Methoxy methane (dimethyl ether) as an alternative fuel for direct fuel cells

The electrooxidation of methoxy methane (dimethyl ether) was studied at different Pt-based electrocatalysts in a standard three-electrode electrochemical cell. It was shown that alloying platinum with ruthenium or tin leads to shift the onset of the oxidation wave towards lower potentials. On the other hand, the maximum current density achieved was lower with a bimetallic catalyst compared to that obtained with a Pt catalyst. The direct oxidation of dimethoxy methane in a fuel cell was carried out with Pt/C, PtRu/C and PtSn/C catalysts. When Pt/C catalyst is used in the anode, it was shown that the pressure of the fuel and the temperature of the cell played important roles to enhance the fuel cell electrical performance. An increase of the pressure from 1 to 3 bar leads to multiply by two times the maximum achieved power density. An increase of the temperature from 90 to 110 °C has the same effect. When PtRu/C catalyst is used in the anode, it was shown that the electrical performance of the cell was only a little bit enhanced. The maximum power density only increased from 50 to 60 mW cm⁻² at 110 °C using a Pt/C anode and a Pt_0.8Ru_0.2/C anode, respectively. But, the maximum power density is achieved at lower current densities, i.e. higher cell voltages. The addition of ruthenium to platinum has other effect: it introduces a large potential drop at relatively low current densities. With the Pt_0.5Ru_0.5/C anode, it has not been possible to applied current densities higher than 20 mA cm⁻² under fuel cell operating conditions, whereas 250 and almost 400 mA cm⁻² were achieved with Pt_0.8Ru_0.2/C and Pt/C anodes. The Pt_0.9Sn_0.1/C anode leads to higher power densities at low current densities and to the same maximum power density as the Pt/C anode.     

Polyol-synthesized PtRu/C and PtRu black for direct methanol fuel cells

PtRu/C and PtRu black catalysts with nominal Pt:Ru atomic ratio of 1:1 are prepared by a modified polyol process (co-reduction of metal precursor salts) as anode catalysts for direct methanol fuel cells (DMFCs). Without the carbon support, PtRu nanoparticles tend to agglomerate, while the PtRu nanoparticles in PtRu/C have a good dispersion as shown by TEM. Both PtRu black and PtRu/C have the almost same alloy degree indicated by XRD, but PtRu supported on carbon could improve the influence of Ru on Pt toward methanol oxidization as shown by cyclic voltammetry. The microstructure of PtRu/C is further studied by high-resolution transmission electron microscopy (HRTEM), and the results indicate that the lattice constant of Pt in PtRu electrocatalyst has contracted despite a few parts of Pt not alloyed with Ru due to the lattice constant of Pt without contracting, which is further proved by the results of temperature-programmed reduction (TPR). Such parts of unalloyed Ru are further proved to have ability to reduce the methanol oxidation potential on Pt by comparing the catalytic behaviors of Pt/C and Pt + Ru/C prepared by mixing carbon with separately prepared Pt and Ru colloids. Moreover, the catalytic behaviors of PtRu black and PtRu/C are also compared with those of commercial ones.     

High voltage stability of nanostructured thin film catalysts for PEM fuel cells

This paper provides a comparative evaluation of electrocatalyst surface area stability in PEM fuel cells under accelerated durability testing. The two basic electrocatalyst types are conventional carbon-supported dispersed Pt catalysts (Pt/C), and nanostructured thin film (NSTF) catalysts. Both types of fuel cell electrocatalysts were exposed to continuous cycling between 0.6 and 1.2 V, at various temperatures between 65 and 95 °C, with H₂/N₂ on the anode and cathode, while periodic measurements of electrochemical surface area were recorded as a function of the number of cycles. The NSTF electrocatalyst surface areas were observed to be significantly more stable than the Pt/C electrocatalysts. A first order rate kinetic model was applied to the normalized surface area changes as a function of number of cycles and temperature, and two parameters extracted, viz. the minimum stable surface area, S_min, and the activation energy, E_a, for surface area loss in this voltage range. S_min was found to be 10% versus 66%, and E_a 23 kJ mole⁻¹ versus 52 kJ mole⁻¹, for Pt/C versus NSTF-Pt, respectively. The loss of surface area in both cases is primarily the result of Pt grain size increases, but the Pt/C XRD grain sizes increase significantly more than the NSTF grain sizes. In addition, substantial peak shifts occur in the Pt/C CVs, which ultimately end up aligning with the NSTF peak positions, which do not change substantially due to the voltage cycling. NSTF catalysts should be more robust against shut down/start-up, operation near OCV and local H₂ starvation effects.     

A study on composite PtRu(1:1)-PtSn(3:1) anode catalyst for PEMFC

Composite PtRu(1:1)/C-PtSn(3:1)/C catalyst layers with various geometries and loadings were designed for a proton exchange membrane fuel cell (PEMFC) anode to improve carbon monoxide (CO) tolerance of the conventional PtRu(1:1)/C catalyst. The idea was based on an experimental finding that the onset potential of the PtSn for CO oxidation was lower than that of the PtRu and the resultant expectation that there seemed to be a possibility of using the PtSn as a CO filter. The CO tolerance of the composite catalyst of each design was judged by the cell performance obtained through a single cell test using H₂/CO gases of various CO concentrations and compared to that of the PtRu/C catalyst. The highest CO tolerance among the composite catalysts tested in this study was obtained for the one with geometry of double layers in the order of PtRu/C and PtSn/C from the electrolyte layer and with respective PtRu and PtSn loadings of 0.25 and 0.12 mg cm⁻². The cell with this composite catalyst showed better performance than the one with the PtRu/C catalyst. When a H₂/100 ppmCO gas was used as the fuel in the single cell test, the cell voltages were measured to be 0.49 and 0.44 V at a current density of 500 mA cm⁻², respectively for the cell with the composite and PtRu/C catalyst.     

Performance of direct methanol fuel cell using carbon nanotube-supported Pt–Ru anode catalyst with controlled composition

The performance of a single-cell direct methanol fuel cell (DMFC) using carbon nanotube-supported Pt–Ru (Pt–Ru/CNT) as an anode catalyst has been investigated. In this study, the Pt–Ru/CNT electrocatalyst was successfully synthesized using a modified polyol approach with a controlled composition very close to 20 wt.%Pt–10 wt.%Ru, and the anode was prepared by coating Pt–Ru/CNT electrocatalyst on a wet-proof carbon cloth substrate with a metal loading of about 4 mg cm⁻². A commercial gas diffusion electrode (GDE) with a platinum black loading of 4 mg cm⁻² obtained from E-TEK was employed as the cathode. The membrane electrode assembly (MEA) was fabricated using Nafion^® 117 membrane and the single-cell DMFC was assembled with graphite endplates as current collectors. Experiments were carried out at moderate low temperatures using 1 M CH₃OH aqueous solution and pure oxygen as reactants. Excellent cell performance was observed. The tested cell significantly outperformed a comparison cell using a commercial anode coated with carbon-supported Pt–Ru (Pt–Ru/C) electrocatalyst of similar composition and loading. High conductivity of carbon nanotube, good catalyst morphology and suitable catalyst composition of the prepared Pt–Ru/CNT electrocatalyst are considered to be some of the key factors leading to enhanced cell performance.     

One-step preparation and characterization of PtRu (1:1)/C electrocatalysts by polyol method for polymer electrolyte fuel cells

A one-step process is designed for the preparation of PtRu (1:1) electrocatalysts by the polyol method. Following investigations with an UV–vis spectrophotometer and an inductive-coupled plasma atomic emission spectrophotometer, it is found that an equimolar solution of Pt and Ru salts dissolved in ethylene glycol at temperatures above 190 °C is essential for the formation of the PtRu (1:1) solid solution. X-ray diffraction analysis is used to characterize the composition and size of the prepared electrocatalysts. The lattice parameter is 3.8663 Å, which corresponds to the value for a PtRu solid solution of equiatomic composition and this atomic ratio is confirmed by energy dispersive X-ray spectroscopy. Based on the Scherrer formula, the average particle size of the electrocatalysts is estimated to be 2.6 nm. It is confirmed by transmission electron microscopy that the nanoparticles are distributed uniformly on carbon, Vulcan XC 72. According to the results of unit cell test and CO-stripping voltammetry, the performance of the prepared electrocatalyst is comparable with that of a commercial one of the same composition.     

Carbon supported Pt70Co30 electrocatalyst prepared by the formic acid method for the oxygen reduction reaction in polymer electrolyte fuel cells

Carbon supported Pt and Pt₇₀Co₃₀ electrocatalysts for the oxygen reduction reaction (ORR) were prepared by reduction with formic acid and tested in polymer electrolyte fuel cells. In the presence of Co an increase of the Pt particle size was observed in the as-prepared electrocatalyst and no evidence of Pt–Co alloy formation was detected from XRD measurements. Following thermal treatment (TT) at 900 °C of the Pt₇₀Co₃₀/C electrocatalyst, the presence in the XRD pattern of secondary Pt reflexions shifted to higher angles indicated partial alloy formation. The fuel cell performance with the as-prepared Pt₇₀Co₃₀/C electrocatalyst was inferior than that with Pt/C. The electrocatalytic activity increased with a TT of the binary electrocatalyst, and the value of the mass activity of the Pt₇₀Co₃₀/C electrocatalyst thermally treated at 900 °C was only slightly lower than that of Pt/C, notwithstanding the larger metal particle size, about five times that of pure Pt. On the other hand, there was a remarkable increase of the specific activity for the ORR of the Co-containing catalyst after TT at 900 °C with respect to Pt alone, which was ascribed to both the increased metal particle size and alloy formation. At high current densities the performance of PEMFC electrodes decreased with increasing Pt particle size.     

CO tolerance of nano-architectured Pt–Mo anode electrocatalysts for PEM fuel cells

PEM fuel cell membrane electrode assemblies with Nafion electrolytes and commercial Pt-based cathodes were tested with Pt_0.8Mo_0.2 alloy and MoO_x@Pt core–shell anode electrocatalysts for CO tolerance and short-term stability to corroborate earlier thin-film RDE results. Polarization curves at 70 °C for the Pt_0.8Mo_0.2 alloy in H₂ with 25–1000 ppm CO showed a significant increase in CO tolerance based on peak power densities in comparison to PtRu electrocatalysts. MoO_x@Pt core–shell electrocatalysts, which showed extremely high activity for H₂ in 1000 ppm CO during RDE studies, performed relatively poorly in comparison to the Pt_0.8Mo_0.2 and PtRu alloys for the same total catalyst loading on a per area basis in MEA testing. The discrepancy is attributed to residual stabilizer from the core–shell synthesis impacting catalyst-ionomer interfaces. Nonetheless, the MoO_x@Pt electrochemical performance is superior on a per-gram-of-precious-metal basis to the Pt_0.8Mo_0.2 electrocatalyst for CO concentrations below 100 ppm. Due to cross-membrane Mo migration, the stability of the Mo-containing anode electrocatalysts remains a challenge for developing stable enhanced CO tolerance for low-temperature PEM fuel cells.     

Effect of temperature on the mechanism of ethanol oxidation on carbon supported Pt,PtRu and Pt3Sn electrocatalysts

The electrochemical oxidation of ethanol on carbon supported Pt, PtRu and Pt₃Sn catalysts was studied in acid solutions at room temperature and in direct ethanol fuel cells (DEFC) in the temperature range 70–100 °C. In all the experiments, an enhancement of the activity for the ethanol oxidation was observed on the binary catalysts. In acid solution the improvement at low current densities was higher on PtRu than on Pt₃Sn. In DEFC tests, at 70 °C the cells with PtRu and Pt₃Sn showed about the same performance, while for T > 70 °C the cells with Pt₃Sn as anode material performed better than those with PtRu as anode material. The apparent activation energy for ethanol oxidation on PtRu catalyst was lower than on Pt₃Sn, particularly at high cell potentials, i.e. at low current densities. At low temperatures and/or low current densities, the positive effect of Ru oxides on the bifunctional mechanism determined the enhancement of activity for the ethanol oxidation reaction, while at high temperatures the positive effect of Sn alloying (enlarged lattice parameter) on CH₃CH₂OH adsorption and C–C cleavage prevails.     

Boosting CO tolerance and stability of Pt electrocatalyst supported on sulfonated carbon nanotubes

CO tolerance and stability are of prominent importance for the anodic electrocatalyst utilized in direct methanol fuel cells (DMFCs). Due to the electrochemical instability of Ru atoms, the state-of-the-art DMFC anodic electrocatalyst (PtRu/C) is unable to survive for long time. Here, we report a newly designed Pt electrocatalyst with robust CO tolerance and stability after coating with poly(vinyl pyrrolidone) (PVP). Electrochemically active surface area (ESA) is negligibly affected by the PVP decoration; meanwhile, almost undetectable ESA loss is obtained for the PVP decorated Pt electrocatalyst. However, the ESA degradations for non-decorated and commercial CB/Pt electrocatalysts are found to be 30% and 40%, respectively. The improved stability is ascribed to the strong interaction between PVP and sulfonated carbon nanotubes. Also, the CO tolerance evaluated from the methanol oxidation reaction is ∼3 and 3.5 fold higher compared to non-decorated and commercial CB/Pt electrocatalysts, respectively, which is attributed to the hydrophilic PVP polymer accelerating the water absorption and formation of Pt(OH)_ads species to re-activate nearby CO poisoned Pt nanoparticles. Thus, decoration with PVP polymer can simultaneously promote the stability and CO anti-poisoning of Pt electrocatalyst.     

High performance rare earth oxides LnOx (Ln = Sc,Y, La,Ce, Pr and Nd) modified Pt/C electrocatalysts for methanol electrooxidation

In this paper, the LnO_x (Ln = Sc, Y, La, Ce, Pr and Nd) modified Pt/C catalysts were prepared by wet precipitation and reduction method. The catalysts were characterized by transmission electron microscopy (TEM), energy dispersive X-ray analysis (EDX) and X-ray diffraction (XRD). TEM showed that the Pt-PrO_x nanoparticles were uniformly dispersed on carbon with an average particle size of 5.0 nm in the Pt₃-(PrO_x)₁/C catalyst. EDX showed that Pt and Pr were successfully loaded on the carbon support without obvious loss. XRD showed that all the Pt/C and LnO_x modified Pt/C electrocatalysts (except for the Pt₃-(ScO_x)₁/C electrocatalyst) displayed the typical character of Pt face centered cubic (fcc) phase, whereas the Pt₃-(ScO_x)₁/C electrocatalyst contained the diffraction pattern of Pt face centered cubic and Sc₂O₃ phase. LnO_x modified Pt/C electrocatalysts were compared with Pt/C in terms of the electrochemical activity and stability for methanol electrooxidation using cyclic voltammetry (CV) and chronoamperometry (CA) in 0.5 M H₂SO₄ + 0.5 M CH₃OH solutions. The results showed that all the LnO_x (except for NdO_x) modified the Pt/C electrocatalysts gave higher catalytic activity and stability than Pt/C. In particular, the Pt₃-(PrO_x)₁/C eloctrocatalyst was found to be superior than others. Under this respect, several Pt-PrO_x/C catalysts with different atomic ratio of Pt/Pr were also identically prepared and characterized. It was found by CV and CA that the Pt₃-(PrO_x)₁/C and Pt₁-(PrO_x)₁/C catalysts showed better catalytic activity and stability than the Pt₅-(PrO_x)₁/C, Pt₁-(PrO_x)₃/C and Pt/C catalysts. The Pt₃-(PrO_x)₁/C and Pt₁-(PrO_x)₁/C catalysts had high catalytic activity and good stability, which could be used as novel electrocatalysts for direct methanol fuel cell.     

Ethanol electrooxidation on Pt/C and Pd/C catalysts promoted with oxide

This research aims to investigate Pd-based catalysts as a replacement for Pt-based catalysts for ethanol electrooxidation in alkaline media. The results show that Pd/C has a higher catalytic activity and better steady-state behaviour for ethanol oxidation than that of Pt/C. The effect of the addition of CeO₂ and NiO to the Pt/C and Pd/C electrocatalysts on ethanol oxidation is also studied in alkaline media. The electrocatalysts with a weight ratio of noble metal (Pt, Pd) to CeO₂ of 2:1 and a noble metal to NiO ration 6:1 show the highest catalytic activity for ethanol oxidation. The oxide promoted Pt/C and Pd/C electrocatalysts show a higher activity than the commercial E-TEK PtRu/C electrocatalyst for ethanol oxidation in alkaline media.     

Experimental investigation on DMFCs using reduced noble metal loading with NiTiO3 as supportive material to enhance cell performances

In this present work, the effect of anode electrocatalyst materials is investigated by adding NiTiO₃ with Pt/C and Pt-Ru/C for the performance enhancement of direct methanol fuel cells (DMFCs). The supportive material NiTiO₃/C has been synthesized first by wet chemical method followed by incorporation of Pt and Pt-Ru separately. Experiments are conducted with the combination of four different electrocatalyst materials on the anode side (Pt/C, Pt-NiTiO₃/C, PtRu/C, Pt-Ru-NiTiO₃/C) and with commercial 20 wt % Pt/C on the cathode side; 0.5 mg_pt/cm² loading is maintained on both sides. The performance tests of the above catalysts are conducted on 5 cm² active area with various operating conditions like cell operating temperatures, methanol/water molar concentrations and reactant flow rates. Best performing operating conditions have been optimized. The maximum peak power densities attained are 13.30 mW/cm² (26.6 mW/mg_pt) and 14.60 mW/cm² (29.2 mW/mg_pt) for Pt-NiTiO₃/C and Pt-Ru-NiTiO₃/C at 80 °C, respectively, with 0.5 M concentration of methanol and fuel flow rate of 3 ml/min (anode) and oxygen flow rate of 100 ml/min (cathode). Besides, 5 h short term stability tests have been conducted for PtRu/C and Pt-NiTiO₃/C. The overall results suggest that the incorporation of NiTiO₃/C supportive material to Pt and Pt-Ru appears to make a promising anode electrocatalysts for the enhanced DMFC performances.     

Electrodeposited PtRu on cryogel carbon–Nafion supports for DMFC anodes

For a high catalytic activity of the anodes in DMFC at low noble metal content a fine dispersion of PtRu on carbon supports is required and to this purpose we prepared and investigated high specific surface area cryogel carbons of controlled mesoporosity. Two carbons CC1 and CC2 with pore-size distribution centered at 6 and 20 nm were obtained by sol–gel polycondensation of resorcinol and formaldehyde, followed by a freeze-drying procedure, a versatile and low-cost method to provide after pyrolysis carbons of controlled porosity. Electrodeposited PtRu on CC2-Nafion support with ca. 100 μg cm⁻² of Pt displayed a good catalytic activity for methanol oxidation of 85 mA mg⁻¹ of Pt after 600 s at 492 mV versus NHE and 60 °C in H₂SO₄ 0.1 M–CH₃OH 0.5 M when the Pt-to-C mass ratio was ca. 10%. The catalytic activity tests and XRD and SEM analyses demonstrated the stability of the prepared electrodes upon catalysis in the time scale of our measurements. Strategies to further increase the catalytic activity of the PtRu/cryogel carbon–Nafion electrodes for methanol oxidation are discussed.     

The influence of carbon support porosity on the activity of PtRu/Sibunit anode catalysts for methanol oxidation

In this paper we analyse the promises of homemade carbon materials of Sibunit family prepared through pyrolysis of natural gases on carbon black surfaces as supports for the anode catalysts of direct methanol fuel cells. Specific surface area (S_BET) of the support is varied in the wide range from 6 to 415 m² g⁻¹ and the implications on the electrocatalytic activity are scrutinized. Sibunit supported PtRu (1:1) catalysts are prepared via chemical route and the preparation conditions are adjusted in such a way that the particle size is constant within ±1 nm in order to separate the influence of support on the (i) catalyst preparation and (ii) fuel cell performance. Comparison of the metal surface area measured by gas phase CO chemisorption and electrochemical CO stripping indicates close to 100% utilisation of nanoparticle surfaces for catalysts supported on low (22–72 m² g⁻¹) surface area Sibunit carbons. Mass activity and specific activity of PtRu anode catalysts change dramatically with S_BET of the support, increasing with the decrease of the latter. 10%PtRu catalyst supported on Sibunit with specific surface area of 72 m² g⁻¹ shows mass specific activity exceeding that of commercial 20%PtRu/Vulcan XC-72 by nearly a factor of 3.     

Performance of direct ammonia fuel cell with PtIr/C,PtRu/C,and Pt/C as anode electrocatalysts under mild conditions

While ammonia (NH₃) is an attractive alternative to pure hydrogen, its direct use in fuel cells is fraught with difficulties. A direct ammonia fuel cell (DAFC) with PtIr/C (Pt:Ir = 1:1), PtRu/C (Pt:Ru = 1:1), and Pt/C anode electrocatalyst was investigated at 25 °C and 100 kPa inlet gas pressure. Due to the synergistic and electronic effects of the PtIr alloy, their open-circuit voltages (OCVs) were rated as PtIr/C > PtRu/C > Pt/C, with the DAFC with PtIr/C anode achieving the highest OCV of 0.50 V and peak power density (PPD) of maximum 1.68 mW cm^?2. Meanwhile, an online Fourier transform infrared (FTIR) spectrometer detected an increase in ammonia permeation in the cathode exhaust gas, indicating a possibility of fuel permeation and cathode electrocatalyst degradation. The degradation of DAFC efficiency with rising cycle numbers may be due to ammonia cross-over and poisoning over the surface of the electrocatalyst.     

A study of oxygen reduction on improved Pt-WC/C electrocatalysts

Pt on a tungsten carbide nanocrystalline support (Pt-WC/C) has been prepared by the direct reduction of a platinum salt precursor combined with intermittent microwave heating (IMH). The Pt-WC/C electrocatalyst shows better performance for oxygen reduction in acidic media than that of pure Pt/C or Pt-WC/C prepared by a mechanical mixing method. The results reveal that the Pt-WC/C electrocatalyst prepared by present method is very active for oxygen reduction reaction (ORR) with an onset potential of 1.05 V versus standard hydrogen electrode (SHE) at ambient temperature, which is over 150 mV more positive compared to that of commercial Pt/C electrocatalysts.     

Particle size dependence of CO tolerance of anode PtRu catalysts for polymer electrolyte fuel cells

An anode catalyst for a polymer electrolyte fuel cell must be CO-tolerant, that is, it must have the function of hydrogen oxidation in the presence of CO, because hydrogen fuel gas generated by the steam reforming process of natural gas contains a small amount of CO. In the present study, PtRu/C catalysts were prepared with control of the degree of Pt-Ru alloying and the size of PtRu particles. This control has become possible by a new method of heat treatment at the final step in the preparation of catalysts. The CO tolerances of PtRu/C catalysts with the same degree of Pt-Ru alloying and with different average sizes of PtRu particles were thus compared. Polarization curves were obtained with pure H₂ and CO/H₂ (CO concentrations of 500-2040 ppm). It was found that the CO tolerance of highly dispersed PtRu/C (high dispersion (HD)) with small PtRu particles was much higher than that of poorly dispersed PtRu/C (low dispersion (LD)) with large metal particles. The CO tolerance of PtRu/C (HD) was higher than that of any commercial PtRu/C. The high CO tolerance of PtRu/C (HD) is thought to be due to efficient concerted functions of Pt, Ru, and their alloy.     

Evaluating the impact of enhanced anode CO tolerance on performance of proton-exchange-membrane fuel cell systems fueled by liquid hydrocarbons

Recent advances in anode electrocatalysts for low-temperature PEM fuel cells are increasing tolerance for CO in the H₂-rich anode stream. This study explores the impact of potential improvements in CO-tolerant electrocatalysts on the system efficiency of low-temperature Nafion-based PEM fuel cell systems operating in conjunction with a hydrocarbon autothermal reformer and a preferential CO oxidation (PROx) reactor for CO clean-up. The incomplete H₂ clean-up by PROx reactors with partial CO removal can present conditions where CO-tolerant anode electrocatalysts significantly improve overall system efficiency. Empirical fuel cell performance models were based upon voltage-current characteristics from single-cell MEA tests at varying CO concentrations with new Pt-Mo alloy reformate-tolerant electrocatalysts tested in conjunction with this study. A system-level model for a liquid-fueled PEM fuel cell system with a 5 kW full power output is used to study the trade-offs between the improved performance with decreased CO concentration and the increased penalties from the air supply to the PROx reactor and associated reduction in H₂ partial pressures to the anode. As CO tolerance is increased over current state-of-the-art Pt alloy catalysts, system efficiencies improve due primarily to higher fuel cell voltages and to a lesser extent to reductions in parasitic loads. Furthermore, increasing CO tolerance of anode electrocatalysts allows for the potential for reduced system costs with minimal efficiency penalty by reducing PROx reactor size through reduced CO conversion requirements.     

PtM/C (M = Sn,Ru, Pd,W) based anode direct ethanol–PEMFCs: Structural characteristics and cell performance

In the present work, the role of the structural characteristics of Pt-based catalysts on the single direct ethanol proton exchange membrane fuel cell (PEMFC) performance is examined. Several PtM/C (M = Sn, Ru, Pd, W) catalysts were characterized by means of transmission electron microscopy (TEM) and X-ray diffraction (XRD) and then evaluated as anode catalysts in single direct ethanol fuel cells. XRD spectra showed that Pt lattice parameter decreases with the addition of Ru or Pd and increases with the addition of Sn or W. According to the obtained experimental results, PtSn catalysts presented better electrocatalytic activity towards ethanol electro-oxidation. Based on these results, PtSn/C catalysts with different Pt/Sn atomic ratio were tested and compared. The maximum power density values obtained were correlated with the structural characteristics of the catalysts. A volcano type behaviour between the fuel cell maximum power density and the corresponding atomic percentage of Sn (Sn%) was observed. It was also observed that Sn% affects almost linearly the Pt_xSn_y catalysts’ lattice parameter.