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Abstract: Porous conducting carbon paper with its unique combination of properties acts as the backing material of electrode in a fuel cell. It not only assists in the flow of electrons and reactant gases but also acts as an effective support for the electrolyte and the catalyst layer. The electrically conducting porous carbon paper was prepared by adopting a modified process of preparation which involves molding together several carbon fiber preforms in the form of laminates rather than a single preform. The method was found to influence the characteristics of the paper significantly and resulted in improved performance of the unit fuel cell employing the laminated paper as electrode. The I–V performance of the fuel cell using carbon paper formed by molding single ply showed a peak power density of 573mW/cm2 as compared to that of 722mW/cm2 for three ply laminates, a value very close to that of achieved by using Toray (Japan) carbon paper (782mW/cm2) under identical operating conditions. [Copyright &y& Elsevier]

Abstract Paper-based microfluidic fuel cells emerge as a promising clean energy sources for small-scale electronic devices, while their broad-based applications require a comprehensive understanding of their structure-performance relationships. Here in this work, we made attempt to identify the key structural parameters that impact the overall performance of paper-based microfluidic fuel cells. The influences of fuel crossover, cell resistance, limitations from both anode and cathode, and in particular microfluidic paper channel properties have been systemically investigated and optimized towards the best practices. Among various structural parameters, we unravel for the first time that the overall performance of these paper-based microfluidic fuel cells is largely dependent on the textural properties of microfluidic paper channels. By correlating the fuel cell performance with the unambiguously determined flow rate of electrolyte within different paper channels, we found that a greater flow rate which was achieved by using paper with larger mean pore diameter, could result in higher peak power density and open circuit voltage. This performance enhancement would benefit from minimized reactant depletion near electrode surfaces and suppressed fuel crossover. Technically, an open circuit voltage of 0.86 V and a maximum power density of 7.10 mW/cm2 can be achieved on a single cell (fuel: 4 M KCOOH; oxidant: air; electrolyte: 1 M KOH; catalyst: 0.2 mg/cm2 Pd/C on 0.15 cm2 graphite foil), and the maximum power output can be sustained for at least 1 h. The fuel cell power can also be easily increased proportionally when connecting two or more cells in series, which makes theses paper-based microfluidic fuel cells capable to power various electronic devices with different power requirements. [ABSTRACT FROM AUTHOR]

• Shrub-like pt-rh catalysts with different metallic ratios on carbon paper were prepared by laser ablation. • The catalysts displayed higher tolerance to CO and higher catalytic activity towards ethanol oxidation. • Pt-Rh catalysts demonstrated long-term poisoning rates eight times lower than pt. Plasmas techniques are novel routes for the preparation of complex nanostructured materials for catalysis and clean hydrogen energy such as fuel cells. CBPLD technique allows enhanced interaction between the catalyst and the support and improved catalytic properties. Herein, a highly active and durable vertically aligned nanostructured shrub-like bimetallic Pt x Rh 100-x alloys with atomic ratios close to nominal values are grown on carbon paper substrate. The tolerance to CO poisoning and ethanol electrooxidation reactions are studied over these new types of shrub-like bimetallic Pt x Rh 100-x /CP catalysts, demonstrating that such structures effectively facilitate both processes and very low long-term poisoning rates. Such high catalytic activity accounts for two mechanisms: Rh a highly oxophilic transition metal activates water dissociation at lower potentials than Pt (bifunctional mechanism), and the ligand effect where Rh alters the electronic structure of the neighboring Pt suggesting a faster supply in OH ads. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Multi-wall carbon nanotubes (MWCNTs) have been synthesized on a carbon fiber paper (CFP) via a simple surface reaction of hydrocarbon decomposition using nickel nanoparticles as catalysts at 1023 K. Pd nanoparticles supported on MWCNTs/CFP are used as electrocatalysts for ethanol electrooxidation in alkaline media. The results shows that the Pd/MWCNTs/CFP electrocatalyst gives higher reaction activity and more stable performance than the commercial Pd/C and Pd/CFP electrocatalyst for ethanol oxidation in alkaline medium. [ABSTRACT FROM AUTHOR]

Highlights: [•] Solution coating of metal oxide layer directly onto carbon paper. [•] Most uniform Metal oxide coating on functionalized carbon paper. [•] Highest electrochemical stability for metal oxide coated functionalized carbon paper. [ABSTRACT FROM AUTHOR]

Self-pumping fuel cells supported on filter papers are constructed by using hydrazine monohydrate as a fuel and potassium permanganate as the oxidant. Cost effective catalysts, namely, Cu nanoparticles (NPs), functionalized multiwalled carbon nanotubes (f-MWCNTs) and Cu-NPs@f-MWCNTs composite are synthesized and loaded onto carbon cloths, which are employed as the electrodes. The cells are operated at room temperature. The Cu-NPs@f-MWCNTs composite contained 75% and 25% of Cu-NPs and f-MWCNTs, respectively. The morphology of the composite comprises of Cu-NPs flanked to the tubular structures of f-MWCNTs, which resulted in improved electrocatalytic activity, compared to pristine Cu-NPs (which tend to aggregate severely) and pristine f-MWCNTs. The electrocatalytic activities of Cu-NPs@f-MWCNTs and Cu-NPs are comparable and superior to f-MWCNTs for hydrazine oxidation. Multiple cells with different catalyst combinations at the anode and cathode are electrochemically characterized. The cell with Cu-NPs@f-MWCNTs composite at the anode and with f-MWCNTs at the cathode produced the highest power density of 3.57 mW/cm 2 at 0.89 V. For this catalyst combination, the cell retained an open circuit voltage between 1.85 V - 1.74 V for more than ten minutes of operation. Although the cell current density declined over time, it could be recovered to its original value by replenishing the cell with fresh anolyte and catholyte streams. [ABSTRACT FROM AUTHOR]

Ethanol co-laminar flow fuel cells operating at room temperature have rarely been reported, primarily due to problems associated with the kinetics of ethanol oxidation. In this work, we present a study of the effect of ethanol concentration, pH of anodic and cathodic streams, and nature of the oxidant on the performances of an acrylic cell and a paper-based, membraneless co-laminar flow fuel cell (LFFC), with total cell volumes of 14.29 cm 3 and 0.62 cm 3 , respectively. Additionally, this work reports the synthesis of a Pd-NiO anodic nanocatalyst by a simple, fast, and environmentally friendly method in order to match the clean, easy-to-use, and simple fabrication methods of these ethanol co-laminar flow fuel cells. The synthesized Pd-NiO exhibited a crystallite size of 8.1 nm and an average particle size of 8.7 nm for Pd-NiO/C. The highest performances were obtained by combining an alkaline anodic stream with an acidic cathodic stream, increasing the cell voltage, and decreasing cathodic limitations caused by the simultaneous occurrence of oxygen reduction as well as hydrogen reduction reactions. With these improvements, power densities of 108 and 85.5 mW cm −2 were obtained for the acrylic and the paper-based co-laminar flow fuel cell, respectively, which are the highest values reported to date for ethanol LFFCs at room temperature. [ABSTRACT FROM AUTHOR]

Abstract: This work presents the results from the development of bio-cathodes for the application on paper-based biofuel cells. Our main goal here is to demonstrate the possibility of using different designs of air-breathing bio-cathodes and ink-based bio-cathodes for this new type of paper based electrochemical cell. The electrochemical performance for the bio-electrocatalytic oxygen reduction reaction was studied by using open circuit voltage and amperometry measurements, as well as polarization curves to probe the four-electron reduction reaction of ambient oxygen catalyzed by bilirubin oxidase (BOx). The electrochemical measurements showed that all procedures allowed the direct electron transfer from the active site of the bilirubin oxidase to the electrode surface with a limiting current density of almost 500μAcm−2 for an air-breathing BOx cathode and 150μAcm−2 for an ink based BOx cathode. Under a load of 300mV a stable current density was obtained for 12h of continuous operation. [Copyright &y& Elsevier]

Abstract: Porous conducting carbon paper acts as an electrode backing material in a fuel cell. It not only assists in the flow of electrons and gases but also provides mechanical support to the MEA. The electrically conducting carbon paper (porosity ∼70%) was prepared using laminated assembly of chopped carbon fiber porous preforms and applying combined paper making and composite making technique. The green paper was subjected to different heat treatment temperatures (HTT), which was found to influence the characteristics of the paper significantly. The processing of the paper was carried out at a very fast carbonization rates, 900°C/h as compared to 10–20°C/h used conventionally, making the complete process highly cost efficient. The paper when used in the unit fuel cell assembly showed I–V performance comparable to that of the commercially available Toray carbon paper. [Copyright &y& Elsevier]

Abstract: The present discussion paper deals with the Gyenge''s [E. Gyenge, Electrochim. Acta 49 (2004) 965] suggestion to add thiourea (H2N–CS–NH2) to the borohydride fuel of the direct borohydride fuel cell (DBFC). It is expected that thiourea inhibits the hydrogen evolution (stem from the borohydride hydrolysis, a side reaction) that occurs at the anode of the DBFC where in fact it is expected the direct oxidation of borohydride. However, thiourea is an organic sulphur compound and it is well known that the sulphur species are poisons for the metallic catalysts. Hence, the present discussion paper asks a question: may thiourea and the sulphur species stem from its decomposition act as poisons of metallic sites of catalysts used as DBFC anodes? [Copyright &y& Elsevier]

Abstract New multi-metallic materials have been synthesized to be used as active anodes in direct alcohol fuel cells. However, the separate steps of synthesis, characterization and preparation of the catalyst layer prior to their use are costly and time-consuming. Here, we propose a sustainable new method to in situ decorate catalysts with ad-atoms in flow-through porous electrode configuration. The ad-atoms are electrodeposited in a microfluidic fuel cell by driving the metallic precursor through the electrode under applied potential while blank electrolyte feeds the other half-cell porous electrode. Pt/C-modified carbon paper is decorated with Fe, which is subsequently used as an anode during operating the cell as a microfluidic direct glycerol fuel cell. The ultralow mass of Fe is calculated by integrating the reduction charge, in which the high residence time under controlled flow conditions increases the amount of Fe on Pt/C. The decoration can also be controlled by changing the concentration of the precursor, which is limited by the availability of Pt active sites. The power density of the obtained cell in flow-through porous electrode configuration is enhanced by 36% using the Fe-decorated anode, reaching ∼54 mW cm−2 at ∼0.7 V under mixed media conditions. Hence, the proposed method provides an effective means to modify, analyze and use bimetallic anodes at the same instrument and can be applied post-fabrication in any fuel cell or other flow cells with porous electrodes. Graphical abstract Image 1 [ABSTRACT FROM AUTHOR]

Symmetrical solid oxide fuel cells (SSOFCs) use the same materials as electrode, thereby reducing fabrication processes, simplifying interface problem and improving tolerance to coking and sulfur. In this paper, the multifunctional Sr 2 Ti 0.8 Ni 0.2 FeO 6– δ (STN02F) oxide is successfully synthesized and evaluated to be as symmetrical electrodes for SOFCs. The Ni-Fe alloy nanoparticles can be exsolved from STN02F sample in high temperature reducing atmosphere. The impedance stability test demonstrates that the polarization resistance (R p) of STN02F exhibited no obvious change in both air and H 2. The fuel cells obtain the maximum power densities of 710 mW cm–2 in H 2 , 581 mW cm–2 in CH 3 OH, 527 mW cm–2 in C 3 H 8 and 213 mW cm–2 in direct C at 800 °C. The fuel cell exhibited no output performance degradation during the 200 h test in H 2. The current densities of 0.84 A cm−2 at 1.3 V in 50%H 2 O/50%H 2 and 0.77 A cm−2 at 1.5 V in CO 2 were obtained for electrolysis cell at 800 °C. The efficient and stable symmetrical electrode STN02F is a promising candidate material for SOCs. [Display omitted] [ABSTRACT FROM AUTHOR]

• The effect of the concentration boundary layer thickness on the MMFC performance is investigated. • The proposed modification enhances mass transport as it thins the concentration boundary layer. • The limiting current density increases by 91.5 % as the concentration overpotentials are reduced. • The oxidant concentration on the electrode surface is increased from 0.055 mol/m3 to 0.19 mol/m3. The concentration boundary layer thickness is one of the most important parameters used to characterize the performance of membraneless microfluidic fuel cells. Low concentration boundary layer thickness leads to a high electrochemical reaction over the electrodes, improving the performance of the fuel cell. For this purpose, this paper proposes a modified microchannel which directs the fuel and the oxidant to the electrode surfaces. According to the results obtained, the amount of concentration on the cathode electrode surface and therefore the amount of current density increased with the modified microchannel. At the same point of the cathode electrode surface, the oxidant concentration in the conventional microchannel was 0.055 mol/m3, while it was 0.19 mol/m3 in the modified microchannel. Since the concentration overpotential reduced, the limiting current density was 0.372 mA/cm2 in the conventional microchannel and 0.741 mA/cm2 in the modified microchannel. Thus, the limiting current density value increased by 91.5 %. [ABSTRACT FROM AUTHOR]

For urban or suburban transport, the power demand of a personal car does not exceed 30 kW/ton, far below the power offered by regular cars designed for any ride. Moreover, it was formerly shown that the above power could be attained by a 10 kW fuel cell directly hybridized to a supercapacitor string able to deliver a 20 kW power peak. This theoretical fact, corresponding to low resource demand in the car manufacturing, was validated up to ½ scale on the bench. Within a research project in University of Lorraine, the target is to validate the low-resource demanding concept in a real hydrogen electric vehicle (fuel cell range extender Renault Kangoo) and to examine related aspects by combining engineering sciences to social and human sciences and economics. After reminding the former validation on a bench, the paper describes current work on how the electrical power is managed in the Renault H 2 ZE Kangoo, by characterization of the fuel cell and thorough analysis of the transients of electrical and non-electrical variables available in the vehicle in various rides. Besides, risks and life cycle analysis of a one-ton hybrid vehicle have been evaluated in comparison with other 30 kW vehicles powered by either a fuel cell, or batteries or an internal combustion engine. Finally, social acceptability of the fuel cell cars by regular citizens is presented, revealing a positive opinion at fuel cells and hydrogen, however with a moderate readiness to its acquisition. [ABSTRACT FROM AUTHOR]

• The first fabric-based, single-stream microfluidic fuel cell is developed. • The performance depends on the fabric properties and the electrode configuration. • Fuel cell performance is better in acidic rather than alkaline electrolytes. • The proposed fabric-based fuel cell shows better durability than paper-based fuel cells. A membraneless microfluidic fuel cell micromachined with a fabric substrate is proposed to enhance the longevity of self-pumping microfluidic fuel cells. The fabric substrate of the fuel cell provides good longevity as well as passive pumping. A stenciling technique is used for patterning the hydrophilic microchannel of the proposed single-stream fuel cell to retain the flexibility of the fabric. The effects of the fabric properties and the electrode configuration on the novel single-layer fuel cell are investigated. The performance of the fuel cell with different fuels (H 2 O 2 , HCOOH, KCOOH, CH 3 OH) in either alkaline or acidic electrolytes is experimentally measured and compared. The peak power density (1.43 mW cm−2), the maximum current density (6.16 mA cm−2), and the open circuit voltage (0.98 V) are highest with the flannel substrate when the fuel is H 2 O 2 and the electrolyte is HCl. Compared to the paper-based, single-stream microfluidic fuel cells, the fuel cell performance is favorable and the duration time (618 min) is the best. This study provides valuable information to develop this easy-to-use power source for portable electronic devices. [Display omitted] [ABSTRACT FROM AUTHOR]

Aluminum/air microfluidic fuel cell (MFC) combines the advantages of co-laminar MFC and aluminum/air batteries with high energy density, low cost, membraneless and miniaturized design, which is a promising device to power the numerous nodes in the Internet of Things (IoT) ecosystems. Here, we propose a recirculating dual-electrolyte aluminum/air MFC with an alkaline anolyte and an acid catholyte. The cell exhibits an outstanding performance with an open-circuit voltage of 2.2 V and a short-current density of 1 A cm−2, benefiting from the dual-electrolyte design. In order to prevent the naturalization reaction between the electrolytes and improve the utilization rate, a regular hierarchical porous carbon paper is applied as the separator, which minimizes the mixing of electrolytes and facilitates the recirculation. This work provides an alternative route for cost-effective and high-performance aluminum/Air MFCs toward real applications. [ABSTRACT FROM AUTHOR]

The catalyst durability at low Pt loading remains a barrier for industrial commercialization of the proton exchange membrane fuel cell. Degradation of low loaded Pt catalyst not only reduced the electrochemical surface area but also revealed a Pt depletion zone adjacent to the cathode/membrane interface where about 80% of the Pt was lost due to dissolution and migration into the membrane. We hypothesized that the Pt degradation can be mitigated using a gradient cathode design without sacrificing the initial fuel cell performance. With a focus on the mitigation, the first of two companion papers focuses on the Type I cathode with larger Pt particles (5 nm average size) near the cathode/membrane interface. In the second of these two papers, the Type II cathode with higher Pt loading (60 wt.% Pt on carbon) near the cathode membrane interface will be investigated. The catalyst coated membranes with gradient cathode were fabricated by reactive spray deposition technology with low Pt loading of 0.05 mg cm −2 on the anode and 0.1 mg cm −2 on the cathode. The DOE defined accelerated stress test was performed by imposing a triangular wave potential cycling from 0.6 V to 1.0 V for 30,000 cycles at 50 mV s −1 scan rate. Results of accelerated stress test showed that the loss of electrochemical surface area and PEMFC performance were reduced for the Type I cathode compared to the control cathodes that consisted of 2 nm averaged Pt particle size only. Microscopy analysis suggested two possible mechanisms for this durability improvement: 1) the reduction of the amount of Pt lost due to Pt dissolution, and 2) the preservation of Pt particles at the cathode/membrane interface. Comparison with the control cathode showed that the loss of Pt near the cathode/membrane interfaced were reduced from 80% to 40% and the overall Pt loss of the cathode were reduced from 30% to 15%. [ABSTRACT FROM AUTHOR]

Hybridization of a fuel cell with a high power energy source reduces the necessary fuel cell size, improves dynamic behaviour, alleviates degradation and allows the recovery of reversible energy, e.g. from magnetic brakes. Direct hybridization, i.e. the connection of a supercapacitor with one or two fuel cells on the unit cell level, is easy to implement, is energy self-managing, provides direct protection against load peaks and avoids power electronics which add weight and increase losses. This paper takes the direct hybridization concept one step further by integrating the supercapacitor into the fuel cell. This avoids redundant system and cell components and leads to a lightweight hybrid system. The supercapacitor electrode is integrated by functionalizing the gas diffusion layer (GDL) of the fuel cell, giving it an electrochemical double layer capacity. Possible synthesis routes for such a functionalization are developed based on physical theory of self-organization and established carbon surface modifications. A self-assembly of an ionomer skin around the carbon fibres of the GDL with a proton-enriched water phase in between leads to a structure with an added double layer capacity, a nanoscopic liquid water transport network and hydrophobic inter-fibre pores allowing unhindered oxygen transport. The dynamic electrode transport processes in the integrated hybrid were analyzed using porous electrode theory. Overall, the integrated hybrid behaves similarly to a direct, parallel hybrid. However, the parallel hybrid has two separate proton pathways, i.e. fuel cell membrane and supercapacitor separator, leading to an overall lower ohmic resistance. Because the pathways are separated, charge balancing oscillations between fuel cell and supercapacitor can occur, especially in asymmetric configurations with differing anode and cathode capacities. In the integrated hybrid, the proton conducting phases of supercapacitor and fuel cell are connected, which avoids such charge balancing and can lead to lower losses in the mid-frequency range. Image 1 [ABSTRACT FROM AUTHOR]

This paper introduces a novel coupled region-to-region numerical procedure for electric field potential calculations. A conventional segregated scheme is also introduced to illustrate the coupling issues that exist in performance calculations in electrochemical devices. Numerical simulations are conducted for a solid oxide cell operating in both fuel cell and electrolysis modes. The cell performance is predicted with both segregated and coupled methods. A comparison between the coupled and segregated schemes shows that the former greatly outperforms the latter, reducing convergence times (from 5000 to 300 iterations) and improving stability. A smaller coupling coefficient contributes to the convergence as well, however, less markedly. The coupled region-to-region approach may readily be applied to numerous other scenarios, e.g., heat transfer problems between multiple phases and regions. [ABSTRACT FROM AUTHOR]

This paper proposes a methodology for characterizing electrochemical parameters in non-isothermal three-dimensional (3 D) simulation models of fuel cell stacks. The proposed methodology involves utilizing only easily measurable construction and non-invasive operational data. In order to achieve a reasonable computational cost, an iterative method developed on various 3 D computational domains is combined with a genetic algorithm optimization technique. The effectiveness of the methodology is demonstrated through its application on a real scale 40-cell high temperature PEM fuel cell (HTPEMFC) stack, with the results indicating good agreement between the model and experimental data. This approach has the potential to significantly reduce the computational cost of optimizing fuel cell designs while still maintaining accuracy. [Display omitted] [ABSTRACT FROM AUTHOR]

• Dynamic inconsistent behavior of the fuel cell stack with severe aging cells is investigated. • Theoretical changing trend of voltage difference between normal and abnormal cells is derived. • Slower dynamic response inside the abnormal fuel cell compared to normal cells is revealed. • Deterioration of the abnormal fuel cell to the dynamic consistency of the stack is quantified. • Accurate diagnosis of in-stack abnormal cells based on Bollinger band and entropy is realized. The abnormal cells within a fuel cell stack can reduce the stack's lifetime and reliability due to the "barrel" effect. In this paper, the dynamic inconsistency of a 20-kW fuel cell stack with two abnormal cells is studied. These abnormal fuel cells with severe aging have a lower voltage but without faults. First, the voltage difference change trend between abnormal and normal fuel cells under different current densities is analyzed by theoretical derivation and experiments. Further, the inconsistent dynamic response of the fuel cell stack under different current steps is investigated. The results show that the voltage difference's variation rate between normal and abnormal fuel cells is greater than 0.005 V·cm2/A at any current density. The particular is that this variation rate increases significantly at high current densities due to the increasing concentration polarization loss inside the abnormal cell. Besides, the slower dynamic response of abnormal cells during the current step deteriorates the stack's dynamic consistency. The voltage standard deviation of the stack is reduced by a maximum of 37.5% when abnormal cells are not taken into account. Therefore, a diagnosis method utilizing voltage information with small computation is proposed. The method can accurately identify in-stack abnormal fuel cells by combining qualitative analysis of voltage values based on the Bollinger band and quantitative measurement of voltage fluctuation degree using Shannon entropy. These efforts provide guidance for fuel cell system control and fault diagnosis. [Display omitted] [ABSTRACT FROM AUTHOR]

Membraneless microfluidic fuel cells (M2FCs) are promising portable power sources, but they suffer from limited scalability. This paper presents a scaling-out strategy for general M2FC applications with their characteristics studied by both experiments and mathematical modeling. The present strategy addresses the issues of flow distribution non-uniformity and shunt current losses by integrating a well-designed fluid circuit. With the present strategy, parallel and series connections of four cells in an array results in a scaling-out efficiency of 93% and 82%, respectively. The effects of different parameters on the array performance as well as further device scalability are also investigated in this paper. Preferable conditions for the array operation include a high branch ionic resistance, small unit cell difference and high unit-cell performance, which can be achieved by appropriately designing the branch geometry, employing high-precision fabrication/assembly techniques and improving the single-cell materials/chemistries. It is expected that the present array can be incremented to 50 cells or above in series with over 75% efficiency as long as there is sufficiently high branch resistance or cell performance. [ABSTRACT FROM AUTHOR]

Abstract: In this study, we have explored the possibility to fabricate microbial biofuel cell operating with carbon nanotube–gold–titania nanocomposites (CNT/Au/TiO2) as anode modifier. The results demonstrate that the CNT/Au/TiO2 electrode could be utilized as a new and effective microbial fuel cell (MFC) anode, which integrate the advantages of relevant nanocomposites such as high conductivity, high specific surface area, and easy adsorption of the microorganism. It is evident that the three-dimensional network nanostructures of CNT/Au/TiO2 are propitious to improve the relevant anode surface area and thus the adsorption of the microorganism, which can efficiently promote the electronic transfer rate between the probe and electrode. Meanwhile, it is noted that open circuit voltage of the CNT/Au/TiO2 nanocomposites modified carbon paper anode increased to 0.77V, which is more than twice that of the open circuit voltage obtained with bare carbon paper anode (0.36V). And the MFC equipped with CNT/Au/TiO2 nanocomposites modified carbon paper anode delivers a maximum power density of 2.4mWm−2, which is three times larger than that obtained from the MFC with bare carbon paper. This observation illustrates that the CNT/Au/TiO2 nanocomposites modified electrode could obviously increase the relevant electron transfer rate and promote the electron exchange at electrode surface, which could readily provide enhanced stability and relatively long life-span to facilitate the high electricity production efficiency, suggesting its promising prospect application in MFCs. [Copyright &y& Elsevier]

Abstract: Decarbonising transport is proving to be one of today''s major challenges for the global automotive industry due to many factors such as the increase in greenhouse gas and particulate emissions affecting not only the climate but also humans, the increase in pollution, rapid oil depletion, issues with energy security and dependency from foreign sources and population growth. For more than a century, our society has been dependent upon oil, and major breakthroughs in low- and ultra-low carbon technologies and vehicles are urgently required. This review paper highlights the current status of hybrid, battery and fuel cell electric vehicles from an electrochemical and market point of view. The review paper also discusses the advantages and disadvantages of using each technology in the automotive industry and the impact of these technologies on consumers. [Copyright &y& Elsevier]

Abstract: Microfluidic vanadium redox fuel cells are membraneless and catalyst-free fuel cells comprising a microfluidic channel network with two porous carbon electrodes. The anolyte and catholyte for fuel cell operation are V(II) and V(V) in sulfuric acid based aqueous solution. In the present work, the electrochemical characteristics of the vanadium redox reactions are investigated on commonly used porous carbon paper electrodes and compared to a standard solid graphite electrode as baseline. Half-cell electrochemical impedance spectroscopy is applied to measure the overall ohmic resistance and resistivity of the electrodes. Kinetic parameters for both V(II) and V(V) discharging reactions are extracted from Tafel plots and compared for the different electrodes. Cyclic voltammetry techniques reveal that the redox reactions are irreversible and that the magnitudes of peak current density vary significantly for each electrode. The obtained kinetic parameters for the carbon paper are implemented into a numerical simulation and the results show a good agreement with measured polarization curves from operation of a microfluidic vanadium redox fuel cell employing the same material as flow-through porous electrodes. Recommendations for microfluidic fuel cell design and operation are provided based on the measured trends. [Copyright &y& Elsevier]

The present paper focuses on the effect of reduced hydrogen stoichiometry on the dynamic behavior of a PEMFC directly hybridized with SC or non-hybridized, using the European standard cycling protocol (FC-DLC) for transport applications. Two gas stoichiometry factors have been considered, at 1.2 and 1.1. Whereas direct hybridization of a single cell enables to reduce the hydrogen overconsumption from 28% to 20% at hydrogen stoichiometry of 1.2, the overconsumption was further reduced to 10% by reducing the stoichiometry to 1.1. The durability of a single fuel cell has been investigated by comparing the long-term cycling operation depending on the hydrogen stoichiometric conditions, for both hybridized and non-hybridized fuel cell. The non-hybridized fuel cell, at hydrogen stoichiometry of 1.2, was operated for 687 h (end of life), whereas the non-hybridized fuel cell at 1.1, could not be operated due to the sudden, excessive voltage drop in the high current density period of the cycle. On the contrary, the hybridized fuel cell was successfully submitted to cycling for more than 1000 h at both conditions of hydrogen stoichiometry. The GDL appears to be responsible for the failure of non-hybridized fuel cell performance, whereas no particular degradation was evidenced with hybridized configurations. Finally, the technique has been successfully applied to a three-cell stack, with very comparable voltage profiles of the individual cells over the cycling protocol. Image 10553 • Hybrid vehicles consisting direct hybridization of fuel cell and supercapacitors are convincing. • Direct hybridization allows to operate even at lower hydrogen supply. • Low hydrogen supply is only sustainable in direct hybridization mode. • Lower hydrogen supply in direct hybridization mode does not impact the durability. • Direct hybridization is also feasible for fuel cell stack. [ABSTRACT FROM AUTHOR]

Abstract This paper presents experimental and modeling study of high temperature polymer electrolyte membrane fuel cell performance. The experiments are performed using in-house prepared MEA with an active area of 2.25 cm2. The experiments are simulated using a one dimensional distributed charge transfer model that resolves the properties along the thickness of the MEA. Six different HOR models and two different ORR models are subjected to initial studies. The model predictions are compared with cell performance on pure H 2 and H 2 with CO contamination. A detailed sensitivity analysis is carried out to understand the influence of various model parameters on cell performance over a range of potentials. [ABSTRACT FROM AUTHOR]

Abstract This work has the difficult task to deeply study the electrochemical processes that occur inside a 100 cm2 of Molten Carbonate Fuel Cells (MCFC) impedance spectra using the high resolution of Distribution of Relaxation Time (DRT) method. Using this method, it is possible to shed light on the different physicochemical processes occurring within these cells, identifying the characteristic relaxation times by means of an appropriate experimental campaign where temperature and gas compositions in anode and cathode were varied one at a time. The quality of the recorded spectra was verified by Kramers-Kronig relation before applying DRT calculations. In this work, five distinct and separated peaks with different time constants ranging from 0.01 to 500 Hz were identified and associated with physiochemical processes of the cell. Three peaks at high frequency represent the charge transfer processes in anode and cathode active sites. The other two, located at low frequency, are associated with the gas diffusion in the electrodes and to the gas conversion process. This study represents the first application of the DRT approach to this technology allowing to understand the physicochemical origin of the individual polarization processes controlling the cell performance and the degradation. The analysis of degradation processes using the DRT method and the physiochemical processes identification presented in this paper will be shown in part II of this work. Highlights • The first application of DRT approach to MCFC impedance Spectra is presented. • Five processes controlling the cell performance are individuated using DRT method. • Repeatability and reproducibility of the DRT results in MCFCs are demonstrated. • Three peaks with a high-frequency domain are related to Charge Transfer Processes. • Two peaks with a low-frequency domain are associated with Mass Transfer Mechanisms. [ABSTRACT FROM AUTHOR]

Abstract: In proton exchange membrane fuel cell (PEMFC) models, oxygen effective diffusivity is the most important parameter to characterize the oxygen transport in the gas diffusion layer (GDL). However, its determination is a challenge due to its complex dependency on GDL structure. In the present study, a three-dimensional network consisting of spherical pores and cylindrical throats is developed and used to investigate the effects of GDL structural parameters on oxygen effective diffusivity under the condition with/without water invasion process. Oxygen transport in the throat is described by Fick''s law and water invasion process in the network is simulated using the invasion percolation with trapping algorithm. The simulation results reveal that oxygen effective diffusivity is slightly affected by network size but increases with decreasing the network heterogeneity and with increasing the pore connectivity. Impacts of network anisotropy on oxygen transport are also investigated in this paper. The anisotropic network is constructed by constricting the throats in the through-plane direction with a constriction factor. It is found that water invasion has a more severe negative influence on oxygen transport in an anisotropic network. Finally, two new correlations are introduced to determine the oxygen effective diffusivity for the Toray carbon paper GDLs. [Copyright &y& Elsevier]

Abstract: Biofuel cells are similar to traditional fuel cells, except the metallic electrocatalyst is replaced with a biological electrocatalyst. This paper details the development of an enzymatic biofuel cell, which employs alcohol dehydrogenase to oxidize ethanol at the anode and bilirubin oxidase to reduce oxygen at the cathode. This ethanol/oxygen biofuel cell has an active lifetime of about 30 days and shows power densities of up to 0.46mW/cm2. The biocathode described in this paper is unique in that bilirubin oxidase is immobilized within a modified Nafion polymer that acts both to entrap and stabilize the enzyme, while also containing the redox mediator in concentrations large enough for self-exchange based conduction of electrons between the enzyme and the electrode. This biocathode is fuel tolerant, which leads to a unique fuel cell that employs both renewable catalysts and fuel, but does not require a separator membrane to separate anolyte from catholyte. [Copyright &y& Elsevier]

This paper presents results of recent investigations to develop an optimized in-house membrane electrode assembly (MEA) preparation technique combining catalyst ink spraying and assembly hot pressing. Only easy steps were chosen in this preparation technique in order to simplify the method, aiming at cost reduction. The influence of MEA fabrication parameters like electrode pressing or annealing on the performance of hydrogen fuel cells was studied by single cell measurements with H2/O2 operation. Toray paper and carbon cloth as gas diffusion layer (GDL) materials were compared and the composition of electrode inks was optimized with regard to most favorable fuel cell performance. Commercial E-TEK catalyst was used on the anode and cathode with Pt loadings of 0.4 and 0.6mg/cm2, respectively. The MEA with best performance delivered approximately 0.58W/cm2, at 65°C cell temperature, 80°C anode humidification, dry cathode and ambient pressure on both electrodes. The results show, that changing electrode compositions or the use of different materials with same functionality (e.g. different GDLs), have a larger effect on fuel cell performance than changing preparation parameters like hot pressing or spraying conditions, studied in previous work. [Copyright &y& Elsevier]

Effects of hydrophobic polymer content within a carbon paper, used as the cathode gas diffusion layer (GDL), on power performance of a H2/air proton exchange membrane fuel cell (PEMFC) have been studied. Electrochemical methods are used in conjunction with morphology and wetting property characterization. Surface contact angle of wet-proof-treated GDL as a function of temperature is measured by a novel capillary rise method. It is shown that the contact angle generally decreases with the temperature, and that there is insignificant difference in contact angle on carbon papers treated with different contents of fluorinated ethylene propylene (FEP) ranging from 10 to 40 wt.%. Under all humidification conditions in this study, a membrane-electrode assembly (MEA) consisting of 10 wt.% FEP-impregnated GDL shows higher power densities than 30 wt.% FEP-impregnated one. Surface morphology of the hydrophobic polymer-treated carbon paper has been analyzed by scanning electron microscopy (SEM) and is identified as playing a crucial role in affecting the power performance of such treated GDL in the PEM fuel cell. [Copyright &y& Elsevier]

The main goal of our research project is to design safe, high energy and power density lithium/water systems. We explored the feasibility of substituting the natural bilayer (formed on the lithium surface when lithium is in contact with water), for a thin polymeric film. By substituting the natural bilayer film we hope to reduce the parasitic reactions occurring at the lithium/water interface, thus yielding an increase in the anodic efficiency. We investigated the effect of placing or casting a thin, (lithium/ion-conducting) polymer layer on the lithium metal surface. This paper is part one in a series of two papers. Paper I presents the results obtained with a lithium/polymer system, where the polymer was a monolayer of a polyphosphazene with 90% trifluoromethylphenoxy and 10% lithium carboxyphenoxy side groups (Polymer 4), or a multilayer film formed of one layer of poly[bis(methoxyethoxyethoxy)phosphazene] (MEEP) and one to three layers of Polymer 4 containing from 0 to 75 wt.% of lithium triflate salts. Paper II presents results obtained when the polymer layers were prepared using a polymer with equal amounts of methoxyethoxyethoxy and phenoxy side groups containing from 0 to 75 wt.% of lithium triflate salts. Phosphazene membranes have been designed and tailored to allow lithium ion conduction and prevent water migration to the surface of lithium metal. The phosphazene membranes enhance the safety of an aqueous lithium cell by inhibiting (or reducing) the reaction of lithium with water that evolves hydrogen at the anode. Original tests of lithium/phosphazene systems led to unpredictable open circuit voltages (OCVs). When the adhesion of the membrane to the lithium metal was improved, the OCV stabilized. The OCVs for the half-cell of lithium polymer aqueous electrolytes varies between −3.1 and −2.8 VSCE, depending on the membrane. The current densities for this polymer system are in the range of 10−6–10−3 A/cm2. The Columbic anodic efficiency is assumed to be near 100%—as hydrogen evolution is not measurable. Some of the polymeric membranes developed pinholes with use. Layered systems have also been designed to avoid the development of pinholes over time. In this paper, we present the results obtained by using polyphosphazenes with a 9:1 ratio of trifluoromethylphenoxy and p-carboxyphenoxy side groups and the lithium salt of the carboxylate function. Poly(organophosphazene) membranes with a single layer and a multilayer structure were tested in 8 M KOH or synthetic seawater for up to 5 days. [Copyright &y& Elsevier]

Abstract In this paper, we report on the synthesis and function of self-humidifying nature of manganese oxide supported platinum (Pt/Mn x O x) electrocatalyst under dry gas condition in proton exchange membrane fuel cells (PEMFC) with excellent electrochemical stability, long-term durability and remarkable fuel cell performance. The high-surface area nano-petal shaped manganese oxide (Mn x O x) clusters are synthesized by anodic deposition and the Platinum (Pt) nanoparticles are electrodeposited on diffusion layer (GDL) having two-layers of Mn x O x coating. The morphology and self-humidifying nature of Pt/Mn x O x were extensively studied through HR-SEM, HR-TEM, XPS, XRD, and water uptake studies. The electrochemical stability and long-term durability were investigated through cyclic voltammetry (CV) studies and single cell fuel cell performance. The MEAs using the spherical clusters of clump-like Pt/Mn x O x exhibited a peak power of 0.65 W/cm2 at 0.48 V under dry gas condition without humidification. Also, the fuel cell delivered stable power output at a constant current density of 0.8 A/cm2 for about 150 h with a negligible potential drop of 26 μV h−1. The long-term durability, excellent electrochemical activity and self-humidifying nature of Pt/Mn x O x may be attributed to the formation of hydroxyl groups on Pt/Mn x O x which facilitates the proton conductivity. [ABSTRACT FROM AUTHOR]

Oxygen electrochemistry on platinum comprises of three well-known phenomena - oxygen reduction reaction (ORR), platinum oxide formation and reduction in cyclic voltammetry (CV) and potentiostatic platinum oxide growth. Many of the elementary reaction steps are common to the three reaction systems but usually separate kinetic models for the three phenomena are reported in the literature. In this paper, we present a single reaction framework comprising multistep mechanism, based on suitable modification of double-trap kinetic model [1], that captures the key characteristics of the ORR, CV and oxide growth. Comparison between experimental data and model as well as other models is presented in this work. [ABSTRACT FROM AUTHOR]

Alkaline anion exchange membrane fuel cell (AEMFC) is a promising technology to replace precious metals used today as fuel cell catalysts. However, AEMFC does not yet demonstrate high performance when running on ambient air where they are exposed to CO 2 . The resulting carbonation reaction reduces membrane conductivity. This paper analyses and quantifies the effect of CO 2 from ambient air on the concentration profiles in the membrane and the anode and, thus, assesses the CO 2 impact on fuel cell performance. The physico-chemical model contains chemical and electrochemical reactions, liquid-gas phase equilibria as well as the transport processes in the cell. Results imply that a significant part of fed CO 2 is absorbed in the cathode and is transported as carbonate ions to the anode. Concentration profiles in the membrane reveal an enrichment zone of CO 2 in the membrane close to the anode, negligible HC O 3 − and a wide distribution of C O 3 2 − across the membrane. The carbonate distribution affects overall anion exchange membrane conductivity. For practical relevant current densities of i > 500 mA cm − 2 and typical excess ratios of 1.5 for the hydrogen feed, less than 10% of the anions in the membrane are C O 3 2 − . We show that while increasing cell temperature has an ambiguous effect on the carbonation process and on the total effect of CO 2 on the cell, current density has a significant effect. The impact of CO 2 on AEMFC performance can be significantly decreased when operating the cell at high current densities above 1000 mA cm − 2 . [ABSTRACT FROM AUTHOR]

This paper shows the developments of an equivalent circuit model adopted to interpret the deconvoluted electrochemical impedance spectra of an Ni-YSZ/YSZ/GDC/LSCF solid oxide fuel cell obtained by varying the operating temperature and the oxygen partial pressure under a fixed load. This allowed to unfold the physicochemical processes occurring within the anode supported cell and to identify which elements are responsible for major polarization losses. Furthermore, this model has proved to be effective even in the high frequency region, which is often beset by the onset of troublesome artifacts, as underlined by the comparison with the galvanic current interruption technique. [ABSTRACT FROM AUTHOR]

Abstract: This paper studies the charge conservation equation in the modeling of fuel cells. It is often useful to have an approximate closed form solution to describe the electronic potential in the whole solution domain. In our problem, no small term exists and the perturbation method cannot be used for this purpose. This paper proposes a simple analytical approach by using the method of separation of variables and Galerkin technology, and an analytical solution is obtained, which is valid for the whole solution domain and outlines the effects of most important operating, geometrical and material parameters on electronic potential. [Copyright &y& Elsevier]

In this paper, the catalytic activity of a ferrite/ceria composite ceramic fuel electrode La 0.9 Ca 0.1 Fe 0.9 Nb 0.1 O 3-δ /Sm 0.1 Ce 0.9 O 2−δ (LCFNb/SDC) for solid oxide reversible cells (SOCs) is studied by using YSZ (Zr 0.84 Y 0.16 O 2-δ ) and LSM/YSZ (LSM(La 0.8 Sr 0.2 MnO 3-δ )) as electrolyte and oxygen electrode, respectively. The asymmetrical LCFNb/SDC|YSZ|LSM/YSZ cells are prepared and evaluated electrochemically by using DC (cyclic voltammetry (CV) and galvanostatic) and AC impedance techniques in 50% CO: 50% CO 2 at the fuel electrode compartment. XRD results indicate LCFNb in the composite fuel electrode is stable in CO and CO 2 at high temperature and the LCFNb/SDC membane fuel electrode prepared by infiltration method presents high performance towards CO 2 reduction and CO oxidation. The polarization resistance under open circuit in a 50% CO: 50% CO 2 gas composition at 800 °C is 0.97 Ω cm 2 . However, both the CV and polarized impedance data show that the cell performance is higher for the electrolysis of CO 2 than for the oxidation of CO. The polarization resistance in 50% CO: 50% CO 2 at 1.4 V at 800 °C is 0.39 Ω cm 2 . Notably, the cell shows a highly stable activity towards CO 2 electrolysis at different applied voltages at the temperature of 800 °C. [ABSTRACT FROM AUTHOR]

The dead-end mode operation of a PEM fuel cell reduces the reactants consumption and the system's complexity, but also decreases its performance due to the accumulation of liquid water, which must be purged periodically. Despite extensive use of the EIS technique in studying PEM fuel cells' internal processes, the inherently transient nature of dead-end mode operation has challenged the application and interpretation of this technique. In this paper, a novel analytical model is proposed to physically investigate the effect of liquid water accumulation on the impedance of a PEM fuel cell in dead-end mode operation. The model is well validated against experimental polarization curves and impedance diagrams in various operating conditions by employing a two-step fitting procedure. The findings of the model indicate the constant presence of a large amount of liquid water in the fuel cell due to the dead-end operation. Additionally, the buildup of liquid water reduces the active area of the catalyst layer and the effective oxygen diffusion coefficient in GDL, increasing both the charge and mass transfer resistances. Finally, with its low computational cost, the developed analytical model can provide a suitable framework for purposes such as fault diagnosis and degradation prognosis. • A new physical impedance model is proposed for a PEMFC operating in dead-end mode. • The influence of liquid water accumulation is incorporated in the impedance model. • The analytical model is validated by V-I and EIS tests using a 2-step fitting scheme. • The impact of saturation level variation on the impedance diagram is investigated. • Liquid water saturation can affect both high and low-frequency arc of an EIS diagram. [ABSTRACT FROM AUTHOR]

The scaling up of microfluidic fuel cells (MFC) with enlarged electrode areas can be very advantageous for their power output and further stacking, which may, however, aggravate the cathode flooding problem due to intensified fuel crossover. In this paper, we first validate this phenomenon in a scaled-up MFC prototype, which has a hydrogen-breathing anode and an air-breathing cathode. Possible influential factors on the flooding extent are studied next, including the electrode area, electrolyte flow rate, and ambient temperature. Furthermore, three different strategies are proposed to improve cathode flooding, which is achieved either by adding an interlayer inside the channel to suppress hydrogen crossover, by adding hydrophilic water remover on the cathode surface to wick the generated water, or by cracking the cathode catalyst layer (CL) to manipulate the water transport direction. Among all these methods, the cracking of cathode CL is found to be remarkably effective especially with acid electrolyte, which exhibits the lowest current density degradation rate of 1.3 mA cm −2 h −1 when discharged at the peak power point for five hours. [ABSTRACT FROM AUTHOR]

Distribution of relaxation times (DRT) is a well-established method for deconvoluting electrochemical impedance spectroscopy (EIS) data from fuel cells. DRT-analysis provides a deeper insight into electrode reactions and supports identification of the most accurate equivalent circuit models. This established method has undergone much change in recent decades and has been applied to many sub-fields. Contemporary studies are highly specialized and produce specialist literature: to further a comprehensive view, this paper provides an overview and retrospective. EIS measurement and subsequent interpretation by DRT are challenging because (i) high-performance electrodes have very low impedances (10–100 mΩ), (ii) the concept of one rate-limiting step is usually not applicable, and (iii) the charge transfer and transport processes in anode and cathode are often coupled; overlapping in the frequency domain. In this paper selected results from advanced EIS and DRT analyses are discussed. We demonstrate the importance of EIS data quality, introduce the use of the Kramers-Kronig transformation, explain the impacts of statistically distributed noise and single errors in EIS spectra, and the selection of the regularization parameter lambda for improved interpretation of DRT curves. Finally, well-selected examples of DRT approaches lead to adequate models with different complexity. As a result, this paper deepens the understanding of how to assess electrochemical measurements of fuel cells based on the DRT. It, therefore, represents a vital guide for DRT analysis. Image, graphical abstract [ABSTRACT FROM AUTHOR]

• PtRhPb/C catalysts were synthesised using a simple chemical reduction method. • The addition of Pb to PtRh improves the electrocatalytic activity towards the EOR. • XANES data corroborate the existence of the bifunctional mechanism promoted by Pb. • The Pt 3 RhPb/C presented the highest CO 2 and CH 3 COOH production at lower potentials. • Pb promotes non-selective oxidation rather than a driven CO 2 production. This paper describes the effect of composition on the catalytic activity of carbon-supported Pt-Pb, Pt-Rh, and Pt-Rh-Pb catalysts towards ethanol oxidation in acid media. The catalysts were synthesised by a polyol reduction method and characterised using several experimental techniques, including X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray absorption near edge structure, and X-ray energy dispersive spectroscopy. The catalytic activity towards ethanol oxidation was evaluated by cyclic voltammetry, chronoamperometry, and in situ Fourier transform infrared spectroscopy (FTIR) experiments. XRD data indicate the presence of Pb in both alloyed and oxide forms. TEM images reveal nanoparticles well-dispersed on the carbon support, with spherical shapes and particle sizes around 2.0–6.5 nm. The Pt 3 RhPb/C catalyst showed the highest catalytic activity for ethanol oxidation, reaching current densities 6.0 times higher than the commercial Pt/C catalyst. The trimetallic catalyst showed the highest CO 2 and acetic acid formation, explaining the higher current densities presented during cyclic voltammetry and chronoamperometry. Additionally, since the oxidation appears to follow a non-selective path, the role of Pb in the trimetallic catalyst is not related to driving the reaction towards the production of CO 2. The improvement in catalytic activity occurred due to the synergy between the metals. [Display omitted] [ABSTRACT FROM AUTHOR]

The global interest in hydrogen/fuel cell systems for distributed power generation and transport applications is rapidly increasing. Many automotive companies are now bringing their pre-commercial fuel cell vehicles in the market, which will need extensive hydrogen generation, distribution and storage infrastructure for fueling of these vehicles. Electrolytic water splitting coupled to renewable sources offers clean on-site hydrogen generation option. However, the process is energy intensive requiring electric energy >4.2 kWh for the electrolysis stack and >6 kWh for the complete system per m 3 of hydrogen produced. This paper investigates using ethanol as a renewable fuel to assist with water electrolysis process to substantially reduce the energy input. A zero-gap cell consisting of polymer electrolyte membrane electrolytic cells with Pt/C and PtSn/C as anode catalysts were employed. Current densities up to 200 mA cm −2 at 70 °C were achieved at less than 0.75 V corresponding to an energy consumption of about 1.62 kWh m −3 compared with >4.2 kWh m −3 required for conventional water electrolysis. Thus, this approach for hydrogen generation has the potential to substantially reduce the electric energy input to less than 40% with the remaining energy provided by ethanol. However, due to performance degradation over time, the energy consumption increased and partial oxidation of ethanol led to lower conversion efficiency. A plausible ethanol electro-oxidation mechanism has been proposed based on the Faradaic conversion of ethanol and mass balance of the by-products identified and quantified using 1 H nuclear magnetic resonance spectroscopy and gas chromatography. [ABSTRACT FROM AUTHOR]

This paper reports the photoelectrocatalytic activities of a ruthenated porphyrin [Ru(phen) 2 (IP-C 4 O-TPP)] 2+ (denoted as Ru(II)PTPP, phen = 1,10-phenanthroline, IP = imidazo[4,5- f ][1,10]phenanthroline and TPP = 5,10,15,20-tetraphenylporphyrin) containing a covalently-linked butoxy chain (-C 4 O-) between IP and TPP moieties by means of various electrochemical techniques in combination with absorption spectroscopy and scanning electronic microscopy. Ru(II)PTPP is assembled on the surface of CdS nanoparticles, showing two Ru(II)-based peaks at 0.296 V and 0.830 V, where uric acid (UA) can be photoelectrocatalytically oxidized in a linear range of 0.01-10.0 mmol L −1 . The −C 4 O- chain endows the Ru(II)PTPP/carbon felt (CF) electrode with favorable dioxygen (O 2 ) binding sites to achieve a couple of new redox peaks at −0.213 V, where O 2 involves electrocatalytic reduction reactions. While employing 5.0 mmol L −1 UA as fuel, and 60 mL min −1 O 2 as oxidant, the proposed photoelectrochemical fuel cell shows open-circuit photovoltage of 0.656 V, short-circuit photocurrent density of 0.136 mA cm −2 , and maximum power density of 31.50 μW cm −2 at 0.497 V under visible-light illumination of 0.18 mW cm −2 . The present study provides an interesting platform for the utilization of renewable energy sources. [ABSTRACT FROM AUTHOR]

This paper reports the paired photoelectrocatalytic reactions of glucose (GLU) by capturing the photogenerated electrons and holes from ultraviolet (UV)-excited TiO 2 nanoparticles (NPs) with the assistance of methylene blue (MB) in neutral media. The blue MB in a mixed system containing TiO 2 NPs and GLU can rapidly capture the photogenerated electrons upon UV irradiation to form colorless leuco methylene blue (LMB), which is recovered in the dark, representing reversible colorimetric reactions controlled by turning on and off UV light. More interestingly, while employing TiO 2 /ITO photoanode and ITO cathode to assemble a UV-excited photoelectrochemical fuel cell, GLU existing in anode and cathode compartments can act as reducing and oxidizing agents to involve the paired photoelectrocatalytic reactions promoted by the MB/LMB-based reversible redox system. The cell current shows a linear response to GLU between 0.5 and 2.0 mol L −1 . Meanwhile, while adding 2.0 mol L −1 GLU and 2.0 mol L −1 GLU/10.0 mmol L −1 MB to the anode and cathode compartments, respectively, the assembled photoelectrochemical fuel cell shows open-circuit photovoltage of 0.828 V, short-circuit photocurrent density of 29.2 μA cm −2 , maximum power density of 7.2 μW cm −2 at 0.345 V under UV irradiation of 55 μW cm −2 . [ABSTRACT FROM AUTHOR]

The development of non-platinum-based cathodes is required in order to commercialize polymer electrolyte fuel cells. We have previously investigated group 4 and 5 transition metal oxides because they exhibit high chemical stability under cathode conditions and are less costly than platinum. In this paper, tantalum oxide-based cathodes were prepared from oxy-tantalum phthalocyanines by heat treatment under low oxygen partial pressures. We successfully obtained nano-sized tantalum oxide-based particles dispersed on multi-walled carbon nanotubes to increase the oxygen reduction reaction (ORR) current density. We investigated the factors which influence ORR activity in terms of the onset potential and ORR current density. The onset potential increased with increasing crystalline distortion of orthorhombic Ta 2 O 5 , which was experimentally observed as changes in the position and full width at half maximum of the Ta 2 O 5 (0 0 1) peak in the X-ray diffraction patterns. In addition, the amount of the deposited carbon strongly influenced the ORR current density because it affected the surface area of the oxides and the formation of local electron conduction paths. [ABSTRACT FROM AUTHOR]

• Robust and fast ECM fitting algorithm has been developed and tested on noisy impedance spectra, with source code available at github.com/leehangyue/EISART. • Accurate Complex Nonlinear Least Square (CNLS) fit has been realized with DRT-based initialization of ECM parameters. • Robust DRT analysis and ECM fitting has been enabled by data screening and weighing. • The estimation error of resistances in ECM from 1% to 26% were obtained for various noise levels and the factors affecting accuracy were revealed. • Time consumption fitting an ECM has been shortened to within 1 s on a typical personal laptop. The Equivalent Circuit Model (ECM) is a powerful technique to quantitatively analyze and compare Electrochemical Impedance Spectroscopy (EIS) data. In practice, noise is prevalent in EIS data, due to fuel cell system fluctuations, limited measuring time, and instruments, challenging the accuracy of ECM. There are algorithms that work well on noisy data, yet in many cases, either run time or robustness remains a problem. In this paper, we proposed a robust and fast algorithm that detects outliers, weighs the EIS data, and automatically fits an ECM within a second. For both experimentally measured and simulated noisy EIS data, the new algorithm reduced the impact of noise drastically. The algorithm is demonstrated in Python as part of the open-source software EISART at github.com/leehangyue/EISART. [Display omitted] [ABSTRACT FROM AUTHOR]

Deactivation is one the main causes still preventing the full exploitation of palladium electrocatalysts in alkaline direct alcohol fuel cells and the electrochemical reforming of alcohols. While often attributed to the adsorption of poisoning species generated in the alcohols oxidation, in the present work we demonstrate that deactivation is provoked by the formation of palladium oxides. A combined approach including i) fuel cell runs, ii) cyclic voltammetry and iii) near edge X-ray absorption spectroscopy has enabled us to draw the conclusions reported in the paper. [ABSTRACT FROM AUTHOR]

Carbon nanotubes (CNTs) have been widely developed for electrochemical energy conversion and storage devices for replacement of high-cost Pt-based catalysts. In this paper, a simple and convenient method is developed for improving the catalytic activity of CNTs in a controlled way. By simple heating treatment in the air, the multi-walled carbon nanotubes (MWCNTs) change with special morphologies, compositions and abundant defects (denoted as h-CNT). Those defects significantly improve the electrocatalytic performances for oxygen reduction reaction (ORR) which proceeds in a nearly four-electron pathway. The heating conditions have important effects on the structures and defect properties of h-CNTs which show a positive correlation between the defect levels and ORR performances. The small amounts of iron residues originated from nanotube growth and nitrogen doping during heating treatment also contribute to some catalytic activity. The inner walls of h-CNT remain intact during heating treatment and provide sufficient conductivity which facilitates charge transport during ORR. The h-CNT electrocatalyst shows better methanol tolerance and long-term durability than commercial Pt/C in alkaline media which makes it an alternative cathode catalyst in fuel cells. [ABSTRACT FROM AUTHOR]