New nanostructured carbons based on porous cellulose: Elaboration,pyrolysis and use as platinum nanoparticles substrate for oxygen reduction electrocatalysis

New nanostructured carbons have been prepared from pyrolysis of recently developed highly porous cellulose, aerocellulose (AC). Aerocellulose is an ultra-light and highly porous pure cellulose material prepared from cellulose gels followed by drying in carbon dioxide supercritical conditions. The carbonized aerocellulose (CAC) materials were obtained after pyrolysis of the aerocellulose under nitrogen flow at 830 °C, and subsequently doped by platinum nanoparticles. The platinum insertion process consisted of (i) thermal activation at various temperatures in CO₂ atmosphere, (ii) impregnation by PtCl₆²⁻ and (iii) platinum salt chemical reduction. The aerocellulose materials and their carbonized counterparts were investigated by scanning and transmission electron microscopy (SEM and TEM), mercury porosimetry and thermogravimetric analysis. The morphology of the platinum particles deposited on the carbonized aerocellulose materials (Pt/CAC) was investigated by transmission electron microscopy (TEM) and X-ray diffraction (XRD): the Pt particles are of 4–5 nm size, mainly agglomerated, as a result of the complex surface chemistry of the CAC. Their electrocatalytic activity was investigated by quasi-steady-state voltammetry in the rotating disk electrode (RDE) setup, regarding the oxygen reduction reaction (ORR). The Pt/CAC materials exhibit ORR specific activities comparable with those of commercial Pt/Vulcan XC72R. Their mass activity is lower, as a result of the ca. 10 times smaller specific area of platinum as compared with the commercial electrocatalyst. We nevertheless believe that provided an appropriate pyrolysis temperature is chosen, such green carbonized aerocellulose could be a promising electrocatalyst support for PEM application.     

Carbon nanotube-supported Pt-HxMoO3 as electrocatalyst for methanol oxidation

Carbon nanotube (CNT)-supported platinum modified with H_xMoO₃ (Pt-H_xMoO₃/CNT) was prepared and used as an electrocatalyst for methanol oxidation. In the preparation of this electrocatalyst, a platinum precursor was loaded on CNTs and reduced by sodium borohydride in ethylene glycol, resulting in CNT-supported platinum without modification (Pt/CNT), and then the Pt/CNT was modified with H_xMoO₃ that was formed by hydrolysis and subsequent reduction of ammonium molybdate. The surface morphology, structure and composition of Pt-H_xMoO₃/CNT and Pt/CNT as well as their activity toward methanol oxidation were investigated by transmission electron microscopy (TEM), X-ray diffraction (XRD), energy-dispersive spectrometry (EDS), Fourier transform infrared spectroscopy (FTIR), cyclic voltammetry (CV), chronoamperometry (CA), chronopentiometry (CP), and electrochemical impedance spectroscopy (EIS). The results, obtained from TEM, XRD, EDS, and FTIR, indicate that the platinum loaded on CNTs has a face-centered cubic structure with particle sizes of 2–5 nm, and the modification of H_xMoO₃ on platinum with an atom ratio of Pt:Mo = 2:1 has little effect on the particle size, distribution and structure of the platinum. The results, obtained from CV, CA, CP, and EIS, show that the Pt-H_xMoO₃/CNT exhibits higher electrocatalytic activity toward methanol oxidation and better carbon monoxide tolerance than Pt/CNT.     

Pt/carbon nanofibers electrocatalysts for fuel cells: Effect of the support oxidizing treatment

Different Pt-based electrocatalysts supported on carbon nanofibers and carbon black (Vulcan XC-72R) have been prepared using a polymer-mediated synthesis. The electrocatalysts have been characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD) and cyclic voltammetry. The effect of carbon nanofibers treatment with HNO₃ solution on Pt particle size and electroactive area has been analyzed. Highly dispersed Pt with homogeneous particle size and an electroactive area around of 100 m² g⁻¹ is obtained in raw carbon nanofibers. The oxidizing treatment of the carbon nanofibers produces agglomeration of the platinum nanoparticles and an electroactive area of 53 m² g⁻¹. Durability studies indicate a decrease of 14% in the electroactive area after 90 h at 1.2 V in 0.5 M H₂SO₄ for platinum supported on raw carbon nanofibers and Vulcan XC-72R. The electrocatalyst supported on oxidized carbon nanofibers are stable under similar conditions.     

Kinetic study of oxygen reduction reaction and PEM fuel cell performance of Pt/TiO2-C electrocatalyst

The electrochemical activity and thermal stability of the Pt/TiO₂-C were evaluated in the oxygen reduction reaction (ORR) in acid medium at different temperatures. The platinum was selectively deposited onto the TiO₂ (E_bg = 2.3 eV) by the photo-irradiation of platinum precursor (Pt⁴⁺→Pt⁰). The Pt/TiO₂-C electrocatalyst prepared was characterized by XRD, TEM/EDS, cyclic and lineal voltammetry techniques. TEM images indicated that platinum nanoparticles (<5 nm) were deposited in agglomerates form around the oxide sites. EDS and XRD results confirm the composition and crystalline structure of Pt/TiO₂-C. The thermal stability and electrochemical activity of the Pt/TiO₂-C for ORR at different temperatures (298–343 K) is higher than Pt/C commercial sample (Pt-Etek). A more favorable apparent enthalpy of activation for Pt/TiO₂-C was greatly influenced by addition of oxide in the catalyst compare to Pt-Etek. Single H₂/O₂ fuel cell performance results of Pt/TiO₂-C show an improvement of the power density with the increase of the temperature.     

The formate electrooxidation on Pt/C and PtSnO2/C nanoparticles in alkaline media: The effect of morphology and SnO2 on the platinum catalytic activity

Pt/C and PtSnO₂/C electrocatalysts with and without cubic preferential morphology were used for formate electrooxidation reaction (FER) in alkaline medium. The synthesis of catalysts was carried out by alcohol reduction method using KBr as a shape directing agent (Bromide Anion Exchange method - BAE). The X-ray diffraction (XRD) showed characteristic peaks of the Pt face-centered cubic (FCC) structure, as well as cassiterite SnO₂. The Transmission Electron Microscopy (TEM) and Scanning Transmission Electron Microscopy (STEM) micrographs show SnO₂ dispersed onto carbon support and adjacent to the Pt nanoparticles (NPs), as well as cubic Pt NPs. The cyclic voltammetry (CV) measurements show that the current density peak for FER on Pt/C (100) is 2.40 times higher than on Pt/C polycrystalline (poly). The current density at end of chronoamperometry (CA) analysis on PtSnO₂/C poly was 1.33 and 5.29 times higher than on Pt/C (100) and Pt/C poly, respectively. The presence of SnO₂ and the (100) facets of platinum cubic morphology might prevent platinum surface deactivation caused by intermediates formed during the FER process.     

Kinetics and electrocatalytic activity of IrCo/C catalysts for oxygen reduction reaction in PEMFC

The purpose of this study is to develop a novel binary Iridium-Cobalt/C catalyst as a suitable substitute for platinum/C applied in proton exchange membrane fuel cells (PEMFCs). The carbon-supported IrCo catalysts were successfully synthesized using IrCl₃ and C₄H₆CoO₄ as the Ir and Co precursors respectively, in ethylene glycol (EG) refluxing at 120 °C. The nanostructured catalysts were characterized by X-ray diffraction (XRD) and high-resolution transmission electron microscope (TEM). Homogeneous catalyst particles supported on carbon showed a size of proximately 2 nm. Cyclic voltammetry (CV) and linear sweep voltammetry (LSV) were conducted for the characterization of the catalyst performances. With a cathodic loading of 0.4 mg_Ir cm⁻², 20%Ir-30%Co/C achieved a maximum power density of 501.6 mW cm⁻² at 0.418 V, with a 50 cm² H₂/O₂ single cell. Although such a performance is about 26% lower than commercial Pt/C catalyst, it is still helpful in terms of Pt replacement and cost reduction.     

Facile synthesis of highly conducting and mesoporous carbon aerogel as platinum support for PEM fuel cells

We report novel method for synthesis of carbon aerogel as platinum support for PEM fuel cells applications. The sol gel polymerization has been carried out using resorcinol and furfuraldehyde in non-aqueous medium followed by gelation at high pressure. This resulted in highly conducting and mesoporous carbon aerogel under ambient drying conditions. Platinum nano-particles are impregnated in the mesoporous carbon aerogel using microwave assisted polyol process. The support material and the catalyst are characterized by different analytical techniques like surface area analyzer, X-ray diffraction, transmission electron microscopy and X-ray photoelectron spectroscopy. Cyclic voltammetry and linear sweep voltammetry are used to evaluate the electro–catalytic activity of the Pt/carbon aerogel catalyst using rotating disk electrode technique. Well dispersed Pt nano-particles of size ∼3 nm on carbon aerogel showed good catalytic activity with onset potential of 964 mV and half wave potential of 814 mV towards oxygen reduction reaction kinetics. A membrane electrode assembly fabricated with the prepared Pt/carbon aerogel catalyst as a cathode and anode is tested in PEMFCs (H₂O₂) single cell, the power density of 536 mW cm⁻² at 0.6 V is obtained at 60 °C under atmospheric pressure.     

Synthesis and characterization of platinum nanoparticles on in situ grown carbon nanotubes based carbon paper for proton exchange membrane fuel cell cathode

Multi-walled carbon nanotubes (MWCNTs) based micro-porous layer on the carbon paper substrates was prepared by in situ growth in a chemical vapor deposition setup. Platinum nanoparticles were deposited on in situ grown MWCNTs/carbon paper by a wet chemistry route at <100 °C. The in situ MWCNTs/carbon paper was initially surface modified by silane derivative to incorporate sulfonic acid–silicate intermediate groups which act as anchors for metal ions. Platinum nanoparticles deposition on the in situ MWCNTs/carbon paper was carried out by reducing platinum (II) acetylacetonate precursor using glacial acetic acid. High resolution TEM images showed that the platinum particles are homogeneously distributed on the outer surface of MWCNTs with a size range of 1–2 nm. The Pt/MWCNTs/carbon paper electrode with a loading of 0.3 and 0.5 mg Pt cm⁻² was evaluated in proton exchange membrane single cell fuel cell using H₂/O₂. The single cells exhibited a peak power density of 600 and 800 mW cm⁻² with catalyst loadings of 0.3 and 0.5 mg Pt cm⁻², respectively with H₂/O₂ at 80 °C, using Nafion-212 electrolyte. In order to understand the intrinsically higher fuel cell performance, the electrochemically active surface area was estimated by the cyclic voltammetry of the Pt/MWCNTs/carbon paper.     

Intermediate hydroxide enforced electrodeposited platinum film for hydrogen evolution reaction

Competitive catalytic activity of platinum (Pt) makes it as a promising cathode material for hydrogen evolution reaction. But cost of Pt makes it impractical for its use in commercial applications. Unlike literature known methods, our study entails on a methodology of ambient temperature electrodeposition of Pt films, without the use of a complexing agent or pH adjustments or both. Pt films are deposited in an electrochemical bath, which is prepared by adding platinum chloride complex [H₂PtCl₆.x H₂O] in triple-distilled water. Pt films deposited at different potentials are analyzed for their morphological (SEM), structural (XRD), electrochemical study (Cyclic Voltammetry and Linear sweep measurements). The growth and catalytic activity of Pt film show strong dependence on applied deposition potential (−0.25 V to −0.40 V) and reduction kinetics of [PtCl₆]²⁻ or [Pt(OH)Cl₅]²⁻ intermediate hydroxide ions, that occurs during the process. Binding energy (BE) of Pt(4f_7/2) peak in a film increases to 72.4 eV (until −0.30 V), which slightly decreases at a deposition potential of −0.40 V. XRD data show changes along (111) and (200) planes, to which [PtCl₆]²⁻ and [Pt(OH)Cl₅]²⁻ intermediate hydroxide ions are found to be responsible. The average particle size with respect to applied potential, obtained from SEM data is found to be 25–40 nm. The catalytic activity (Peak current density in cyclic voltammetry) versus deposition potential data is correlated with Pt film formation by reduction of intermediate hydroxide ions.     

A new durable and high performance platinum supported on Ag–Ni-porous coordination polymer as an anodic DMFC nano-electrocatalyst: DFT and experimental investigation

Due to the poor performance and intermediates poisoning of available catalysts in direct methanol fuel cells (DMFC), the researcher is confronted with a considerable challenge for obtaining modified electrocatalyst. Ag–Ni porous coordination polymer (ANP) as a new electrocatalyst supporter was synthesized by a hydrothermal method. To achieve favorable electrocatalyst for DMFC systems, platinum nanoparticles was deposited upon ANP by an electrochemical method and platinum supported on Ag–Ni porous coordination polymer (Pt-ANP) was formed. Fourier transform infrared spectroscopy (FTIR) analysis ensured correct synthesized of ANP and Pt-ANP. In addition, the morphologies investigation of ANP and Pt-ANP were carried out by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and transmission electron microscopy (TEM). The FE-SEM images indicate that the platinum nanoparticles have been greatly deposited on ANP surface. Electrochemical behaviors of prepared catalyst for methanol oxidation were evaluated by cyclic voltammetry (CV), linear sweep voltammetry (LSV), and chronoamperometry (CA) techniques. Electrochemical cyclic voltammetry tests (CV) indicate that the forward peak current density of Pt-ANP is about 105 mA/cm² which it is 33% more than the forward peak current density of pure Pt catalyst (70.21 mA/cm²). Moreover, electrochemical surface area (ECSA) of Pt-ANP is 26.42 m²/g_Pt. In addition, density functional theory (DFT) computations show that with the deposition of Pt upon ANP, the HOMO-LOMO energy gap of ANP has been decreased which they are suitable for electrochemical reactions. Theoretical results are greatly in accordance with the experiments. Based on the results, Pt-ANP could be a superior electrocatalyst for methanol oxidation.     

Kinetics of direct ethanol fuel cell based on Pt-PoPD nano particle anode catalyst

The poly(o-phenylenediamine) (PoPD) film was synthesized on the carbon ceramic electrode (CCE) surface and then platinum nano-particles were incorporated into the polymer matrix. Next the Pt|PoPD|CCE was used for ethanol electrooxidation in H₂SO₄ solution by different electrochemical techniques and the results compared with Pt|CCE. The electrocatalysts were characterized by Scanning electron microscopy (SEM), X-ray diffraction (XRD) and cyclic voltammetry (Cv). In continuation the kinetic parameters of ethanol oxidation, i.e. reaction orders for ethanol and H⁺, Tafel slope and activation energy (E_a) were determined on Pt|PoPD|CCE. Finally, chronoamperometric (CA) experiment was used for calculating of the anodic rate constant and fractal dimension. The Pt|PoPD|CCE showed high mass activity for ethanol oxidation reaction (EOR) in comparison with Pt|CCE.     

Carbon supported Pt hollow nanospheres as anode catalysts for direct borohydride-hydrogen peroxide fuel cells

The carbon supported Pt hollow nanospheres were prepared by employing cobalt nanoparticles as sacrificial templates at room temperature in aqueous solution and used as the anode electrocatalyst for direct borohydride-hydrogen peroxide fuel cell (DBHFC). The physical and electrochemical properties of the as-prepared electrocatalysts were investigated by transmission electron microscopy (TEM), X-ray diffraction (XRD), cyclic voltammetry (CV), chronoamperometry (CA), chronopotentiometry (CP) and fuel cell test. The results showed that the carbon supported Pt nanospheres were coreless and composed of discrete Pt nanoparticles with the crystallite size of about 2.8 nm. Besides, it has been found that the carbon supported Pt hollow nanospheres exhibited an enhanced electrocatalytic performance for BH₄⁻ oxidation compared with the carbon supported solid Pt nanoparticles, and the DBHFC using the carbon supported Pt hollow nanospheres as electrocatalyst showed as high as 54.53 mW cm⁻² power density at a discharge current density of 44.9 mA cm⁻².     

Platinum/vivianite bifunction catalysts for DMFC

Bi-functional catalysts are used to solve the poisoning problem caused by carbon monoxide (CO) which is the intermediate of direct methanol fuel cells (DMFCs). Flower-like vivianite (Fe₃(PO₄)₂·8H₂O) spheres with diameter around 10 μm are originally used as supports of Pt to form bifunction catalysts. The cyclic voltammetry in 1 M H₂SO₄ indicates that the electrochemical surface area (ECSA) of Pt reduced on as-prepared vivianite (Pt/Vi) was 105, greater than 91 m² g⁻¹ for the commercial Pt/C. Besides, Pt/Vi reveals the less CO poisoning effects, including the greater mass activity in methanol oxidation and the lower onset potential in CO-stripping than Pt/C. These excellent performances on electrolyzes are related to the chemical state of Fe³⁺ and the coexistence of Pt⁰ and Pt²⁺ in Pt/Vi. The former activates the water and yields Fe-OH_ads at lower potential and the latter may offer an easy way of electron transition.     

Polybenzimidazole-modified carbon nanotubes as a support material for platinum-based high-temperature proton exchange membrane fuel cell electrocatalysts

We fabricate polybenzimidazole (PBI) wrapped carbon nanotubes (MWCNTs) as support material for platinum-based fuel cell electrocatalyst. With the aid of microwave-assisted polyol reduction, we obtain very fine platinum (Pt) nanoparticles on PBI/MWCNT support while reducing the amount of Pt waste during synthesis. Cyclic voltammetry (CV) concludes that Pt-PBI/MWCNT has 43.0 m² g⁻¹ of electrochemically active surface area (ECSA) to catalyze hydrogen oxidation. Furthermore, after the 1000th cycle, Pt-PBI/MWCNT preserves almost 80% of its maximum ECSA, meaning that Pt-PBI/MWCNT is much more durable than the Pt/MWCNT and commercial Pt/C. High-temperature proton exchange membrane fuel cell (HT-PEMFC) performance tests are conducted under H₂/Air conditions at the temperatures ranging from 150 °C to 180 °C. Nevertheless, tests conclude that the maximum power density values of the Pt-PBI/MWCNT are found inferior to the Pt/C at all temperatures (e.g., 47 vs. 62 mW cm⁻² at 180 °C), suggesting that some balance between durability and performance has to be taken into consideration.     

Low Pt-loading Ni-Pt and Pt deposits on Ni: Preparation, activity and investigation of electronic properties

A unique, self-limiting, galvanostatic deposition was used to synthesize co-deposits of Ni and Pt onto nickel substrates from sonicated solutions of 0.2 M NiCl₂ in 2.0 M NH₄Cl, with a platinum blacked counter electrode as the sole platinum source. Depositions of only Pt onto the nickel substrates were also performed using this method. Cyclic voltammetry, chronoamperometry, carbon monoxide stripping voltammetry, inductively coupled plasma mass spectrometry, scanning electron microscopy, energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy were performed on the deposits. Results demonstrate that, due to the self-regulating nature of this deposition, the Pt-content of the co-deposits does not exceed 8 mol% loading and most of the Pt resides at or near the catalyst surface. The surface atom normalized activities of the co-deposits (Ni-Pt on Ni foam) and Pt-only deposits (Pt on Ni foam) were up to 37 times higher than platinum black towards 2-propanol electro-oxidation in base at 500 mV vs. RHE; the order of activity is Pt on Ni foam ? Ni-Pt on Ni foam > Pt black. The Ni-Pt and Pt on Ni foam catalysts are more active than Pt black at >500 mV mainly via the bi-functional mechanism and some electronic effects. The Pt on Ni foam was the most superior catalyst due to a combination of geometric and bi-functional effects.     

The performance and degradation of Pt electrocatalysts on novel carbon carriers for PEMFC applications

Electrocatalyst stability is an important factor influencing the performance of polymer electrolyte membrane (PEM) fuel cells and is essential in maintaining the cell output. The aim of this work was to elucidate factors which influence the stability of platinum supported onto graphitic nanofibres (Pt/GNFs) and to compare the performance of these materials with the commonly used Pt/Vulcan electrocatalyst. Platinum nanoparticles (average diameter of 6.9 nm) were supported on GNFs which were prepared by chemical vapour deposition over an unsupported nickel oxide (NiO) catalyst precursor. The performance of Pt/GNFs based electrodes were studied by cyclic voltammetry and a single-cell fuel cell test and were compared with a commercially available carbon nanostructure, Vulcan XC-72, which was also impregnated with Pt nanoparticles. Characterisation of the pre- and post-operation of the Pt/GNFs by XRD and TEM showed that structural changes of the Pt had occurred during testing. It was found that the average diameter of each grain and the degree of agglomeration among particles was increased, creating elongated clusters of Pt along the carbon fibre. Analysis of electrocatalyst post-operation also identified that the sulphate from the Nafion membrane was reacting with the Pt surface forming platinum sulphide (PtS). These phases were confirmed by the presence of low intensity, but sharp XRD peaks, attributed to a few large diameter particles (49 nm). These two factors resulted in current density dropping from 0.2 A/cm² to 0.1 A/cm² (at 0.70 V) over a 25 h test period.     

Mesoporous tungsten carbide-supported platinum as carbon monoxide-tolerant electrocatalyst for methanol oxidation

This paper reports a CO-tolerant electrocatalyst, mesoporous tungsten carbide-supported platinum (Pt/m-WC), for methanol oxidation. The support m-WC was synthesized by evaporation-induced triconstituent co-assembly method in which phenol formaldehyde polymer resin was used as the carbon precursor, tungsten hexachloride as the tungsten precursor and an amphiphilic triblock copolymers (P123) as the template. Nano-sized platinum particles were loaded on the m-WC to prepare Pt/m-WC. The structure and morphology of the prepared electrocatalyst were characterized by transmission electron microscopy (TEM), Brunauer–Emmett–Teller (BET) and X-ray diffraction (XRD), and its activity toward methanol oxidation and its tolerance for CO were determined by cyclic voltammetry (CV) and chronopotentiometry (CP). It is found that the m-WC carburized at 900 °C(m-WC-900) has a larger specific surface area (182 m² g⁻¹) and a appropriate crystal structure compared to the m-WC carburized at 800 °C or 1000 °C, and thus is better as the support of platinum. The prepared Pt/m-WC-900 exhibits higher activity toward methanol oxidation and better tolerance for CO than Pt/Vulcan XC-72. The onset potential of CO electro-oxidation on Pt/m-WC is 0.449 V, which is more negative than that on Pt/Vulcan XC-72 (0.628 V).     

Studies of electrochemical performance of carbon supported Pt-Cu nanoparticles as anode catalysts for direct borohydride-hydrogen peroxide fuel cell

Carbon supported Pt-Cu bimetallic nanoparticles are prepared by a modified NaBH₄ reduction method in aqueous solution and used as the anode electrocatalyst of direct borohydride-hydrogen peroxide fuel cell (DBHFC). The physical and electrochemical properties of the as-prepared electrocatalysts are investigated by transmission electron microscopy (TEM), X-ray diffraction (XRD), cyclic voltammetry (CV), chronoamperometry (CA), chronopotentiometry (CP) and fuel cell test. The results show that the carbon supported Pt-Cu bimetallic catalysts have much higher catalytic activity for the direct oxidation of BH₄⁻ than the carbon supported pure nanosized Pt catalyst, especially the Pt₅₀Cu₅₀/C catalyst presents the highest catalytic activity among all as-prepared catalysts, and the DBHFC using Pt₅₀Cu₅₀/C as anode electrocatalyst and Pt/C as cathode electrocatalyst shows as high as 71.6 mW cm⁻² power density at a discharge current density of 54.7 mA cm⁻² at 25 °C.     

Preparation and activity of carbon-supported porous platinum as electrocatalyst for methanol oxidation

In this paper, we reported a novel electrocatalyst, Vulcan XC-72-supported porous platinum nano-particles (Pt_p/C) for methanol oxidation. In the preparation of Pt_p/C, platinum precursor was first adsorbed on carbon and then reduced by l-ascorbic acid in ethylene glycol solution. The structure and morphology of Pt_p/C and its activity toward methanol oxidation were characterized by transmission electron microscopy (TEM), Brunauer–Emmett–Teller (BET) measurement, X-ray diffraction (XRD), energy-dispersion spectrometer (EDS), cyclic voltammetry (CV), and chronoamperometry (CA), with a comparison of the electrocatalyst prepared with sodium borohydride as reducer (Pt_s/C). It is found that both electrocatalysts have similar particle size but have different surface morphology of platinum and thus exhibit different electrocatalytic activity toward methanol oxidation. The platinum particle size of both electrocatalysts is 3–5 nm, but the corresponding BET surface areas are different significantly, 131.6 m² g⁻¹ and 87.7 m² g⁻¹ for Pt_p/C and Pt_s/C, respectively, indicative of the porous structure of platinum particles in Pt_p/C. The peak current for methanol oxidation on CV is 167 mA mg⁻¹ and 44 mA mg⁻¹ for Pt_p/C and Pt_s/C, respectively, indicative of the high electrocataytic activity of Pt_p/C toward methanol oxidation. The result from CA shows that Pt_p/C has good stability as the electrocatalyst for methanol oxidation.     

Performance of carbon-supported PtPd as catalyst for hydrogen oxidation in the anodes of proton exchange membrane fuel cells

In this work, the replacement of platinum by palladium in carbon-supported catalysts as anodes for hydrogen oxidation reaction (HOR), in proton exchange membrane fuel cells (PEMFCs), has been studied. Anodes with carbon-supported Pt, Pd, and equiatomic Pt:Pd, with various Nafion^® contents, were prepared and tested in H₂|O₂ (air) PEMFCs fed with pure or CO-contaminated hydrogen. An electrochemical study of the prepared anodes has been carried out in situ, in membrane electrode assemblies, by cyclic voltammetry and CO electrooxidation voltammetry. The analyses of the corresponding voltammograms indicate that the anode composition influences the cell performance. Single cell experiments have shown that platinum could be replaced, at least partially, saving cost with still good performance, by palladium in the hydrogen diffusion anodes of PEMFCs. The performance of the PtPd catalyst fed with CO-contaminated H₂ used in this work is comparable to Pt, thus justifying further work varying the CO concentration in the H₂ fuel to assert its CO tolerance and to study the effect of the Pt:Pd atomic ratio.