Harvesting energy via stimuli-free water/moisture dissociation by mesoporous SnO2–based hydroelectric cell and CuO as a pump for atmospheric moisture

Water dissociation, in general, requires external stimuli such as light energy or electricity. Here, we present a stimuli-free water dissociation using mesoporous SnO₂–based hydroelectric cell that can directly be exploited to generate electric power for portable applications. The device configuration is almost identical to metal-air batteries but follows altogether a different reaction pathway. The mesoporous SnO₂–based hydroelectric cell dissociates water molecule into hydroxyl ions (OH^-) and hydronium ion without any stimuli, transports hydronium ions to the opposite end, and simultaneously acts as the separator. The OH^- react with Al electrode to release the electrons, whereas hydronium ions get reduced at the Ag electrode to produce a potential difference as high as ~1000 ± 20 mV between the electrodes that is stable over 3500 hours. The device also shows its potential toward electric power generation from atmospheric moisture with the help of CuO layer that acts as moisture pump.     

Significance of interface barrier at electrode of hematite hydroelectric cell for generating ecopower by water splitting

Recent increase in energy demand and associated environmental degradation concern has triggered more research towards alternative green energy sources. Eco‐friendly energy in facile way has been generated from abundantly available iron oxides using only few microliters of water without any external energy source. Hydroelectric cell (HEC) compatible to environment benign, low cost oxygen‐deficient mesoporous hematite nanoparticles has been used for splitting water molecules spontaneously to generate green electricity. Hematite nanoparticles have been synthesized by coprecipitation method. Chemidissociated hydroxyl group presence on hematite surface has been confirmed by infrared spectroscopy (IR) and X‐ray photoelectron spectroscopy (XPS). Surface oxygen vacancies in nanostructured hematite have been identified by transmission electron microscopy (TEM), XPS, and photoluminescence (PL) measurement. Hematite‐based HEC delivers 30 mA current with 0.92 V emf using approximately 500 μL water. Maximum off‐load output power 27.6 mW delivered by 4.84 cm² area hematite‐based HEC is 3.52 times higher than reported 7.84 mW power generated by Li‐magnesium ferrite HEC. Electrochemistry of HEC in different irreversible polarization loss regions has been estimated by applying empirical modeling on V‐I polarization curve revealing the reaction and charge transport mechanism of cell. Tafel slope 22.7 mV has been calculated by modeling of activation polarization overvoltage region of 0.11 V. Low activation polarization indicated easy charge/ion diffusion and faster reaction kinetics of Ag/Zn electrode owing to lesser energy barrier at interface. Dissociated H₃O⁺ ions diffuse through surface via proton hopping, while OH^? ions migrate through interconnected defective crystallite boundaries resulting into high output cell current.     

Electricity generation by splitting of water from hydroelectric cell: An alternative to solar cell and fuel cell

Harnessing green electricity by hydroelectric cell from water molecule splitting based on uniquely processed ferrites, multiferroic, composites and metal oxides has astonished the world. The specially processed oxygen deficient Nano porous ferrite/metal oxide attached with two dissimilar electrodes known as hydroelectric cell to generate electricity using a few drops of water for the first time it was invented in 2016. It is a primary source of energy that operates on the principle of spontaneous water molecule dissociation (OH⁻ and H₃O⁺) by oxygen deficient and Nano porous materials such as Mg_0.8Li_0.2Fe₂O₄, SiO₂, SnO₂, MgO, Fe₂O₃, Fe₃O₄, and TiO₂. The electrodes attached on oxide pellets are the Zn sheet anode and inert cathode Ag paste fabricated as hydroelectric cell. Chemi-dissociation of water molecule on the pellet surface followed by physi-dissociation results into H₃O⁺ ion hopping and that ultimately leads to hopping of H⁺ ions into nanopores. This phenomenon generates enough electric potential that spontaneously dissociates physisorbed water molecules on the pellet surface, thus sustaining current in the cell. Redox reactions of OH⁻ and H₃O⁺ at Zn and Ag electrodes, respectively, generate cell potential, which allows the flow of electric current in the external circuit of the cell. A pellet of size 1 in. square of Mg_0.8Li_0.2Fe₂O₄, SnO₂, and Fe₃O₄ etc. is able to deliver current of 8, 22, and 50 mA with a voltage of 0.98, 0.78, and 0.83 V, respectively. Hydroelectric cell working in different functional mode is able to produce high purity hydrogen gas and zinc hydroxide nanoparticles also. This review compiled the detailed working mechanism of recently invented hydroelectric cell, with studies done on different oxide materials in order to understand their water splitting properties, its advantages and limitation along with future prospect for complementing other sources for power generation. Hydroelectric cell has brought a big revolution recently in green energy sector by opening a new field in energy materials based on water splitting by non-photocatalytic process and is progressing rapidly its development, therefore there is a need of concise and comprehensive article to introduce its working to advance this new green energy device knowledge to young researchers globally. Conduciveeconomics, ubiquitous resources, user friendly technology with no disposal issue make hydroelectric cell a future potential green energy source as a better low cost alternative to solar and fuel cell.     

N-doped graphene quantum dots incorporated cobalt ferrite/graphitic carbon nitride ternary composite for electrochemical overall water splitting

Multicomponent electrocatalysts containing carbon supports play a crucial role in influencing the hydrogen and oxygen evolution reactions which enhance the total water splitting. Herein, we report a ternary composite with cobalt ferrite, graphitic carbon nitride, and N-doped graphene quantum dots prepared via hydrothermal technique. The purity of the samples is established by carrying out various characterization methods. The intrinsic characteristics of the obtained materials are investigated by employing electrocatalytic processes in an alkaline media toward hydrogen and oxygen evolution reactions. Cobalt ferrite/graphitic carbon nitride/N doped graphene quantum dots electrocatalyst demonstrates a very low overpotential towards hydrogen evolution reaction of 287 mV at a constant 10 mA cm^?2 current density in 1.0 M KOH. Tafel slope and R_ct values generated are 94 mV dec^?1 and 0.86 cm², respectively. Oxygen evolution reaction studies reveal an overpotential of 445 mV at 10 mA cm^?2 with a Tafel slope of 69 mV dec^?1. Finally, the cell potential needed for the cobalt ferrite/graphitic carbon nitride/N doped graphene quantum dots electrode to achieve 10 mA cm^?2 in total water splitting is only 2.0 V while displaying long-term stability.     

Synthesis of high crystalline nickel‐iron hydrotalcite‐like compound as an efficient electrocatalyst for oxygen evolution reaction

The nickel‐iron hydroxide‐like catalyst for oxygen evolution reaction (OER) is prepared by an improved coprecipitation method. The crystallization degree of hydrotalcite‐like compound is high, and the lamellar structure is homogeneous with no agglomeration, which helps to build efficient mass‐transfer layer channel of OH^? ions. The NiFe layered double hydroxide (LDH)/carbon nanotubes (CNTs) electrode shows good performance and stability for OER. The potential of NiFe LDH/CNTs electrode is only 0.592 V (vs HgO/Hg) at 200 mA·cm^?2 in 6 mol·L^?1 potassium hydroxide (KOH) electrolyte, which shows excellent catalytic activity for OER. The NiFe LDH/CNTs electrode works continuously for 620 hours at 200 mA·cm^?2, with the groove voltage only rises 0.1 V.     

The effect of 3D silver nanodome size on hydrogen evolution activity in alkaline solution

Three-dimensional (3D) Ag nanodomes (AgNDs) having different sizes (400, 800, 1200 and 1600 nm) were fabricated using combination of nanosphere lithography and soft lithography. The surface structures of 3D assembled latex particles, nanovoids and metal nanodomes (ND) were examined using scanning electron microscopy (SEM). Their heights and widths analyses were performed with the help of atomic force microscopy (AFM). The effect of diameter of the NDs on their hydrogen evolution activity was examined in 6 M KOH solution at 298 K using electrochemical techniques. Their activities were compared with the activity of bulk Ag electrode. The preparation of 3D-AgNDs having various diameters and examination of their size effects on the water splitting activity have not been studied yet and are being reported firstly. It was found that very well-structured and very uniformly distributed NDs can be fabricated using this procedure. AgNDs exhibit higher hydrogen evolution activity with respect to bulk Ag. Their hydrogen evolution activity depends on their diameters; 1200 nm NDs were the best among them. The current density at ?1.40 V(Ag/AgCl) which is proportional to the rate of hydrogen releasing reaction increases from 0.70 mA cm^?2 to 44.13 mA cm^?2 at this ND electrode with respect to the bulk Ag electrode. At the same 3D-AgNDs electrode and potential, the resistance against the HER reduces from 148.7 Ω cm² to 1.12 Ω cm² (99.6%) by comparing with the bulk Ag electrode. The average surface roughness factors of bulk Ag, 400 nm, 800 nm, 1200 nm and 1600 nm AgNDs are 8, 123, 100, 291 and 176, respectively. The superior hydrogen evolution performance of this electrode is related to its well-structured surface and large real surface area.     

Vertical Nickel–Iron layered double hydroxide nanosheets grown on hills-like nickel framework for efficient water oxidation and splitting

Herein, the vertical thin nickel–iron layered double hydroxide nanosheets grown on the hills-like nickel framework (NiFe LDH/Ni@NF) are employed for the oxygen evolution reaction (OER), securing at the low overpotentials of 197 and 270 mV to obtain the current densities of 20 and 100 mA cm⁻², respectively, with a Tafel slope of 73.34 mV dec⁻¹. The electrodeposited nickel film induces the NiFe LDH nanosheets grow vertically and thinly. As well, the nickel abundant interfaces and inner space makes this catalyst effective for OER. It was further served as the OER electrode in a water splitting system coupled the Pt/C cathode, and a cell voltage was at 1.52 and 1.67 V to achieve the current density of 10 mA cm⁻² and 50 mA cm⁻². In addition, the water electrolyzer can suffer a long time of 24 h at 50 mA cm⁻², showing the feasibility in a practical unbiased alkaline water splitting system.     

Silver-modified Ba0.5Sr0.5Co0.8Fe0.2O3−δ as cathodes for a proton conducting solid-oxide fuel cell

Electrochemical performance of silver-modified Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3−δ (BSCF-Ag) as oxygen reduction electrodes for a protonic intermediate-temperature solid-oxide fuel cell (SOFC-H⁺) with BaZr_0.1Ce_0.8Y_0.1O₃ (BZCY) electrolyte was investigated. The BSCF-Ag electrodes were prepared by impregnating the porous BSCF electrode with AgNO₃ solution followed by reducing with hydrazine and then firing at 850 °C for 1 h. The 3 wt.% silver-modified BSCF (BSCF-3Ag) electrode showed an area specific resistance of 0.25 Ω cm² at 650 °C in dry air, compared to around 0.55 Ω cm² for a pure BSCF electrode. The activation energy was also reduced from 119 kJ mol⁻¹ for BSCF to only 84 kJ mol⁻¹ for BSCF-3Ag. Anode-supported SOFC-H⁺ with a BZCY electrolyte and a BSCF-3Ag cathode was fabricated. Peak power density up to 595 mW cm⁻² was achieved at 750 °C for a cell with 35 μm thick electrolyte operating on hydrogen fuel, higher than around 485 mW cm⁻² for a similar cell with BSCF cathode. However, at reduced temperatures, water had a negative effect on the oxygen reduction over BSCF-Ag electrode, as a result, a worse cell performance was observed for the cell with BSCF-3Ag electrode than that with pure BSCF electrode at 600 °C.     

Ag current collector for honeycomb solid oxide fuel cells using LaGaO3-based oxide electrolyte

Honeycomb type solid oxide fuel cell (SOFC) using a Ag mesh as a current collector and La_0.9Sr_0.1Ga_0.8Mg_0.2O₃ (LSGM) as an electrolyte was studied for reducing production cost. When an Ag mesh was used as a current collector, the power density of the cell became lower than that of a cell using a Pt mesh due to the relatively worse contact caused by the lower calcination temperature, particularly in the case of the anode. The preparation method and the electrode structure were investigated for the purpose of increasing the power density of the cell using the Ag current collector. It was found that an interlayer of Ni–Sm_0.2Ce_0.8O_1.9 (1:9) between the NiFe–LSGM cermet anode and the LSGM electrolyte was effective for decreasing the pre-calcination temperature for anode fabrication. Much higher power densities of 300 mW cm⁻² and 140 mW cm⁻² at 1073 K and 973 K, respectively, were achieved by inserting an interlayer. These results for the power density of the cell using the Ag mesh current collector after the optimization of the electrode structure and the preparation procedure are close to those of the cell using the Pt mesh current collector cell presented in our previous work.     

23,000 h steam electrolysis with an electrolyte supported solid oxide cell

An electrolyte supported solid oxide cell of 45 cm² area was operated in the steam-electrolysis mode during more than 23,000 h before scheduled shutdown, of which 20,000 h with a current density of j = ?0.9 A cm^?2. The cell consisted of a scandia/ceria doped zirconia electrolyte (6Sc1CeSZ), CGO diffusion-barrier/adhesion layers between electrolyte and electrodes, a lanthanum strontium cobaltite ferrite (LSCF) oxygen electrode, and a nickel/gadolinia-doped ceria (Ni/GDC) steam/hydrogen electrode. Voltage degradation in the operation period with j = ?0.9 A cm^?2 was 7.4 mV/1000 h (0.57%/1000 h) and the increase in the area specific resistance 8 mΩ cm²/1000 h. The final cell voltage was 1.33 V (at 851 °C cell temperature). After dismantling, the cell showed no mechanical damage at electrolyte and H₂/H₂O electrode; a small fraction of the oxygen electrode was delaminated. Impedance spectroscopy applied at the steady state DC current density confirmed a degradation dominated by an increasing ohmic term, mainly due to ionic conductivity decay in the electrolyte. In addition, a small non-ohmic and at least partly reversible O₂ electrode contribution to degradation was identified, affected by a pollution from the (compressor) purge air.     

Significant impact of the current collection material and method on the performance of Ba0.5Sr0.5Co0.8Fe0.2O3−δ electrodes in solid oxide fuel cells

The effects of the current collection material and method on the performance of SOFCs with Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3−δ (BSCF) cathodes are investigated. Ag paste and LaCoO₃ (LC) oxide are studied as current collection materials, and five different current collecting techniques are attempted. Cell performances are evaluated using a current-voltage test and electrochemical impedance spectra (EIS) based on two types of anode-supported fuel cells, i.e., NiO + SDC|SDC|BSCF and NiO + YSZ|YSZ|SDC|BSCF. The cell with diluted Ag paste as the current collector exhibits the highest peak power density, nearly 16 times that of a similar cell without current collector. The electrochemical characteristics of the BSCF cathode with different current collectors are further determined by EIS at 600 °C using symmetrical cells. The cell with diluted Ag paste as the current collector displays the lowest ohmic resistance (1.4 Ω cm²) and polarization resistance (0.1 Ω cm²). Meanwhile, the surface conductivities of various current collectors are measured by a four-probe DC conductivity technique. The surface conductivity of diluted Ag paste is 2-3 orders of magnitude higher than that of LC or BSCF. The outstanding surface conductivity of silver may reduce the contact resistance at the current collector/electrode interface and, thus, contributes to better electrode performance.     

Ethylene glycol assisted solvo-hydrothermal synthesis of NGr-Co3O4 nanostructures for ethanol electrooxidation

Different morphologies of Co₃O₄ nanostructures grown on nanographitic flakes have been synthesized based on the decomposition of cobalt acetate precursor in water, ethylene glycol and water (50%)-ethylene (50%) solution at 180 °C for 18 h via a solvo-hydrothermal process. A subsequent electrophoretic deposition process is used to form composite layers on stainless steel plates. The composite layer fabricated in the water (50%)-ethylene (50%) solution is found to have the best electrocatalytic performance for ethanol electrooxidation due to the hierarchical nanoporous microstructures of Co₃O₄ exhibiting the lowest onset voltage for ethanol electrooxidation (around −0.3 V vs. Ag/AgCl) among the fabricated electrocatalyst layers. Moreover, the ethanol electrooxidation current for the electrode fabricated in the water (50%)-ethylene glycol (50%) reaches roughly 6.6 mA/cm², while it is about 3.3 mA/cm² at 0.5 V (vs. Ag/AgCl) for the electrode fabricated in pure ethylene glycol (values obtained after 1-h stability tests). The electrode fabricated in pure water is confirmed to not exhibit significant ethanol electrooxidation.     

Highly active nanostructured water oxidation catalyst electrodeposited from Co(cyclam) complex

The water soluble molecular complex [Co(cyclam)(ClO₄)]ClO₄ (cyclam = 1,4,8,11-tetraazacyclotetradecane) is utilized as a precursor for deposition of highly active cobalt based nanostructured material on the electrode surface upon electrooxidation. The electrolysis of the complex at +1.1 V vs Ag/AgCl in 0.1 M potassium phosphate at pH 12 leads to the formation of a nanoporous Co(II) hydroxide/phosphate thin film on the printed carbon electrode. The deposited surface was characterized by scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDX), and X-ray photoelectron spectroscopy (XPS). The modified electrode (Co-PCE-12) is stable for more than 34 h during the continuous electrolysis. The modified electrode exhibits a high water oxidation catalytic activity of 6.5 mA cm^?2 at an overpotential of 580 mV (0.9 V vs Ag/AgCl (3 M KCl) at pH 12) with 98% Faradaic yield.     

Study of operating conditions and cell design on the performance of alkaline anion exchange membrane based direct methanol fuel cells

Direct methanol fuel cells using an alkaline anion exchange membrane (AAEM) were prepared, studied, and optimized. The effects of fuel composition and electrode materials were investigated. Membrane electrode assemblies fabricated with Tokuyama^® AAEM and commercial noble metal catalysts achieved peak power densities between 25 and 168 mW cm⁻² depending on the operating temperature, fuel composition, and electrode materials used. Good electrode wettability at the anode was found to be very important for achieving high power densities. The performance of the best AAEM cells was comparable to Nafion^®-based cells under similar conditions. Factors limiting the performance of AAEM MEAs were found to be different from those of Nafion^® MEAs. Improved electrode kinetics for methanol oxidation in alkaline electrolyte at Pt-Ru are apparent at low current densities. At high current densities, rapid CO₂ production converts the hydroxide anions, necessary for methanol oxidation, to bicarbonate and carbonate: consequently, the membrane and interfacial conductivity are drastically reduced. These phenomena necessitate the use of aqueous potassium hydroxide and wettable electrode materials for efficient hydroxide supply to the anode. However, aqueous hydroxide is not needed at the cathode. Compared to AAEM-based fuel cells, methanol fuel cells based on proton-conducting Nafion^® retain better performance at high current densities by providing the benefit of carbon dioxide rejection.     

Proton exchange membrane water electrolysis at high current densities: Investigation of thermal limitations

In this work the thermal limitations of high current density proton exchange membrane water electrolysis are investigated by the use of a one dimensional model. The model encompasses in-cell heat transport from the membrane electrode assembly to the flow field channels. It is validated by in-situ temperature measurements using thin bare wire thermocouples integrated into the membrane electrode assemblies based on Nafion® 117 membranes in a 5 cm² cell setup. Heat conductivities of the porous transport layers, titanium sinter metal and carbon paper, between membrane electrode assembly and flow fields are measured in the relevant operating temperature range of 40 °C – 90 °C for application in the model. Additionally, high current density experiments up to 25 A/cm² are conducted with Nafion® 117, Nafion® 212 and Nafion® XL based membrane electrode assemblies. Experimental results are in agreement with the heat transport model. It is shown that for anode-only water circulation, water flows around 25 ml/(min cm²) are necessary for an effective heat removal in steady state operation at 10 A/cm², 80 °C water inlet temperature and 90 °C maximum membrane electrode assembly temperature. The measured cell voltage at this current density is 2,05 V which corresponds to a cell efficiency of 61 % based on lower heating value. Operation at these high current densities results in three to ten-fold higher power density compared to current state of the art proton exchange membrane water electrolysers. This would drastically lower the material usage and the capital expenditures for the electrolysis cell stack.     

Technical feasibility of a proton battery with an activated carbon electrode

The technical feasibility of a small-scale ‘proton battery’ with a carbon-based electrode is demonstrated for the first time. The proton battery is one among many potential contributors towards meeting the gargantuan demand for electrical energy storage that will arise with the global shift to zero greenhouse emission, but inherently variable, renewable energy sources. Essentially a proton battery is a reversible PEM fuel cell with an integrated solid-state electrode for storing hydrogen in atomic form, rather than as molecular gaseous hydrogen in an external cylinder. It is thus a hybrid between a hydrogen-fuel-cell and battery-based system, combining advantages of both system types. In principle a proton battery can have a roundtrip energy efficiency comparable to a lithium ion battery. The experimental results reported here show that a small proton battery (active area 5.5 cm²) with a porous activated carbon electrode made from phenolic resin and 10 wt% PTFE binder was able to store in electrolysis (charge) mode very nearly 1 wt% hydrogen, and release on discharge 0.8 wt% in fuel cell (electricity supply) mode. A significant design innovation is the use of a small volume of liquid acid within the porous electrode to conduct protons (as hydronium) to and from the nafion membrane of the reversible cell. Hydrogen gas evolution during charging of the activated carbon electrode was found to be very low until a voltage of around 1.8 V was reached. Future work is being directed towards increasing current densities during charging and discharging, multiple cycle testing, and gaining an improved understanding of the reactions between hydronium and carbon surfaces.     

A model for the effects of temperature and structural parameters on the performance of a molten sodium hydroxide direct carbon fuel cell (MHDCFC) based on hydroxide ion mass transfer

To understand the parametric effects on the performance of a molten sodium hydroxide direct carbon fuel cell, an experimentally validated mathematical model is established to investigate the influences of temperature, temperature distribution, anode rod radius, electrode spacing, and inner cell diameter on the cell behaviour. Mass transfer, heat transfer, and secondary current distribution theories are considered in the model cell. A high temperature, small anode rod radius, small electrode spacing, and small inner diameter of the cell are recommended to enhance the cell behaviour, which are conducive to the transmission of hydroxide ions (OH⁻) based on mass and heat transfer. The small temperature difference distribution in the cell has a weak effect on the cell performance, and the three-phase boundary is the key factor influencing the cell behaviour in all cases. An orthogonal test was conducted to determine the best parameter combination for the maximum cell performance, and the Pearson correlation coefficient was used to evaluate the relevance of the investigated parameters to the cell performance. The order of the influence of each factor on the maximum power density of the cell is as follows: temperature > anode rod radius > electrode spacing > cell diameter. When the temperature is 973 K, the anode rod radius is 0.55 cm, the electrode spacing is 2.2 cm, and the inner diameter of the cell is 5 cm, and the optimized power density is 25.40 mW cm⁻².     

Facile SILAR preparation of Fe(OH)3/Ag/TiO2 nanotube arrays ternary hybrid for supercapacitor negative electrode

The ternary hybrid composite electrode of Fe(OH)₃/Ag/TNTA (where TNTA stands for TiO₂ nanotube arrays) was prepared by a simple successive ionic layer adsorption and reaction method. The effects of calcination temperature of Ag/TNTA, drying temperature of Fe(OH)₃/Ag/TNTA, and deposition amount of Ag and Fe(OH)₃ on the supercapacitor performance of the composite electrode were investigated, and the related reasons were discussed in detail. The results show that Ag modification can obviously improve the performance of Fe(OH)₃/TNTA composite electrode. Both the calcination temperature of Ag/TNTA and the deposition amount of Ag affect the particle size of Ag and the reaction resistance of the electrode. The deposition amount of Fe(OH)₃ also has influence on the reaction resistance of the electrode. Under the optimized conditions, the capacitance value of the Fe(OH)₃/Ag/TNTA composite electrode is as high as 84.67 mF cm^?2@5 mV s^?1（596.30 F g^?1@5 mV s^?1）, and the electrode has high rate performance and good cycle stability. The asymmetric supercapacitor assembled with Fe(OH)₃/Ag/TNTA as the negative electrode and activated carbon as the positive electrode can store energy stably under the potential window of 0–1.5 V. When the power density is 2.77 kW kg^?1 (50 mW cm^?3), the energy density can reach 18.34 Wh kg^?1 (0.33 mWh cm^?3).     

A promising strontium and cobalt-free air electrode Pr1-xCaxFeO3-δ for solid oxide electrolysis cell

A promising strontium and cobalt-free ferrite Pr_1-xCa_xFeO_3-δ (PCF, x = 0, 0.1, 0.2, 0.3, 0.4, 0.5) has been synthesized successfully by glycine-nitrate combustion method and used as the air electrode of solid oxide electrolysis cell (SOEC) for steam electrolysis. The crystal structure and electricity conductivity of PCF are investigated in detail. According to the conductivity test, Pr_0.6Ca_0.4FeO_3-δ (PCF64) with higher conductivity is selected as the air electrode to preparing the single cell with structure of PCF64|GDC|SSZ|YSZ-NiO. Under SOFC mode, the maximum power density of the single cell is 462.93 mW cm⁻² at 800 °C with hydrogen as fuel. Under SOEC mode, the current density reaches 277.14 mA cm⁻² and the corresponding hydrogen production rates is 115.84 mL cm⁻² h⁻¹ at 800 °C at 1.3 V. In the 10 h short-term stability test, the cell shows good electrolysis stability.     

Fluorene-containing poly(arylene ether sulfone)s with imidazolium on flexible side chains for anion exchange membranes

Anion exchange membranes with high ionic conductivity and dimensional stability attract a lot of research interests. In present study, a series of fluorene-containing poly(arylene ether sulfone)s containing imidazolium on the flexible long side-chain are synthesized via copolycondensation, Friedel-Crafts reaction, ketone reduction, and Menshutkin reaction sequentially. The membranes used for characterization and membrane electrode assembly are obtained by solution casting and ion exchange thereafter. The morphology of the membranes is studied via transmission electron microscopy, and the microphase separation is observed. The long side-chain structure is responsible for the distinct hydrophilic-hydrophobic microphase separation, which facilitates the transport of hydroxide ions in the membranes. The incorporation of imidazolium on the flexible long side-chain is favorable for the ionic aggregation and transport in the membranes. The resulted membranes exhibit high hydroxide conductivities in the range of 48.5–83.1 mS cm⁻¹ at 80 °C. All these membranes show good dimensional stability and thermal stability. The single cell performance shows a power density of 102.3 mW cm⁻² at 60 °C using membrane electrode assembly based-on one of the synthesized polymers.