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.     

Fast ion channels for crab shell-based electrolyte fuel cells

Biomaterials possess abundant micro and macrospores in their microstructures, which can be functionalized as higher ion-transport channels. Herein we report calcined crab shell (CCS) forming nanocomposites with La_0.6Sr_0.4Co_0.2Fe_0.8O₃ (LSCF) perovskite as functional electrolytes for low temperature solid oxide fuel cells (LTSOFCs). The single CCS electrolyte fuel cell achieved open circuit voltage (OCV) at 0.9 V and a peak power density of 70 mW cm⁻² at 550 °C; while the highest OCV of 1.21 V and a maximum power density of 440 mW cm⁻² were achieved for the CCS-LSCF (40 wt. % LSCF) electrolyte fuel cell. The results are attributed to the ion channel construction and interface effect built in the CCS-LSCF composite. This work may provide a new strategy to develop novel biomaterial-based materials for LTSOFCs.     

A novel Chinese parasol leaf biochar fuelled direct carbon solid oxide fuel cell for high performance electricity generation

A direct carbon solid oxide fuel cell is a new technology for clean and efficient utilization of carbon resources to generate electricity, with the advantages of high power generation efficiency and wide available fuel flexibility. Biomass, in virtue of large specific surface area, numerous oxygen-containing functional groups which can promote the electrooxidation of carbon, and low ash content which can increase the cell stability, reveals promising feasibility as a fuel for direct carbon fuel cells. Here we report a high-performance direct carbon fuel cell utilizing Chinese parasol leaf biochar as fuel, among which Ag–Gd_0.1Ce_0.9O_2-δ and Al₂O₃ doped yttria-stabilized zirconia are employed as symmetrical electrodes and electrolyte materials, respectively. The cell with pure leaf biochar fuel gives a maximum power density of 249 mW cm^?2 and an open circuit voltage (OCV) of 1.008 V at 850 °C while an improved performance of 272 mW cm^?2 and OCV of 1.01 V are achieved for the cell fuelled by Fe catalyst-loaded leaf biochar. The above results demonstrate that Chinese parasol leaf biochar can be applied as a potential fuel for high performance direct carbon solid oxide fuel cells.     

A hybrid aluminum/hydrogen/air cell system

A hybrid aluminum/hydrogen/air cell system is developed to solve the parasitic hydrogen-generating problem in an alkaline aluminum/air battery. A H₂/air fuel cell is integrated into an Al/air battery so that the hydrogen generated by the parasitic reaction is utilized rather than wasted. A systematic study is conducted to investigate how the parasitic reaction and the added H₂/air cell affect the performance of the aluminum/air battery. The aluminum/air sub-cell has an open circuit voltage of 1.45 V and the hydrogen/air sub-cell of 1.05 V. The maximum power density of the entire hybrid system increases significantly by ∼20% after incorporating a H₂/air sub-cell. The system maximum power density ranges from 23 to 45 mW cm⁻² in 1–5 M NaOH electrolyte. The hybrid system is adaptable in concentrated alkaline electrolyte with significantly improved power output at no sacrifice of its overall efficiency.     

An alkaline direct ethylene glycol fuel cell with an alkali-doped polybenzimidazole membrane

An alkaline direct ethylene glycol fuel cell (DEGFC) with an alkali-doped polybenzimidazole membrane (APM) is developed and tested. It is demonstrated that the use of APMs enables the present fuel cell to operate at high temperatures. The fuel cell results in the peak power densities of 80 mW cm⁻² at 60 °C and 112 mW cm⁻² at 90 °C, respectively. The power output at 60 °C is found to be 67% higher than that by DEGFCs with proton exchange membranes, which is mainly attributed to the superior electrochemical kinetics of both ethylene glycol oxidation and oxygen reduction reactions in alkaline media.     

High-performance metal (Au,Cu)–polypyrrole nanocomposites for electrochemical borohydride oxidation in fuel cell applications

Gold polypyrrole (AuPPy) and copper polypyrrole (CuPPy) nanocomposites were prepared by a simple one-step in situ oxidative polymerization of pyrrole monomer by Au³⁺ and Cu²⁺ ions. Owing to their characteristic physicochemical properties confirmed by optical and structural characterization methods, the behavior of these materials as electrocatalysts for borohydride oxidation reaction (BOR) was considered. BOR apparent activation energy was found to be 16 and 22 kJ mol^?1 for AuPPy and CuPPy electrocatalyst, respectively. The stability of the two electrocatalysts was assessed by chronoamperometry. Moreover, fuel cell tests were carried out with AuPPy and CuPPy as anode electrocatalyst of a direct borohydride-peroxide fuel cell (DBPFC). Open circuit voltage (OCV) of 1.30 V was obtained with both AuPPy and CuPPy, with the OCV increasing to 1.45 V upon adding a small amount of carbon (AuPPy-C). The peak power density of a DBPFC with BOR at AuPPy-C anode and hydrogen peroxide reduction reaction at Pt cathode was found to be ca. 162 mW cm^?2 at 65 °C.     

A direct borohydride fuel cell employing a sago gel polymer electrolyte

The electrochemistry of a direct borohydride fuel cell based on a gel polymer electrolyte was studied. Sago is a type of natural polymer, was employed as the polymer host for the electrolyte. An electrolyte with a composition of sago + 6 M KOH + 2 M NaBH₄ was prepared and evaluated as a novel gel polymer electrolyte for a direct borohydride fuel cell system because it exhibited a high electrical conductivity of 0.270 S cm⁻¹. The rate at which oxygen was consumed at the cathode can be related to the electric current by comparing the calculated number of electrons reacted per molecule of oxygen for different currents supplied to the fuel cell. From the oxygen consumption data, it was deduced that four electrons reacted per molecule of oxygen. The performance of the fuel cell was measured in terms of its current–voltage, discharge and open circuit voltage measurements. The maximum power density obtained was 8.818 mW cm⁻² at a discharge performance of ∼230 mA h and nominal voltage of 0.806 V. The open circuit voltage of the cells was about 0.900 V and sustained for 23 h.     

Application of biochar derived from used cigarette filters in direct carbon solid oxide fuel cell

As a typical waste, used cigarette filters (UCFs) are difficult to biodegrade and harmful to the environment. The direct carbon solid oxide fuel cell (DC-SOFC) is an energy conversion device that can utilize carbon directly, including biochar, as fuel. We report a superior DC-SOFC powered by Fe-loaded UCF biochar in this paper. The microstructure and composition are characterized, indicating that the UCF biochar is micron-sized and contains metal elements such as K and Ca that are beneficial to the performance of DC-SOFC. The peak power density of the cell fueled by pure UCF biochar is 308 mW cm^?2 and increases to 341 mW cm^?2 after loading Fe as the catalyst, which is comparable to that of the cell with Fe-loaded activated carbon (368 mW cm^?2). It proves the feasibility of the UCF biochar as fuel for DC-SOFCs, providing a theoretical basis and technical demonstration for the disposal and transformation of solid waste.     

A direct formate microfluidic fuel cell with cotton thread-based electrodes

A direct formate microfluidic fuel cell with cotton thread-based electrodes is proposed. The palladium catalyst is directly coated on cotton threads by repeated dipping method to prepare electrodes, which integrates the flow channel and electrode together and provides exposed active sites for enhancing the mass transfer on the anode and cathode. The aqueous anolyte and catholyte transport through cotton threads by capillary force with aid of gravity, eliminating the use of any external pump and facilitating the integration and miniaturization of the whole system. In the experiment, a three-flow channel structure is employed. The fuel is sodium formate and the oxidant is hydrogen peroxide. 1 M Na₂SO₄ solution is introduced into the middle channel formed by cotton threads with no catalyst to alleviate the reactant crossover. Performance is evaluated under various catalyst loadings, fuel concentrations and differences in height between the inlet and outlet. Results show that the fuel cell produces an open circuit voltage (OCV) of 1.41 V. The maximum current density of 74.56 mA cm⁻² and the peak power density of 24.75 mW cm⁻² are yielded when the palladium loading is 1 mg cm⁻¹ and the difference in height between the inlet and outlet is 7 cm, using 4 M HCOONa as fuel. Furthermore, the performance of the fuel cell increases first and then decreases with increasing the palladium loading. The same variation is observed with increasing the fuel concentration. However, the performance gradually increases with increasing the difference in height from 3 cm to 7 cm. The proposed microfluidic fuel cell with cotton thread-based electrodes shows enormous potential as a micro power source for portable devices.     

Compositing protonic conductor BaZr0.5Y0.5O3 (BZY) with triple conductor BaCo0.4Fe0.4Zr0.1Y0.1O3-δ (BCFZY) as electrolyte for advanced solid oxide fuel cell

BaZr_0.5Y_0.5O₃(BZY) electrolyte exhibited enormous potential for low temperature solid oxide fuel cell (SOFC) due to its proton dominant mobile carriers rather than oxygen ions during the electrochemical process. In order to enhance the ionic conductivity, triple conductor BaCo_0.4Fe_0.4Zr_0.1Y_0.1O_3-δ (BCFZY) was composited with proton conductor BZY to form semiconductor-ionic conductor composite (SIM), which was applied as electrolyte to fabricate symmetrical fuel cell. The microstructural and electrochemical properties for BZY, BCFZY and BZY-BCFZY composites were studied. After optimizing the weight ratio of composite content, the ionic conductivity and electronic conductivity reached an equilibrium state to obtain the maximum cell performance, namely the highest output of 902.5 mW cm^?2 and an open circuit voltage (OCV) of 1.043 V at 550 °C. The BZY-BCFZY cell also presented decent power output at low temperature, a power density of 265.625 mW cm^?2 was received even at 500 °C, demonstrating that the BZY-BCFZY composite was a potential electrolyte for low temperature SOFCs.     

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.     

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.     

A core-shell NiCu@NiCuOOH 3D electrode induced by surface electrochemical reconstruction for the ammonia oxidation reaction

A direct ammonia microfluidic fuel cell is a potential portable carbon-free clean energy device. In this work, a NiCu-based core-shell 3D electrode is obtained by electrodeposition and surface electrochemical reconstruction on the nickel foam substrate. The physical characterization results confirm the core-shell structure with NiCu as the core and Cu(OH)₂ and NiOOH as the shell. In the 3D electrode, the metal core continuously transfers charge to the surface to transform into active species (NiCu hydroxides), thus accelerating the slow ammonia oxidation reaction kinetics. Furthermore, the 3D porous structure is conducive to the rapid diffusion and transport of ions, which effectively improves the fuel depletion boundary layer problem. Consequently, electrochemical tests indicate that the NiCu@NiCuOOH-NF electrode show excellent ammonia oxidation reaction activity and good stability, reaching a maximum current density of 90 mA cm^?2 at the potential of 0.7 V vs. saturated calomel electrode (SCE). When 2 M NaOH + 3 M NH₄Cl is adopted as fuel for the DAMFC, an open circuit voltage of 0.72 V and a peak power density of 17.1 mW cm^?2 can be obtained, while the limiting current density is as high as 102 mA cm^?2.     

A direct flame solid oxide fuel cell for potential combined heat and power generation

A sealant-free solid oxide fuel cell (SOFC) micro-stack was successfully operated inside a liquefied petroleum gas (LPG) flame during cooking. This micro-stack consisted of 4 single cells with infiltrated La_0.75Sr_0.25Cr_0.5Mn_0.5O_3-δ (LSCM) based composite anodes, achieving an open circuit voltage of 0.92 V and a peak power density of 348 mW cm⁻². This performance is significantly better than that of stack with its cathode operation outside flame. The results confirmed that the perovskite oxide anode showed good properties of carbon-free, redox-stability, quick-start (less than 1 min) and successful operation under a wide range of oxygen partial pressure. For comparison, the conventional Ni/yttria-stabilized zirconia (Ni/YSZ) anode was prepared and tested under the same conditions, showing an open circuit voltage of 0.915 V and a peak power density of 366 mW cm⁻², but obvious carbon deposition, poor stability and slow/difficult-start. The direct flame SOFC (DFFC) with a new configuration and design has a potential for combined heat and power generation for many applications.     

Effects of Pt/C, Pd/C and PdPt/C anode catalysts on the performance and stability of air breathing direct formic acid fuel cells

Pt/C, Pd/C and PdPt/C catalysts are potential anodic candidates for electro-oxidation of formic acid. In this work we designed a miniature air breathing direct formic acid fuel cell, in which gold plated printed circuit boards are used as end plates and current collectors, and evaluated the effects of anode catalysts on open circuit voltage, power density and long-term discharging stability of the cell. It was found that the cell performance was strongly anode catalyst dependent. Pd/C demonstrated good catalytic activity but poor stability. A maximum power density of 25.1 mW cm⁻² was achieved when 5.0 M HCOOH was fed as electrolyte. Pt/C and PdPt/C showed poor activity but good stability, and the cell can discharge for about 10 h at 0.45 V (Pt/C anode) and 15 h at 0.3 V (PdPt/C) at 20 mA.     

Fabrication and testing of coplanar single-chamber micro solid oxide fuel cells with geometrically complex electrodes

Coplanar single-chamber micro solid oxide fuel cells (SC-μSOFCs) with curvilinear microelectrode configurations of arbitrarily complex two-dimensional geometry were fabricated by a direct-write microfabrication technique using conventional fuel cell materials. The electrochemical performance of two SC-μSOFCs with different electrode shapes, but comparable electrode and inter-electrode dimensions, was characterized in a methane–air mixture at 700 °C. Both cells exhibited stable open circuit voltage and peak power density of 0.9 V and 2.3 mW cm⁻², respectively, indicating that electrode shape did not have a significant influence on the performance of these fuel cells.     

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.     

Direct hydrazine-hydrogen peroxide fuel cell using carbon supported Co@Au core-shell nanocatalyst

Carbon-supported Co@Au core-shell/C and Au/C nanoparticles are synthesized by a successive reduction method in an aqueous solution and used as the anode and cathode electrocatalysts for the direct hydrazine-hydrogen peroxide fuel cell, respectively. The physical and electrochemical properties of the as-prepared electrocatalysts are investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and fuel cell field tests. In this work, the effects of different operation conditions including operation temperature, fuel and oxidant concentration and fuel and oxidant flow rate on the performance of fuel cell are systematically investigated. The experimental results exhibit an open circuit voltage of about 1.79 V and a peak power density of 122.75 mW cm^?2 at a current density of 128 mA cm^?2 and a cell voltage of 0.959 V operating on 2.0 M N₂H₄ and 2.0 M H₂O₂ at 60 °C.     

Electrical properties of Ni-doped Sm2O3 electrolyte

Nowadays, semiconductor ionic materials have drawn significant attention for developing new electrolytes in low temperature solid oxide fuel cells (LT-SOFCs). Here we investigate the effect of nickel doping on ionic conductivity of Sm₂O₃ as an electrolyte material for low temperature SOFCs. The amount of Ni ion doping has an intense effect on the electrochemical properties and power generation. An optimized composition of 10 mol% nickel doped samarium oxide (10NSO) as an electrolyte in the fuel cell has a high open circuit voltage (OCV) of 1.09 V and a notable power output of 1080 mW cm^?2 at 520 °C. Further investigation revealed that the 10NSO displays a superior ionic conduction up to 0.26 S cm^?1 at 520 °C. Moreover, the cell demonstrates high stability up to 80 h. The high electrochemical property and good stability recommend that the NSO is a favorable candidate for symmetrical SOFC electrolyte.     

Performance of a direct ethylene glycol fuel cell with an anion-exchange membrane

This paper reports on the development and performance test of an alkaline direct ethylene glycol fuel cell. The fuel cell consists of an anion-exchange membrane with non-platinum electrocatalysts at both the anode and cathode. It is demonstrated that this type of fuel cell with relatively cheap membranes and catalysts can result in a maximum power density of 67 mW cm⁻² at 60 °C, which represents the highest performance that has so far been reported in the open literature. The high performance is mainly attributed to the increased kinetics of both the ethylene glycol oxidation reaction and oxygen reduction reaction rendered by the alkaline medium with the anion-exchange membrane.