Advanced mathematical model for the passive direct borohydride/peroxide fuel cell

In the literature a mathematical model has been developed for the direct borohydride fuel cells by Verma et al. [1]. This model simply simulates the fuel cell system via kinetic mechanisms of the borohydride and oxygen. Their mathematical expression contains the activation losses caused by the oxidation of the borohydride and the concentration overpotential increased by the reduction of oxygen. In this study a direct borohydride/peroxide fuel cell has been constructed using hydrogen peroxide (H₂O₂) as oxidant instead of the oxygen. Therefore we created an advanced model for peroxide fuel cells, including the activation overpotential of the peroxide. The goal of our model is to provide the information about the peroxide reduction effect on the cell performance. Our comprehensive mathematical model has been developed by taking Verma’s model into account. KH₂O₂ used in the advanced model was calculated as 6.72 × 10⁻⁴ mol cm⁻² s⁻¹ by the cyclic voltammogram of Pt electrode in the acidic peroxide solution.     

Copper hexacyanoferrate as cathode material for hydrogen peroxide fuel cell

The current need for handheld electronic devices with high energy autonomy has amplified research into clean and mobile energy source developments. Among suitable and promising technologies for this application, fuel cells, FCs are highlighted because of their minimal emission of pollutants and high efficiency. One type of FCs that has yet to be studied is the hydrogen peroxide/direct hydrogen peroxide fuel cell (DPPFCs). The present work is dedicated to the development of DPPFCs of one compartment using copper hexacyanoferrates (CuHCFs) as cathodic material and a Ni grid as anodic material. CuHCFs containing Fe^II and/or Fe^III were synthesized, characterized and their electrocatalyst performances were compared in 0.1 mol L⁻¹ HCl and 0.5 mol L⁻¹ H₂O₂. The maximum power densities reached for the CuFe^II was 8.3 mW cm⁻² and for the CuFe^IIFe^III was 2.9 mW cm⁻². The CuHCFs cathode materials show promising results, standing out as innovative materials for such an application.     

Response to Disselkamp: Direct peroxide/peroxide fuel cell as a novel type fuel cell

Besides hydrogen peroxide is known as conventionally oxidizer, it is both a fuel and a source of ignition. Platinum is not suitable catalyst for oxidation and reduction of hydrogen peroxide, because it directly converts the hydrogen peroxide to oxygen gas. In this study, the oxidation mechanism of peroxide is investigated and a fuel cell operating with acidic peroxide as oxidant and basic peroxide as fuel is constructed. The peroxide oxidation reaction in novel alkaline direct peroxide/peroxide fuel cell (DPPFC), shown feasible here using less expensive carbon supported Nickel catalyst, makes the alkaline direct peroxide/peroxide fuel cell a potentially low cost technology compared to PEM fuel cell technology, which employs platinum catalysts. The power density of 3.75 mW cm⁻² at a cell voltage of 0.55 V and a current density of 14 mA cm⁻² was achieved in our fuel cell.     

Performance of an alkaline direct ethanol fuel cell with hydrogen peroxide as oxidant

An alkaline direct ethanol fuel cell (DEFC) with hydrogen peroxide as the oxidant is developed and tested. The present fuel cell consists of a non-platinum anode, an anion exchange membrane, and a non-platinum cathode. It is demonstrated that the peak power density of the fuel cell is 130 mW cm⁻² at 60 °C (160 mW cm⁻² at 80 °C), which is 44% higher than that of the same fuel cell setup but with oxygen as the oxidant. The improved performance as compared with the fuel cell with oxygen as the oxidant is mainly attributed to the superior electrochemical kinetics of the hydrogen peroxide reduction reaction and the reduced ohmic loss associated with the liquid oxidant.     

A fuel cell with selective electrocatalysts using hydrogen peroxide as both an electron acceptor and a fuel

We have realized a novel hydrogen peroxide fuel cell that uses hydrogen peroxide (H₂O₂) as both an electron acceptor (oxidant) and a fuel. H₂O₂ is oxidized at the anode and reduced at the cathode. Power generation is based on the difference in catalysis toward H₂O₂ between the anode and cathode. The anode catalyst oxidizes H₂O₂ at a more negative potential than that at which the cathode catalyst reduces H₂O₂. We found that Ag is suitable for use as a cathode catalyst, and that Au, Pt, Pd, and Ni are desirable for use as anode catalysts. Alkaline electrolyte is necessary for power generation. The performance of this cell is clearly explained by cyclic voltammograms of H₂O₂ at these electrodes. This cell does not require a membrane to separate the anode and cathode compartments. Furthermore, separate paths are not needed for the fuel and electron acceptor (oxidant). These properties make it possible to construct fuel cells with a one-compartment structure.     

Enhanced performance of direct peroxide/peroxide fuel cell by using ultrafine Nickel Ferric Ferrocyanide nanoparticles as the cathode catalyst

Direct peroxide-peroxide fuel cell (DPPFC) employing with H₂O₂ both as the fuel and oxidant is an attractive fuel cell due to its no intermediates, easy handling, low toxicity and expense. However, the major gap of DPPFC is the cathode performance as a result of the slow reaction kinetics of H₂O₂ electro-reduction and thus the target issue is to design cathode catalysts with high performance and low cost. Herein, different with using noble metal of state-of-the-art, we have successfully synthesized ultra-fine NiFe ferrocyanide (NiFeHCF) nanoparticles (the mean particles size is 2.5 nm) through a co-precipitation method, which is used as the cathode catalyst towards H₂O₂ reduction in acidic medium. The current density of H₂O₂ reduction on the resultant NiFeHCF electrode after the 1800 s test period at ?0.1, 0 and 0.1 V are 121, 93 and 76 mA cm², respectively. Meanwhile, a single two-compartment DPPFC cell with NiFeHCF nanoparticles as the cathode and Ni/Ni foam as the anode is assembled and displayed a stable OCP of 1.09 V and a peak power density of 36 mW cm^?2 at 20 °C, which is much higher than that of a DPPFC employed with Pd nano-catalyst as cathode.     

A direct borohydride fuel cell employing Prussian Blue as mediated electron-transfer hydrogen peroxide reduction catalyst

A direct borohydride-hydrogen peroxide fuel cell employing carbon-supported Prussian Blue (PB) as mediated electron-transfer cathode catalyst is reported. While operating at 30 °C, the direct borohydride-hydrogen peroxide fuel cell employing carbon-supported PB cathode catalyst shows superior performance with the maximum output power density of 68 mW cm⁻² at an operating voltage of 1.1 V compared to direct borohydride-hydrogen peroxide fuel cell employing the conventional gold-based cathode with the maximum output power density of 47 mW cm⁻² at an operating voltage of 0.7 V. X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), and Energy Dispersive X-ray Analysis (EDAX) suggest that anchoring of Cetyl-Trimethyl Ammonium Bromide (CTAB) as a surfactant moiety on carbon-supported PB affects the catalyst morphology. Polarization studies on direct borohydride-hydrogen peroxide fuel cell with carbon-supported CTAB-anchored PB cathode exhibit better performance with the maximum output power density of 50 mW cm⁻² at an operating voltage of 1 V than the direct borohydride-hydrogen peroxide fuel cell with carbon-supported Prussian Blue without CTAB with the maximum output power density of 29 mW cm⁻² at an operating voltage of 1 V.     

A study of the direct dimethyl ether fuel cell using alkaline anolyte

The electrooxidation behavior of dimethyl ether (DME) dissolved in acidic, neutral or alkaline anolyte has been studied. The cyclic voltammetry measurements reveal that DME in alkaline anolyte demonstrates higher electrooxidation reactivity than that in acidic or neutral anolyte. With increasing the NaOH concentration in the anolyte, the electrooxidation reactivity of DME can be further improved. Direct dimethyl ether fuel cells (DDFCs) are assembled by using Nafion membrane as the electrolyte, Pt/C as the cathode catalyst, and Pt-Ru/C as the anode catalyst. It is found that the use of alkaline anolyte can significantly improve the performance of DDFCs. A maximum power density of 60 mW cm⁻² has been achieved when operating the DDFC at 80 °C under ambient pressure.     

A novel direct ethanol fuel cell with high power density

A new type of direct ethanol fuel cell (DEFC) that is composed of an alkaline anode and an acid cathode separated with a charger conducting membrane is developed. Theoretically it is shown that the voltage of this novel fuel cell is 2.52 V, while, experimentally it has been demonstrated that this fuel cell can yield an open-circuit voltage (OCV) of 1.60 V and a peak power density of 240 mW cm⁻² at 60 °C, which represent the highest performance of DEFCs that has so far been reported in the open literature.     

Effects of hydrazine addition on gas evolution and performance of the direct borohydride fuel cell

A fuel cell configuration using alkaline NaBH₄–N₂H₄ solutions as the fuel is suggested. Gas evolution behaviors and cell performances of alkaline NaBH₄–N₂H₄ solutions on different catalysts have been studied. It is found that gas evolution behaviors are influenced by the applied anodic catalysts and the concentration of NaBH₄ and N₂H₄. NaBH₄ is mainly electro-oxidized on Pd but N₂H₄ is mainly electro-oxidized on Ni and surface-treated Zr–Ni alloy when using NaBH₄–N₂H₄ solutions as the fuel and a composite of Pd, Ni and surface-treated Zr–Ni alloy as the anodic catalyst. The cyclic voltammetry results show that electrochemical oxidation potential of NaBH₄ is higher than that of N₂H₄. Adding hydrazine into alkaline sodium borohydride solutions can suppress gas evolution and improve the cell performance of the DBFC. The performances of fuel cells using NaBH₄–N₂H₄ solutions are comparable to that of fuel cell using N₂H₄ solution.     

Direct borohydride fuel cell using Ni-based composite anodes

In this study, nickel-based composite anode catalysts consisting of Ni with either Pd on carbon or Pt on carbon (the ratio of Ni:Pd or Ni:Pt being 25:1) were prepared for use in direct borohydride fuel cells (DBFCs). Cathode catalysts used were 1 mg cm⁻² Pt/C or Pd electrodeposited on activated carbon cloth. The oxidants were oxygen, oxygen in air, or acidified hydrogen peroxide. Alkaline solution of sodium borohydride was used as fuel in the cell. High power performance has been achieved by DBFC using non-precious metal, Ni-based composite anodes with relatively low anodic loading (e.g., 270 mW cm⁻² for NaBH₄/O₂ fuel cell at 60 °C, 665 mW cm⁻² for NaBH₄/H₂O₂ fuel cell at 60 °C). Effects of temperature, oxidant, and anode catalyst loading on the DBFC performance were investigated. The cell was operated for about 100 h and its performance stability was recorded.     

Performance improvement in direct borohydride/peroxide fuel cells

Direct borohydride/peroxide fuel cells (DBPFCs) show progressively deteriorating performance during operation for various reasons such as decreasing reactant concentrations, gas evolution and uneven distribution of liquids. The present study aims to emphasize the importance of certain design parameters, such as bipolar plate materials, flow fields and manifold design, in determining the DBPFC performance. Bipolar materials and flow channel design have been investigated. A power density of 67 mW cm^?2 has been obtained with composite graphite and parallel flow channel bipolar plates. It has increased to 87 mW cm^?2 using sintered graphite and then to 93.3 mW cm^?2 using sintered graphite with serpentine flow fields. The stacking of DBPFCs results in a loss of performance and unstable output. The performance has remained nearly unchanged as the cell number was increased by applying an independent cell liquid distribution network (ICLDN). Using an ICLDN, power densities of 98.3, 83.3 and 82 mW cm^?2 have been obtained for single-cell, 3-cell and 6-cell stacks, respectively. Finally, a controlled oxidant feeding system (COFS) has been developed to provide stable output power, and it has demonstrated a stable output power of 6 W for 2.5 h.     

A tank in series model for alkaline fuel cell in cogeneration of hydrogen peroxide and electricity

This work presents a Tank in Series Reactor (TSR) model for the alkaline fuel cell operating in potentiostatic mode in cogeneration of H₂O₂ and electricity. The developed TSR model accounts for the component and the energy balances in gas channels, liquid alkaline and catalyst layers together with charge balances at electrode/electrolyte interfaces. The TSR model is able to predict the limiting two-dimensional profiles in alkaline fuel cell. The simulation results indicate the influence of mass transfer on the distribution of concentration, temperature and current density.     

Cathode electrocatalyst selection and deposition for a direct borohydride/hydrogen peroxide fuel cell

Catalyst selection, deposition method and substrate material selection are essential aspects for the design of efficient electrodes for fuel cells. Research is described to identify a potential catalyst for hydrogen peroxide reduction, an effective catalyst deposition method, and supporting material for a direct borohydride/hydrogen peroxide fuel cell. Several conclusions are reached. Using Pourbaix diagrams to guide experimental testing, gold is identified as an effective catalyst which minimizes gas evolution of hydrogen peroxide while providing high power density. Activated carbon cloth which features high surface area and high microporosity is found to be well suited for the supporting material for catalyst deposition. Electrodeposition and plasma sputtering deposition methods are compared to conventional techniques for depositing gold on diffusion layers. Both methods provide much higher power densities than the conventional method. The sputtering method however allows a much lower catalyst loading and well-dispersed deposits of nanoscale particles. Using these techniques, a peak power density of 680 mW cm⁻² is achieved at 60 °C with a direct borohydride/hydrogen peroxide fuel cell which employs palladium as the anode catalyst and gold as the cathode catalyst.     

Development of a hydrogen dual sensor for fuel cell applications

The development and application of a hydrogen dual sensor (HDS) for the application in the fuel cell (FC) field, is reported. The dual sensing device is based on a ceramic platform head with a semiconducting metal oxide layer (MOx) printed on Pt interdigitated contacts on one side and a Pt serpentine resistance on the back side. MOx layer acts as a conductometric (resistive) gas sensor, allowing to detect low H₂ concentrations in air with high sensitivity and fast response, making it suitable as a leak hydrogen sensor. The proposed Co-doped SnO₂ layer shows high sensitivity to hydrogen (R₀/R = 90, for 2000 ppm of H₂) at 250 °C in air, and with fast response (<3 s). Pt resistance serves as a thermal conductivity sensor, and can used to monitor the whole range of hydrogen concentration (0–100%) in the fuel cell feed line with short response-recovery times, lower than 13 s and 14 s, respectively. The effect of the main functional parameters on the sensor response have been evaluated by bench tests. The results demonstrate that the dual sensor, in spite of its simplicity and cheapness, is promising for application in safety and efficiency control systems for FC power source.     

Experimental evaluation and mathematical modeling of a direct alkaline fuel cell

The performance of a direct alkaline fuel cell (AFC) is studied separately using methanol, ethanol and sodium borohydride as fuel. Potassium hydroxide solution was used as an electrolyte. Pt-black and manganese dioxide catalyst were used to prepare the anode and cathode electrodes. Ni mesh was used as current collector. The direct alkaline fuel cell was constructed with the prepared anode and cathode electrodes and Ni mesh. The current density–cell voltage characteristics of the fuel cell were determined by varying load and at different experimental conditions, e.g., electrolyte concentration, fuel concentration and temperature. The fuel cell performance increases initially with the increase in electrolyte (KOH) concentration and then decreases with further increase of the same. The cell performance increases initially and then no appreciable improvement noticed with the increase in fuel concentration. The performance of the fuel cell increases with increase in temperature in general with the exception to NaBH₄ alkaline fuel cell. A mathematical model for the direct alkaline fuel cell is developed based on reaction mechanism available in the literature to predict the cell voltage at a given current density. The model takes into account activation, ohmic, concentration overpotentials and other losses. The model prediction is in fair agreement with the experimental data on current–voltage characteristics and captures the influence of different experimental conditions on current–voltage characteristics.     

Investigating the stability and degradation of hydrogen PEM fuel cell

The hydrogen proton exchange membrane (PEM) fuel cells are promising to utilize fuel cells in electric vehicle (EV) applications. However, hydrogen PEM fuel cells are still encountering challenges regarding their functionality and degradation mechanism. Therefore, this paper aims to study the performance of a 3.2 kW hydrogen PEM fuel cell under accelerated operation conditions, including varying fuel pressure at a level of 0.1–0.5 bar, variable loading, and short-circuit contingencies. We will also present the results on the degradation estimation mechanism of four fuel cells working at different operational conditions, including high-to-low voltage range and high-to-low temperature variations. These experiments examine over 180 days of continuous fuel cell working cycle. We have observed that the drop in the fuel cells' efficiency is at around 7.2% when varying the stack voltage and up to 14.7% when the fuel cell's temperature is not controlled and remained at 95 °C.     

Fuzzy control of hydrogen pressure in fuel cell system

Precise control of hydrogen pressure is crucial for the performance and durability of fuel cell systems. With the widely used common-rail injection system, traditional PID controller still dominates. For a long time, the hydrogen pressure fluctuates acutely when hydrogen purge valve switches or load sharply changes with using PID controller. In recent studies, several new control strategies are presented. However, mostly of them are theoretical and experimental. In this study, an improved common-rail injection system, hydrogen injector/ejector assembly is introduced. Based on a real fuel cell system, a Mamdani fuzzy controller is designed to regulate the hydrogen pressure. The algorithm of fuzzy controller is explained in detail. A comparative study is carried out between fuzzy controller and PID controller. According to the results, the stability of hydrogen pressure with using fuzzy controller is better than using PID controller. This research could be useful for the control of fuel cell system.     

Convenient storage of concentrated hydrogen peroxide as a CaO2·2H2O2(s)/H2O2(aq) slurry for energy storage applications

Prior investigations have proposed, and successfully implemented, a stand-alone supply of aqueous hydrogen peroxide for use in fuel cells. An apparent obstacle for considering the use of aqueous hydrogen peroxide as an energy storage compound is the corrosive nature of the nominally required 50 wt.% maximum concentration. Here we propose storage of concentrated hydrogen peroxide in a high weight percent solid slurry, namely the equilibrium system of CaO₂·2H₂O₂(s)/H₂O₂(aq), that mitigates much of the risk associated with the storage of such high concentrations. We have prepared and studied surrogate slurries of calcium hydroxide/water that are assumed to resemble the peroxo compound slurries. These slurries have the consistency of a paste rather than a distinct two-phase (liquid plus solid) system. This paste-like property of the prepared surrogates enable them to be contained within a 200 lines-per-inch. (LPI) nickel mesh screen (33.6% open area) with no solids leakage, and only liquid transport driven by an adsorbent material is placed in physical contact on the exterior of the screen. This hydrogen peroxide slurry approach suggests a convenient and safe mechanism of storing hydrogen peroxide for use in, say, vehicle applications. This is because fuel cell design requires only aqueous hydrogen peroxide use, that can be achieved using the separation approach utilizing the screen material here. This proposed method of storage should mitigate hazards associated with unintentional spills and leakage issues arising from aqueous solution use.