1.1 nm was synthesized via a colloidal chemistry strategy. The as-made ultrathin PtRu NWs can not only expose large active sites but also enhance the kinetics of methanol oxidation reaction, which was confirmed by the in situ Fourier transform infrared (FTIR) spectroscopy. Consequently, ultrathin PtRu NWs exhibit greatly boosted activity and stability for methanol and ethanol oxidation reactions in an alkaline medium.

Stable NiPt–Mo2C active site pairs enable boosted water splitting and direct methanol fuel cell

Sluggish kinetics of methanol oxidation reaction (MOR) and alkaline hydrogen evolution reaction (HER) even on precious Pt catalyst impede the large-scale commercialization of direct methanol fuel cell (DMFC) and water electrolysis technologies. Since both of MOR and alkaline HER are related to water dissociation reaction (WDR), it is reasonable to invite secondary active sites toward WDR to pair with Pt for boosted MOR and alkaline HER activity on Pt. Mo2C and Ni species are therefore employed to engineer NiPt–Mo2C active site pairs, which can be encapsulated in carbon cages, via an in-situ self-confinement strategy. Mass activity of Pt in NiPt–Mo2C@C toward HER is boosted to 11.3 A mgpt−1, 33 times higher than that of Pt/C. Similarly, MOR catalytic activity of Pt in NiPt–Mo2C@C is also improved by 10.5 times and the DMFC maximum power density is hence improved by 9-fold. By considering the great stability, NiPt–Mo2C@C exhibits great practical application potential in DMFCs and water electrolysers.

Mesoporous CeO2–C hybrid spheres as efficient support for platinum nanoparticles towards methanol electrocatalytic oxidation

The development of direct methanol fuel cells (DMFCs) is partially limited by the poor kinetics of methanol oxidation reaction (MOR) at the anode side. It was reported that the interaction between Pt and CeO2 enhances the electrocatalytic performance of Pt catalyst for MOR. In this work, a hybrid material (CeO2–C) composed of CeO2 and carbon was successfully prepared by a simple hydrothermal method followed by calcination in inert atmosphere. The hierarchically porous nanostructure and especially good electronic conductivity of CeO2–C make it an excellent support for Pt particles for application in electrocatalytic process. TEM investigation reveals that triple-phase interface of Pt, carbon and CeO2 forms in Pt/CeO2–C catalyst. Performance of the as-prepared catalyst for MOR was studied in alkaline medium. The Pt/CeO2–C catalyst shows superior catalytic performance for MOR compared with Pt/CeO2 and the physical mixture of Pt/CeO2 and acetylene black (Pt/CeO2+C). The significantly improved performance can be attributed to the synergetic effect between Pt particles and CeO2–C support, and the better conductivity of CeO2–C. This study provides a possible method to expand the application potential of CeO2 materials in MOR, and may also be used in other electrocatalytic process.

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.

Significantly enhanced performance of direct methanol fuel cells at elevated temperatures

The performance of direct methanol fuel cells (DMFCs) is constrained by the sluggish kinetics of methanol oxidation reaction. Increasing the temperature can effectively increase the methanol oxidation kinetics, offering new opportunities to achieve high performance. Here we studied the performance of DMFCs based on the newly developed silica impregnated phosphoric acid doped polybenzimidazole (PA/PBI/SiO2) composite membrane. The composite membrane shows a proton conductivity of 2.9–4.1 × 10−2 S cm−1 at temperatures between 200 and 250 °C and is stable at high temperatures. The cells using the composite membrane successfully delivered a peak power density of 136 mW cm−2 and 237 mW cm−2 at 260 °C using the Pt/C and PtRu/C as the anode catalysts, respectively. The cells with the PA/PBI/SiO2 composite membrane show a much higher power output than that with conventional PA/PBI membranes. Most importantly, the results demonstrate that there exists a distinct transition temperature around 205 °C for the performance of DMFCs. Above this transition temperature, the increase in power density with temperature is 208 mWcm−2/100 °C, which is more than 4 times higher than 50 mWcm−2/100 °C obtained at temperatures below 205 °C. The presence of such transition temperature for DMFCs is most likely due to the significantly enhanced kinetics of the methanol oxidation reaction at elevated temperatures. Operation at elevated temperatures, i.e., above 205 °C, is most effective to significantly enhance the power performance of DMFCs.

Titanium dioxide encapsulated in nitrogen-doped carbon enhances the activity and durability of platinum catalyst for Methanol electro-oxidation reaction

The development of advanced catalyst supports is a promising route to obtain active and durable electrocatalysts for methanol electro-oxidation reaction. In the current work, nitrogen-doped carbon encapsulated titanium dioxide composite (TiO2@NCX) is constructed and serves as support material for the Pt catalyst. The TiO2@NCX support is fabricated by the procedure of an in-situ polymerization and subsequent pyrolysis. The synthesized Pt/TiO2@NCX catalysts show enhanced electrocatalytic performance towards methanol electro-oxidation compared with the commercial Pt/C catalyst. The enhancement can be ascribed to combinatory effect of N-doped carbon and TiO2, in which the tolerance to CO-poisoning and the intrinsic kinetics of methanol oxidation reaction are simultaneously improved by the bifunctional mechanism and the electronic effect. As a result, the as-developed TiO2@NCX composite is a promising catalyst support material for the application in fuel cell.

Platinum–Ruthenium Nanotubes and Platinum–Ruthenium Coated Copper Nanowires As Efficient Catalysts for Electro-Oxidation of Methanol

The sluggish kinetics of methanol oxidation reaction (MOR) is a major barrier to the commercialization of direct methanol fuel cells (DMFCs). In this work, we report a facile synthesis of platinum–ruthenium nanotubes (PtRuNTs) and platinum–ruthenium-coated copper nanowires (PtRu/CuNWs) by galvanic displacement reaction using copper nanowires as a template. The PtRu compositional effect on MOR is investigated; the optimum Pt/Ru bulk atomic ratio is about 4 and surface atomic ratio about 1 for both PtRuNTs and PtRu/CuNWs. Enhanced specific MOR activities are observed on both PtRuNTs and PtRu/CuNWs compared with the benchmark commercial carbon-supported PtRu catalyst (PtRu/C, Hispec 12100). X-ray photoelectron spectroscopy (XPS) reveals a larger extent of electron transfer from Ru to Pt on PtRu/CuNWs, which may lead to a modification of the d-band center of Pt and consequently a weaker bonding of CO (the poisoning intermediate) on Pt and a higher MOR activity on PtRu/CuNWs.

The construction of nitrogen-doped graphitized carbon–TiO2 composite to improve the electrocatalyst for methanol oxidation

The exploration of advanced catalyst supports is a promising route to obtain electrocatalysts with high activity and durability. Herein, the nitrogen-doped graphitized carbon/TiO2 composite was fabricated and explored as support for the Pt catalyst. The composite support was constructed by carbonization of polypyrrole/TiO2 using cobalt nitrate and nickel nitrate as graphitizing catalysts. The resulting catalyst shows enhanced electrocatalytic performance for methanol electrooxidation compared with the commercial Pt/C catalyst. The enhancement can be ascribed to combinatory effect of N-doped graphitized carbon and TiO2, in which the tolerance to CO-poisoning and the intrinsic kinetics of methanol oxidation reaction were simultaneously improved by the bifunctional effect and the modification of the electronic structure. As a result, the as-developed nitrogen-doped graphitized carbon/TiO2 composite present attractive advantages for the application in fuel cell electrocatalyst.