Catalysts For Direct Methanol Fuel Cells 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.

Pd/TiO2 decorated carbon fibers as an efficient anode catalyst for methanol electro‐oxidation

AbstractIn this study, Pd/TiO2 decorated carbon nanofibers (Pd/TiO2@CNFs) and Pd@CNFs were prepared by the impregnation method for application in direct methanol fuel cells (DMFCs). Pd and TiO2 particles were supported on the surface of carbon fibers. Noticeably, When the mass fraction of PdCl2 added is 4%, the Pd@CNFs catalyst (Pd‐4@CNFs) showed higher electrocatalytic activity and stability, which were about 28.4 and 13.2 times higher than those of commercial Pd/C catalyst, respectively. On the basis of Pd‐4@CNFs catalyst, TiO2 with a mass fraction of 10% was added to produce Pd/TiO2@CNFs catalyst (Pd‐4/TiO2‐10@CNFs). The electrocatalytic activity of Pd‐4/TiO2‐10@CNFs increased to 3,850.4 A·g−1, which was 31.9 times higher than that of commercial Pd/C catalysts. These results demonstrated that the novel Pd/TiO2@CNFs catalyst is expected to be an efficient and durable catalyst for DMFC.

Poly (3, 4-propylenedioxythiophene)/Hollow carbon sphere composites supported Pt NPs to facilitate methanol oxidation reactions

Direct methanol fuel cells (DMFCs) are thought of as portable, sustainable, and non-polluting energy devices. The exploration of efficient and affordable catalysts for the methanol oxidation reaction (MOR) is significant for the industrial application of DMFCs. In this study, nitrogen-doped hollow carbon spheres (HCS) derived from polydopamine were proposed for the catalyst support for platinum nanoparticles (Pt NPs) for serving as the anode catalyst for DMFCs, and a composite support material was fabricated by in-situ oxidation of 3,4-ethylenedioxythiophene (ProDOT) with HCS to get core-shell structured poly(3,4-propylenedioxythiophene) (PProDOT)-embellished hollow carbon spheres (HCS) (PProDOT/HCS) for further improving the catalytic activity for supported catalyst. The results indicated that the platinum (Pt) on the surface of HCS was well dispersed, and the Pt became smaller and more evenly distributed with the introduction of PProDOT. Simultaneously, the Schottky junction formed between PProDOT and Pt NPs contributes to enhanced charge transfer and catalytic activity of the catalyst. Notably, the core-shell structure of the ternary catalyst, its excellent charge transfer capability, and the interaction between platinum and the support contribute to its high electrocatalytic activity. Electrochemical tests demonstrated that the PProDOT/HCS/Pt catalyst exhibited a mass activity of 1169.6 mA mg−1Pt for methanol oxidation in acidic electrolytes, surpassing the activity of the HCS/Pt catalyst (472.4 mA mg−1Pt) and commercial Pt/C (281.0 mA mg−1Pt).

Enhancing Direct Methanol Oxidation with Pt-Pd Alloy Nanoparticles Synthesized By Gas Diffusion Electrocrystallization (GDEx)

Direct methanol fuel cells (DMFCs) are a promising sustainable energy solution due to their high energy density, low-temperature operation, and portability. However, sluggish methanol oxidation reaction (MOR) kinetics hinders their successful commercialization.1,2 Pt is a highly active MOR catalyst due to its ability to adsorb and decompose methanol on its surface. However, when pure Pt is used, the adsorption of oxidation intermediaries, i.e., CO, occurs, blocking catalytically-active sites and reducing the catalytic efficiency.2 A promising strategy to improve the catalytic activity and CO tolerance of Pt is by alloying. Among several candidates, Pd stands out due to its identical crystal structure and similar lattice constant to Pt, resulting in single-phase bimetallic materials with strong coupling and improved catalytic performance. In addition, the active surface area is enhanced, and stability is improved by using Pt-Pd alloys.3 We recently reported an electrochemical method for synthesizing platinum group (PGMs, i.e., Pt, Pd, Rh) nanoparticles (NPs) using Gas-Diffusion Electrocrystallization, best known as the GDEx process.4 In GDEx, CO2 and water are reduced using a gas diffusion electrode, producing CO and H2, which in turn reduce PGMs ions in solution, forming metal nanoclusters of 10 nm–40 nm composed of even smaller nanocrystals of 2 nm–4 nm. In this work, we used GDEx to synthesize Pt-Pd alloy NPs with different metal ratios (Pt100, Pt75-Pd25, Pt50-Pd50, Pt25-Pd75 and Pd100). The Pt-Pd alloy NPs were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy. The size distribution of the synthesized nanomaterials was between 15 nm–30 nm, increasing in size with increasing Pd content. The catalytic activity of the Pt-Pd alloy NPs toward methanol oxidation was measured in 0.1 M HClO4. The electrochemical surface area (ECSA), measured by the Cu underpotential deposition method,5 was 37.1 ± 2.1, 36.1 ± 2.7, 42.5 ± 1.7 and 56.1 ± 2.9 m2 gPt -1 for Pt100, Pt75-Pd25, Pt50-Pd50, and Pt25-Pd75 respectively. The mass activity (MA, fig.1a), defined by the current density per unit mass of Pt loading at the forward peak, was 452 ± 10, 345 ± 16, 365 ± 21 and 189 ± 15 for Pt100, Pt75-Pd25, Pt50-Pd50, Pt25-Pd75. Even though the MA for Pt75-Pd25 and Pt50-Pd50 was lower than for Pt100, their onset potential was smaller (0.503 VRHE for Pt75-Pd25 and 0.488 VRHE for Pt50-Pd50) than for Pt100 (0.530 VRHE) indicating that the MOR is more favourable on those alloys. Besides, during the accelerated stability test (ADT, Fig.1b), after 1000 cycles, Pt75-Pd25 and Pt50-Pd50 showed higher stability and resistance towards CO poisoning than Pt100 by holding 80% and 70% of their peak current density. In comparison, Pt100 only kept ∼60% of its peak current density under the same conditions.In summary, the GDEx process allows the synthesis of Pt-Pd alloy NPs with a similar or superior catalytic performance towards MOR than pure Pt NPs, i.e., similar MA but with a better tolerance towards CO poisoning. The selectivity of the GDEx process for PGMs allows the synthesis of Pt-Pd catalysts for DMFCs not only from synthetic solutions but also from complex matrixes that contains a mixture of both PGMs (i.e., leachates from spent automotive catalytic converters).This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreements No. 958302 (PEACOC project) and No. 101091715 (FIREFLY project). Yuda A, Ashok A, Kumar A. Catalysis Reviews. 2022;64(1):126-228.Ren X, Lv Q, Liu L, Liu B, Wang Y, Liu A, Wu G. Sustain. Energy Fuels. 2020;4(1):15-30.Yousaf AB, Imran M, Uwitonze N, Zeb A, et al. J . Phy s. Chem . C. 2017;121(4):2069-79.Martinez-Mora O, Pozo G, Leon-Fernandez LF, Fransar J, Dominguez-Benetton X., RSC Sustain. 2023; DOI: 10.1039/D3SU00046J.Green CL, Kucernak A. J. Phys. Chem. B. 2002;106(5):1036-47. Figure 1

Precision tuning of highly efficient Pt-based ternary alloys on nitrogen-doped multi-wall carbon nanotubes for methanol oxidation reaction

The electrochemical methanol oxidation is a crucial reaction in the conversion of renewable energy. To enable the widespread adoption of direct methanol fuel cells (DMFCs), it is essential to create and engineer catalysts that are both highly effective and robust for conducting the methanol oxidation reaction (MOR). In this work, trimetallic PtCoRu electrocatalysts on nitrogen-doped carbon and multi-wall carbon nanotubes (PtCoRu@NC/MWCNTs) were prepared through a two-pot synthetic strategy. The acceleration of CO oxidation to CO2 and the blocking of CO reduction on adjacent Pt active sites were attributed to the crucial role played by cobalt atoms in the as-prepared electrocatalysts. The precise control of Co atoms loading was achieved through precursor stoichiometry. Various physicochemical techniques were employed to analyze the morphology, element composition, and electronic state of the catalyst. Electrochemical investigations and theoretical calculations confirmed that the Pt1Co3Ru1@NC/MWCNTs exhibit excellent electrocatalytic performance and durability for the process of MOR. The enhanced MOR activity can be attributed to the synergistic effect between the multiple elements resulting from precisely controlled Co loading content on surface of the electrocatalyst, which facilitates efficient charge transfer. This interaction between the multiple components also modifies the electronic structures of active sites, thereby promoting the conversion of intermediates and accelerating the MOR process. Thus, achieving precise control over Co loading in PtCoRu@NC/MWCNTs would enable the development of high-performance catalysts for DMFCs.

Highly Dispersed Pt‐Au/rGO Catalysts Prepared by Hyperbranched Polyglycerols for Efficient Electrooxidation of Methanol

AbstractRecently, fuel cells especially direct methanol fuel cells (DMFCs), have attracted great interest because of their high energy density, their pollution‐free operation mode and thus their prospect for use in convenient transportation. Although platinum (Pt) catalyst is an efficient catalysts for DMFCs, it has some problems such as high price, poor stability and durability. Therefore, the research of high performance Pt catalysts becomes the focus. Firstly, the hyperbranched polyglycerols (HPG) were synthesized by the one‐step anionic ring‐opening polymerization. The Pt‐Au bimetallic catalysts supported on reduced graphene oxide (Pt‐Au‐HPG/rGO) were synthesized via a hydrothermal method, using HPG as the template and stabilizer. The electrocatalytic performances for the electrooxidation of methanol were investigated by electrochemical methods. Compared with commercial Pt/C (10 wt %) catalysts, Pt‐Au‐HPG/rGO has the larger electrochemically active surface area (ECSA, 108.8 m2 g−1), higher catalytic performance (0.498 A mgmetal−1) and better stability. This excellent performance is attributed to the good dispersion and conductivity of Pt‐Au‐HPG/rGO for the addition of HPG, rGO and Au. Meanwhile, the bifunctional and electronic effects between Au and Pt improved the electrochemical performance of the samples.

Rational Design of NiZnx@CuO Nanoarray Architectures for Electrocatalytic Oxidation of Methanol.

Methanol oxidation reaction (MOR) in anodes is one of the significant aspects of direct methanol fuel cells (DMFCs), which also plays a critical role in achieving a carbon-neutral economy. Designing and developing efficient, cost-effective, and durable non-Pt group metal-based methanol oxidation catalysts are highly desired, but a gap still remains. Herein, we report well-defined hierarchical NiZnx@CuO nanoarray architectures as active electrocatalysts for MOR, synthesized by combining thermal oxidation treatment and magnetron sputtering deposition through a brass mesh precursor. After systematically evaluating the electrocatalytic performance of NiZnx@CuO nanoarray catalysts with different preparation conditions, we found that the NiZn1000@CuO (thermally oxidized at 500 °C for 2 h, nominal thickness of the NiZn alloy film is 1000 nm) electrode delivers a high current density of 449.3 mA cm-2 at 0.8 V for MOR in alkaline media as well as excellent operation stability (92% retention after 12 h). These outstanding MOR performances can be attributed to the hierarchical well-defined structure that can not only render abundant active sites and a synergistic effect to enhance the electrocatalytic activity but also can effectively facilitate mass and electron transport. More importantly, we found that partial Zn atoms could leach from the NiZn alloy, resulting in rough surface nanorods, which would further increase the specific surface area. These results indicate that the NiZn1000@CuO nanoarray architecture could be a promising Pt group metal alternative as an efficient, cost-effective, and durable anode catalyst for DMFCs.

Bimetallic palladium-copper nanoplates with optimized d-band center simultaneously boost oxygen reduction activity and methanol tolerance.

The methanol-poisoning of electrocatalysts at the cathodic part of direct methanol fuel cells (DMFCs) can severely degrade the overall efficiency. Therefore, engineering cathodic catalysts with outstanding oxygen reduction activity, and simultaneously, superior methanol tolerance is greatly desired. Herein, bimetallic palladium-copper (PdCu) nanoplates with the optimized d-band center are designed as promising cathodic catalysts for DMFCs. It shows outstanding oxygen reduction activity with a mass activity (MA) of 0.522AmgPd-1 in alkaline electrolyte, overwhelming the benchmarked commercial Pt/C and Pd/C. Meanwhile, it has prominent stability with only 4.0 % loss in MA after continuous 20K cycles. More importantly, the PdCu nanoplates are almost inert toward methanol oxidation and show excellent anti-methanol capability. The theoretical calculations reveal that the downshift of d-band center in PdCu nanoplates and the electronic interaction between Pd and Cu atoms could effectively lower the methanol adsorption energy, thus leading to enhanced methanol tolerance. This work highlights the important role of tuning the electronic structure and optimized geometry of electrocatalysts to simultaneously boost their oxygen reduction activity, stability, and methanol tolerance for their future application in DMFCs.

Advances in platinum-based and platinum-free oxygen reduction reaction catalysts for cathodes in direct methanol fuel cells.

Direct methanol fuel cells (DMFCs) have been the focus of future research because of their simple structure, abundant fuel sources, high energy conversion efficiency and low cost. Among the components in DMFC, the activity and stability of the cathode catalyst is the key to the performance and lifetime of the DMFCs. Oxygen reduction reaction (ORR) is an important electrode reaction on DMFC cathode. It is known that Pt is widely used in the fabrication of ORR catalysts, but the limited earth storage of Pt and its high price limit the use of Pt-based commercial catalysts in DMFCs. To overcome these problems, advances have been made on new low Pt-based catalysts and Pt-free catalysts in recent years. In this article, the development of novel ORR catalysts and the carbon supports is reviewed and discussed.

Ultrafine Rh nanocrystals grown onto a boron and nitrogen codoped carbon support with a horn-shaped structure for highly efficient methanol oxidation.

The design and fabrication of non-Pt catalysts with excellent electrocatalytic performance toward methanol oxidation play a crucial role in the commercialization of direct methanol fuel cells (DMFCs). Herein, we propose a facile and robust strategy for the preparation of ultrafine Rh nanocrystals grown onto a boron and nitrogen codoped carbon support with a horn-shaped structure as Pt-alternative anode catalysts for DMFCs. The as-obtained hybrid nanoarchitecture possesses interesting structural features, including large specific surface area, numerous internal open pores, abundant B and N species, and homogeneous Rh dispersion. Benefiting from these superior properties, the resulting catalyst exhibits exceptional methanol oxidation performance with a large electrochemically active surface area of 182.4 m2 g-1, a high mass activity of 2350.5 mA mg-1, and good long-term durability, significantly outperforming Rh catalysts supported by conventional carbon supports and widely used Pt/carbon black and Pd/carbon black catalysts.

Fabrication of nanocomposite networks using Pd nanoparticles/Polydiphenylamine anchored on the surface of reduced graphene oxide: An efficient anode electrocatalyst for oxidation of methanol

Direct methanol fuel cells (DMFCs) are an essential aspect of electricity and fuel concerns. Herein, we report a new combination of Palladium nanoparticles anchored on polydiphenylamine with reduced graphene oxide network (rGO/PDPA/Pd) nanohybrid synthesized via an in-situ chemical strategy. The rGO/PDPA/Pd electrocatalyst shows excellent electrocatalytic activity, lower oxidation potential (−0.1 V), improved current density (2.85 mA/cm2), excellent cyclic stability (94%), and longevity (1200 s) towards methanol oxidation reaction (MOR) in the alkaline medium, when compared to commercial Pd/C electrocatalyst. Significantly, the forward oxidation peak potential of rGO/PDPA/Pd electrocatalyst was shifted negatively by 110 mV as compared to commercial Pd/C electrocatalyst. These results suggest that rGO/PDPA/Pd electrocatalyst is considered as an effective anode catalyst for DMFCs.

Selective transformation of aqueous methanol to value-added formic acid and hydrogen on bifunctional Mo2P monolayers in fuel cells

Direct methanol fuel cell (DMFC) running on hydrogen is an attractive alternative power source for a wide range of applications. Importantly, the required hydrogen can be in situ released from the stable liquid, which ensures its safe transformation and storage. However, the catalyst in DMFC is usually poisoned by the generated CO species, thus it is challenging to find an efficient and durable catalyst for practical applications. Here, the mechanism of methanol oxidation reaction (MOR) on the Mo2P monolayer is first studied using density functional theory. Compared with the initial C–H and C–O bond scissions, the initial O–H bond scission is found to be the most favorable. The reason is systematically analyzed based on steric effect, activation Gibbs free energy (Gact) decomposition and the Brønsted − Evans − Polanyi (BEP) relationships. The further dehydrogenation of CH2OH via the O–H bond scission has a significantly lower Gact than that of CH3O, thus the methanol decomposition on the Mo2P monolayer may proceed via two competitive pathways, i.e., CH3OH→CH3O→CH2O→CHO→CO and CH3OH→CH2OH→CH2O→CHO→CO. Then, through overcoming a relatively low barrier, the generated CO species can be combined with hydroxyl group from water dissociation on the Mo2P monolayer to produce formic acid, which can be easily desorbed from the catalyst surface to avoid the block of active sites. This study provides a better understanding of the MOR mechanism and paves the way for further advancing the catalyst in DMFCs.

Porous layered cobalt nanocrystal/nitrogen-doped carbon composites as efficient and CO-resistant electrocatalysts for methanol oxidation reaction

The development of active, stable and poison-resistant electrocatalysts for methanol oxidation reaction (MOR) has become a key challenge to improve the performance of direct methanol fuel cells (DMFCs). Herein, we report a simple strategy to prepare cobalt nanoscrystal/nitrogen-doped carbon (Co/N-C) composites as efficient and carbon monoxide (CO) resistant electrocatalysts for MOR. The Co/N-C composites are synthesized by the pyrolysis of porous CoCl2-polyaniline hydrogels. While CoCl2 is reduced to Co nanocrystals as active electrocatalyst for MOR, the polyaniline hydrogel is pyrolyzed to porous layered N-doped carbon that immobilize and protect Co nanocrystals, and also facilitate the mass and charge transfer through the electrolyte and electrode. After systematically exploring the preparation conditions of Co/N-C composites, we have found the optimal Co/N-C-1-500 (pyrolyzed at 500 °C) can achieve a high current density of 231 mA∙cm−2 at 0.8 V vs SCE for MOR in alkaline media. Meanwhile, the Co/N-C-1-500 catalyst presents a good durability and a high resistance to CO poisoning (93.5% retention of MOR activity), superior to the performance of Pt/C catalysts. With its high activity, good stability and superior resistance to CO poisoning, Co/N-C-1-500 is promising as a low-cost and efficient anode catalyst for DMFCs.

Pd supported on 3D graphene aerogel as potential electrocatalyst for alkaline direct methanol fuel cells

Direct methanol fuel cells (DMFCs) have been shown potential interest in several portable electronics for “green” power generation, however their large-scale commercial production are mostly hampered due to the low activity and high cost of the anode catalysts. In the present study, we report a facile, environmentally friendly, and cost-effective Pd supported on 3D graphene aerogel (Pd/GA) by one step freeze-casting process. The as-synthesized Pd/GA was broadly characterized by XRD, Raman, SEM, and TEM. Morphology observations show that 3D-porous cellular structure of Pd/GA with uniform distribution of 10 nm Pd nanoparticles on the surface of graphene sheets. Based on structural merits, the performance of Pd/GA has been investigated as an anode catalyst for alkaline DMFCs. Pd/GA catalyst shows significantly superior electrocatalytic performance, abnormally high poison tolerance, and stability as compared to the conventional Pd/ carbon black (Vulcan XC-72R) with the same loading (∼20%) of Pd.The superior electrocatalytic performance of Pd/GA towards methanol oxidation can be used in practical application as a promising anode material for DMFCs.

Growth of binder free mesoporous 3D-CuCo2O4 electrocatalysts with high activity and stability for electro-oxidation of methanol

Designing an active and reliable electrocatalyst is the urgent need for the desirable improvement in direct methanol fuel cells (DMFCs). In recent time, binary metal oxides have shown much attention as possible electrocatalysts for the future DMFCs. Herein, we have reported direct growth of 3D-CuCo2O4 on Nickel foam (NF) by hydrothermal route for electrochemical methanol oxidation. The electrochemical performance was examined by cyclic voltammetry (CV), chronoamperommetry (CA) and electrochemical impedance spectroscopy (EIS) techniques. Electrochemical analysis of 3D-CuCo2O4 exhibits high current density of 112 A g−1 at scan rate of 10 mV s−1 and retains 91% of initial current density after 1000 C V cycles. The high electrocatalytic activity of mesoporous 3D-CuCo2O4 is mainly ascribed to the synergetic effect of bimetallic element (Cu and Co), high surface area and enhanced charge-transfer because of direct growth of catalyst on NF. The present synthesis strategy and use of spinel oxides can offer promising feature for the development of non-precious catalysts for DMFCs.

Enhanced Electrocatalytic Oxidation of Methanol on Pt‐Decorated Bi2WO6/Graphene Nanosheets with Visible Light Assistance

Noble metal/semiconductor–based electrocatalysts have been proverbially used as the anode material in direct methanol fuel cells (DMFCs) recently. Combined with the advantage of the properties of noble metals and semiconductors, photo‐assisted electrocatalytic methanol oxidation is a valid route to increase the catalytic activity of catalysts in DMFCs. Herein, a 2D composite of bismuth tungstate/reduced graphene oxide (Bi2WO6/RGO) with excellent optical, electrical, and thermal stability is used as the support for the decoration of platinum nanoparticles (Pt NPs) to synthesize a new electrocatalyst of Pt‐Bi2WO6/RGO. Under ambient conditions, the methanol oxidation reaction (MOR) activity of the Pt‐Bi2WO6/RGO electrocatalyst increases relative to the Pt/Bi2WO6 electrode. Note that, under visible light irradiation, it deals with big enhancement of methanol oxidation activity on Pt‐Bi2WO6/RGO electrode, highlighting the effect of RGO used as Bi2WO6 cocatalysis for the MOR activity under illumination. Meanwhile, the corresponding reaction mechanisms with/without visible light are presented, and the roles of Pt‐Bi2WO6/RGO for photo‐assisted electrochemical reactions are proposed.

Water-alcohol dispersible and self-cross-linkable sulfonated poly(ether ether ketone): Application as ionomer for direct methanol fuel cell catalyst layer

A sulfonated poly(ether ether ketone) containing hydroxyl groups (HO-SPEEK) has been synthesized for investigation as the ionomer in cathode of direct methanol fuel cells. Na salt-formed HO-SPEEK shows excellent solubility in some aqueous solutions of monohydric alcohol and can be successfully self-cross-linked in-situ during the hot-pressing process of membrane-electrode assembly (MEA) fabrication. The resulted cross-linked HO-SPEEK displays improved stability and mechanical strength. MEA incorporating the HO-SPEEK as both membrane and ionomer shows excellent peak power density of 29.0 mW cm−2 at 25 °C with 4 M methanol, which is comparable to the Nafion reference MEA (31.8 mW cm−2) and 2.9-fold higher than that of the MEA prepared from catalyst ink that contained dimethyl sulfoxide (10.3 mW cm−2). Thanks to the avoidance of high-boiling point solvent, the resulted HO-SPEEK-based cathode is loosened with many large pores for reactant gas and product transportation. These results demonstrate that water-alcohol dispersible and cross-linkable sulfonated hydrocarbons hold technological promise as ionomer for electrode.

A Synthesis of Efficient Composite Catalyst Based on Fe-N-C Catalyst and Platium for Oxygen Reaction Reduction

Globally, because of the consumption of fossil fuel, the proton exchange membrane fuel cells (PEMFC) have received great attention. Among them, direct methanol fuel cells(DMFC) have been applied into many fields, such as computers, global positioning systems(GPS) and portable devices. Platinum catalysts are considered as one of the most efficient catalysts for the oxygen reduction reaction(ORR),which is one of the most essential processes for the DMFC. However, the low methanol resistance limits the application of Platinum catalyst in DMFC. Fe-N-C catalyst has an excellent methanol selectivity and showes a good ORR activitity with great potential as a non-precious metal catalyst. However, the performance of Fe-N-C catalysts is impossible to exceed that of Pt-based catalysts, leading to the irreplacebility of Pt catalyst in DMFC.As a result, the composite catalyst made by Fe-N-C catalyst and Platnum catalyst was synthesized and expected to take advantage of the high methanol resistance of Fe-N-C catalyst and brilliant ORR activity of Platinum catalyst. Herein, we reported a synthesis of an efficient composite catalyst based on Fe-N-C catalyst and Pt catalyst. The Fe-N-C catalyst was gained as described by Piotr Zelenay. Furthermore, 50mg Fe-N-C catalyst dissolved into 12ml isopropanol and 48ml ethanediol was fixed with 4.42ml H2PtCl2-ethanediol solution with a density of 20mg/ml and stirred for 3h. After making the pH of the solution 12 by 1M NaOH-ethanediol and N2 injection for 10 min, the solution was put into the microwave to heat until 130-150 degrees. After cooling to the room temperature, the pH was set as 3 by 1M HNO3. The FeNC-Pt catalyst was obtained after filtration and freeze drying. For RDE tests on the FeNC-Pt catalyst, the ink was prepared by mixing 3mg catalyst dissolved into 2.1ml isopropanol and 29µl Nafion, which was stirred for 40min to achieve a good dispersion. 7µl ink was coated on the surface of RDE, making the loading of Pt 20µg cm-2. The linear sweep voltammetry(LSV) tests were conducted at the speed of 1600rpm in O2 and N2 saturated 0.1M HClO4 solution respectively. The half-wave potential of FeNC-Pt catalysts was about 20mV higher than Pt-C catalyst(0.86V vs 0.84V), which proved a more efficient performance of FeNC-Pt catalyst. The electrochemical areas(ECA) of the catalysts were gained by cyclic voltammetry(CV) tests, and the FeNC-Pt catalyst showed a larger ECA than the Pt-C catalyst. The methanol resistance test was conducted in N2-saturated 0.5M H2SO4-0.5M CH3OH solution, and the FeNC-Pt catalyst showed a better performance. Figure 1

Synthesis of carbon nanofibers/poly(para-phenylenediamine)/nickel particles nanocomposite for enhanced methanol electrooxidation

Several studies have been conducted on direct methanol fuel cells (DMFCs) to resolve major issues such as the high cost of the catalyst and the poisoning of the electrode. Herein, a low-cost catalyst based on nickel particles (NiPs), carbon nanofibers (CNF) and poly(para-phenylenediamine) (PpPD) was carried out using a simple electrochemical method. The morphology and structure of the nanocomposite electrodes are characterized by field-emission gun scanning electron microscopy coupled with an energy dispersive X-ray detector, X-ray diffraction, Fourier transform infrared spectroscopy and Raman spectroscopy. The effects of various parameters such as the PpPD film thickness and the NiPs content on the electrocatalytic performance of CPE/CNF/PpPD/NiPs are evaluated which lead to the optimized composition. The results of the methanol electrooxidation reaction at room temperature showed that the optimized CPE/CNF/PpPD/NiPs nanocomposite exhibits a high catalytic activity (Ip = 38.11 mA cm−2), good stability and durability for more than 6 h in comparison with CPE/CNF/NiPs. These findings truly highlight the synergetic effect of CNF/PpPD in enhancing the electrochemical activity and stability and the vast potential of CPE/CNF/PpPD/NiPs as low-cost catalyst and electrodes for DMFCs.

High Methanol Electro-Oxidation Using PtCo/Reduced Graphene Oxide (rGO) Anode Nanocatalysts in Direct Methanol Fuel Cell.

The higher methanol utilization efficiency in direct methanol fuel cell (DMFC) is one of the key parameter to show the performance of an anode catalyst. Here in, we have synthesized a highly efficient and stable PtCo anode nanocatalysts (2-4 nm size) supported on reduced graphene oxide (rGO) for the electro-oxidation of methanol in a DMFC. Three different compositions of anode catalysts PtCo (1:7)/rGO, PtCo (1:9)/rGO and PtCo (1:11)/rGO comprising of 20% metal loading by weight of rGO are being investigated for methanol electro-oxidation in acidic medium with different methanol concentration using cyclic voltammetry. The electrochemical response from three different catalysts revealed that the PtCo (1:9)/rGO catalyst has efficiently oxidized 5 M methanol in a half cell configuration. A peak anodic current density of 46.8 mA/cm² and a power density of 136.8 mW/cm² are achieved using PtCo (1:9)/rGO anode catalyst at 100 °C for DMFC with 5 M methanol supply with negligible amount of methanol crossover. About 34% Faradaic efficiency and 22% energy efficiency is attained using PtCo (1:9)/rGO anode catalyst for a DMFC. Further, the 3% methanol oxidation reaction (MOR) efficiency is attained as revealed by evaluating the MOR by-products i.e., formic acid and formaldehyde formation. The results indicate excellent catalytic behavior of PtCo (1:9)/rGO towards MOR and its potential application as anode catalyst in DMFC.