Power Density Of Cell Research Articles

Investigation of corrosion protection with conductive chromium-aluminum carbonitride coating on metallic bipolar plates

To further enhance the performance of metal bipolar plates, the CrAlCN coating with high corrosion resistance and conductivity was deposited on the SS316L substrate by using Closed Field Unbalanced Magnetron Sputter Ion Plating (CFUMSIP) technique. Meanwhile, the inexpensive acetylene gas (C2H2) was utilized as a carbon source. XRD and XPS results indicate that the proportion of carbides in the coating increase with increasing carbon contents. Electrochemical measurements show that the C-doped coating significantly improves the corrosion resistance of the SS316L bipolar plates. The C doping enhances the conductivity of the CrAlN coating, and the C-doped sample obtains the lowest ICR value (2.94 mΩ cm2, before corrosion), which is well below the DOE target (≤10 mΩ cm2). The excellent conductivity and hydrophobicity of C-doped coating increase the power density of a single cell. This study demonstrates that the CrAlCN coatings have great application prospects in the bipolar plates field.

Neurofuzzy modelling on the influence of Pt–Sn catalyst properties in direct ethanol fuel cells performance: Fuzzy inference system generation and cell power density optimization

Pt-based materials are commonly employed as catalysts in the electrooxidation of ethanol in direct ethanol fuel cells (DEFC). However, due to the complex nature of electrooxidation, the effect of catalyst properties on fuel cell power generation is not easily described by mechanistic models. Fuzzy systems can be used instead precisely for their ability to provide a more direct and qualitative/semiquantitative cause-effect relationship. In this study, a neurofuzzy model was developed to relate the effect of 5 input variables (4 catalyst properties, namely, crystal size, surface area, presence of PtSn phase and Pt L3-edge whiteline integrated intensity, and the cell potential) on cell current density. The fuzzy inference system (FIS) structure was constructed in MATLAB with ANFIS (Adaptive network-based FIS) based on experimental data used for training and validation. A 4-variable FIS (not including integrated intensity) was initially created and used as a basis for developing the 5-variable FIS, thus addressing the issue of fewer experimental data points available for integrated intensity. Both FIS structures exhibited very good fits to experimental data. The addition of integrated intensity as an input variable did not affect the fitted fuzzy model parameters for the other input variables and, therefore, a broader and more relevant model that included an electronic property of the catalyst was created. Response surface analyses, corroborated by particle swarm optimization, indicated that decreasing crystal size has the greatest effect in maximizing power density. Medium potentials and medium integrated intensity are also favorable. In addition, presence of the PtSn phase in moderate amounts is not unfavorable. With these values it was possible to predict the optimization of the power density value to 24.3 mW/cm2, compared to the best experimental value of 19.6 mW/cm2.

Polyaromatic anion exchange membranes for alkaline fuel cells with high hydroxide conductivity and alkaline stability

AbstractPoly (terphenylene‐methyl piperidine‐biphenyl) was synthesized using biphenyl, terphenyl, and N‐methyl‐4‐piperidone as raw materials to prepare anion exchange membranes (AEMs). Biphenyl and terphenyl as the copolymer monomers were used to regulate the morphology and properties of the AEMs. The flexible copolymer backbone promoted efficient transport of hydroxyl ions. The obtained AEMs show a high ion conductivity of 49.16 mS/cm at 80°C. Furthermore, the stable piperidine cation and polyarylene chain contributed to the excellent alkaline stability of AEMs that showed only 0.63% deterioration in ion conductivity after soaking in 1 M KOH at 80°C for 720 h. The peak of single cell power density of 54 mW cm−2 was obtained at a load current density of 150.1 mA cm−2 using an aqueous solution containing 1 M methanol and 1 M potassium hydroxide as the anode fuel, and pure oxygen gases as the cathode fuel at 30°C.

Microwave-induced oxygen vacancy-rich surface boosts the cathode performance for proton-conducting solid oxide fuel cells

In this study, both cathode powder preparations and fuel cell fabrications for proton-conducting solid oxide fuel cells (H–SOFCs) were performed using the microwave sintering technique. The microwave sintering approach produced Sr2Fe1.5Mo0.25Sc0.25O6-δ (SFMS) cathode particles with a lower phase formation temperature and smaller grain size than the standard muffle furnace sintering method. The advantages of microwave sintering were also recognized during the fuel cell manufacturing process. Using the same electrolyte and anode, conventional sintering and microwave sintering were used to produce SFMS cathodes, resulting in varied fuel cell performance. The fuel cell output of the conventionally sintered cell was 1312 mW cm−2 at 700 °C, whereas the power density of the microwave-prepared cell achieved 1452 mW cm−2 under the same testing conditions, which was also higher than the performance of a number of recently reported H–SOFCs. Surface chemistry research revealed that microwave sintering generated more oxygen vacancies (Vo). Calculations based on first-principles indicated that the greater surface abundance of Vo increased the oxygen reduction reaction (ORR) activity. The benefits of microwave sintering can be discovered in both the powder preparation and cell construction stages, making it an intriguing and simple way to enhance the performance of H–SOFCs.

A coking-tolerance dendritic anode with exceptional power density toward direct ethanol-fueled solid oxide fuel cells

The highly efficient utilization of liquid biofuels is a major challenge for the current economic society. As one of the most promising energy conversion devices, solid oxide fuel cells (SOFCs) offer a feasible approach to alleviate this problem, yet the output power is limited by the concentration loss. In this work, Ni-gadolinium doped ceria anode with dendritic microchannels is prepared to accelerate mass transport and boost the electrochemical performance of ethanol-fueled SOFCs. The peak power densities of button cells with dendritic anode achieve 1.66 and 1.37 Wcm−2 at 700 °C using wet hydrogen and dry ethanol as fuels, respectively. More importantly, the concentration polarization can be almost negligible when using 30 vol% dry ethanol as fuel. Simultaneously, the button cell shows a favorable coke tolerance in a 100 h short-term durability test. These results demonstrate that the dendritic microchannel for SOFCs is a high-efficiency solution to facilitate mass transfer and improve the electrochemical performance of hydrocarbon fuels.

Quenching-induced surface reconstruction of perovskite oxide for rapid and durable oxygen catalysise

Rapid degradation of catalytic activity for oxygen reduction reaction has become key factor in restricting practical applications of perovskite oxide in solid oxide fuel cells. Herein, quenching is disclosed to be an effective method to bring rapid and durable oxygen catalysis of perovskite-structured Pr0.5Ba0.25Ca0.25CoO3-δ. The quenching processing, cooling rate is around 8000 times higher than that of traditional annealing process, could turn the output power density of single cells from the decay process with a rate of 17.1% into an upsurge process with a rate of 18.4%, resulting in a stable power density of 0.72 W cm−2. This relates to a large number of point defects, dislocations, disorder and nanocrystalline domains are formed in perovskite oxides by quenching. These chemical defects can drive cationic diffusion to the surface indiscriminately, forming electroactive perovskite-structured nanoparticles. This work provides a new technology and concept to optimize the performance of perovskite-structured oxygen catalysts.

Highly Permeable Bucky Paper for the Gas Diffusion Layer of Fuel Cell Prepared by a Whole‐Process Solid Template Method

Due to the control of porosity and pore size on mass transfer, the structure of the gas diffusion layer (GDL) has a critical impact on the performance of fuel cells. The bucky paper has high conductivity and abundant pores, which has potential to be used as GDL in fuel cells. Herein, a whole‐process solid template method is used to prepare the bucky paper with microcrystalline cellulose (MCC), whose porosity and pore size can be regulated quantitatively. The bucky paper with MCC as a pore‐forming agent has more larger pores, and these pores are mostly connected, which meet the needs of fuel cell application. The result of gas flux shows that the permeability of the bucky paper increases from the initial 12 to 240 mL min−1 kPa−1 cm−2 with MCC. The pore structure of bucky paper are significantly improved, so that the bucky paper with MCC leads to a higher fuel cell power density. Furthermore, the impedance result presents that with the addition of MCC, the mass transfer resistance of the fuel cells decreases significantly. It is fully supported in these results that MCC can modify the pores of the bucky paper and applied in proton exchange membrane fuel cells well.

2,6-Diaminopyridine-Based Polyurea as an ORR Electrocatalyst of an Anion Exchange Membrane Fuel Cell

In order to yield more Co(II), 2,6-diaminopyridine (DAP) was polymerized with 4,4-methylene diphenyl diisocyanates (MDI) in the presence of Co(II) to obtain a Co-complexed polyurea (Co-PUr). The obtained Co-PUr was calcined to become Co, N-doped carbon (Co-N-C) as the cathode catalyst of an anion exchange membrane fuel cell (AEMFC). High-resolution transmission electron microscopy (HR-TEM) of Co-N-C indicated many Co-Nx (Co covalent bonding with several nitrogen) units in the Co-N-C matrix. X-ray diffraction patterns showed that carbon and cobalt crystallized in the Co-N-C catalysts. The Raman spectra showed that the carbon matrix of Co-N-C became ordered with increased calcination temperature. The surface area (dominated by micropores) of Co-N-Cs also increased with the calcination temperature. The non-precious Co-N-C demonstrated comparable electrochemical properties (oxygen reduction reaction: ORR) to commercial precious Pt/C, such as high on-set and half-wave voltages, high limited reduction current density, and lower Tafel slope. The number of electrons transferred in the cathode was close to four, indicating complete ORR. The max. power density (Pmax) of the single cell with the Co-N-C cathode catalyst demonstrated a high value of 227.7 mWcm-2.

Dual functionalized graphene oxide incorporated with sulfonated polyolefin proton exchange membrane for fuel cell application

This study presented a strategy of incorporating hydrocarbon-based proton exchange membrane (PEM) with dual-functionalized GO attached phosphonic and sulfonic functional groups to improve proton conductivity, ion exchange capacity (IEC) and methanol permeability for direct methanol fuel cell application. It was found that the proton conductivity, IEC of PEM and fuel cell power density enhanced remarkably through doping functionalized GO. The PEM doped with 8% PS-MGO exhibited the IEC value of 2.06 mmol g−1, proton conductivity of 0.084 S cm−1, and power density of 78 mW cm−2 at 25 °C. The methanol permeability of doped PEM was constrained effectively, reduced to 18.42 10−7 cm2 S−1. In addition, the results suggested the properties improvements were proportional to the functionalized GO contents and the improving effects of dual-functionalized GO on PEM were superior to the single functionalized GO. These improvements were attributed to the additional acidic sites offered by functionalized GO construct consecutive proton conduction pathways for facilitating protons transportation and the potential differences between phosphonic and sulfonic groups provided extra energy to drag water-connected protons through the membrane under the vehicular mechanism. This study proposed a promising strategy to use dual functionalized GO preparing PEM with excellent proton conductivity, IEC, power density and methanol permeability properties for fuel cell application.

Phosphonium-based deep eutectic solvents: Physicochemical properties and application in Zn-air battery

Electrolytes play a significant role in metal-air batteries and influence the battery's performance. Deep eutectic solvents (DESs) are viable and attractive candidates as high-performance electrolytes in batteries. This study investigated the temperature-dependent physicochemical properties of several phosphonium-based DESs such as the freezing point, density, viscosity, surface tension, and conductivity. The viscosity of the DES electrolyte is correlated as a function of molar conductivity using Walden's rule. Subsequently, the electrochemical characterizations of a Zn-air battery with the DES electrolyte, such as the cell voltage, power density, and current limit are studied. The electrochemical and physicochemical profiles of the phosphonium-based DESs possess dependence on the salt-to-hydrogen bond donor (HBD) molar ratio and appear viable for further exploration in metal-air battery applications. To the best of our knowledge, this is the first study that investigates the efficacy of the phosphonium-based DESs as the electrolyte in Zn-air batteries.

Numerical Optimization of Triple-Phase Components in Order-Structured Cathode Catalyst Layer of a Proton Exchange Membrane Fuel Cell

Proton exchange membrane fuel cell (PEMFC) is generally regarded as a promising energy conversion device due to its low noise, high efficiency, low pollution, and quick startup. The design of the catalyst layer structure is crucial in boosting cell performance. The traditional catalyst layer has high oxygen transmission resistance, low utilization rate of Pt particles and high production cost. In this study, we offer a sub-model for an order-structured cathode catalyst layer coupled to a three-dimensional (3D) two-phase macroscopic PEMFC model. In the sub-model of the cathode catalyst layer, it is assumed that carbon nanowires are vertically arranged into the catalyst layer structure, platinum particles and ionomers adhere to the surface, and water films cover the cylindrical electrode. The impacts of triple-phase contents in the catalyst layer on cell performance are investigated and discussed in detail after the model has been validated using data from existing studies. The results show that when the triple-phase contents ratio of the order-structured cathode catalyst layer is the best, the overall cell power density of the cell can be maximized, that is, the Pt loading of 0.15 mg cm−2, carbon loading of 1.0 mg cm−2, and ionomer volume fraction of 0.2. The above study may provide guidance for constructing the PEMFC catalyst layer with high catalyst utilization and high performance.

Hydrogen evolution and electric power generation through photoelectrochemical oxidation of cellulose dissolved in aqueous solution

Photoelectrochemical (PEC) cells capable of generating electricity or hydrogen through the oxidation of cellulose dissolved in an aqueous solution were constructed. As distinct from solid cellulose, the cellulose liquid fuel was beneficial for enabling a continuous reactant supply. Product analyses revealed that the cellulose macromolecules were cleaved to small organic acids and finally decomposed to CO2. During the electricity generation, the maximum power density of the PEC cell reached 1.13 mW cm−2. The influence of the photoelectrode structure on the PEC performance was elucidated. The monolithic structure of photoanodes consisting of an approximate monolayer of SrTiO3 particles anchored onto the backside metal layer provided a high photocurrent during oxygen evolution. The porous photoanode composed of heavily stacked TiO2 nanoparticles was found to be suitable for cellulose decomposition because of the high specific surface area. The present study should serve as a foundation for the direct energy utilization of waste biomass.

Cobalt-Free Double Perovskite Oxide as a Promising Cathode for Solid Oxide Fuel Cells.

Double perovskite oxide PrBaFe2O5+δ is a potential cathode material for intermediate-temperature solid oxide fuel cells. To improve its electrochemical performance, the trivalent element Ga is investigated to partially replace Fe, forming PrBaFe2-xGaxO5+δ (PBFGx, x = 0.05, 0.1, and 0.15). The doping effects on physicochemical properties and electrochemical properties are analyzed regarding the phase structures, element valence states, amount of oxygen vacancies, content of oxygen species, oxygen surface exchange coefficients (kchem), electrochemical polarization resistance, and single-cell performance. Specifically, PBFG0.1 exhibits improved kchem, such as a 19% improvement from 4.09 × 10-4 to 4.86 × 10-4 cm s-1 at 750 °C, due to the increased concentration of reactive oxygen species and oxygen vacancies. Consequently, the interfacial polarization resistance is decreased by 28% from 0.057 to 0.041 Ω cm2 at 800 °C. The subreaction steps of the oxygen reduction reaction in the PBFG0.1 cathode are further investigated, which suggests that the oxygen dissociation process is greatly enhanced by doping Ga. Meanwhile, doping Ga increases the peak power density of the anode-supported single cell by 36% from 629 to 856 mW cm-2 at 800 °C. The single cell with the PBFG0.1 cathode also exhibits good stability in 100 h of long-term operation at 750 °C.

Bimodal effect on mass transport of proton exchange membrane fuel cells by regulating the content of whisker-like carbon nanotubes in microporous layer

The excellent microporous layers (MPLs) in the gas diffusion layer requires superior mass transfer capacity, which is essential to high-performance proton exchange membrane fuel cells. However, the correspondence between MPL structure and mass transfer performance is ambiguous. Here, we design efficient mass transfer channels in MPLs with evolutionary structures by adjusting the content of whisker-like carbon nanotubes (WCNTs). The cell power density exhibits a bimodal shape with the increase of WCNTs in MPLs, which verifies that the perforated cracks of 5–10 μm in the MPL provide the separated channels for water and gas transport, and the optimal hydrophobic mesopores (34.87%) promote the mass transfer efficiency by elevating the capillary force of water transport. At 100% relative humidity (RH), the peak power densities of cells with the two MPLs are increased to 2.321 W cm−2 and 2.117 W cm−2, respectively. The electrochemical impedance spectroscopy confirms that the impedance of both MPLs are 109.35 mΩ cm2 and 63.55 mΩ cm2 at 100% RH and 3 A cm−2. The simple and scalable strategy provides a novel idea to relieve the mass transport loss of fuel cells.

Intercalative pseudocapacitive anhydrous NiC2O4 quantum dot electrode for the fabrication of supercapacitor using aqueous KOH and neutral Na2SO4 electrolyte

The energy storage capacity of a material depends on the active-ion arrangement and electron transfer rate at the electrode−electrolyte interface. Overcoming the low power density issues of batteries, the pseudocapacitive electrode can be an excellent alternative to improve the power density of the full cell in Asymmetric Supercapacitors (ASCs) mode to make grid-scale energy storage and delivery feasible. Quantum dots (QDs) is another class of nanomaterial that exhibits unique optical and electrical properties due to the quantum confinement effect and shows high mobility of diffused ions due to nanoscale dimension resulting in a very high surface area. Anhydrous NiC2O4 QDs are envisaged here as a potential energy storage material partly because of the presence of planer oxalates anions (C2O42−) resulting in a quasi-zero 2d arrangement. Superior specific capacity equivalent to 227.5mAh/g (capacitance:1638 F/g) at 1A/g in the potential window of 0.5 V was observed for Anhydrous NiC2O4 QDs electrodes in an aqueous 2 M KOH electrolyte. The battery-type intercalative pseudocapacitance mechanism seems to operate behind the high charge storage capacity of anhydrous NiC2O4 QDs. Almost 22 % (surface controlled) and 78 % (diffusion-controlled intercalative) storage was observed for anhydrous NiC2O4 QDs electrodes. Further, in a full cell, asymmetric supercapacitors (ASCs) mode in which porous anhydrous NiC2O4 QDs are made as the positive electrode and Activated Carbon (AC) as the negative electrode, operating potential window 1.6 V, the highest specific energy of 292 Wh/kg at a specific power of ~772 W/kg and Even at a high power density of 2884 W/kg− at an energy density equivalence of 87 Wh/kg was obtained with high cyclic stability in aqueous 2 M KOH electrolyte. Even in neutral 1 M aqueous Na2SO4 electrolyte, and in the operating potential window 1.6 V, The highest specific energy of 126 Wh/kg and specific power of ~480 W/kg at 1 A/g current density was observed in 1 M Na2SO4 was obtained with high cyclic stability for NiC2O4 QDs full cell in ASCs mode.

Distribution of relaxation times as an accessible method to optimize the electrode structure of anion exchange membrane fuel cells

Recent significant progress in performance of anion exchange membrane fuel cells (AEMFCs) is proving this technology to be a meaningful low-cost alternative to commercial proton-conducting fuel cells. This progress has been largely driven by improved water management through electrode layer engineering. The plethora of membrane and ionomer chemistries makes the optimization of the electrode composition often unreproducible, leading to inaccurate performance comparisons. In this study we introduce the distribution of relaxation times (DRT) as an accessible and convenient tool to diagnose the limiting polarization processes in AEMFCs, which significantly simplifies the electrode optimization. To demonstrate the potential of DRT diagnosis, we fabricate cells with different anode electrode compositions simulating the effects of water transport limitations, such as anode flooding and cathode dry-out. The DRT separates and quantifies the contributions to the polarization resistance of the following processes: cathode and anode charge transfer, ion transport in the catalyst layer and gas diffusion. The anode catalyst layer optimization using information from the DRT has helped to increase the peak power density of the current cells from 550 to 690 mW/cm2. We foresee a large potential in using the DRT approach for the diagnosis and optimization of AEMFCs’ operational, structural, and compositional parameters.

A submillimeter bundled microtubular flow battery cell with ultrahigh volumetric power density

Flow batteries are a promising energy storage solution. However, the footprint and capital cost need further reduction for flow batteries to be commercially viable. The flow cell, where electron exchange takes place, is a central component of flow batteries. Improving the volumetric power density of the flow cell (W/Lcell) can reduce the size and cost of flow batteries. While significant progress has been made on flow battery redox, electrode, and membrane materials to improve energy density and durability, conventional flow batteries based on the planar cell configuration exhibit a large cell size with multiple bulky accessories such as flow distributors, resulting in low volumetric power density. Here, we introduce a submillimeter bundled microtubular (SBMT) flow battery cell configuration that significantly improves volumetric power density by reducing the membrane-to-membrane distance by almost 100 times and eliminating the bulky flow distributors completely. Using zinc-iodide chemistry as a demonstration, our SBMT cell shows peak charge and discharge power densities of 1,322 W/Lcell and 306.1 W/Lcell, respectively, compared with average charge and discharge power densities of <60 W/Lcell and 45 W/Lcell, respectively, of conventional planar flow battery cells. The battery cycled for more than 220 h corresponding to >2,500 cycles at off-peak conditions. Furthermore, the SBMT cell has been demonstrated to be compatible with zinc-bromide, quinone-bromide, and all-vanadium chemistries. The SBMT flow cell represents a device-level innovation to enhance the volumetric power of flow batteries and potentially reduce the size and cost of the cells and the entire flow battery.

Recycling Used-Coffee Grounds into Hierarchical Nanostructured Carbon for Supercapacitor Application

Hierarchical nanostructured activated carbon electrode material was prepared from the used-coffee grounds to fabricate a cost-effective, scalable and high-performance symmetric supercapacitor. The interconnected, disordered and microporous material was synthesized in a simple two-stage method of chemical activation with zinc chloride followed by direct pyrolysis of the coffee grounds at 900 ºC in nitrogen atmosphere. The N2 adsorption and desorption analysis showed that the prepared material had an extraordinary surface area of ~1178 m2 g-1. The fabricated symmetric supercapacitor device in non-aqueous tetraethylammonium tetrafluoroborate (TEABF4) electrolyte exhibited 2.7 V cell voltage with superior specific capacitance, energy and power density of 129 F g–1, 56.4 Wh kg–1 and 797.9 W kg–1, respectively. Besides, it also had a high specific capacitance retention of 99% even after 10,000 cycles. This work demonstrated an effective approach to transform coffee grounds into high performance electrode material for renewable energy devices. The observed electrochemical performance evidently showed that the materials derived from waste coffee grounds could be recycled into potential electrode material for supercapacitors. The cost-effectiveness and abundance of waste coffee grounds combined with the simple activation process and high performance of the synthesized material increased its feasibility for commercial applications in energy storage devices.

CeO2 stabilized by tourmaline as a novel inorganic filler to simultaneously increase the conductivity and durability of proton exchange membranes

Optimized PFSA/TM-CeO2 (1 wt%) showed enhanced fuel cell power density while maintaining outstanding chemical stability compared to pristine PFSA.

Different alkaline earth metals doped Sm0.5A0.5Fe0.9Ni0.1O3-δ (A=Ca, Sr and Ba) for symmetric solid oxide fuel cells

Symmetric solid oxide fuel cells have gained increasingly attention due to their characteristics of simple fabrication and low cost. Due to the same anode and cathode used, the oxygen reduction reaction (ORR) and hydrogen oxidation reaction (HOR) of the electrodes are very demanding. In this work, Sm0.5 × 0.5Fe0.9Ni0.1O3-δ (X = Ca, Sr, Ba, SCFN, SSFN, SBFN) were synthesized, and the physico-chemical properties of three materials and their electrochemical performance as electrodes were systematically studied. They all maintain stable phase structures under oxidizing and reducing atmospheres below 750 °C. X-ray photoelectron spectroscopy (XPS) results showed that metal nanoparticles was exsolved and oxygen vacancies were increased after the treatment in reducing atmosphere at 750 °C. For electrochemical performance test, the peak power densities of symmetrical cells with SCFN-GDC, SSFN-GDC and SBFN-GDC electrodes can reach 26.7, 186.78, and 138.8 mWcm−2 at 750 °C, respectively. Moreover, SSFN-GDC cell showed better long-term stability than the other two.