Catalyst Support In Fuel Cells Research Articles

Designing fuel cell catalyst support for superior catalytic activity and low mass-transport resistance

The development of low-Platinum content polymer electrolyte fuel cells (PEFCs) has been hindered by inexplicable reduction of oxygen reduction reaction (ORR) activity and unexpected O2 mass transport resistance when catalysts have been interfaced with ionomer in a cathode catalyst layer. In this study, we introduce a bottom-up designed spherical carbon support with intrinsic Nitrogen-doping that permits uniform dispersion of Pt catalyst, which reproducibly exhibits high ORR mass activity of 638 ± 68 mA mgPt−1 at 0.9 V and 100% relative humidity (RH) in a membrane electrode assembly. The uniformly distributed Nitrogen-functional surface groups on the carbon support surface promote high ionomer coverage directly evidenced by high-resolution electron microscopy and nearly humidity-independent double layer capacitance. The hydrophilic nature of the carbon surface appears to ensure high activity and performance for operation over a broad range of RH. The paradigm challenging large carbon support (~135 nm) combined with favourable ionomer film structure, hypothesized recently to arise from the interactions of an ionic moiety of the ionomer and Nitrogen-functional group of the catalyst support, results in an unprecedented low local oxygen transport resistance (5.0 s cm−1) for ultra-low Pt loading (34 ± 2 μgPt cm−2) catalyst layer.

The Synthesis of Activated Carbon from Waste Tyre as Fuel Cell Catalyst Support

The Synthesis of Activated Carbon from Waste Tyre as Fuel Cell Catalyst Support

Raw and pyrolyzed (with and without melamine) graphene nanoplatelets with different surface areas as PEM fuel cell catalyst supports

Platinum (Pt) catalysts dispersed on carbon-based support materials are generally used in the polymer electrolyte membrane (PEM) fuel cells. In this study, commercial graphene nanoplatelets (GNPs), with different surface areas (320, 530, 800 m2 g−1), were used as catalyst supports in PEM fuel cells. These GNPs were also pyrolyzed under the inert atmosphere, with and without melamine, as the nitrogen (N) source. Various characterizations (Elemental analysis, FTIR, Raman spectroscopy, BET, TEM, HRTEM, SAED, XRD, TGA, ICP-MS, contact angle measurement, CV, ORR, chronoamperometry, EIS, PEM fuel cell performance test) were performed for the detailed analysis of Pt/GNPs. Based on the three-electrode cell system, the lowest electrochemical surface area (ECSA) loss (29.9%), Pt mass activity loss (20.3%) and overall (charge and mass) resistance (42.2 Ω) were obtained with the Pt/M-530 catalyst. According to the in-situ PEM fuel cell performance results, the specific peak power density was recorded as (450 mW mg Pt−1) for the Pt/R-530 catalyst, which has also the second most hydrophobic catalyst layer surface with the 146.5° ± 1.28° contact angle value. On the heels of Pt/R-530, the two best performances also belong to the Pt/M-530 (391 mW mg Pt−1) and Pt/P-530 (378 mW mg Pt−1) catalysts of the same group.

Conductive Metal Oxide-Based Fuel Cell Catalyst Supports Prepared by Doping TiO2 with Si: Understanding the Role of Si Content

We report the synthesis of a Ti3O5-Si (TOS) conductive metal oxide fuel cell catalyst support. TOS is prepared by doping TiO2 with Si, endowing the resultant material with enhanced electronic conductivity and durability. Support with various amounts of dopant were prepared and a 15-20 wt% Si was determined to be optimal. Intensive electrochemical durability testing shows that the TOS supports are highly stable making them highly suitable for use as a fuel cell catalyst support.

Utilization of the graphene aerogel as PEM fuel cell catalyst support: Effect of polypyrrole (PPy) and polydimethylsiloxane (PDMS) addition

In this study, three-dimensional (3D) graphene aerogel (GA) was synthesized by a self-assembly hydrothermal process as a PEM fuel cell catalyst support. The synthesized GA was also modified with the polypyrrole (PPy) by in-situ chemical oxidative polymerization of the pyrrole monomer (PPy-GA). The electrocatalytic performance of the platinum (Pt) nanoparticles (NPs) supported with both GA and PPy-GA materials towards oxygen reduction reaction (ORR) was investigated. In addition, the hydrophobic polydimethylsiloxane (PDMS) polymer was added to the catalyst ink media in order to enhance the hydrophobic property and durability of the synthesized GA and PPy-GA supported Pt catalysts. Pt NPs were decorated over the support materials with the microwave irradiation technique. Various characterization techniques such as FTIR, Raman Spectroscopy, BET, SEM, EDX, TEM, TGA, contact angle measurements, 3D topography images and four-point probe electrical conductivity measurements were performed in order to analyze the GA based support materials. Electrochemical characterizations were also carried out with cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) measurements. It was observed that PDMS addition to the catalyst ink media increased the electrocatalytic activity and durability of the GA supported Pt catalyst. Otherwise, the performance of the PPy modified GA supported Pt catalyst was negatively affected by the addition of PDMS to the catalyst media.

A highly durable N-enriched titanium nanotube suboxide fuel cell catalyst support

Reduced bandgap metal oxide materials are consider an alternative to carbon black supports for fuel cell catalysts. Here we report a unique N-enriched titanium nanotube suboxide doped with molybdenum (TNTS-Mo) fuel cell catalyst support. The support was prepared by the surface modification of a TNTS-Mo with a terpyridine (TPY) ligand, yielding TPY/TNTS-Mo. We have deposited Pt onto this support and evaluated its activity and stability. The Pt/TPY/TNTS-Mo catalyst was subjected to stringent accelerated stress tests (AST) designed to induce catalyst degradation similar to automotive operation and startup-shutdown conditions. The Pt/TPY/TNTS-Mo was compared with Pt/TNTS-Mo and a benchmark carbon supported Pt catalyst (Pt/C). These stability protocols confirmed that TPY modification greatly enhances the stability and durability of the Pt nanoparticles via strong metal support interaction (SMSI). In addition, the covalently attached TPY layer stabilizes the doped metal oxide supports itself, preventing changes in its surface state and composition at high potentials.

Ultra-Durable Ti3O5Mo0.2Si0.4 Fuel Cell Catalyst Supports with Enhanced Conductivity

Polymer electrolyte membrane fuel cells (PEMFCs) are a clean energy technology with potential application in automotive and station power systems. However, the high cost of Pt catalyst and long-term durability of electrode materials is a barrier that hinder market penetration. The support material greatly influences electrocatalytic activity and durability of the Pt nanoparticle catalysts. Carbon black has been the primary catalyst support in fuel cells over the last 30 years due to its high surface area and high electronic conductivity. However, carbon corrosion occurs readily during start-up/shutdown conditions. Therefore, more advanced support materials are need in order to overcome these problems. Many low-cost metal oxide materials like as TiO2, NbOx, WOx, and MoOx have high oxidative and thermal stability. As such, there has been a growing interest to exploit these materials in fuel cell catalysts layers. However, the potential benefits of adding these metal oxides to the catalyst layer are often negated by their inadequate electronic conductivity. Recently, there has been a growing interest in designing metal oxides with sufficient electrical conductivity to be a practical catalyst support. Significant attention has been paid to titanium suboxides (TixO2x−1) materials since they possess acceptable electronic conductivity. Furthermore, the addition of a dopant can further enhance electronic conductivity by creating oxygen vacancies within the lattice structure. Recently, Esfahani and co-worker have reported a process of modifying TiO2 with Mo to form Mo-doped titanium suboxide (Ti3O5-Mo). While this has been shown to be a promising fuel cell catalyst support, the support still had a sizable band gap of (2.6 eV)[1]. We have hypothesized that the introduction of the second dopant could further reduce the electronic band gap and enhance conductivity. Specifically, we have examined the use of Si as the second dopant due to its high stability and the demonstrated compatibility of silicates in fuel cell catalyst layers [2-4]. Therefore we prepared a dual-doped metal oxide support materials with a composition of Ti3O5Mo0.2Si0.4 (hereafter referred to as TOMS). The TOMS support displays a remarkably low band gap of 0.31 eV, leading to a high electronic conductivity compared to other metal oxide supports. We have prepared fuel cell catalysts by depositing Pt nanoparticles onto the TOMS support. The resultant catalysts show remarkable stability and performance, which is due to a strong metal support interaction [5]. In this presentation, I will describe how doping alters the conductivity of metal oxides. In addition, we will demonstrate the performance of Pt/TOMS systems as well as its stability under several accelerated stress test protocols.

Selective exposure of platinum catalyst embedded in protective oxide layer on conductive titanium carbide support

Despite high conductivity and large surface area, poor corrosion resistance limits the use of carbon black as a fuel cell catalyst support. Here, the formation of two titanium carbide-based core-shell nanostructures with an ultrathin layer of cobalt oxide were studied as alternative to carbon black. Titanium carbide was selected due to its electrical conductivity and high corrosion resistance. Two different nanostructures on TiC supports were prepared with Pt either on or below a cobalt oxide layer. For the sub-oxide Pt catalyst, the oxide could be removed selectively where it covered the Pt to make it partially exposed and catalytically available, yet sufficient Pt was anchored to the remaining oxide to provide stability. This anchoring prevented Pt nanoparticle detachment and aggregation as determined by ∼100% catalytic activity remained at 0.1 M KOH, and ∼92% catalytic activity remained at 0.1 M HClO4 after 16.7 h, room temperature. A core-shell model has computationally been investigated to confirm the function of the cobalt shell as diffusion barrier to protect carbide from oxidation.

Necessity to Avoid Titanium Oxide As Catalyst Support in PEM Fuel Cells

Although fuel cell electric vehicles (FCEVs) has become a commercial reality, overall cost reduction as well as durability improvement continue to remain as the key challenges facing fuel cell developers. One of the area of durability concern in proton exchange membrane (PEM) fuel cells relates to the degradation of carbon supported Pt-based electro catalysts. [1] Carbon-supported (e.g., Vulcan or Ketjen black) Pt or Pt-alloy (e.g., PtCo) catalysts are used in PEM fuel cells to catalyse the oxygen reduction reaction (ORR) and hydrogen oxidation reaction (HOR). In an automotive environment, the catalysts must survive highly dynamic operations. State-of-the-art high surface area carbon support suffer from severe corrosion at potentials above 1.1 V. [1] A few transient operations that contribute to the corrosion of carbon support including vehicle start-up/shutdown, cell reversal due to fuel starvation, as well as load cycling. The degradation of carbon support and the electrocatalyst can induce significant performance decay. Therefore, material that is inherently more corrosion resistant has been actively investigated as alternative catalyst support to carbon in PEM fuel cell applications. In recent years, transition metal oxides are of interest as an alternate to carbon electro catalyst support due to their improved stability at higher potentials [2-3]. Furthermore, it is also believed that metal-oxide supports can possibly influence the intrinsic activity of the supported Pt (Pt-alloy) catalyst toward ORR due to strong metal-support interactions(SMSI). Titanium oxide has been demonstrated to be one of the suitable metal oxide, and was frequently reported as effective ORR catalyst support showing both significantly improved stability at high potential as well as improved ORR activity [3]. However, no long-term durability and possible negative effects of oxide supports on PEM fuel cell durability has been reported. In this study, for the first time we report that the use of titanium oxide (TiO2) as catalyst support in the PEM fuel cell electrode can lead to significant degradation of the polymeric membrane, causing membrane thinning and increased gas crossover. Experiments were conducted using Pt supported on titanium oxide (TiO2) as either the anode HOR catalyst or the cathode ORR catalyst. The impact on membrane chemical degradation is evaluated at open circuit voltage (OCV) condition at 115 oC and 25% RH for 100 hours. The exhaust water from both the anode and cathode of the fuel cell during the OCV hold was collected and analyzed using ion chromatography (IC) to quantify the concentration of fluoride and determine the fluoride release rate (FRR) which is a measure of the rate of membrane chemical degradation. With measured FRR, a total fluorine inventory loss of the membrane is also calculated. It was found that the total fluorine inventory loss is 26% and 15% for Pt/TiO2 used as anode and cathode catalyst, respectively, after 100hrs of OCV test. A comparable electrode with carbon supported Pt catalyst exhibit only about 0.3% total fluorine inventory loss at identical OCV conditions, which is more than 50X lower. Additional experiments were designed to confirm the impact of titanium oxide by adding titanium oxide only (without Pt) to either anode or cathode electrode while using Pt/C as anode or cathode catalyst. One reduced form of TiO2, i.e., Magneli phase (Ti4O7) which is shown to have improved electrical conductivity and has been investigated as Pt support is also tested in this experiment. The results show that by adding TiO2 or Ti4O7 to anode or cathode both increase the FRR compared titanium oxide free electrodes. The FRR release rate data with titanium oxide added in the cathode is shown in Fig. 1. In this presentation, we will discuss the details of the experimental study on the impact of titanium oxide on polymeric membrane chemical degradation, including fluoride release rate, fluorine inventory loss, as well as the change in hydrogen crossover rate. Additional analysis on the location of chemical degradation (membrane close to anode vs. membrane close to the cathode) has also been conducted which may shed additional light on the fundamental mechanisms of TiOx induced membrane degradation. Finally, the necessity to find alternative metal oxide support rather than TiOx in PEM fuel cell application is highlighted Figure 1

Electrospun carbon nanofiber catalyst layers for polymer electrolyte membrane fuel cells: fabrication and optimization

Current polymer electrolyte membrane fuel cell catalyst support in a form of carbon black is linked with poor Pt utilization, non-optimized triple-phase boundary, mass transport losses, non-uniform microstructure, and durability issues. Little improvement has been made in creating a novel catalyst support microstructure and design to address the challenges associated with the use of carbon blacks. Of particular importance is the ability to control the microstructure of the catalyst layer. There is a lack of fundamental understanding of the relationship between the well-controlled catalyst layer microstructure and fuel cell performance. As catalyst layers require a structure that offers large porosity and surface area, it is envisioned that electrospun nanofibers are an excellent choice, providing a number of structural parameters that could be controlled, i.e., porosity, fiber diameter, fiber alignment, layer thickness. In this work, the fabrication parameters of electrospun carbon nanofibers (CNF) are optimized by factorial design to target key membrane electrode assembly design criterion. Validation of the structural and material properties concludes that optimized CNF surpassed design targets, achieving ~ 80% porosity, ~ 30 S cm−1 in-plane electrical conductivity, and ~ 330 nm fiber diameter. The optimization reveals that CNF properties were successfully tailored and appear feasible as novel catalyst support. The results from the detailed and systematic design of experiments provide a basis for correlating the material and structural properties to key fuel cell performance factors.

A fuel cell catalyst support based on doped titanium suboxides with enhanced conductivity, durability and fuel cell performance

A low-band gap metal-oxide based fuel cell catalyst support with enhanced durability and fuel cell performance.

Investigation of Reduced Graphene Oxide with F-Doped SnO2 as Catalyst Support in Fuel Cells

A main challenge in commercialisation of fuel cells is the performance loss with time of operation. The platinum catalyst is subjected to electrochemical instability, and carbon black as commonly used catalyst support suffers from corrosion.[1,2] To improve the fuel cell stability, alternative support materials can be used. Application of graphene-based carbon in low temperature PEMFCs has demonstrated higher durability than conventional carbon black.[3] The combination with corrosion resistant metal oxides provides additional binding sites for Pt nanoparticles[4,5] and can prevent graphene materials from restacking causing mass transport limitations in fuel cells.[6] In this study, reduced graphene oxide (rGO) is synthesised in two steps. Graphene oxide is received via Hummer’s method[7] and then thermally reduced to rGO. In the following synthesis, fluorine-doped tin (IV) oxide (FTO) nanoparticles are deposited on rGO sheets. Therefore, a sol-gel method using tin tetrachloride precursor followed by addition of NH4F and hydrothermal treatment is carried out on rGO.[8,9] Figure 1a shows the achieved crystalline FTO structure which is similar to cassiterite tin (IV) oxide. Using Scherrer equation an average FTO particle size of 4.8±0.4 nm is calculated. Transmission electron microscopy (TEM) in Figure 1b reveals successful deposition of the FTO nanoparticles on rGO. In the last synthesis step, Pt is precipitated on FTO-rGO via chemical reduction of chloroplatinic acid with ethylene glycol.[4] Then, Pt/FTO-rGO catalyst is intensively investigated for electrochemical stability under fuel cell operation conditions by the use of an accelerated stress test (AST). Within an electrochemical cell the catalyst is exposed to 1,000 potential cycles between -0.02 and 1.40 VRHE at a scan rate of 500 mV s-1under oxygen saturation. To ensure a holistic analysis of possible catalyst and support degradation, this AST is performed twice. During the first test, a rotating disk electrode allows the study of the oxygen reduction reaction (ORR) mechanism and activity at different rotation speeds (400, 900, 1200, 1600, 2000 and 2500 rpm). The electrochemical active surface area (EASA) is carefully determined by hydrogen underpotential deposition as well as carbon monoxide stripping voltammetry. In the second test run, the rotating disk electrode as working electrode is replaced by a catalyst coated grid for identical location TEM analysis. First, the untested Pt/FTO-rGO catalyst on the grid is analysed by TEM and then the catalyst on grid is stressed by exactly the same potential cycling. After performing AST, the same Pt/FTO-rGO particles are investigated again under the microscope. Thus, possible Pt degradation processes like agglomeration can be revealed which allows the supplementation of electrochemical investigations. Fig. 1: XRD pattern of FTO-rGO with comparison to crystalline structure of cassiterite SnO2 (ICDD 98-000-9463) (a) and TEM image of deposited FTO particles on rGO (b). [1] D. Schonvogel, M. Rastedt, P. Wagner, M. Wark, A. Dyck, Fuel Cells 2016, 16, 480-489. [2] Y. Shao-Horn, W. C. Sheng, S. Chen, P. J. Ferreira, E. F. Holby, D. Morgan, Top. Catal. 2007, 46, 285-305. [3] Y. Shao, S. Zhang, C. Wang, Z. Nie, J. Liu, Y. Wang, Y. Lin, J. Power Sources 2010, 195, 4600-4605. [4] R. Kou, Y. Shao, D. Mei, Z. Nie, D. Wang, C. Wang, V. V. Viswanathan, S. Park, I. A. Aksay, Y. Lin, Y. Wang, J. Liu, J. Am. Chem. Soc. 2011, 133, 2541-2547. [5] Y. Liu, W. E. Mustain, J. Am. Chem. Soc. 2013, 135, 530-533. [6] S. Park, Y. Shao, H. Wan, P. C. Rieke, V. V. Viswanathan, S. A. Towne, L. V. Saraf, J. Liu, Y. Lin, Y. Wang, Electrochem. Commun. 2011, 13, 258-261. [7] S. Ratso, I. Kruusenberg, M. Vikkisk, U. Joost, E. Shulga, I. Kink, T. Kallio, K. Tammeveski, Carbon 2014, 73, 361-370. [8] D.-J. Guo, Z.-H. Jing, J. Colloid Interface Sci. 2011, 359, 257-260. [9] H. Xu, L. Shi, Z. Wang, J. Liu, J. Zhu, Y. Zhao, M. Zhang, S. Yuan, ACS Appl. Mater. Interfaces 2015, 7, 27486-27493. Figure 1

Conflicting Roles of Nitrogen Doping in Carbon Nanotubes As Anode and Cathode Catalyst Support for Direct Methanol Fuel Cells

Nitrogen doping in carbon nanotubes (CNTs) is of great interest because it endows the inherently inert surface of CNTs with a variety of chemical functionalities. For instance, nitrogen-doped carbon nanotubes (NxCNTs) have been shown a promising electrode catalyst support for polymer electrolyte membrane fuel cells because the doped nitrogen atoms can promote a high dispersion of the metal catalyst nanoparticles on the NxCNT surface, which is essential for achieving a high utilization and thus high catalytic performance. However, beyond the role in nanoparticle dispersion, how nitrogen doping affects the catalytic performance in the anode and in the cathode of a realistic membrane-electrode-assembly (MEA), still remains elusive. In this report, we performed a comparative study of NxCNTs at three different N doping levels as the anode and cathode catalyst support in both rotating disk electrode (RDE) and realistic direct methanol fuel cell (DMFC) test. Our results show that nitrogen doping can play significantly conflicting roles in the anode and cathode performance: (i) A very low doping level (1at.%) is sufficient to induce a homogenous distribution of both anode (PtRu) and cathode (Pt) catalyst nanoparticles. (ii) In RDE test, while nitrogen doping can substantially increase the specific activity of the anodic methanol oxidation, it brings no specific activity enhancement in the cathodic oxygen reduction reaction (ORR), suggesting that nitrogen doping can hardly affect the ORR electrocatalysis on the Pt surface. (iii) In MEA test, a low nitrogen doping level at 1 at.% in NxCNTs as anode catalyst support resulted in a higher power density compared to non-doped CNT support at both 30 and 60°; increasing nitrogen-doping content decreased the power density, likely due to a decreased electron conduction. In contrast, at the cathode, NxCNTs support mainly showed a lower power density, particularly at 60°, which is rationalized by the increased hydrophicility and thus unflavored removal of the water. Taken together, our results provide important guidelines for application of NxCNT support at the appropriate electrode of DMFCs.

Investigation of Reduced Graphene Oxide with F-Doped SnO2 as Catalyst Support in Fuel Cells

Degradation of commonly used platinum on carbon black results into performance losses of proton exchange membrane fuel cells (PEMFC). A nanocomposite of fluorine-doped SnO2 (FTO) and reduced graphene oxide (rGO) is used as Pt support and studied on electrochemical stability by potential cycling between 0.05–1.47 VR HE. Highly dispersed Pt with anchoring at FTO–rGO interfaces is observed by use of high resolution transmission electron microscopy (HR-TEM). Stripping voltammetry shows weaker CO binding on Pt/FTO–rGO than on Pt/C, indicating higher CO tolerances. During potential cycling, the catalyst shows a loss of electrochemical active surface and a reduced activity for oxygen reduction, whereas the support exhibits unchanged amounts of hydroquinone/quinone functionalities and stable double layer capacitance. Additionally, identical location TEM shows unchanged FTO particles on rGO surface, demonstrating electrochemical stability of FTO–rGO substrate. Thus, this composite material meets the stability criteria for catalyst support in PEM fuel cells.

PEDOT/C Composites used as a Proton Exchange Membrane Fuel Cell Catalyst Support: Role of Carbon Amount

AbstractCarbon‐based support materials are mostly used in proton exchange membrane fuel cells (PEMFCs); however, they often suffer from degradation under the operating conditions. In this context, conducting polymers and their composites stand out as a good alternative support material thanks to their chemical stability, high electrical conductivity, and higher oxidation‐resistant properties, which fulfills the requirements for possible utilization as electrocatalyst in PEMFCs. This study reports the preparation of poly(3,4‐ethylenedioxythiophene)/carbon (PEDOT/C) composite‐supported Pt nanoparticles for PEMFC electrodes. First, PEDOT/C composites were prepared using different carbon amounts by in situ chemical oxidative polymerization of EDOT monomer on carbon particles. Then, Pt nanoparticles (about 20 % loading) were obtained by using a microwave irradiation technique as it is fast, inexpensive, energy and time saving, and ecofriendly. The successful synthesis was confirmed by XRD, TEM, and thermogravimetric analysis investigations. The surface area and pore structure of the PEDOT/C supports was also investigated by using the BET technique. The ex situ and in situ electrochemical analyses were performed by using cyclic voltammetry and PEMFC performance tests. The obtained results for the fuel cell open the way for the use of PEDOT/C composite support materials as electrocatalysts for fuel cells.

Gold nanoparticle-polymer nanocomposites synthesized by room temperature atmospheric pressure plasma and their potential for fuel cell electrocatalytic application

Conductive polymers have been increasingly used as fuel cell catalyst support due to their electrical conductivity, large surface areas and stability. The incorporation of metal nanoparticles into a polymer matrix can effectively increase the specific surface area of these materials and hence improve the catalytic efficiency. In this work, a nanoparticle loaded conductive polymer nanocomposite was obtained by a one-step synthesis approach based on room temperature direct current plasma-liquid interaction. Gold nanoparticles were directly synthesized from HAuCl4 precursor in poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS). The resulting AuNPs/PEDOT:PSS nanocomposites were subsequently characterized under a practical alkaline direct ethanol fuel cell operation condition for its potential application as an electrocatalyst. Results show that AuNPs sizes within the PEDOT:PSS matrix are dependent on the plasma treatment time and precursor concentration, which in turn affect the nanocomposites electrical conductivity and their catalytic performance. Under certain synthesis conditions, unique nanoscale AuNPs/PEDOT:PSS core-shell structures could also be produced, indicating the interaction at the AuNPs/polymer interface. The enhanced catalytic activity shown by AuNPs/PEDOT:PSS has been attributed to the effective electron transfer and reactive species diffusion through the porous polymer network, as well as the synergistic interfacial interaction at the metal/polymer and metal/metal interfaces.

Ultrananocrystalline diamond decoration on to the single wall carbon nano tubes

We have demonstrated the decoration of the ultrananocrystalline diamonds on single walled carbon nanotubes using a hot filament assisted chemical vapor deposition. Study reveals the critical influence of the filament to substrate distance on the formation of ultrananocrystalline diamonds on to the single walled carbon nanotubes. It is also observed that etching of carbon nanotubes, due to the presence of unavoidable atomic hydrogen throughout the chemical vapor deposition processes, can be significantly reduced by adjusting the filament to substrate distance. Morphological and structural investigations performed using high resolution transmission electron microscope suggests the growth of ultrananocrystalline diamond is subsequent to the formation of crystalline sp2 carbon layer on the nanotube wall, enabling us to suggest a growth model. The composite synthesized can be thought not only to use as a fuel cell catalyst support but also as chemical sensors, bio-sensors and micro electromechanical systems (MEMS).

Synthesis and electrochemical characterization of TixTayAlzN1-δOγ for fuel cell catalyst supports

Quinary TixTayAlzN1-δOγ of various compositions have been prepared by a co-precipitation method followed by ammonolysis. The nitride samples were examined as potential catalyst supports in polymer electrolyte membrane fuel cells. The nitride products crystallized in the rock salt (NaCl) structure over a wide range of compositions. The addition of Ta and Al was highly beneficial towards improving the chemical and electrochemical stability of TiN, without a significant loss of electrical conductivity. Platinum particles were successfully deposited on the (oxy)nitride samples, and the composite samples at some compositions were found to be comparable to Pt/carbon in their stability and catalytic activity even without optimizing the Pt deposition and dispersion processes.

Use of Carbon Nanomaterials as a Catalyst Support in Fuel Cells

PtRu or Pt catalysts were supported on four types of carbon nanomaterials with different shapes, sizes, and graphitic and electrical properties, and their resulting catalytic activities were evaluated by electrochemical methods. The carbon nanomaterials used included two types of particles: Arc Black (AcB) and Vulcan XC-72R (Vulcan), and two types of nanofibers: carbon nanocoils (CNC) and VGCF-X. Pt and Ru were loaded onto the nanomaterials by a reduction method using sodium borohydride. Transmission electron microscopy and X-ray diffraction (XRD) revealed the PtRu catalyst particles to be 4–6 nm in diameters. The shifts in the Pt (111) XRD peaks of the catalysts on CNC and VGCF-X were larger than those on AcB and Vulcan, indicating a higher degree of alloying between Pt and Ru. The diameters of the CNC-supported Pt and PtRu catalyst particles had the narrowest distributions and were constant within the range of catalyst loadings investigated. Electrochemical studies of the catalysts during methanol oxidation were carried out using cyclic voltammetry. The catalyst particles supported on CNC and VGCF-X exhibited higher catalytic activity than those on AcB and Vulcan. The effect of the surface area of the carbon nanomaterials on the catalytic activity is discussed.

Graphitic Carbon Nitride as a Catalyst Support in Fuel Cells and Electrolyzers

Electrochemical power sources, such as polymer electrolyte membrane fuel cells (PEMFCs), require the use of precious metal catalysts which are deposited as nanoparticles onto supports in order to minimize their mass loading and therefore cost. State-of-the-art/commercial supports are based on forms of carbon black. However, carbon supports present disadvantages including corrosion in the operating fuel cell environment and loss of catalyst activity. Here we review recent work examining the potential of different varieties of graphitic carbon nitride (gCN) as catalyst supports, highlighting their likely benefits, as well as the challenges associated with their implementation. The performance of gCN and hybrid gCN-carbon materials as PEMFC electrodes is discussed, as well as their potential for use in alkaline systems and water electrolyzers. We illustrate the discussion with examples taken from our own recent studies.