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Persulfate is a potential oxidant in direct liquid fuel cells (DLFCs), and the commercial carbon paper (CP) can directly serve as the cathode due to strong oxidizability of persulfate. However, the poor catalytic activity and low specific surface area of CP limit the electrode performance. Herein, a defect-enriched, pyridine-N-dominated and self-standing carbon paper electrode with abundant carbon nanosheets is successfully prepared by hydrothermal treatment combined with in-situ electrochemical exfoliation. Benefitting from the integrated structure, plentiful defects and high-content pyridine-N dopants of the prepared electrode result in the superior electrocatalytic activity and long-term stability in persulfate reduction reaction. Remarkably, a membraneless DLFC with the prepared electrode as cathode and persulfate as the oxidant acquires prominent cell performance and extremely high open circuit voltage of 2.13 V. The maximum power density of the DLFC achieves 241.0 mW cm−2, far higher than those of the previously reported similar membraneless DLFCs. A three-dimensional computational model for the DLFC is developed, which is help to reveal the importance of improving the reaction kinetics and electrical conductivity for the cathode with persulfate as oxidant. A facile approach for in-situ preparation of highly N-doped CP electrode is provided to yield outstanding cell performance for low-cost DLFCs. [Display omitted] • A facile way to introduce high-content nitrogen on carbon paper is proposed. • Massive defective sites, carbon nanosheets and pyridine-N dopants are introduced. • N doping enhances charge transfer and electrocatalytic activity of the electrode. • Effects of hydrothermal duration and precursor concentration are discussed. • The N-doped cathode yields the outstanding cell performance for low-cost DLFC. [ABSTRACT FROM AUTHOR]

Micro Fuel cells or microfluidic fuel cells (μMFCs) are one of the most promising power supplies for portable electronics. However, the necessary electrode spacing is required to prevent fuel-crossover and maintain the stable operation, introducing the unavoidable ohmic resistance and retarding the miniaturization. Herein, we propose a novel μMFC device combining the cellulose paper as separator, with selective catalysts at the cathode side to eliminate the unwanted side reactions and increase the system compactness. One single reactant solution containing fuel and electrolyte is applied to keep the device stable operation. The power-generation properties are evaluated in typical alkaline conditions. A great construction simplification makes the device a substantial high-power density of 2.14 W cm−3 and maximum current density of 15.82 A cm−3. The μMFC stacks are arranged in series and parallel manners, which delivers a maximum power output of 23.6 mW and current of 194.6 mA. It is expected that innovative and customizable performance from commercial paper and low-cost carbonaceous catalysts can provide a forum for future advancement in chip-based electrochemical energy generation and storage devices. • Filter paper served as a membrane for μMFC is proposed. • The electrode-pair distance is greatly minimized (∼140 μm). • The optimized μMFC delivers an ultrahigh power density of 2.14 W cm−3. • The μMFC stacks power output of 23.6 mW and current output of 194.6 mA are achievable. [ABSTRACT FROM AUTHOR]

A facile and scalable approach to modify electrodes with achieving excellent performance and low-cost is urgently needed for direct liquid fuel cells (DLFCs). A carbon paper (CP) electrode with porous carbon nanosheets is successfully fabricated by electrochemical exfoliation to enhance the charge transfer and increase reaction sites in DLFCs. After in-situ electrochemical exfoliation for 4 min, the carbon fiber surface becomes porous and rough to enlarge specific surface area and produce abundant defects for the electrode, greatly increasing reaction active sites. In addition, massive oxygen functional groups are introduced to significantly improve the reaction kinetics and wettability of the electrode. The exfoliated CP shows superior electrocatalytic activity with minimum overpotential and highest reduction reaction rate, benefitting from the larger specific surface area, abundant defects, and superhydrophilic property. Moreover, the exfoliated CP without catalysts is directly used as the cathode for a membraneless DLFC with sodium persulfate as an oxidant to yield outstanding performance. The peak power density of the DLFC with the exfoliated CP is 188.6 mW cm−2, 93.4% higher than that with the pristine CP. Results show that a feasible way to acquire excellent cell performance and low cost is obtained by electrochemically exfoliated CP electrode for DLFCs. [Display omitted] • An effective method to modify cathode is proposed for low-cost DLFCs. • Carbon fiber surface becomes porous and rough to enlarge specific surface area. • Abundant defects and oxygen functional groups are introduced. • Electrochemical exfoliation enhances charge transfer and increases active sites. • The exfoliated cathode without catalysts yield the outstanding cell performance. [ABSTRACT FROM AUTHOR]

The regenerative hydrogen/vanadium fuel cell (RHVFC) is investigated with Freudenberg carbon paper electrodes (CPs). Along with thermal treatment, the Freudenberg CPs are also treated with reduced graphene oxide (rGO) using electrophoretic deposition at 300 V. The rGO modified CP results in 25% higher power density than its untreated counterpart under the same operating conditions. In comparison to the first preliminary study, the power density reported herein is more than four times higher. Additionally, the Freudenberg CPs modified with heat treatment followed by rGO deposition facing the membrane (rGOHTFM) provide the best electrolyte discharge utilization (UE) of 99%, followed by untreated (98%) and heat treated samples (97%) at 50 mA cm−2. The rGOHTFM also record high charge and discharge energy efficiencies (η E) of 93% at the same current density, which is slightly higher than untreated CPs (η E = 91%). Cycling the system 10 times also results in higher η E and UE for rGOHTFM CP (η E = 92% and UE = 99% on average) in comparison to untreated electrodes (η E = 86% and UE = 97% on average). In comparison the widely investigated SGL 10AA CP has lower efficiencies and utilization as expected (η E = 74% and UE = 83% on average). Image 1 • Freudenberg carbon paper electrodes are studied in hydrogen/vanadium fuel cell. • Freudenberg electrodes give much better charge/discharge response to SGL 10AA. • Untreated samples have similar performance to rGO modified ones at 50 mA cm−2. • Reduced graphene oxide modification of heat treated samples gave best results. • High cycling efficiencies (92%) and electrolyte utilization (99%) are reported. [ABSTRACT FROM AUTHOR]

Microfluidic fuel cells that use microorganisms to oxidize different organic substances to generate electricity are gaining importance due to their versatility to use different fuels. Saccharomyces cerevisiae has used for various purposes due to its capacity to ferment broad spectrum of carbohydrates. In this research, the development of bioanodes based on the immobilization of this yeast was carried out to apply them in the evaluation of a paper lateral-flow microfluidic fuel cell. Immobilization was performed using two different supports, Vulcan carbon and graphene oxide, and four carbohydrates as fuel (saccharose, glucose, fructose, and maltose). The results indicated that the yeast is better distributed and reaches a higher capacity to oxidize carbohydrates when is immobilized on graphene oxide, this bioanode shows better performance in the microfluidic device, reaching a potential above 0.9V when saccharose are used as fuel, representing a promising approach to use microbial bioanodes in small energy conversion devices. • Electrodes based on the Saccharomyces cerevisiae immobilization were used to make paper lateral-flow microfluidic fuel cells. • Immobilization was performed using Vulcan carbon (VC) and graphene oxide (GO) as supports. • Saccharose, glucose, fructose, and maltose were used as fuel in the microfluidic device. • The GO-based bioanode shows better performance, reaching a potential greater than 0.9V when saccharose is supplied. [ABSTRACT FROM AUTHOR]

High-performance carbon fiber paper (CFP) is usually an important part of the fuel cell gas diffusion layer (GDL). However, the preparation of CFP for GDL is still a challenge due to its arduous preparation process. Here, inspired by the structure of bird's nest in nature, we present the original design of PPS spherical sites welding three-dimensional (3D) carbon fiber network to produce high-performance CFP by facile wet papermaking and heat treatment. With a 3D CF network as the skeleton and PPS spherical sites as the welding points, CFs/PPS composite paper exhibits good mechanical strength and outstanding flexibility. Meanwhile, the excellent conductivity (6.8 S/cm) is integrated with super-hydrophobic performance, electrothermal performance (T max = 365 °C), heat resistance (DTG max >575 °C), and corrosion resistance, becoming a high-performance multifunctional CFP. The mythical combination of these properties makes CFs/PPS composite paper an ideal candidate in the field of fuel cell GDL. In addition, the evolution of chemical structure of CF/PPS during carbonization is emphasized, which is of great significance for the properties of composite paper. This work presents a leap forward in the preparation of multi-property high-performance CFP in a simple method and is a key step toward exploring how the structural changes of CFs/PPS composite paper can be understood during carbonization. [Display omitted] • Inspired by the structure of bird's nest in nature. • High-performance carbon paper prepared without graphitization. • The fabulous multi-performance combination makes composite paper an ideal candidate for the fuel cell gas diffusion layer. [ABSTRACT FROM AUTHOR]

[Display omitted] • A two-phase mass transfer model of paper-based microfluidic fuel cell is proposed. • The coupling characteristics of capillary action and two-phase flow are revealed. • The fluctuation mechanism of cell performance and gas distribution is explored. • Gas removal strategies are summarized, with a maximum gas removal rate of 42.30%. Paper-based microfluidic fuel cell powered by capillary force has the advantages of compactness, low cost, and high sensitivity, presenting broad application prospects in portable electronic devices. However, the gas-liquid mass transfer mechanism within the porous medium remains unclear, with a lack of two-phase flow theories adapted to the unique paper-based system. In this study, a two-dimensional two-phase numerical model of a Y-shaped paper-based microfluidic fuel cell is developed to reveal the two-phase flow characteristics under capillary action and explore gas removal strategies. The reliability of the model is validated by real experimental data. By coupling multiple physical fields, the study elucidates the working principle and gas-liquid flow phenomena within the cell. Then, the effects of contact angle, inlet fuel concentration, and paper type on output performance, gas distribution, parasitic effect, and fuel utilization are discussed. The results indicate that increasing the contact angle and using paper with a larger average pore size and porosity as the channel substrate are ideal for promoting gas discharge. The optimal gas removal rate reached 42.30 %, with a favorable power density of 33.92 mW/cm2. This study provides a theoretical basis for a deeper understanding of the two-phase mass transfer process in paper-based microfluidic fuel cell. [ABSTRACT FROM AUTHOR]

Paper-based self-pumping microfluidic fuel cells (PMFCs) typically exploit the wicking effects in porous papers to enable passive reactant delivery and co-laminar flow, eliminating micro pumps and physical membranes. PMFCs have been regarded as promising micro-power sources for next-generation paper-based electrochemical microfluidic assays for biomedical applications. However, the PMFC performance is fundamentally limited by the low capillary flow velocity and ineffective diffusive fuel transport. In this study, a novel PMFC with an anodic wedge-shaped channel is developed. The anodic wedge-shaped channel enables reactant convection at improved fuel flow velocity. Visualization experiments suggest that the fuel flow velocity can be improved by about 23 times in this anodic wedge-shaped channel configuration as compared to that in conventional single-layer paper-based flow channel. In addition, favorable features like localized enhancement of fuel transport and reduced fuel crossover are also observed in this novel configuration. Due to enhanced convective-diffusive fuel transport, the cell performance can be improved 245.8 % as compared to the single-layer case. The peak power density reaches 59.9 mW cm−2 and the limiting current density achieves 305.9 mA cm−2, outperforming most of the previous PMFCs. This anodic wedge-shaped channel configuration can also be potentially used in paper-based assays to enhance reactant delivery. • Wedge-shaped channel is formed by inserting anode between two-layer flow channel. • The anodic wedge-shaped channel can significantly increase fuel flow velocity. • The anodic wedge-shaped channel also helps to reduce fuel crossover. • Anodic fuel transport is enhanced by convection and diffusion. • The peak power density is increased 245.8 % by using wedge-shaped channel. [ABSTRACT FROM AUTHOR]

As a mainstream power storage and supply device, batteries are continuously upgraded. The microfluidic fuel cell has great development potential, and the paper-based microfluidic fuel cell is the latest achievement of its lightweight, which can be applied in the field of medical and biological detection. In this work, the cell models with various folding forms and unconventional absorption pads are creatively constructed, then the influence mechanism on cell performance is revealed by numerical simulation. Both transient and steady-state simulation methods are employed to monitor the whole process of paper-based microfluidic fuel cell. Conclusions show that the cell performance decreases with the increase of folding angle, the peak power density is as low as 1.71 mW/cm2, and the corresponding fuel utilization is only 2.73%. The changes in the absorbent pad shapes have little improvement on cell performance, thus the most direct way is increasing the absorbent pad volume. Moreover, materials with better water absorption capacity can increase the maximum current density to 28.70 mA/cm2, and the appropriate increase of operating temperature can also increase the peak power density to 2.36 mW/cm2, but the effect on the cell is significantly weakened if the temperature exceeds a certain limit. [ABSTRACT FROM AUTHOR]

• Efforts to enhance PMFC performance are reviewed. • Both exciting advancements and current limitations are discussed. • An innovative strategy of multi-scale simultaneous optimization is proposed. Paper-based microfluidic fuel cell (PMFC) has attracted great attention in the microfluidic fuel cell field in recent years. It utilizes the spontaneous capillary flow of reactant solutions in paper-based porous substrate to achieve passive transportations of fuel and oxidant, solving the fluid driving issue encountered in traditional microfluidic fuel cells and thus having broad application prospects in medical detection, wearable devices, micro sensors, environmental monitoring, and many other fields. However, the commercialization of this technology is impeded by the low output performance caused by the limited mass and energy transfer in PMFCs. To enhance the mass and energy transfer in PMFCs, numerous research studies have been conducted via experimental optimization of the cell materials and structures. Numerical analyses focusing on the structure–activity relationship of PMFCs were also performed recently. To provide a comprehensive and thorough review about the efforts devoted to improving performance of PMFC, research papers relevant to PMFC since its invention in 2014 have been extracted in this work and significant works were filtered to highlight the exciting advancements. The experimental studies were classified and discussed based on the key components involved in the PMFC system, followed by a critical review of the limited computational models. Potential directions for future research were also provided, aimed at overcoming the current technological challenges in PMFCs. Importantly, an innovative strategy of multi-scale simultaneous optimization of the cell properties is proposed considering the typical multi-scale feature of the PMFC system, which could inspire the designing of advanced cell materials with optimal multi-scale structures for applications of PMFCs. [ABSTRACT FROM AUTHOR]

Owing to the challenge of irregular morphology, the impact of compressed carbon fiber paper (CFP) on fuel cell performance and durability is intricate. As a carbon-carbon composite, the internal contact state of CFP directly determines its mechanical and physical properties. In this paper, fiber distribution and intersection of uncompressed CFP are achieved by X-ray computed tomography. Then we established an analytical model of bulk resistance based on the electron transfer path and provided a function to describe the internal contact state with strain. The results imply that the increasing number of electron paths and the variation of the contact state are the main factors for the decrease in bulk resistance under compression. The turning points in the contact state curve divide the range of pressure into fiber contact, elastic-plastic deformation and fiber fracture region, which can be used to assess the mechanical properties of CFP and determine the optimal pressure for fuel cell assembly. [Display omitted] • Fiber distribution and intersection of uncompressed CFP is given. • The effect of contact resistance between fibers on bulk resistance is evaluated. • The structural information to electric and mechanical properties is connected. [ABSTRACT FROM AUTHOR]

Herein, we develop a facile and efficient Thermal-Vaporization-Transformation (TVT) approach to prepare a highly active BP directly grown on carbon paper as the electrode for Oxygen evolution reaction (OER), showing a low onset potential of 1.45 V versus RHE. Simultaneously, the current density of BP-CP illustrates the excellent electro-catalysis stability only decreases by 3.4% after continuous operation for 10,000 s. [Display omitted] • BP-CP for OER is successfully synthesized by a novel efficient TVT approach. • The raw materials of the reaction are only the red phosphorus and carbon. • BP-CP exhibits a low onset potential and excellent electro-catalysis stability. • Electrocatalytic performance is fully demonstrated by DFT calculation in details. Black phosphorus (BP), as a new 2D material, is normally synthesized by a high-pressure and high-temperature (HPHT) method from white and red phosphorus, which severely hinders the further development of BP for any potential applications and leads to search for other potential applications of BP with big challenge. Herein, we develop a facile and efficient Thermal-Vaporization-Transformation (TVT) approach to prepare a highly active BP directly grown on carbon paper as the electrode for Oxygen evolution reaction (OER), showing a low onset potential of 1.45 V versus RHE. Simultaneously, the current density of BP-CP illustrates the excellent electro-catalysis stability only decreases by 3.4% after continuous operation for 10000 s. Meanwhile, the density functional theory (DFT) calculations further illustrates the P-doped carbon layer in the upper side of BP layer is actually responsible for its enhanced OER property, and the adjacent carbon atoms of the embedded P atoms are actually the active sites due to the induced local change distribution by intramolecular change transfer. Considering the facile, but efficient and scalable, TVT approach can directly synthesize BP-CP with excellent OER performance, which is promising for BP electrocatalysts used for OER in metal-air batteries, fuel cells, water-splitting devices, even other key renewable energy. [ABSTRACT FROM AUTHOR]

Microfluidic paper based microbial fuel cells (μP-MFCs) have gained considerable popularity due to their compact, quick and low-cost fluid manipulation paradigm. Compared to conventional technologies, paper as a substrate with advanced nanomaterial electrode material has many distinct advantages from point-of-care monitoring to energy harvesting. As a result, these have been used and are more popular in a variety of fields, such as health diagnostics, environmental and food quality management. By this encouragement, herein a portable microbial fuel cell as an origami array has been demonstrated using custom carbon electrodes with a modified the transition metal oxide MnO 2 nanomaterial. This customized electrode design was first printed using a tabletop PCB inkjet printer where the anode was further modified with synthesized MnO 2 nanoparticles. The entire cell was formed by folding the paper along predefined edges where the fuel, Shewanella putrefaciens , was streamed continuously via inherent capillary cation. Various studies, such as morphological, surface catalyst coating, amount loading and volumetric culture optimization experiments, have also been accomplished to find the most appropriate optimum parameter to enhance power conversion efficiency. The developed origami arrayed microbial fuel generated an open-circuit potential (OCP) for two parallel connected MFCs of 0.534 V and a maximum power density of 15.9 μW/cm2 with a maximum current density of 130 μA/cm2. In the end, the harvested power was used by powering the digital watch circuit through the ultra-low DC-DC booster board. Such an MFC origami array, with simple electrode manufacturing and modification process, has a great potential and bright future in Internet of Things (IoT) applications by making multiple stacks where the data can be monitored. [Display omitted] • Origami array-type MFC with printed electrode was fabricated by a PCB inkjet printer. • Several surface modification and loading (MnO 2 and bacteria) optimizations were done. • The developed device generates a maximum power density of 17.5 μW/cm2. • The device was used to power a digital watch using DC-DC booster. [ABSTRACT FROM AUTHOR]

The purpose of this study is to identify the indicators needed to analyze the competitiveness of major countries' energy technologies and to conduct empirical analysis accordingly. In this paper, nine measurement variables were derived as an index centered on patents and papers for energy technology competitiveness analysis. For each of the nine set measurement variables, the index for each of the major energy technologies (photovoltaics, fuel cells, and secondary batteries) was calculated, compared, and analyzed for each of the eight major countries. [ABSTRACT FROM AUTHOR]

Abstract: A carbon paper electrode was modified with the conducting copolymer of 3-methylthiopene and thiophene-3-acetic acid prepared electrochemically on the electrode, and an enzyme electrode was fabricated by covalent immobilization of glucose oxidase on the modified electrode. The modification with the conducting copolymer increased the surface area of the electrode and the amount of the immobilized enzyme. As a result, the enzyme electrode showed a high catalytic activity. Moreover, it was found that the increased surface area led to a high rate of electron transfer reaction between the electrode and p-benzoquinone employed as an electron mediator. The enzyme electrode fabricated with the modified carbon paper gave a larger glucose oxidation current than that fabricated with the bare one. In addition, the glucose oxidation current was found to increase with increasing content of the conducting copolymer in the modified carbon paper. Corresponding to the large glucose oxidation current, high performance was confirmed for the glucose fuel cell constructed with the enzyme electrode based on the modified carbon paper. [Copyright &y& Elsevier]

In this work, a paper-based hydrogen fuel cell is developed without the need for hydrogen storage. Instead, an embedded aluminum foil inside the paper is utilized for in-situ hydrogen generation. The electrodes and current collectors are also deposited on the paper, leading to a lightweight, compact and flexible hydrogen fuel cell with an OCV reaching 0.93 V and a peak power density of 4 mW cm−2. Benefited from the impeded hydroxyl ion diffusion, the hydrogen generation rate is well controlled, leading to a high faradaic efficiency of 72%. In addition, the cell can be operated under different bending angles with negligible power loss. Furthermore, it can be conveniently stacked in the same piece of paper for higher voltage and power outputs. Such a novel fuel cell design is especially suitable for powering various flexible devices with small rated power. • A paper-based hydrogen fuel cell is developed with an OCV of 0.93 V. • The peak power density is 4 mW cm−2 and the maximum current density is 8 mA cm−2. • Faradaic efficiency and energy efficiency are as high as 72% and 18%, respectively. • 75–87.5% of the cell performance remains when bended by angles from 45° to 135°. • A 4-cell stack is developed with an OCV of 3.8 V and a stacking efficiency of 90.6%. [ABSTRACT FROM AUTHOR]

Gas diffusion layer (GDL), as an important transmission component of gas, electricity and liquid, is usually composed of carbon paper, which needs hydrophobic treatment before it is applied in fuel cell. In the paper, ultrasonic dispersion technique is added to the traditional method of preparing hydrophobic carbon paper, and the effect of ultrasonic dispersion on the PTFE load in hydrophobic carbon paper is studied. The theoretical study shows that the ultrasonic dispersion increases the movement of the liquid, thus improving the diffusion performance of the liquid molecules. The experimental results show that compared with the hydrophobic performance of the original carbon paper, the hydrophobic carbon paper prepared by ultrasonic method improves the hydrophobic performance by 13.24%. However, there is no obvious relationship between the PTFE content of the carbon paper treated by ultrasonic dispersion and the hydrophobicity of the carbon paper surface. In addition, ultrasonic dispersion also has a great influence on the gas permeability of hydrophobic treated carbon paper, but the effect on the surface conductivity of carbon paper is not obvious. The results can provide a guidance for the preparation of hydrophobic carbon paper for fuel cells. • Properties of hydrophobic carbon paper prepared by ultrasonic method are studied. • The Carbon paper prepared by ultrasonic method has better gas permeability. • Ultrasonic method can significantly improve the content of PTFE in carbon paper. • Ultrasonic method can improve the uniformity of PTFE material distribution. [ABSTRACT FROM AUTHOR]

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: The effect of the microporous layer (MPL) and wet proofing on the MacMullin number has been evaluated for a custom series of Toray TGP-H-060 carbon paper gas diffusion layer (GDL). Complementary characterizations for these GDLs were performed by using scanning electron microscopy (SEM) images, pore size distribution (PSD) and fuel cell performance. The GDLs were customized by the addition of a microporous layer (MPL) and the treatment of, either or both, the substrate and MPL with 10% and 40% hydrophobic agent. SEM images correlated very well with the data shown for PSD. Distinction between the substrate layer and the MPL were clearly shown as two different slopes in the integral distribution and two different peaks in the differential distribution. The MacMullin number increased with increase in wet proofing but decreased with the addition of the MPL. The MacMullin number is a key parameter that contains the missing information for the path length in GDLs, which is generally approximated with the Bruggeman expression. The results provided an overview for the interpretation of the combined effect of the substrate and MPL properties as well as the cell operating conditions. [Copyright &y& Elsevier]

This paper presents a novel design and operation of microbial fuel cells (ΜFCs), which contain monolayer paper-based substrate/electrodes and microchannels with co-laminar flow. The electrodes with multi-wall carbon nanotubes are fabricated by the screen-printing method and the microchannels are patterned using photo-lithography. A double-inlet and diverging channel design is incorporated in the fuel cell configuration and demonstrated significantly improved performance. The fluid flows of electrolytes through the porous paper media are simulated using steady-state and transient computational fluid dynamics The best performance is achieved under the following conditions: an electroactive microbial (S. oneidensis) concentration of OD 600 1.5, 50 mM electron donor (lactate), and direct immobilized of the inoculum on the anode surface. The developed MFCs achieves a peak power density of 19.4 ± 0.23 μW cm−2 and maximum current density of 190.4 ± 1.39 μA cm−2, surpassing the performance of all previously reported paper-based single MFCs that utilize paper-based electrodes. In addition, hybrid-type MFCs that containing enzymatic air-breathing cathodes are investigated to enhance their performance. The novel paper based self-pumping MFC has the potential to make lab-on-a-chip type portable medical diagnosis devices with integrated power sources practical and feasible. [Display omitted] • A paper-based membraneless co-laminar flow microbial fuel cell was developed. • Microfluidic fuel cell was micromachined as a monolayer structure in paper substrate. • Co-laminar flow of the electrolyte through paper was simulated using CFD analysis. • Inoculation method, anolyte type, and cell configuration were tested and optimized. • A hybrid microbial-enzymatic fuel cell was also examined for performance improvement. [ABSTRACT FROM AUTHOR]

Abstract The poor wettability and high cost of the carbonaceous electrodes materials prohibited the practical applications of microbial fuel cells (MFCs) on large scale. Here, a novel nanoparticles of metal sheathed with metal oxide is electrodeposited on carbon paper (CP) to introduce as high-performance anodes of microbial fuel cell (MFC). This thin layer of metal/metal oxide significantly enhance the microbial adhesion, the wettability of the anode surface and decrease the electron transfer resistance. The investigation of the modified CP anodes in an air-cathode MFCs fed by various biocatalyst cultures shows a significant improving in the MFC performance. Where, the generated power and current density was 140% and 210% higher as compared to the pristine CP. Mixed culture of exoelectrogenic microorganism in wastewater exhibited good performance and generated higher power and current density compared to yeast as pure culture. The excellent capacitance with a distinctive nanostructure morphology of the modified-CP open an avenues for practical applications of MFCs. Graphical abstract Image 1 Highlights • Metal/Metal oxide nanoparticles are introduced as effective anode catalyst of MFC. • Catalyst layer enhances the surface wettability of carbon paper anode materials. • The introduced anode catalyst showed promising results with pure and mixed culture. • The nanoparticles layers enhanced power and current generation more than 2 times. • The coulomb efficiency and COD removal percent were strongly increased. [ABSTRACT FROM AUTHOR]

Abstract: While carbon fiber paper (CFP) has been widely used in batteries, fuel cells, and supercapacitors, its effect on device performance can be rather complicated. In this study, we examined the effect of CFP from different batches on the performance of a CFP-supported MnOx hybrid supercapacitor (CFP/MnOx). It is found that the contribution of the MnOx to the capacitance is dominating if the MnOx coating on CFP is dense and conformal, but becomes much less significant if the MnOx coating on CFP is porous or non-conformal. This is because annealing CFP/MnOx at 400 °C in air is necessary to obtain proper MnOx phases for high capacitance; the annealing process may increase the specific surface area of CFP if it is not fully covered by MnOx. Also, the etching of carbon surface weakens the attachment of MnOx to CFP and worsens the electrical connection of MnOx to CFP, further reducing the contribution of MnOx to capacitance. Finally, much to our surprise, it is found that the properties of the CFP varied from batches to batches, which critically influence the MnOx coating morphology/density. These factors in turn greatly affect the contribution of each component to the capacitance of the CFP/MnOx hybrid supercapacitors. [Copyright &y& Elsevier]

This study aims to explore the relationship between science and technology via analyzing cross citations between papers and patents in fuel cells. To calculate cross citation indicators, papers were retrieved from the WOS database and patent data from the USPTO during the period between 1991 and 2010, resulting in a total of 20,758 papers and 8112 patents. This study shows that there is a gradually increasing convergence between science and technology, particularly of science linkage in recent years. Papers citing patents are more time-sensitive than patents citing papers. Academic institutions are more likely to cite papers and patents published by other academic institutions. [ABSTRACT FROM AUTHOR]

The gas diffusion layer (GDL) is considered one of the most significant components in the proton exchange membrane fuel cell (PEMFC). Its electrical impedance is crucial to the performance of power generation for PEMFC. The study of the conduction mechanism of the GDL substrate-carbon fiber paper(CFP) treated with PTFE is still a considerable challenge. This work reveals that the type and number of contact points are direct factors that affect CFP through-plane resistance. The CFP resistance along the through-plane direction is a function of the contact point density inside CFP, rather than traditional loading pressure. Based on the structural characteristics of CFP, a graph theory model that can express the complex three-dimensional structure and anisotropy of CFP is constructed instead of the finite element model or formula model—using the characterization of the distribution of PTFE in the CFP section. The accuracy of model prediction for the CFP resistance of 0 wt% and 20 wt% PTFE can reach 95% and 90%, respectively. This study provides a fundamental basis for the design and processing of CFP with lower electrical loss and is of great significance for further improving the power generation efficiency of PEMFC. Image 1 • A mechanism to explain the essential effect of PTFE on the conduction is proposed. • PTFE affects electrical resistance by changing the contact state of carbon fibers. • Graph theory model can be well used to simulate the conductivity of carbon paper. • There is huge potential for the reduction of electrical resistance in carbon paper. [ABSTRACT FROM AUTHOR]

A flexible paper-structured catalyst (PSC) that can be applied to the anode of a solid oxide fuel cell (SOFC) was examined for its potential to enable direct internal reforming (DIR) operation. The catalytic activity of three types of Ni-loaded PSCs: (a) without the dispersion of support oxide particles in the fiber network (PSC-A), (b) with the dispersion of (Mg,Al)O derived from hydrotalcite (PSC B), and (c) with the dispersion of (Ce,Zr)O 2-δ (PSC C), for dry reforming of CH 4 was evaluated at operating temperatures of 650–800 °C. Among the PSCs, PSC-C exhibited the highest CH 4 conversion with the lowest degradation rate. The electrochemical performance of an electrolyte-supported cell (ESC) was evaluated under the flow of simulated biogas at 750 °C for cases without and with the PSCs on the anode. The application of the PSCs improved the cell performance. In particular, PSC-C had a remarkably positive effect on stabilizing DIRSOFC operation fueled by biogas. • Direct internal reforming (DIR) SOFC fueled by biogas has been investigated. • Paper-structured catalyst (PSC) was examined for the application to DIRSOFC. • Coking-tolerant PSC for dry reforming was developed by the dispersion of (Ce,Zr)O 2-δ. • On-paper synthesis of (Ce,Zr)O 2δ contributed to its higher dispersion. • Performance of DIRSOFC was stabilized by applying the developed PSC on anode. [ABSTRACT FROM AUTHOR]

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]

Paper, in addition to its frequent usage in writing, packaging, printing, etc., has gained comprehensive utility as a flexible and conductive base in sensors, solar energy harvesting, conversion, and storage applications. This is due to its strategic-aiding aspect in terms of environmental friendliness, cost-effectiveness, recyclability, thin, flexible and lightweight nature, biocompatibility, etc., required to develop next-generation flexible devices. The signs of progress in paper-based devices are seen in matured technologies of the paper-based sensor for varied sectors. Also, there have been wide-ranging research efforts on developing paper-based high-performance energy harvesting, conversion, and storage solutions. However, it is a newly emerging area and needs a fundamental and state-of-the-art understanding for future devices development. Thus, the current review summarizes the research progress in this field utilizing paper, understanding fundamental properties w.r.t application, performance enhancement w.r.t material advancements (i.e. paper modification), and technological trends, which is otherwise not yet reviewed earlier. It further sheds light upon the perspectives for their associated and allied technological developments in the energy sector. [Display omitted] • Role of paper properties in energy related applications are discussed. • Paper based electrodes for energy harvesting and conversion devices. • Utilty of papers in energy storage i.e. supercapacitors and batteries is presented. • Challenges and perspectives of realization of paper based devices for energy sector are projected. [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]

A paper-based membraneless single-compartment hydrogen peroxide power source prepared by micro-electromechanical systems (MEMS) technology is reported. The cell utilizes hydrogen peroxide as both fuel and oxidant in a low volume cell fabricated on paper. The fabrication method used is a simple method where precise, small-sized patterns are produced which include the hydrophilic paper bounded by hydrophobic resin. Open circuit potentials of 0.61 V and 0.32 V are achieved for the cells fabricated with Prussian Blue as the cathode and aluminium/nickel as the anode materials, respectively. The power produced by the cells is 0.81 mW cm −2 at 0.26 V and 0.38 mW cm −2 at 0.14 V, respectively, even after the cell is bent or distorted. Such a fuel cell provides an easily fabricated, environmentally friendly, flexible and cost saving power source. The cell may be integrated within a self-sustained diagnostic system to provide the on-demand power for future bio-sensing applications. [ABSTRACT FROM AUTHOR]

This work presents the integration of a paper-based microfluidic fuel cell inside a lateral flow assay-human immunodeficiency virus (HIV) test. To modify the HIV test, a bioanode that oxidizes the glucose present in a serum or blood sample and a cathode that reduces the oxygen delivered from air were stacked on the bottom and top, respectively, of a paper-strip test. A mixture of glucose oxidase enzyme, Nafion ® , glutaraldehyde, deionized water and tetrabutylammonium bromide were deposited on a methylene blue electro-polymerized Toray ® paper and used as the bioanode. Meanwhile, Pt/C (Vulcan XC-72) on Toray ® paper was used as an air-breathing cathode. The GOx enzyme anchored on the carbon-based surface was examined by scanning electron microscopy. The electrochemical response of the bioanode array demonstrated the oxidation of 0.1 M glucose, leading to a current density increase due to FAD + /FADH reactions. The above procedure was corroborated through scanning electrochemical microscopy, which showed an increase in the current (400 pA) in the presence of glucose on the bioanode. The paper-based microfluidic fuel cell performance showed power densities of 0.16 and 0.12 mW cm −2 using human serum and blood samples, respectively. Furthermore, the stability of the device was measured in terms of the recovery after obtaining four polarization curves that lasted 30 min, after which the sample dried out. This work represents a great advancement in the integration of a paper-based microfluidic fuel cell towards autonomous lateral flow assays. [ABSTRACT FROM AUTHOR]

[Display omitted] • Novel hand-made methanol fuel cell designed on a paper substrate. • Cathode and anode designed in both sides of the paper substrate. • Anode modified with a molecularly imprinted polymer for sarcosine. • Fuel cell operation dependent upon sarcosine concentration. • Sarcosine as a cancer biomarker that needs to be monitored. This work describes for the first time a paper-based direct methanol fuel cell platform (PB-DMFC) that functions as an energy source and biosensor, assembled on a simple paper substrate for point-of-care (POC) applications, targeting sarcosine as proof-of-concept. Specifically, a methanol fuel cell strip was developed from a square of Whatman paper, acting as substrate. The paper strip was treated with an impermeable agent (paraffin solution) and supported all fuel cell device components, including the electrolyte (Nafion®), anode electrode (carbon black Pt/Ru), cathode electrode (carbon black Pt), and current collectors (silver edges). All the described components formed a flexible single layer that operated in a completely passive mode by adding few microliters of a methanol solution on the anode side and by using atmospheric oxygen on the cathode side. The obtained platform had a stable electrical signal with an average OCV value of 0.45–0.55 V and a maximum power density of 20–50 µW/cm2, depending on the methanol concentration used (0.5 M–2 M). A sensing layer was built in situ on the anode electrode by electropolymerization of a solution of 3,4-ethylenedioxythiophene (EDOT) and pyrrole (Py) as monomers. The obtained PB-DMFC/biosensor was calibrated at room temperature in buffer and healthy human urine and showed linear responses from 1.0 × 10−7 to 1.0 × 10−3 M with a detection limit of 6.6 × 10−8 M. Selectivity studies evidenced signals changing within 1–10%, both in positive and negative directions. Results evidenced good reproducibility. Overall, the obtained results demonstrate a self-sufficient biosensor for the detection of sarcosine consisting of an innovative paper-based methanol fuel cell strip. This concept can open new horizons for massification of biosensors even in places with energy shortage. [ABSTRACT FROM AUTHOR]

Easily disposable low cost fuel cells as power sources are environmentally benign alternates to batteries for powering micro-analytical systems. In this regard, for the first time, an ethanol-dichromate fuel-oxidant microfluidic fuel cell is implemented on a paper scaffold. In this cell, a proton conducting poly (4-styrenesulfonate) based gel electrolyte enables proton transport from the anode to the cathode. Hydrothermally synthesized molybdenum oxide nanorods catalyze dichromate reduction and ethanol oxidation at the respective electrodes. A peak power density of 6.32 mWcm −2 is achieved with the catalyst. However, the cell without catalyst delivers a maximum power density of only 2.74 mWcm −2 . The compositions of the catholyte and anolyte streams and molybdenum oxide loadings are optimized. A stack of two cells connected in series illuminates a 3 mm red light emitting diode for over 40 min. This real time demonstration showcases the potential of this cell as an alternative to batteries for powering micro-analytical devices. [ABSTRACT FROM AUTHOR]

A paper microfluidic fuel cell was developed that is powered by urea and compares favorably to recent literature reports of paper microfluidic fuel cells. During fuel cell testing, we found the maximum power density to be as high as 0.91 mW cm −2 and the maximum current density to be as high as 4.3 mA cm -2  at room temperature using 0.3 M urea as fuel. Under continuous reactant flow, the fuel cell voltage is stable for at least 1 h. Under stopped flow conditions, the voltage was stable for up to 20 min. When 3 fuel cells (using Ni anode) were connected in series, sufficient energy was produced to power the LCD screen of a paper-based, over-the-counter pregnancy test for at least 30 min. Since this fuel cell is constructed on paper, it does not require continuous flow of reactants as a micro-channeled microfluidic fuel cell would. Hence, it could be possible with this chemistry to integrate energy production with urinalysis on paper since human urine contains both urea (fuel) and hormones (analyte) to provide power and analyte simultaneously. [ABSTRACT FROM AUTHOR]

Carbon Papers (CPs) have been widely used as a Gas Diffusion Layer (GDL) for high performance fuel cells. Herein we report a novel method for production of GDL, without the need to carbonization and graphitization steps that is common steps in GDL production. CP is provided by a dry-laying of carbon fibers (CFs) and expanded graphite (EG) in the phenolic resin and the composites are compared with carbon paper of Toray Co., Ltd. The effect of paper thickness, aspect ratio of CF and EG value of the composite are investigated. The characterizations are performed by scanning electron microscope, maximum pore size, mean pore size, permeability, electrical conductivity, flexibility, and performance (I-V) curve. The results shown that in the optimized state of the composition in the manufactured composite, the values of mean pore size, permeability, electrical conductivity, and performance curve is reasonable and near the Toray paper, however the manufactured composite show a much higher flexibility than that of Toray paper in a qualitative test. In addition, due to removing the graphitization and carbonization steps for production of carbon paper, the produced carbon paper costs are much lower than Toray paper. [ABSTRACT FROM AUTHOR]

With emerging stability issues in fuel cell technology, a non-conventional catalyst not supported on carbon materials has been highlighted because it can avoid negative influences of carbon support materials on the stability, such as carbon corrosion. The nanostructured thin film catalyst is representative of non-conventional catalysts, which shows improved stability, enhanced mass specific activity, and fast mass transfer at high current densities. However, the nanostructured thin film catalyst usually requires multi-step processes for fabrication, making its mass production complex and irreproducible. We introduce a Pt-Cu alloy nanostructured thin film catalyst, which can be simply prepared by electrodeposition. By using hydrogen bubbles as a template, a three-dimensional free-standing foam of Cu was electrodeposited directly on the micro-porous layer/carbon paper and it was then displaced with Pt by simple immersion. The structure characterization revealed that a porous thin Pt-Cu alloy catalyst layer was successfully formed on the micro-porous layer/carbon paper. The synthesized Pt-Cu alloy catalyst exhibited superior durability compared to a conventional Pt/C in single cell test. [ABSTRACT FROM AUTHOR]

Electrospinning process was optimized by using response surface methodology (RSM) to fabricate MWCNTs/PAN nanofibril composite non-woven fabrics of 180 nm average fiber diameter. The as-electrospun fabrics were hot-pressed to produce strong and flexible carbon nanofibril composite papers of 130 nm average fibril composite diameter. Dielectric constant of 300 and conductivity of 310 S/m were measured for these papers by using H10K13532-50LCR meter at 25,000 Hz. Analytical approach was introduced based on Lichtenecker modification formula to evaluate the electrical properties of the embedded MWCNTs, single nanofibers and single nanofibril composites as function in fabrics measured properties. 4156 S/m for MWCNTs, 360 S/m for carbonized electrospun PAN single nanofibers and 517 S/m for carbonized electrospun 5 wt% MWCNTs/PAN single nanofibril composites were reported. The ability to control the electrical properties of these papers over a wide range should position them as a versatile advanced material for numerous electronic, sensors and inter-connect applications. [ABSTRACT FROM AUTHOR]

Abstract: Preparation of Pt–Ru electrocatalyst was successfully performed on carbon paper by one-step co-electrodeposition method. Particle size and density were controlled by deposition potential and time. Coverage of the catalysts deposited on the carbon paper was significantly related to the composition of the electrolyte. Catalyst particles were characterized by field emission scanning electron microscopy (FESEM), and the crystal structure was analyzed by X-ray diffraction (XRD). Bulk and surface compositions of the electrocatalysts were obtained by inductively coupled plasma mass spectroscopy (ICPMS) and X-ray photoelectron spectroscopy (XPS), respectively. The Pt–Ru electrocatalyst with a surface molar ratio of 51.7 Pt and 48.3 Ru showed the highest catalytic activity for methanol oxidation and the strongest tolerance against carbon monoxide poisoning. [Copyright &y& Elsevier]

Abstract: The multiple-relaxation-time (MRT) lattice Boltzmann method (LBM) with multi-reflection solid boundary conditions is used to study anisotropic permeabilities of a carbon paper gas diffusion layer (GDL) in a fuel cell. The carbon paper is reconstructed using the stochastic method, in which various porosities and microstructures are achieved to simulate different samples. The simulated permeability and tortuosity show anisotropic characteristics of the reconstructed carbon papers with in-plane permeability higher than through-plane, and in-plane tortuosity lower than through-plane. The calculated permeabilities are in good agreement with existing measurements. The relationship between the permeability and the porosity is fitted with empirical relations and some fitting constants are determined. Furthermore, the obtained relationship of tortuosity and porosity is used in a fractal model for permeabilities. The results indicate that the fractal model and the Kozeny–Carman equation provide similar predictions on the through-plane permeability of the carbon paper GDL. [Copyright &y& Elsevier]

Hydrazine is often regarded as one of the most appealing fuels for fuel cells due to its high energy content, and also because it gives off only environmentally benign byproducts when it is used in fuel cells ( cf. many other fuels produce the greenhouse gas CO 2 ). However, current electrocatalysts for the hydrazine oxidation reaction (HOR) in direct hydrazine fuel cells involve the expensive, unsustainable noble metals such as Pt. Herein, using cellulose filter paper both as a precursor and a self-template, we show the synthesis of nanoporous carbon electrocatalysts that can efficiently electrocatalyze HOR. To make the electrocatalysts, first cellulose filter paper is modified with metal-amine complexes and then with silica shells. After carbonization of the resulting composite material at different temperatures, followed by removal of the silica shells, nanoporous carbon-based electrocatalysts are obtained. Notably, the intertwined structure of the cellulose matrix in the filter paper is taken advantage of to serve as a self-template, allowing the formation of the desired fibrous, nanoporous carbon electrocatalysts. The materials show a good electrocatalytic activity toward HOR, giving a low overpotential and a high current density. Thus, such nanoporous carbons can be good candidate materials to replace conventional metal-based catalysts commonly used in HOR and other related reactions. [ABSTRACT FROM AUTHOR]

The oxygen electrodes in unitized regenerative fuel cells (URFC) must have high activities towards oxygen reduction reaction (ORR) as well as oxygen evolution reaction (OER), thus requiring high loading of noble metal electrocatalysts. In this study, porous Pt/IrO 2 /carbon paper (CP) electrocatalysts were developed to reduce the metal loading. The Pt/IrO 2 /CP electrodes were fabricated by sequential formation of IrO 2 layers (loading 0.1 mg cm − 2 ) and porous Pt layers (0–0.3 mg cm − 2 ) on CP substrates by electrodeposition and spraying techniques, respectively. The fuel cell (FC) performances increased linearly up to 0.69 A cm − 2 with increasing Pt loading (up to ~ 0.3 mg cm − 2 ) at 0.6 V, whereas the water electrolysis (WE) activity was highest at Pt loading of 0.2 mg cm − 2 . The current densities in the FC and WE modes and round-trip efficiency of the developed Pt/IrO 2 /CP electrodes with the oxygen electrocatalysts loadings of 0.3 and 0.4 mg cm − 2 were higher or comparable to previously reported values with higher loading (1.5–4.0 mg cm − 2 ). These high performances with low loading are probably due to the facile oxygen and water transport through well-developed macropores originating from the open CP structures, providing effective utilization of the IrO 2 and Pt electrocatalysts towards OER and ORR, respectively. [ABSTRACT FROM AUTHOR]

The printable paper-based enzymatic biofuel cell (PBFC) to directly power small devices is an important objective for realizing cost-effective and disposable energy harvesting devices. In the present study, a screen-printed circular-type PBFC, composed of a series of 5 individual cells, was constructed. The PBFC exhibited the open circuit potential of 2.65 V and maximum power of 350 μW at 1.55 V, which were sufficient to illuminate an LED without requiring a booster circuit. The output voltage of this PBFC can also be easily adjusted as required. [ABSTRACT FROM AUTHOR]

This work demonstrates a stand-alone power source that integrates a paper-based hydrogen fuel cell with a customized chemical heater that produces hydrogen in-situ upon the addition of a liquid. The presented approach operates by capillary action and takes advantage of the hydrogen released as a by-product of an exothermic reaction used in point-of-care diagnostics. The paper-based fuel cell produces a maximum power of 25.8 mW (103.2 mW cm −2 ), which is suitable for powering a diversity of electrical devices such as commercially available digital pregnancy tests and glucometers. While device shape and dimensions can be customized, here it is shown that the fuel cell can be designed in a compact form factor and footprint comparable to a lateral flow test while providing a remarkable power output. This approach holds great promise for powering portable diagnostics, as the generated electric power could enable device functionalities required for advanced assays, such as device timing, actuation, and signal quantification. Part of the same liquid sample that is to be analyzed (urine, saliva, water, etc) could be used to trigger the hydrogen generation and start the fuel cell operation. [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]

Abstract: Copper-zinc oxide catalyst/ceramic fiber composites were successfully prepared using a papermaking technique. As-prepared catalyst materials, called catalyst paper, were used in autothermal reforming (ATR) of methanol to produce hydrogen for fuel cell applications. The performance of the catalyst paper for hydrogen production in the ATR process at 250°C was twice as high as that of commercially available catalyst pellets. The concentration of carbon monoxide, which acts as a catalytic poison for the Pt anode electrocatalyst of fuel cells, decreased remarkably. Furthermore, the gas generation with catalyst paper was much more stable than with catalyst powder or with pellets, resulting in constant hydrogen production. Such interesting features may be caused by the unique porous structure of paper composites that allows heat and reactants to be supplied effectively onto the catalyst surfaces. In addition, the ATR stability with catalyst paper improved considerably when ZSM-5 zeolite was mixed within the catalyst paper. Therefore, the porous, flexible and easy-to-handle catalyst paper is expected to be a promising catalytic material for enhancing practical performance in the catalytic reforming process. [Copyright &y& Elsevier]

[Display omitted] • A H 2 O 2 paper fuel cell with hydrogel-aided dual electrolytes has been developed. • High performance is achieved by toning the alkaline-acid dual electrolytes. • Firstly investigate the electrochemical reaction mechanisms via radical analysis. • The fuel cell shows excellent performance of ∼ 10 mW cm−2 and the best durability. Cellulose paper has been employed to develop pumpless microfluidic fuel cells. Meanwhile, hydrogen peroxide as both the fuel and oxidant has attracted attention since it is eco-friendly for producing only water. However, low open-circuit voltage (OCV) and power density of reported H 2 O 2 fuel cells due to the mixed potentials (simultaneous oxidation and reduction at the same electrode) preclude its applications. In this study, a H 2 O 2 paper fuel cell with a gel-aided dual-electrolyte configuration has been proposed for the first time to solve this problem. An ion-conductive hydrogel has been sandwiched between the independent catholyte and anolyte flows to serve as part of the electrolyte. Its OCV has been elevated to 1 V and a high peak power density of 10.2 mW cm−2 has been achieved by toning the electrolytes, which exceeds most reported H 2 O 2 fuel cells. The results demonstrate that alkaline anolyte benefits the cell performance more significantly than acidic catholyte does. The reaction mechanism at each electrode was further studied to provide insights for future development of H 2 O 2 fuel cells: the reduction at the cathode follows the Fenton reaction; as for the oxidation at the anode, it was first revealed that H 2 O 2 oxidation was facilitated by free radicals generated from H 2 O 2 in alkaline media. Besides, the radicals also help to maintain a large voltage difference between the electrodes. Furthermore, this fuel cell shows great durability and can be instantly re-activated upon refueling. This gel-aided dual-electrolyte fuel cell design can pave a way for practical applications of direct H 2 O 2 fuel cells. [ABSTRACT FROM AUTHOR]

In this work, we demonstrate a novel low-cost, self-powered paper-based biosensor for glucose monitoring. The device operating mechanism is based on a glucose/oxygen enzymatic fuel cell using an electrochemical energy conversion as a transducing element for glucose monitoring. The self-powered glucose biosensor features (i) a 3D origami paper-based structure for easy system integration onto paper, (ii) an air-cathode on paper for low-cost production and easy operation, and (iii) a screen printed chitosan/glucose oxidase anode for stable current generation as an analytical signal for glucose monitoring. The sensor showed a linear range of output current at 1–5 mM glucose ( R 2 =0.996) with a sensitivity of 0.02 µA mM −1 . The advantages offered by such a device, including a low cost, lack of external power sources/sophisticated external transducers, and the capacity to rapidly generate reliable results, are well suited for the clinical and social settings of the developing world. [ABSTRACT FROM AUTHOR]

A paper-structured catalyst (PSC) is a flexible planar catalyst that can be stacked on the anode of SOFCs and exhibits excellent catalytic activity for the reforming of hydrocarbon fuels at the operating temperature of the SOFC. Although our final goal is the realization of direct internal reforming (DIR) SOFCs fueled by biogas by applying a PSC, the tolerance of PSCs to sulfur impurities in biogas (H 2 S) must be improved for the practical application of PSCs to DIR-SOFCs operated by biogas. In this study, an inorganic fiber network in which a layered double hydroxide (Mg/Al-hydrotalcite denoted as HT) is dispersed was prepared by a paper-making process, and Ni was then loaded in this paper matrix via an impregnation process. This Ni-loaded HT-dispersed PSC exhibited considerably higher tolerance to H 2 S than that of HT-free PSC. [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]

The generated gas bubbles in microfluidic fuel cells (MFCs) cover the active surface area of the electrode and greatly limit the cell performance. In this study, a feasible approach is proposed to effectively accelerate bubbles removal and enhance cell performance by embedding a paper separator in the middle of the microchannel. Visualization of bubble behaviors and the corresponding electrochemical measurements are performed to investigate the effect of bubbles on the cell performance. Periodical process of the bubble growth and removal leads to the fluctuation in the current density of the MFC. The rapid gas removal and the low ohmic resistance are observed after embedding a layer of filter paper in the microchannel, causing improved fuel transfer and smaller ohmic loss. Although the current density fluctuates more frequently, the fluctuation amplitude decreases and the cell performance is enhanced. Compared with the MFC without paper separator, the maximum power density and the limiting current density of the MFC with paper separator is increased by 25.2% and 130%, respectively. Moreover, the cell performance is improved with increasing the flow rate of reactant solution and the peak power density achieves 25.9 mW cm−2 under flow rate of 1500 μL min−1. • A microfluidic fuel cell with paper separator is proposed to enhance gas removal. • Bubble behaviors as well as its effect on the performance are studied. • The paper separator can restrict bubble size and improve cell performance. • Effect of flow rate on the bubble behavior and cell performance is studied. • Embedding a paper separator is a good and effective way for gas management. [ABSTRACT FROM AUTHOR]