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A high-performance and durable electroosmotic (EO) pump is developed by using electropolymerized PANI:PSS/C electrodes. PANI: PSS was electrochemically synthesized on the carbon fiber paper using cyclic voltammetry and characterized by a variety of physicochemical methods including field emission scanning electron microscopy (FESEM), electron probe microanalyzer (EPMA), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). There was a linear relationship with a regression coefficient R² ⩾ 0.97 between the applied potential and the peak current (Ipeak), maximum flow rate (Qmax), maximum pressure (Pmax), respectively. The EO pump built with PANI:PSS/C electrodes, with an active area of 1.0 cm², generated the maximum stall pressure of 122 kPa and the maximum flow rate of 203 ul min−1 at 4 V by using deionized (DI) water as a working fluid. The EO pumps assembled with PANI:PSS/C electrodes showed much better overall performances than those made with the bare carbon paper and exhibited good long-term stability without substantial decay for 5 days of continuous operation even at a high potential of 4 V. [ABSTRACT FROM AUTHOR]

The Cu2S-Polyaniline (Cu-P) counter electrode (CE) was prepared by electropolymerization of polyaniline (PANI) on a FTO/Cu2S film. The surface morphology and crystallinity of the counter electrode were examined. The FTO/Cu-P CE provided significantly enhanced electrochemical activity and a faster charge transfer rate compared to the platinum (Pt), Cu2S, PANI, and PANI-Cu2S (P-Cu) CEs because of the synergistic effect between the high carrier mobility of PANI and the good electrocatalytic activity of Cu2S on the polysulfide electrolyte. Besides, the FTO/Cu-P CE exhibited excellent electrochemical stability, due to the strong interaction between the metal particles and electronegative nitrogen of PANI. The quantum dot-sensitized solar cell (QDSSC) with the FTO/Cu-P heterostructure CE exhibited a higher energy conversion efficiency (4.12%) than those with Pt (1.85%), Cu2S (3.71%), PANI (0.77%), and PANI-Cu2S (P-Cu) (1.01%) CEs. [ABSTRACT FROM AUTHOR]

Microspheres of cubic spinel ZnCo2O4 were synthesized using a facile ethylene glycol-mediated hydrothermal method. The size and crystallinity of the ZnCo2O4 microspheres were tuned by simply varying the reaction times. The as-synthesized ZnCo2O4 microspheres had porous structures that were constructed by numerous small building blocks of primary nanoparticles, leading to the formation of sphere-like morphology. The ZnCo2O4 microspheres exhibited a large surface area of 37.27 m2 g-1 with mesopores, 24.66 nm in size, resulting in significantly enhanced electrochemical activity toward pseudocapacitors. Remarkably, the as-made ZnCo2O4 microspheres electrode delivered a high specific capacitance (853.6 F g-1 at a current density of 2 A g-1), good rate performance (417.1 F g-1 at 10 A g-1) and excellent cyclic stability (92.7% capacitance retention after 3000 cycles at a current density of 10 A g-1). Moreover, a symmetric supercapacitor based on ZnCo2O4 microsphere electrodes achieved an energy density of 11.8 Wh kg-1 and a maximum power density of 2.5 kW kg-1. The good electrochemical performances can be attributed to the unique porous microsphere texture, high surface area and good electrical conductivity due to the synergistic effect between the two metal elements. [ABSTRACT FROM AUTHOR]

Ionic liquid-based electrolytes composed of diethylene glycol diethyl ether (DEGDEE) and 1-butyl-1-methyl pyrrolidinium bis(trifluoromethane) sulfonyl imide (BMP-TFSI) were prepared and evaluated for non-aqueous lithium-air cell applications. Adding an appropriate amount of BMP-TFSI to the electrolyte solution improved ionic conductivity, oxidative stability and interfacial stability, and reduced flammability and volatility. When BMP-TFSI was mixed with DEGDEE under optimal condition, the cycle performance was remarkably improved as compared with either the organic electrolyte or ionic liquid electrolyte alone. The Li-air cell assembled with an optimized ionic liquid-based mixed electrolyte initially delivered a high discharge capacity of 10,620 mAh g-1 and exhibited good cycling stability exceeding 150 cycles at a current density of 0.1 mA cm-2 by limiting depth of discharge to 500 mAh g-1. [ABSTRACT FROM AUTHOR]

Diethylene glycol diethyl ether (DEGDEE) was evaluated as an electrolyte solvent for a non-aqueous lithium-air cell. An electrolyte solution of 1 M LiTFSI in DEGDEE showed a high ionic conductivity of 4.7 mS cm-1 at room temperature and considerably high oxidative stability. The full discharge and charge cycles of the lithium-air cells demonstrated that the DEGDEE-based electrolyte provided the unique ability to facilitate the reversible reduction and oxidation processes at the porous carbon electrode without a catalyst. The lithium-air cell employing the DEGDEE-based electrolyte exhibited fairly stable cycling behavior when the carbon loading was 0.5 mg cm-2 and the depth of discharge of the carbon electrode was limited to 1,000 mAh g-1. [ABSTRACT FROM AUTHOR]

Cu2-xS films in situ formed on brass substrates were annealed at different temperatures (100, 200, 300, and 400°C) in flowing Ar gas, and introduced as the counter electrodes (CEs) for CdSe quantum dot-sensitized solar cells (QD-SSCs). The QD-SSC with the bare Cu2-xS CE exhibited higher cell performance than that with the Pt CE. The QD-SSC with the 300°C-annealed Cu2-xS CE achieved the best energy conversion efficiency of 4.25%, showing a 34% increase compared to the cell performance of that with the bare Cu2-xS CE. This is because the Cu2-xS film annealed at 300°C provided rapid charge transport and the increased electrochemical active sites due to the improved crystallinity and surface roughening, leading to significantly enhanced electrocatalytic activity. On the other hand, when the Cu2-xS film was annealed at 400°C, secondary phases, such as CuO, Cu2O, CuSO4 and ZnO, formed, which reduced the cell performance of the QD-SSC with the 400°C-annealed Cu2-xS CE due to the poor electrocatalytic activity. [ABSTRACT FROM AUTHOR]

This paper uses a variety of physicochemical methods to elucidate the mechanism by which cathode inlet relative humidity (RH) degrades a proton exchange membrane fuel cell (PEMFC) during startup-shutdown cycling. The results revealed that the pro- nounced Pt coarsening (agglomeration)/oxidation/dissolution (detachment) and migration were observed along with corrosion of the carbon support at the majority of cathode catalyst layers when PEMFCS were exposed to a higher cathode inlet RH during 1500 startup-shutdown cycles. These changes contributed to the significant loss of Pt mass available for electrochemical reactions and an active Pt surface area at the cathode, thus decaying the performance of the fuel cell. hi addition, the rate of these multiple processes was RH-dependent. However, the degradation at the anode and membrane was not as severe as those observed at the cathode and did not show any dependence on the cathode inlet RH. Based on these results, a modified mechanism for the degradation of the cathode catalyst layer during startup-shutdown cycling of PEMFCs is proposed to explain the effects of RH on fuel cell performance and durability. [ABSTRACT FROM AUTHOR]

Two new ullazine-based organic dyes have been synthesized for applications in nanocrystalline TiO2-based dye-sensitized solar cells (DSSCs). Overall conversion efficiencies up to 3.63% were obtained for DSSCs based on these dyes. The dye with a tert-butyl antenna exhibited a higher and redshifted absorption pattern resulting in increased light-harvesting property. Compared to the unsubstituted dye, the photocurrent density, open-circuit photovoltage and overall power conversion efficiency (PCE) of solar cells based on the tert-butyl substituted dye are improved. The decreased PCE of the solar cell based on unsubstituted dye results mainly from the increased recombination rate and decreased electron lifetime, as evidenced from impedance and photovoltage decay measurements. Density functional theory (DFT) and time-dependent DFT calculations were performed to predict the geometries, electronic structure, and the optical and electrochemical properties of the dyes. [ABSTRACT FROM AUTHOR]

The photovoltaic properties of dye co-sensitized solar cells were compared with those of mono-sensitized devices. Co-sensitized TiO2 photo-electrodes were prepared from a phenothiazine chromophore for the RED dye and a squaraine chromophore for the BLUE dye to achieve panchromatic light absorption in dye co-sensitized solar cells (DSSCs). Co-sensitization on the TiO2 photo-electrode could reduce the aggregation of the BLUE dye adsorbed on the TiO2 surface, which led to an enhancement of the short circuit current (Jsc) of the co-sensitized solar cells. The dye co-sensitized solar cells with the RED and BLUE dyes optimized according to the dipping time showed an increase in the photon-to-current efficiency compared to that of the solar cell with a mono-sensitized photo-electrode. The photovoltaic and aggregation properties of the DSSCs were examined by measuring the current–voltage curve, incident photon-to-current efficiency, and electrochemical impedance spectra. [ABSTRACT FROM AUTHOR]

Ag/Ag _2 O electrodes were fabricated on both carbon fiber paper (CP) and carbon fiber cloth (CC) substrates via galvanostatic electrodeposition to develop an electroosmotic (EO) pump. The results showed that Ag was deposited along the carbon fibers and further grew into Ag particles. The Ag loading on CP was higher than that of CC at the same current density, and the difference increased further with the current density increase. Nafion coating was applied on the as-electrodeposited Ag/Ag _2 O/CP electrode to prevent the degradation of Ag particles using dip coating, followed by drop coating. The Nafion-coated Ag/Ag _2 O/CP electrodes showed much better electroosmotic pump performance and long-term stability than the uncoated electrodes, revealing that the Nafion ionomer can enhance the proton conductivity and mitigate the degradation of Ag particles during the electrochemical reactions. The EO pumps built with Nafion-modified Ag/Ag _2 O/CP electrodes with an active area of 0.28 cm ^2 generated a maximum pressure of 157 kPa and a maximum flow rate of 28.21 u l min ^−1 . The Postmortem analysis of the pumped working fluids collected from the EO pumps operated at a constant potential for three days was performed to further investigate the effects of Nafion coating on Ag degradation.