Peak Specific Power Research Articles

Analysis of Droplet Characteristics and Kinetic Energy Distribution for Fixed Spray Plate Sprinkler at Low Working Pressure

HighlightsAn experiment was conducted to investigate the hydraulic performance of a fixed spray plate sprinkler (FSPS).A model was developed for estimating the cumulative kinetic energy of the FSPS under a moving system.The droplet characteristics and kinetic energy distribution were affected by the working pressure and FSPS structure.A high cumulative kinetic energy could lead to a low water infiltration rate into the soil.Abstract. The kinetic energy of droplets from a fixed spray plate sprinkler (FSPS) has a substantial influence on runoff and soil erosion, as well as on the energy consumption of moving sprinkler irrigation systems. To determine the droplet characteristics and kinetic energy of an FSPS, an experiment was conducted to investigate the effects of working pressure, plate structure, and nozzle size on the droplet diameter, velocity, and kinetic energy. Two plates (the FSPSB with a concave trajectory and deep grooves in the blue plate, and the FSPSY with a flat trajectory and shallow grooves in the yellow plate) were used in the tests. The cumulative kinetic energy and water depth were calculated for a single sprinkler moving in a straight line. The results show that the FSPSB, which had deeper grooves in the plate, produced a larger droplet diameter than the FSPSY, with shallow grooves in the plate. The droplet landing velocities presented a logarithmic relationship with the droplet diameter, and velocities increased with an increase in droplet diameter. The peak specific power (SP) value of the FSPSB was 1.14 to 16.76 times that of the FSPSY. When the working pressure was less than 150 kPa, the peak SP of the FSPSB remained at a high level. With an increase in working pressure, the peak SP of the FSPSB initially increased and then decreased, while the peak SP of the FSPSY increased. The cumulative kinetic energy of the FSPSB was higher than that of the FSPSY under mobile spray conditions. Compared with the cumulative water depth, the cumulative kinetic energy of the FSPSB increased and then decreased as the working pressure increased for the same applied water volume. Because the soil had a lower infiltration rate under the FSPSB, surface ponding was more likely to occur with the FSPSB than with the FSPSY at low working pressure. Keywords: Cumulative kinetic energy, Droplet size, Specific power, Sprinkler irrigation, Working condition.

Effects of Pressure and Nozzle Size on the Spray Characteristics of Low-Pressure Rotating Sprinklers

Using low-pressure sprinklers in agricultural irrigation has become an alternative way of reducing water and energy stress. To determine the applicability of the low-pressure rotating sprinkler, an experiment was conducted to evaluate the effects of working pressure and nozzle size on sprinkler rotation speed, application rate, droplet size, droplet velocity, droplet trajectory angle, and kinetic energy distribution. The results showed that the mean droplet diameter increased exponentially along with the increase in distance from the sprinkler, and a logarithmic relation was derived between droplet diameter and droplet velocity. Due to the low breakup degree of the jet under the lowest working pressure of 100 kPa, the peak values of specific power and application rate were high, which reached 0.09 W m−2 and 11.35 mm h−1, and were 3.1–5.4 times and 2.5–3.1 times those of other working conditions. Meanwhile, the peak specific power of the biggest nozzle (diameter = 5.2 mm) was 2.4–2.8 times that of smaller nozzles. With an increase in working pressure, the sprinkler time per rotation decreased and the distributions of kinetic energy and water became more uniform. Thus, it is not recommended to equip the sprinkler with a large nozzle under low working pressure.

Импульсный DC/DC-преобразователь напряжения с уменьшенными массогабаритными параметрами

In development of energy converter for feeding the phase rotators and modulators in the system of active phased antenna lattice special requirements to sizes with the specified nominal and peak power of the converter have been presented. In the paper, the concept of manufacturing DC/DC energy converter with reduced weight and size parameters has been presented. It has been proposed to use the switching boards based on aluminitride ceramic with a thermal conductivity of 180–200 W / (m·K). To further reduce the energy losses due to overheating of the components, a digital control system for switching the power switches has been used. A significant reduction in height corresponds to the replacement of a coil transformer with a planar one. The following results can be achieved: an increase of specific power from 2.18 to 3.23 kW / dm3; an increase of peak specific power from 5.66 to 8.4 kW / dm3; a reduction of the height of the experimental sample from 32 to 13 mm; a decrease of volume from 0.115 to 0.0773; an increase of efficiency from 85 to 88.6%.

Dietary nitrate supplementation increases diaphragm peak power in old mice.

Respiratory muscle function declines with ageing, contributing to breathing complications in the elderly. Here we report greater in vitro respiratory muscle contractile function in old mice receiving supplemental NaNO3 for 14days compared with age-matched controls. Myofibrillar protein phosphorylation, which enhances contractile function, did not change in our study - a finding inconsistent with the hypothesis that this post-translational modification is a mechanism for dietary nitrate to improve muscle contractile function. Nitrate supplementation did not change the abundance of calcium-handling proteins in the diaphragm of old mice, in contrast with findings from the limb muscles of young mice in previous studies. Our findings suggest that nitrate supplementation enhances myofibrillar protein function without affecting the phosphorylation status of key myofibrillar proteins. Inspiratory muscle (diaphragm) function declines with age, contributing to ventilatory dysfunction, impaired airway clearance, and overall decreased quality of life. Diaphragm isotonic and isometric contractile properties are reduced with ageing, including maximal specific force, shortening velocity and peak power. Contractile properties of limb muscle in both humans and rodents can be improved by dietary nitrate supplementation, but effects on the diaphragm and mechanisms behind these improvements remain poorly understood. One potential explanation underlying the nitrate effects on contractile properties is increased phosphorylation of myofibrillar proteins, a downstream outcome of nitrate reduction to nitrite and nitric oxide. We hypothesized that dietary nitrate supplementation would improve diaphragm contractile properties in aged mice. To test our hypothesis, we measured the diaphragm function of old (24months) mice allocated to 1mm NaNO3 in drinking water for 14days (n=8) or untreated water (n=6). The maximal rate of isometric force development (∼30%) and peak power (40%) increased with nitrate supplementation (P<0.05). There were no differences in the phosphorylation status of key myofibrillar proteins and abundance of Ca2+-release proteins in nitrate vs. control animals. In general, our study demonstrates improved diaphragm contractile function with dietary nitrate supplementation and supports the use of this strategy to improve inspiratory function in ageing populations. Additionally, our findings suggest that dietary nitrate improves diaphragm contractile properties independent of changes in abundance of Ca2+-release proteins or phosphorylation of myofibrillar proteins.

Development of a High‐Performance Handheld Triboelectric Nanogenerator with a Lightweight Power Transmission Unit

AbstractA triboelectric nanogenerator (TENG) is a promising energy harvester that exploits the combination of contact electrification between two different material surfaces and electrical induction. In this study, a handheld‐TENG (HH‐TENG) is developed to harvest biomechanical energy effectively, especially energy generated from finger motions, which is one of the most common body movements involving lots of energy. To enhance the electrical output performance of the device while minimizing the inconvenience caused by carrying it, a rationally designed lightweight power transmission unit is adopted. As a result, an extremely high number of output cycles with high specific peak power (greater than 10 µW g–1) can be achieved in a single operation of the HH‐TENG. Although the proposed HH‐TENG weighs less than 70 g, the developed HH‐TENG can be connected with commercially available electric circuits such as an AC‐DC converter to generate not only reliable and continuous DC voltage to power portable electronics, but also further boosted open‐circuit voltage greater than 2.5 kV, which is sufficient to generate microplasma in a room environment. Adoption of a lightweight power transmission unit with the TENG can be considered as an effective strategy to significantly enhance the specific power, which advances the TENG toward practical implementation.

Multisource Inverter Based Energy Management System in Electric Vehicle

Day after day, natural energy sources are dwindling. Energy saving plays a crucial role in reducing the amount of pollution. Electric Vehicle consists of an energy storage system. Full car efficiency relies on energy storage system capacities. Driving cycle with high specific energy requirements that are met by the source of the battery. The battery will supply specific peak power demands with great current stress. Great present stresses directly affect battery life as a battery with less power density. It was discovered from the literature that supercapacitor has elevated power density and can be used as a specific power supply energy during the driving cycle's peak energy requirements. The supercapacitor can be used during car break to store dynamic power storage source. All power/energy requirements of the driving cycle have simultaneously regulated the operation of both sources. A new multi-source inverter can be used to improve the vehicle's driving cycle. During an unstable case triggered by the power scheme, it can also use as a vibrant energy restore. Paper is a multisource inverter (MSI) analogy, MSI simulation, and multi-source inverter operation with hardware outcome debate.

Gold nanorod-polyaniline composites: Synthesis and evaluation as anode electrocatalysts for direct borohydride fuel cells

Two gold nanorod-polyaniline (Au-PANI) composites with different contents of Au were prepared by two methods. An ex situ method, in the presence of preformed gold nanorods (AuNRs) and in situ one, when an AuNRs and PANI matrix is produced simultaneously, were used. Both methods were performed in immiscible water/toluene biphasic system as a simple interfacial polymerization process. Optical, structural and morphological characteristics of the formed nanocomposites were identified. It was found that AuNRs are embedded in the conducting emeraldine salt form of PANI. Nanocomposites containing 2.0 and 28.9 wt% of Au were subsequently systematically studied for borohydride oxidation reaction (BOR) for potential application in direct borohydride-peroxide fuel cell (DBPFC). Reaction parameters: number of electrons exchanged, order of reaction and activation energy, were evaluated. Both Au-PANI nanocomposites showed activity for BOR. A laboratory DBPFC was tested reaching specific peak power density of 184 Wg-1 at 65 °C with Au-PANI 1 nanocomposite (containing only 2.0 wt% of Au) as anode.

Western Diet-Induced Obesity Does Not Cause Diaphragm Muscle Abnormalities

PURPOSE: Obese individuals demonstrate ventilatory abnormalities at rest and during exercise, which may reflect inspiratory (diaphragm) muscle weakness. Several studies have shown diaphragm abnormalities in genetically obese animal models. However, the effects of an obesogenic diet on the diaphragm are not well defined. The purpose of this study was to determine if a Western diet (high-saturated fat, high-sugar: HFHS) causes diaphragm muscle pathology, perhaps related to oxidative stress. METHODS: Adult male Wistar rats were randomly allocated to one of two ad libitum diets for 24 weeks: healthy control (n=8) or HFHS diet (n=8). Diaphragm muscle then underwent i) in vitro contractile function assessment, ii) histology and immunohistochemistry for determination of fibrosis and fiber cross-sectional area (CSA) and iii) analysis of mitochondrial reactive oxygen species (ROS) emission. Data are mean ± SE. RESULTS: We previously reported that HFHS diet did not impair diaphragm maximal specific force or peak power. Alongside this maintenance of contractile function, HFHS-fed rats did not differ in diaphragm muscle interstitial fibrosis (in %: lean 3.4±0.8, HFHS 2.7±1.7), type I fiber CSA (in μm2: lean 1954±121, HFHS 2174±103), type IIa fiber CSA (in μm2: lean 2062±329, HFHS 2412±155), or type IIb/x fiber CSA (in μm2: lean 4165±1232, HFHS 4523±526). Additionally, no shifts in fiber type occurred. Interestingly, HFHS diaphragm demonstrated a trend toward a lower succinate-induced increase in ROS emission (in pmol/min: lean 1.313 ± 0.2, HFHS 0.73 ± 0.2, p = 0.09). Analyses of glutathione and antioxidant enzymes are ongoing. CONCLUSION: A high-saturated fat, high-sugar diet did not induce diaphragm muscle dysfunction or morphological changes. These results, combined with our previous findings of normal contractile function, suggest that intrinsic diaphragm muscle abnormalities do not contribute to breathing difficulties in obesity.

Application of platinum-cobalt-boron as the anode material for sodium borohydride-hydrogen peroxide fuel cells

The electroless deposition and galvanic displacement methods were used for the fabrication of cobalt–boron (CoB) catalysts modified with small amounts of platinum crystallites in the range of 9.8 to 14.4 μgPt cm–2. The prepared catalysts were studied as the anode materials for direct borohydride–hydrogen peroxide (NaBH4/H2O2) fuel cells at temperatures of 25–55°C. Polarization curves have been recorded with the aim to evaluate the fuel cell performance using the prepared CoB and that modified with Pt crystallites as the anode catalysts. For all catalysts (pure CoB and PtCoB) investigated, the peak power density values increase consecutively with the increment in temperature from 25°C up to 55°C. The values from 86–146 mV cm–2 and 146–234 mV cm–2 were determined for pure CoB and PtCoB catalysts, respectively. The highest specific peak power density of 21.5 kWgPt–1 was achieved at 55°C temperature when the PtCoB catalyst with the Pt loading of 9.8 μgPtcm–2 was employed as the anode catalyst in the NaBH4/H2O2 single fuel cell.

Evaluation of Fe and Mn co-doped layered perovskite PrBaCo2/3Fe2/3Mn1/2O5+δ as a novel cathode for intermediate-temperature solid-oxide fuel cell

A B-site cation-deficient double-perovskite oxide, PrBaCo2/3Fe2/3Mn1/2O5+δ (PBCFM2), was successfully synthesized by a sol-gel method and systematically investigated as an efficient cathode for IT-SOFC. The PBCFM2 exhibits good thermally stability and broad chemical compatibility at high temperature. Appropriate substitution of Mn and Fe for Co dramatically decreases the thermal expansion coefficient (TEC) from 21.5 × 10–6 K–1 for PrBaCo2O5+δ to 17.8 × 10–6 K–1 to PBCFM2 at a temperature range of 30–1000 °C. The temperature dependence of conductivity of the PBCFM2 was tested from 300 °C to 850 °C and then confirmed using the p-type small-polaron transport mode. The maximum conductivity value was 72 S cm–1 at 600 °C. When using 300 µm of Sm0.2Ce0.8O1.9 (SDC) as an electrolyte, the area specific resistance (ASR) and peak power density values were 0.028 Ω cm2 and 588 mV cm–2 at 800 °C, respectively. The activity and performance of the PBCFM2 cathode are further improved by impregnation with nano-sized SDC particles. The composite cathode with two times impregnation provided the optimal nano-scale SDC loading and microstructure where the ASR and peak power densities were 0.023 Ω cm2 and 621 mV cm–2 at 800 °C, respectively. Our preliminary results lead us to propose that PBCFM and its composite cathodes are good candidate cathodes for IT-SOFC.

Membrane–Electrode Assemblies with Patterned Electrodes for Proton-exchange Membrane Fuel Cells

A spray-coated membrane–electrode assembly (SMEA) and two types of inkjet-printed MEAs (GMEA and GVMEA) are investigated as proton-exchange membrane fuel cells. GMEA possesses a gas channel-shaped catalyst electrode for the flow field; GVMEA is composed of this and a rib-shaped Vulcan electrode. The GVMEA peak specific power density increased by 35% relative to SMEA, though it possessed 60% of the Pt amount. The Vulcan electrode plays a crucial role in protonic, electronic, and gas transport for improved fuel cell performance.

Ultra-Low Loading of Highly Active Pt and PtSn Catalysts on Hierarchical Tin as Anodes in Direct Methanol Fuel Cells

Pt and PtSn catalysts were synthesized by a single-step electroless process on hierarchical three-dimensional electrodeposited branched metallic Sn structures (BMS). The controlled electrodeposition of Sn on a carbon-paper substrate resulted in a high surface area of BMS, on which the Pt and PtSn alloy catalysts were deposited as thin layers. The PtSn species were reduced on the Sn substrate from Pt-Sn complexes formed in the solution. Several synthetic aspects were studied, such as the acidity of the electroless solution and the electroless process time span. The prepared electrodes were applied as anodes in direct methanol fuel cells. Methanol oxidation on these electrodes exhibited a specific peak power density of 476 mW mg−1 Pt at 0.45 V, 90 mA cm−2 and 70°C, using only 75 μg cm−2 of Pt, which is significantly higher than previously reported platinum-based catalysts.

A Preceding Bout of Endurance Exercise Decreases Peak Power of the Arm Extensor Muscles

The combination of aerobic exercise (AE) and resistance exercise (RE) within a given training protocol, termed concurrent training (CT), lacks sufficient analysis concerning the upper body. In the lower body knee extensor muscles, we have previously demonstrated reduced peak power when AE precedes RE. However, postural requirements of the lower body, as compared to the upper body, may give rise to unique responses following CT. Thus, further investigation as to specific peak power alterations of the upper body muscles are warranted. PURPOSE: To investigate the effects of a preceding AE bout on muscle strength to subsequent RE of the arm extensors. METHODS: Healthy men (n=8) performed AE+RE (CT) for the elbow extensors in one arm, while the contralateral arm performed RE only. The AE consisted of unilateral, moderate endurance exercise (43±2 min of repeated elbow extensions) using an isokinetic dynamometer. After 15-min rest, subjects performed unilateral RE (4x7 iso-inertial RE) with a flywheel device for both arms targeting the arm extensor muscles. Work produced during AE and peak concentric power during RE were recorded. RESULTS: The AE bout resulted in a gradual increase in heart rate (126±12 bpm) with a parallel increase in RPE reaching the termination threshold (18±0.5 RPE). The implementation of AE prior to RE led to a 21% decrease (p=0.045) in arm extensor peak concentric power from 98W to 78W, respectively. There was no change in performance from pre- to post in the RE-only arm (94W to 89W). CONCLUSIONS: These results demonstrate that the implementation of AE prior to RE, as compared to RE alone, compromises peak concentric power adaptations of the arm extensors. The noticeable decrement in peak concentric power between pre- and post from the CT intervention (21%), relative to a similar study with the same testing protocol which targeted the lower body (10%), gives credence to the possibility that upper and lower body muscles respond differently to concurrent training.

Employment of Fiber-Shaped Co Modified with Au Nanoparticles as Anode in Direct NaBH4-H2O2 and N2H4-H2O2 Fuel Cells

In this study, fiber-shaped cobalt (Cofiber) was electroplated on the copper surface and modified with various amounts of gold nanoparticles (denoted as AuCofiber/Cu) with the aim to use it as the anode material in direct NaBH4-H2O2 (DBHPFC) and N2H4-H2O2 (DHHPFC) fuel cells. The galvanic displacement technique has been used for the deposition of Au nanoparticles onto the Cofiber surface. The AuCofiber/Cu catalysts were prepared with the Au loadings in the range of 10.9–84.4 μgAu cm−2. Single fuel cell tests were performed by employing the prepared Cofiber/Cu and different AuCofiber/Cu catalysts as the anode and a Pt sheet as the cathode. It was found that the peak power densities up to 162 mW cm−2 for DHHPFC and 188 mW cm−2 for DBHPFC were obtained at a temperature of 25°C using the AuCofiber/Cu catalyst with the Au loading of 84.4 μgAucm–2 as the anode. The highest specific peak power density values of 12018 mW mg–1Au for DHHPFC and 14954 mW mg–1Au for DBHPFC were obtained, when employing the AuCofiber/Cu catalyst with the lowest Au loading of 10.9 μgAu cm–2 as the anode material.

Au Nanoparticles Modified Co/Titania Nanotubes as Electrocatalysts for Borohydride Oxidation

AbstractGold‐cobalt catalysts were deposited on the surface of titania nanotubes (TiO2‐NTs) via galvanic displacement technique. The catalysts were characterized using field emission scanning electron microscopy, energy dispersive X‐ray spectroscopy and inductively coupled plasma optical emission spectroscopy. The electrocatalytic activity of the Au(Co)/TiO2‐NTs catalysts was examined in respect to the oxidation of BH4− ions in an alkaline media by cyclic voltammetry and chronoamperometry. It was found that the Au(Co)/TiO2‐NTs catalysts with Au loadings in the range of 10 up to 59 µgAu cm−2 had a higher activity compared to that of Co/TiO2‐NTs and bare Au. A direct NaBH4‐H2O2 single fuel cell was constructed with the Au(Co)/TiO2‐NTs catalysts as anode and Pt as the cathode. The fuel cell exhibited an open circuit voltage of ca. 1.9 V and peak power densities up to 217 mW cm−2 at 25 °C. The highest specific peak power density of 16.3 kW g−1Au was obtained when employing Au(Co)/TiO2‐NTs with the Au loading of 10 µgAu cm−2 as the anode catalyst.

Gold-Cobalt Deposited on Titania Nanotubes as Anode Catalyst for Direct Borohydride Fuel Cells

In the present work gold-cobalt catalysts deposited on titania nanotubes surface (denoted as Au(Co)/TiO2-NTs) were investigated as anode material in direct borohydride fuel cells (DBFCs). The catalysts were prepared by a simple and cost-effective galvanic displacement technique [1]. At first, the sub-layer of Co was deposited on the titania nanotubes surface via electroless deposition. The gold crystallites were then deposited on the Co/TiO2-NTs electrodes by their immersion into gold(III)-containing solution for different time periods. It has been determined that the Au loadings were in the range from 10 to 60 µg cm–2 in the Au(Co)/TiO2-NTs catalysts. Field emission scanning electron microscopy (FESEM) and energy dispersive X-ray spectroscopy (EDXS) were used to characterize the surface morphology and composition of the samples, respectively. The activity of the Au(Co)/TiO2-NTs catalysts for borohydride oxidation reaction (BOR) was evaluated by cyclic voltammetry and chronoamperometry measurements. The performance of a DBFC operating with 1 M NaBH4 + 4 M NaOH as fuel and 5 M H2O2 + 1.5 M HCl as oxidant, while employing Pt as the cathode catalyst and Au(Co)/TiO2-NTs with different Au loadings as the anode catalyst were investigated. Peak power densities up to 122 mW cm-2 were attained at 25 ºC. It was found that the highest specific peak power density of 9.6 kW g–1 Au was obtained when employing Au(Co)/TiO2-NTs with the Au loading of 10 µg cm–2as the anode catalyst.

Effects of chemical fuel composition on energy generation from thermopower waves

Thermopower waves, which occur during combustion within hybrid structures formed from nanomaterials and chemical fuels, result in a self-propagating thermal reaction and concomitantly generate electrical energy from the acceleration of charge carriers along the nanostructures. The hybrid structures for thermopower waves are composed of two primary components: the core thermoelectric material and the combustible fuel. So far, most studies have focused on investigating various nanomaterials for improving energy generation. Herein, we report that the composition of the chemical fuel used has a significant effect on the power generated by thermopower waves. Hybrid nanostructures consisting of mixtures of picric acid and picramide with sodium azide were synthesized and used to generate thermopower waves. A maximum voltage of ∼2 V and an average peak specific power as high as 15 kW kg−1 were obtained using the picric acid/sodium azide/multiwalled carbon nanotubes (MWCNTs) array composite. The average reaction velocity and the output voltage in the case of the picric acid/sodium azide were 25 cm s−1 and 157 mV, while they were 2 cm s−1 and 3 mV, in the case of the picramide/sodium azide. These marked differences are attributable to the chemical and structural differences of the mixtures. Mixing picric acid and sodium azide in deionized water resulted in the formation of 2,4,6-trinitro sodium phenoxide and hydrogen azide (H-N3), owing to the exchange of H+ and Na+ ions, as well as the formation of fiber-like structures, because of benzene π stacking. The negative enthalpy of formation of the new compounds and the fiber-like structures accelerate the reaction and increase the output voltage. Elucidating the effects of the composition of the chemical fuel used in the hybrid nanostructures will allow for the control of the combustion process and help optimize the energy generated from thermopower waves, furthering the development of thermopower waves as an energy source.

Design of segmented thermoelectric generator based on cost-effective and light-weight thermoelectric alloys

Abstract A segmented thermoelectric (TE) generator was designed with higher temperature segments composed of n-type Mg 2 Si and p-type higher manganese silicide (HMS) and lower temperature segments composed of n- and p-type Bi–Te based compounds. Since magnesium and silicon based TE alloys have low densities, they produce a TE module with a high specific power density that is suitable for airborne applications. A two-pair segmented π-shaped TE generator was assembled with low contact resistance materials across bonding interfaces. The peak specific power density of this generator was measured at 42.9 W/kg under a 498 °C temperature difference, which has a good agreement with analytical predictions.

Direct sorbitol proton exchange membrane fuel cell using moderate catalyst loadings

Recent progress in biomass hydrolysis has made it interesting to study the use of sorbitol for electricity generation. In this study, sorbitol and glucose are used as fuels in proton exchange membrane fuel cells having 0.9mgcm−2 PtRu/C at the anode and 0.3mgcm−2 Pt/C at the cathode. The sorbitol oxidation was found to have slower kinetics than glucose oxidation. However, at low temperatures the direct sorbitol fuel cell shows higher performance than the direct glucose fuel cell, attributed to a lower degree of catalyst poisoning. The performance of both fuel cells is considerably improved at higher temperatures. High temperatures lower the poisoning, allowing the direct glucose fuel cell to reach a higher performance than the direct sorbitol fuel cell. The mass specific peak power densities of the direct sorbitol and direct glucose fuel cells at 65°C was 3.2mWmg−1catalyst and 3.5 mWmg−1catalyst, respectively. Both of these values are one order of magnitude larger than mass specific peak power densities of earlier reported direct glucose fuel cells using proton exchange membranes. Furthermore, both the fuel cells showed a considerably decrease in performance with time, which is partially attributed to sorbitol and glucose crossover poisoning the Pt/C cathode.

Chip-embedded thin film current collector for microfluidic fuel cells

Microfluidic fuel cells are an attractive candidate for low-power applications and provide a unique advantage over traditional fuel cells by elimination of the membrane. More importantly, microfluidic fuel cells enable a simple single-layer structure similar to common lab-on-chip devices, which makes conventional microfabrication or micromachining techniques readily applicable. Microfabrication is a preferable fabrication tool for microscale devices due to the benefits of high precision and repeatability at relatively low cost. However, the performance of most microfluidic fuel cells reported to date was negatively influenced by intrinsic contact resistances arising due to the highly porous nature of the electrodes. In the present work, a chip-embedded thin film current collector for vanadium fueled microfluidic fuel cells is proposed, fabricated, and evaluated as a potential mitigation strategy. The micromachining based thin film process is compatible with the overall cell fabrication, comprising photolithography and soft lithography, and does not require a substantial modification of the original cell design. Cells with and without current collectors are directly compared experimentally: the cell with current collectors demonstrates a 79% increase in peak power density, indicating that the contact resistance is significantly reduced by this approach. A volume specific peak power density of 6.2 W cm−3 is achieved, which is significantly higher than for previously reported microfluidic fuel cells. Electrochemical impedance spectroscopy (EIS) analysis is carried out to measure the combined ohmic cell resistance and confirmed a 32% reduction using the current collectors, which shows a good agreement with slope decrements in the polarization curves.