Rotating Disk Electrode Method Research Articles

The Pt–Co alloying effect on the performance and stability of high temperature PEMFC cathodes

High temperature (HT) PEMFC technology offers a number of advantages over its low temperature counterpart, including high tolerance to fuel impurities, system simplifications and generation of high-quality waste heat. Nevertheless, the operating temperature and the presence of phosphoric acid necessitate the use of high amounts of platinum metal at the electrodes, especially the cathodic one. In this work, we report the facile preparation of a Pt–Co alloy supported on multi-wall carbon nanotubes. Using the rotating disk electrode method in HClO4, the activity of this catalyst towards the oxygen reduction reaction, as well as its tolerance to phosphoric acid is evaluated. A comparison is made with two electrocatalysts with similar characteristics (support, nanoparticle size and spatial distribution), where one is based on Pt and the other is a physical mixture of the aforementioned metals (Pt and Co). The superior behavior of the alloyed electrocatalyst urged its electrochemical characterization in-situ, at the cathode of a HT-PEMFC, where performance and, very importantly, stability are thoroughly evaluated and discussed. A comparison with a commercial state-of-the-art electrocatalyst shows the potential to decrease the metal loading of HT-PEMFC electrodes without compromising performance.

Electrode Kinetic Study of Cu Electrodeposition with Supercritical CO2 by High Pressure Rotating Disk Electrode Method

The electrochemical reaction mechanism on the electrode surface for the activation of Cu electrodeposition in a sulfate-based Cu plating solution containing poly ethylene glycol (PEG) and supercritical CO2 (Sc-CO2) was studied by hydrodynamic voltammetry experiments and electrochemical impedance spectroscopy performed using a rotating disk electrode system specially designed for high pressure environment. The experimental results demonstrated that the mixed Sc-CO2 had a significant inhibitory effect on Cu electrodeposition. In addition, a kinetics model was attempted to be constructed for the Sc-CO2 mixed system based on the conventional model for the system with suppressor. As a result, the same mechanism as in the conventional model can be used to explain the Sc-CO2 mixed system, Sc-CO2 micelles in the solution were suggested to adsorb on the electrode surface in the same manner as the PEG molecules, which affected the reaction mechanism and was expected to inhibit the reduction reaction of Cu ions. Furthermore, the mixed Sc-CO2 was presumed to reduce the transition coefficient by suppressing the reduction reaction of Cu2+ ions to the Cu+ complex by adsorption on the electrode surface.

Electrocatalytic Properties of Ni(II) Schiff Base Complex Polymer Films.

Platinum electrodes were modified with polymers of the (±)-trans-N,N′-bis(salicylidene)-1,2-cyclohexanediaminenickel(II) ([Ni(salcn)]) and (±)-trans-N,N′-bis(3,3′-tert-Bu-salicylidene)-1,2-cyclohexanediaminenickel(II) ([Ni(salcn(Bu))]) complexes to study their electrocatalytic and electroanalytical properties. Poly[Ni(salcn)] and poly[Ni(salcn(Bu))]) modified electrodes catalyze the oxidation of catechol, aspartic acid and NO2−. In the case of poly[Ni(salcn)] modified electrodes, the electrocatalysis process depends on the electroactive surface coverage. The films with low electroactive surface coverage are only a barrier in the path of the reducer to the electrode surface. The films with more electroactive surface coverage ensure both electrocatalysis inside the film and oxidation of the reducer directly on the electrode surface. In the films with the most electroactive surface coverage, electrocatalysis occurs only at the polymer–solution interface. The analysis was based on cyclic voltammetry, EQCM (electrochemical quartz crystal microbalance) and rotating disc electrode method.

The Bipolar Mode of One‐Step Plasma Electrochemical Synthesis of Few Layer Graphene Structures Decorated with Transition Metal Oxides

AbstractWe present the method of conjugated bipolar plasma electrochemical synthesis of aqueous suspensions of composites of few‐layer graphene structures with Co3O4 and Mn3O4 oxides and creation of mixed electrocatalysts based on them. As shown by the rotating disk electrode method, the best catalytic activity towards oxygen reduction reaction exceeding that for each individual component is demonstrated by the composition containing equal amounts of these composites.

Oxygen electroreduction on small (

Oxygen reduction reaction (ORR) was studied on {100}-oriented Pt nanoparticles with sizes from 3 to 7 nm in sulphuric acid solution. The distribution and size of nanoparticles was analysed by transmission electron microscopy and metal loading was determined by inductively coupled plasma optical emission spectroscopy. The synthesised nanoparticles have about 40% of Pt(100) facet and 10% Pt(111) as determined from Ge and Bi adsorption, respectively. The four Pt/C catalysts with metal loading from 25 to 38 wt% were tested for ORR activity in 0.5 M H2SO4 solution using the rotating disk electrode method. It was found that the ORR proceeds mainly via a 4-electron pathway with the rate-limiting step being the transfer of the first electron to O2 molecule. The mass activities for ORR increase with decreasing the particle size, but specific activity has a maximum at 4.6 nm particle size. This means the most optimal {100}-oriented Pt size for ORR is around 4.6 nm in sulphuric acid solution.

Precise Electrochemical Testing in Half-Cells: Controlling Catalyst Layer Formation and the Three-Phase Boundary in Gas Diffusion Electrodes

Novel and tailored electrocatalysts need solid benchmarking for evaluation of e.g. the oxygen reduction reaction activity (ORR), and the performance in a model approach should strictly reflect their eventual performance in the fuel cell devices. It is strongly believed that the routinely used testing methods, like rotating disk electrode (RDE) method, provide erroneous results, as they do not mimic the original fuel cell conditions in terms of water management, presence of ionomer, relevant current densities, etc. Half-cell tests of gas diffusion electrodes (GDEs) have been shown to be a good compromise as these tests exhibit comparable oxygen mass transport to the electrode as a fuel cell device, in contrast to the limited mass transport in RDEs. Realistic operational conditions, such as potential range and higher current densities in the GDE set-ups, are more akin to membrane electrolyte assemblies (MEA) testing than RDEs without the hassle and cost of full-cell tests [1-4]. In this presentation, half-cell test results will be reported for gas diffusion electrodes prepared using various methods, namely: 1) Drop-casting; 2) Spray coating with sonication; 3) Air brushing with spray gun; and 4) Hand painting. Commercially available Pt/C HiSpec 4000 was used as electrocatalyst and results of parallel RDE and MEA tests with similar Pt loadings will be discussed. Detailed electrochemically active surface area (ECSA) analysis using Hupd and CO stripping studies of various loadings from 5μg cm-2 Pt loading to 50 μg cm-2 will be reported. Drop-casting method on GDE was found to be the most efficient process to study the ECSA using Hupd (38 m2 gPt -1) and CO-stripping (61 m2 gPt -1) which were achieved at a loading of 20 μgPt cm- 2. Spray-coating with ultrasonication with a diluted catalyst ink was the ideal procedure to fabricate a uniform thin layer of catalyst with multiple deposition cycles. The current densities achieved during ORR evaluation in half-cell set-up were almost 2 orders of magnitude higher than those achieved using the RDE method. Different strategies of implementing the Nafion ionomer were utilized and compared, like: 1) Nafion 117 membrane hot-pressed on the GDE; 2) Nafion solution sprayed on the surface of the GDE reaching a loading of 2 mg cm-2 and; 3) GDE without a membrane. This report will also aim to assess how the presence of phosphoric acid in the perchloric acid electrolyte and its purity affects the catalyst’s performance for the ORR reaction. Scanning electron microscopy (SEM) was used to study the catalyst layer formation on the gas diffusion layers (GDLs). The GDEs were characterized using X-Ray Absorption Spectroscopy (XAS) [5, 6], ex-situ and in-situ, allowing us to extract structural information through the extended X-ray absorption fine structure analysis (EXAFS) (catalyst particle size, composition, morphology, and oxidation state); furthermore, by using a subtractive-normalization technique in the near-edge region (Δμ XANES) it is possible to obtain adsorbate coverage (H, O, PO4 species adsorbed on Pt surface) and binding-site information for a detailed comparison between the above samples.

Analysis of Oxygen Transport in Structure-Modified Electrodes by the Rotating Disk Electrode Method

Analysis of Oxygen Transport in Structure-Modified Electrodes by the Rotating Disk Electrode Method

Study the effects of methane disulfonic acid sodium salt on Cr (VI) reduction using rotating disk electrode

Chromium (VI) electroplating plays a vital role in the surface engineering industry for metallic materials due to its high hardness and excellent chemical stability. However, the reduction of Cr (VI) is a series of complex reactions that exhibits low current efficiency. As such, this low current efficiency in the process poses a significant challenge in the adoption of CR (VI) electroplating in the surface engineering industry. Methane disulfonic acid sodium salt (MDAS) is an essential catalyst for Cr (VI) electroplating. In this work, the effects of MDAS on the current efficiency of Cr (VI) electroplating process is studied. It is discovered that the current efficiency increases to about 17% when 4–6 g l−1 MDAS is added in the bath, which is an improvement over the current efficiency of 12% for its counterpart without MDAS. Furthermore, rotating disk electrode method is employed to investigate its interaction mechanism with regards to the reactions which have occurred during this process. It indicates that MDAS demonstrates a remarkable catalytic ability towards the electrochemical reaction which occurs at the lower-potential peak. This lower potential peak corresponds to the electrochemical reaction of Cr (VI) to Cr (0) or Cr (III) to Cr (0).

Eco-Friendly Nitrogen-Doped Graphene Preparation and Design for the Oxygen Reduction Reaction.

Four N-doped graphene materials with a nitrogen content ranging from 8.34 to 13.1 wt.% are prepared by the ball milling method. This method represents an eco-friendly mechanochemical process that can be easily adapted for industrial-scale productivity and allows both the exfoliation of graphite and the synthesis of large quantities of functionalized graphene. These materials are characterized by transmission and scanning electron microscopy, thermogravimetry measurements, X-ray powder diffraction, X-ray photoelectron and Raman spectroscopy, and then, are tested towards the oxygen reduction reaction by cyclic voltammetry and rotating disk electrode methods. Their responses towards ORR are analysed in correlation with their properties and use for the best ORR catalyst identification. However, even though the mechanochemical procedure and the characterization techniques are clean and green methods (i.e., water is the only solvent used for these syntheses and investigations), they are time consuming and, generally, a low number of materials can be prepared, characterized and tested. In order to eliminate some of these limitations, the use of regression learner and reverse engineering methods are proposed for facilitating the optimization of the synthesis conditions and the materials’ design. Thus, the machine learning algorithms are applied to data containing the synthesis parameters, the results obtained from different characterization techniques and the materials response towards ORR to quickly provide predictions that allow the best synthesis conditions or the best electrocatalysts’ identification.

Iron‐Containing Nitrogen‐Doped Carbon Nanomaterials Prepared via NaCl Template as Efficient Electrocatalysts for the Oxygen Reduction Reaction

AbstractIron‐containing nitrogen‐doped carbon catalysts for the electrochemical oxygen reduction reaction (ORR) were prepared by high‐temperature pyrolysis of glucose, K3[Fe(CN)6], and dicyandiamide or urea as precursors. Sodium chloride was used as a template and a confining agent during the pyrolysis, while graphitic carbon nitride formed from dicyandiamide decomposed at higher temperatures, contributing to the enhancement of the porosity and nitrogen doping. The ratio of the precursors and the template was varied to improve the catalysts′ ORR activity, determined in alkaline solution by the rotating disk electrode method. The ORR inhibition tests by cyanide anions revealed the existence of nitrogen‐coordinated Fe centres as electrocatalytically active sites in the doped catalyst. The high durability and methanol tolerance of the catalyst material prepared with an optimised precursor ratio make it a promising catalyst for applications in alkaline membrane fuel cells.

Influence of Proton Activity in H2/H2 Cells: Implications for Fuel-Cell Operation with Low Relative Humidities

The proton activity term is typically ignored in the Nernst equation because of the definition of the unit activity of protons within catalyst layers in proton-exchange membrane fuel cells although the relative humidities of an anode (RHA) and a cathode (RHC) can be different. Herein, we investigate the effect of proton activity on the open-circuit voltage (OCV) of a H2/H2 cell by individually controlling RHA and RHC at ≤30%. The OCV was thermodynamically estimated by applying the correlations of the RH and water uptake of a Nafion® membrane. The OCV experimentally increased with an increase in the humidity difference: the highest OCV of 77 mV was observed at RHA 30% and RHC 0%. The electro-osmotic coefficient (ξ) was calculated and found to be 0.73 at 5%–30% RHC and 30% RHA. The kinetic current (i k ) of the oxygen-reduction reaction was measured by the rotating disk electrode method to verify the influence of proton activity (a H+ ). i k was described as i k ∝ a H+ −β , with β values of 0.29 and 0.45 for H2SO4 and CF3SO3H, respectively, at 0.9 V. The results demonstrate that for the dry operation of fuel cells, especially for heavy-duty applications, proton activity effects within ionomers must be considered.

Oxygen reduction on silver catalysts electrodeposited on various nanocarbon supports

In this work, Ag particles were electrodeposited onto nitrogen-doped graphene oxide, graphene, multi-walled carbon nanotube (MWCNT), and Vulcan carbon XC-72R supports by varying the upper potential limit. The surface morphology of the resulting Ag-based catalysts was examined by scanning electron microscopy. The electrochemical oxygen reduction reaction (ORR) was tested in alkaline media employing the rotating disk electrode method. The variation of the upper potential limit influenced the size of silver nanoparticles and their number density on the substrate surface. All the Ag-based electrocatalysts studied in this work showed remarkable ORR activity in terms of half-wave potentials. The ORR results combined with hydrogen peroxide reduction results prove that all Ag catalysts tested are suitable for both reactions. Ag/NGO2 catalyst possesses the highest mass activity for ORR, which indicates a relationship between the Ag loading and electrocatalytic activity. The electroreduction of oxygen on all the electrodeposited silver catalysts follows a four-electron pathway in alkaline environment. These materials are promising alternatives for Pt/C catalyst to be used as alkaline membrane fuel cell cathodes.

(Vittorio de Nora Award Address) Analysis of the Catalyst Requirements with Regards to Catalyst Structure and Catalyst Durability Studies for PEM Water Electrolysis

Proton exchange membrane (PEM) based water electrolyzers are a promising technology for the large-scale production of hydrogen from renewable energy. The most efficient and durable catalysts for PEM water electrolysis are platinum to catalyze the hydrogen evolution reaction (HER) and iridium oxide to catalyze the oxygen evolution reaction (OER). While the currently rather high noble metal loadings (≈0.3-0.5 mgPt/cm2 and ≈1-3 mgIr/cm2) have only a minor impact on the overall water electrolyzer system cost [1], the large-scale global implementation of PEM water electrolysis would require a substantial reduction of the noble metal loadings due to the limited availability of Pt and Ir. This is easy to achieve for the Pt cathode catalyst, owing to its fast HER kinetics and the fact that a high dispersion of Pt is readily achieved with carbon-supported Pt (Pt/C). However, lowering the Ir loading below ≈0.5 mgIr/cm2 is not possible with currently available Ir catalysts (Ir black, nano-IrO2, or IrO2 supported on a TiO2 substrate), as it results in too thin, non-contiguous electrode layers with poor in-plane conductivity, owing to their low iridium packing density of ≈2.3 gIr/cm3 electrode (this is in contrast to ≈0.05-0.10 gPt/cm3 electrode for a typical Pt/C catalyst) [2]. Thus, to reach the long-term target of an Ir-specific power density of ≤0.01 gIr/kW [2], novel catalysts with a lower iridium packing density are required, which could be achieved, e.g., by supporting iridium or iridium oxide nanoparticles on conductive supports or by other approaches [3]. A detailed analysis leading to this conclusion will be discussed in this presentation.The development and implementation of such novel catalysts also requires the evaluation of their long-term stability. Conventionally, this is either done by measurements in liquid electrolyte, typically using the rotating disk electrode (RDE) technique, or testing in an actual PEM electrolyzer. Unfortunately, recent studies revealed that the RDE based approach does not yield reliable catalyst durability data, since for yet unknown reasons, the catalyst life-times obtained by the RDE method are three to four orders of magnitude lower than what is observed in PEM electrolyzers [3, 4]. On the other hand, catalyst durability testing in a PEM electrolyzer requires very long measurement times, so that accelerated durability test protocols are necessary [5]. These aspects will also be discussed.

N-Doped Carbon Materials Modified with Cobalt Nanoparticles As Catalysts for Oxygen Reduction Reaction

The oxygen reduction reaction is one of the main reactions which occur in fuel cells and other renewable energy technologies. In addition to this, oxygen reduction reaction on the cathode is more difficult reaction compare to anodic reaction, because the greater amount of Pt must be used as the cathode material to catalyze the reaction. The search for an efficient electrocatalyst for oxygen reduction reaction to replace platinum in fuel cell cathode materials is one of the hottest topics in electrocatalysis in relation to platinum high price and limited resources. That is the reason why researches put an effort in finding low cost, higher efficient and great performance catalysts. Various alternative catalysts have been studied including noble or non-noble metal catalysts. It is known that carbon is considered as one of the most promising electrocatalytic material for replacement of Pt. Therefore, researches have been trying multifarious methods with the purpose to increase the activity of the carbon. The fabricated N-doped carbon materials, 2D nitrogen-doped hierarchically porous carbon, N and P co-functionalized three-dimensional porous carbon networks, N, S-codoped porous exfoliated carbon nanosheets, N-doped carbon nanotubes, nitrogen-doped carbide-derived carbon catalysts or nitrogen-rich carbon dots decorated graphene oxide hybrid were described as materials having very similar electrocatalytic activity towards oxygen reduction reaction to Pt. Moreover N-doped carbon catalysts show high electrocatalytic activity forward oxygen reduction reaction in both – acidic and alkaline media. Among the many non-noble metal catalysts, metal/nitrogen/carbon composites containing Fe, Cu, Co metals are a promising alternative to Pt.In this study, the biological waste, such as black liqueur and alder wood chips, were used for the fabrication of catalytic material. Activated carbon and black liqueur were doped with cheap nitrogen precursor dicyandiamide and used as substrates for the deposition of cobalt nanoparticles (CoNPs) with the aim to use them as electrocatalysts for the oxygen reduction reaction. The synthesized catalysts were characterized by Inductively Coupled Plasma Optical Emission Spectroscopy, Field Emission Scanning Electron Microscopy, Transmission Electron Microscopy and X-ray Photoelectron Spectroscopy. Activity of the prepared catalysts was evaluated for oxygen reduction reaction in O2 - saturated 0.1 M NaOH solution employing the rotating disk electrode method. Electrocatalytic activity of CoNPs-N-doped black liqueur and CoNPs-N-doped activated carbon catalysts were compared with catalytic activities of commercial Pt/C wt. 46.4 % Pt.It has been found that the N-doped black liqueur and N-doped activated carbon substrates show high electro-catalytic activity for the oxygen reduction reaction. The modification of N-doped black liqueur and N-doped activated carbon with Co nanoparticles enhanced electrocatalytic activity of catalysts towards oxygen reduction reaction. It has been determined that the N-doped black liqueur and CoNPs- N-doped black liqueur samples demonstrated more similar electrocatalytic activity towards oxygen reduction reaction to Pt/C.

Silicon Phthalocyanine Modified Multi-Walled Carbon Nanotubes As a Novel Metal-Free Catalyst for the Oxygen Electroreduction

Finding an alternative catalysts for the oxygen reduction reaction (ORR) has been a key issue in modern electrocatalysis. Traditional platinum-based catalysts are not viable in the long term and thus much effort has been focused on non-precious metal catalysts. Heteroatom doped and metal-heteroatom co-doped carbon materials have emerged as the main candidate for replacing the platinum-based catalysts. Different MN4 macrocycles, such as metal phthalocyanines and porphyrins, have been studied as promising materials to prepare electrocatalysts for ORR in alkaline media [1]. While the development of non-precious metal and non-metal carbon catalysts has gained a lot of attention recently, non-metal phthalocyanines are a less studied topic [2].In this work a novel catalyst material including multi-walled carbon nanotubes (MWCNT) and silicon phthalocyanine dichloride (SiPcCl2) was synthesised and the electrochemical activity towards the oxygen reduction reaction (ORR) in alkaline media was studied. Different ratios of phthalocyanine-to-nanotubes were pyrolysed at 800 °C. After optimising the ratio of phthalocyanine-to-nanotubes, the pyrolysis process was also carried out at different temperatures, but the results showed that the best temperature for pyrolysis is still 800 °C. ORR activity on SiPc/MWCNT catalyst was studied in 0.1 M KOH by employing rotating disc electrode method. Physical characterisation was carried out with X-ray photoelectron spectroscopy and transmission electron microscopy. The results showed successful incorporation of silicon and nitrogen into the carbon framework. We show that doping MWCNTs with a non-metal phthalocyanine creates a highly active ORR catalyst rivaling the activity of metal-based catalysts in alkaline conditions. This work clearly demonstrates that non-metal macrocyclic compound modified carbons, similar to the the SiPc/MWCNT can be used as alternative cathode catalysts for the metal-air batteries and alkaline membrane fuel cells.[1] Y. Liu, X. Yue, K. Li, J. Qiao, D.P. Wilkinson, J. Zhang, PEM fuel cell electrocatalysts based on transition metal macrocyclic compounds, Coord Chem Rev. 315 (2016) 153-177.[2] K.-K. Türk, K. Kaare, I. Kruusenberg, M. Merisalu, U. Joost, L. Matisen, V. Sammelselg, J.H. Zagal, K. Tammeveski, Oxygen electroreduction on zinc and dilithium phthalocyanine modified multiwalled carbon nanotubes in alkaline media, J. Electrochem. Soc. 164 (2017) H338-H344.

One-Pot Synthesis of Fe-N-Containing Carbon Aerogel for Oxygen Reduction Reaction

Three-dimensional Fe-N-C aerogel catalysts for the oxygen reduction reaction (ORR) are prepared with resorcinol–formaldehyde–melamine and iron precursor using one-pot sol-gel process followed by supercritical drying and heat treatment in nitrogen (N2) and then ammonia (NH3) atmospheres. We studied the effect of the synthesis conditions (Fe precursor and Fe content) of organic aerogel and the heat treatment parameters (including temperature and duration) under N2/NH3 atmosphere on the structural properties and ORR catalytic activities of the resulting Fe-N-C aerogel catalysts. The Fe-N-C aerogel catalysts were characterized by X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, and N2-adsorption/desorption, and the ORR activities were studied by the rotating disk electrode method. It was found that the pore structure, the chemical composition, and ultimately the ORR performance were largely affected by the nature of iron precursor, iron content, and the conditions of heat treatment. The catalysts using Iron (III) acetylacetonate as Fe precursor incorporated with 3 wt% of Fe followed by the HT at 800 °C for 1 h under N2 and then 950 °C under NH3 for 30 min showed the highest content of active site (Fe-Nx) and largest mesopore volume, resulting in an enhanced catalytic activity and mass-transport property.

Oxygen reduction reaction on Pd nanocatalysts prepared by plasma-assisted synthesis on different carbon nanomaterials

In this work He/H2 plasma jet treatment was used to reduce Pd ions in the aqueous solution with simultaneous deposition of created Pd nanoparticles to support materials. Graphene oxide (GO) and nitrogen-doped graphene oxide (NrGO) were both co-reduced with the Pd ions to formulate catalyst materials. Pd catalyst was also deposited on the surface of carbon black. The prepared catalyst materials were physically characterized using transmission electron microscopy, scanning electron microscopy and x-ray photoelectron spectroscopy. The plasma jet method yielded good dispersion of small Pd particles with average sizes of particles being: Pd/rGO 2.9 ± 0.6 nm, Pd/NrGO 2.3 ± 0.5 nm and Pd/Vulcan 2.8 ± 0.6 nm. The electrochemical oxygen reduction reaction (ORR) kinetics was explored using the rotating disk electrode method. Pd catalyst deposited on nitrogen-doped graphene material showed slightly improved ORR activity as compared to that on the nondoped substrate, however Vulcan carbon-supported Pd catalyst exhibited a higher specific activity for oxygen electroreduction.

Highly Active Wood-Derived Nitrogen-Doped Carbon Catalyst for the Oxygen Reduction Reaction

In this recent decade, great interest has risen to develop metal-free and cheap, biomass-derived electrocatalysts for oxygen reduction reaction (ORR). Herein, we report a facile strategy to synthesize an electrochemically active nanocarbon material from the renewable and biological resource, wood biomass. The ORR activity of the catalyst material was investigated in 0.1 M KOH solution by employing the rotating disc electrode method. Scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy were employed to obtain more information about the catalyst material’s morphology and composition. The material exhibits outstanding electrocatalytic activity with low onset potential and high current density, similar to that of a commercial Pt/C catalyst in an alkaline medium. The results clearly ascertain that wooden biomass can be easily transformed into novel carbon nanostructures with superior ORR activity and possibility to be used in fuel cells and metal–air batteries.

Nano-sized Pt\u2013NbOx supported on TiN as cost-effective electrocatalyst for oxygen reduction reaction

Proton exchange membrane fuel cells (PEMFC) play a key role for sustainable energy; however, catalyst degradation remains one of the main challenges for competing with traditional energy technologies. The Pt/C commercially available electrocatalysts are susceptible to Pt dissolution and carbon support corrosion. In this context, we design a Pt–NbOx catalyst supported on TiN nanoparticles as an alternative electrocatalyst for the oxygen reduction reaction (ORR). The use of Pt–NbOx reduces materials’ costs by lowering the required platinum loading and improving catalyst performance. The TiN support is selected to improve support stability. The electrocatalyst is successfully synthesized by a one-step flame spray process called reactive spray deposition technology. Electrocatalyst with two different very low Pt loadings (0.032 mg cm−2 and 0.077 mg cm−2) are investigated and their performance as cathode is evaluated by the rotating disk electrode method. The new electrocatalyst based on Pt–NbOx supported on TiN has ORR performance that is comparable to the state-of-the-art Pt/C electrocatalyst. A half-wave potential of 910 mV was observed in the polarization curves, as well as a mass activity of 0.120 A∙mgPt−1 and a specific activity of 283 μA∙cmPt−2 at 0.9 V. These results demonstrate that Pt–NbOx on TiN electrocatalyst has the potential for replacing Pt/C cathode in PEMFC.

Electrospun Polyacrylonitrile‐Derived Co or Fe Containing Nanofibre Catalysts for Oxygen Reduction Reaction at the Alkaline Membrane Fuel Cell Cathode

AbstractElectrospun polyacrylonitrile (PAN) based carbon nanofibres (CNF) are employed as cathode catalysts in anion‐exchange membrane fuel cell (AEMFC) for the first time. The catalysts are prepared via pyrolysis of Co or Fe salt‐containing PAN fibre with and without the ionic liquid (IL) additive. The catalyst material preparation is optimised by assessing the oxygen reduction reaction (ORR) activity of different transition metal and nitrogen‐doped CNFs in 0.1 M KOH by rotating disc electrode method followed by testing in real AEMFC configuration. The best performance in the AEMFC is observed in case of Fe and IL containing PAN fibre that was pyrolysed at 1000 °C and additionally treated in an acid solution (Fe/IL‐PAN‐A1000). In the AEMFC, the Fe/IL‐PAN‐A1000 catalyst showed the maximum power density (Pmax) of 289 mW cm−2, which is 82 % of the Pmax obtained with commercial Pt/C cathode catalyst (352 mW cm−2).