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In an effort to exploit low-cost tin and sulfur as active materials in the lithium ion hybrid capacitor, we prepare a SnS-Sn/CNT negative electrode through molten slag coating the acidified carbon ...

Energy storage of the lithium-ion hybrid capacitor can be upgraded through adjusting the mismatched rate qualities between the positive and negative electrodes because the positive electrode of the electrical double layer (EDL) stores and releases electricity in a smaller quantity, yet much faster than the negative battery electrode. To increase the EDL capacity, nitrogen-doped carbon (KPN900) with a hollow-onion structure is prepared with phenylphenol, achieving a surface area above 3000 m

Perkembangan pengetahuan di bidang teknologi material sangat pesat dalam beberapa tahun terakhir ini. Kebutuhan akan material penyimpan energi menjadi sebuah tantangan tersendiri. Seiring dengan ditemukannya material graphene, berkembanglah penelitian mengenai aplikasi graphene sebagai material superkapasitor karena nilai luas permukaan aktif teoritis nya mencapai 2675 m2/gr dan konduktivitas yang juga sangat baik. Reduced Graphene Oxide (rGO) adalah few atau layer graphene yang diperoleh melalui proses pengelupasan kimia dari graphite oxide. Salah satu faktor yang mempengaruhi dalam proses sintesis rGO adalah proses ultrasonikasi, dimana fungsi dari proses ini adalah mengubah graphite oxide menjadi graphene oxide, yang ditandai adanya pengelupasan (exfoliation) dari lembaran graphene sehingga menjadi lebih tipis. Dalam penelitian ini, digunakan waktu ultrasonikasi sebesar 1.5, 2, dan 2.5 jam. Pengujian karakterisasi yang dilakukan adalah pengujian XRD, SEM, Raman, dan FTIR. Dari hasil pengujian didapatkan bahwa material rGO berhasil disintesis. Kemudian dilakukan pengujian performa elektrokimia dengan menggunakan Cyclic Voltammetry (CV). Dari hasil pengujian CV didapatkan bahwa performa terbaik pada pada proses ultrasonikasi 1.5 jam, yaitu kapasitansi nya mencapai 195.15 F/gr.Kata kunci: Ultrasonikasi ; Reduced Graphene Oxide; Superkapasitor; Material Penyimpan Energi

In view of insufficient protection against corrosion provided by plasma electrolytic oxidation (PEO) coating on magnesium alloys, we have prepared and analyzed the duplex PEO coatings using the polytetrafluoroethylene (PTFE)-based polymer. Four duplex coatings have been prepared to compare with the two PEO coatings with and without nickel hydroxide sealing. Without the protection of PTFE, the PEO coating cracks with hairline fissures after 50 h immersion in 3.5% sodium chloride solution. With the sealing treatment of nickel hydroxide, the fissure width becomes slimmer, yet the fissure number is still plenty. The PTFE overlay prevents the cracks and offers a much improved corrosion protection and surface hydrophobicity. The improvement is evidenced by an impedance leap of two orders of magnitude. The overlay of colloidal Teflon dispersion raises the contact angle from 76.5° (oxide coating) to 129.9° (duplex coating); on the other hand, Zeffle of PTFE copolymer provides a thinner and less hydrophobic coating with contact angle 91.4°. Among the four duplex coatings, protection of Teflon (SY3) and Zeffle (SY5), without prior sealing, outperforms SY4 and SY6 in potentiodynamic polarization measurements. When the soak time is 50 h, the corrosion currents of SY3 and SY5 are practically the same, 1.69 × 10−7 A cm−2. When the soak time is 150 h, SY5, with corrosion current 2.09 × 10−6 A cm−2 and polarization resistance 6.85 × 104 Ω cm2, surpasses SY3 in protection durability.

Plasma electrolytic oxidation (PEO) has attracted increasing attention since the transportation industry adopts more lightweight metal components and requires an improved version of anodizing for surface protection. In response to the demand, researchers enrich the technical connotation of PEO through diversifying the growth paths and adopting new precursors. Foreign electrolyte additives, involving ceramic and polymeric particles, organic dye emulsions, are incorporated to accomplish various goals. On the other hand, significant progress has been made on comprehension of softening sparks; denoting the adverse trend of growing discharge intensity can be re-routed by involving cathodic current. I–V response shows the cathodic pulse current not only cools down the ensuing anodic pulse, but also twists the coating conductivity, and the residuals of twists accumulate over a long time frame, plausibly through oxide protonation. Thus, the cathodic current provides a tool to control the discharge intensity via integration of the coating conductivity deviations. So far, these cathodic current studies have been performed in the electrolytes of KOH and Na2SiO3. When exotic additives are included, for example Cr2O3, the cathodic current effect is also shifted, as manifested in remarkable changes in its current–voltage (I–V) behavior. We anticipate the future study on cathodic current influences of inclusion shall lead to a precise control of micro arc.

Soft sparking can be utilized to dismiss the intrinsic porosity problem of plasma electrolytic oxidation (PEO) coatings on aluminum alloy, since this type of surface treatment generates a dense inner layer. Researchers usually recognize soft sparking through the anodic voltage drop, along with the decline in light and acoustic emissions. Analysis of V-I transients in the anodic pulse of bipolar DC current reveals the decline in RC time constant is a forerunner, which reflects the transition in micro arc state prior to the conventional definition. In studying the negative current dependence and the current frequency dependence of soft sparking, the results suggest the time constant may serve as an auxiliary indicator, monitoring growth activity variations and further assuring the dense inner layer. The role of time constant is exemplified in the soft sparking experiments at 500 Hz and duty 40%. Microstructure analysis reveals three relatively dense stacks separated by two layers of pores and loose grains. The porous layer is attributed to the micro arc state of less intense microdischarges, marked as a substantial drop in the R2C2 value. Matching between stratified layers and R2C2 rises-and-falls is verified in two electrolytic solutions with and without chromia inclusions. Thus, we suggest time constant as a probing tool of microdischarges softening to help analyze the events prior to voltage drop.

Intended for the electrolyte of PEM fuel cell, three poly (2,5-benzimidazole) ABPBI membranes, denoted as Sb-PA, Sn-PA, Fe-PA, are doped with phosphoric acid and one metal phosphate of antimony, tin, and iron. For comparison, another membrane (PA) is doped with an equal amount of phosphoric acid without metal phosphate. Proton conductivities of the Sb-PA, Sn-PA, and Fe-PA membranes are higher than that of the PA membrane at 60–240 °C, indicating metal phosphate enhances the membrane conductivity. The enhancement effect is most prominent in Sb-PA, with the maximum conductivity at 160 °C, 6.7 × 10−2 S cm−1. Mechanically, Sb-PA is also stiffer and stronger than Sn-PA, Fe-PA, PA, with a Young's modulus 390 ± 60 MPa and a tensile strength 14.3 ± 0.9 MPa. A H2/air fuel cell is assembled to prove the Sb-PA membrane is viable for electrolyte application, with the peak power performance 515 mW cm−2 at 160 °C in hydrogen, and 399 mW cm−2 when its hydrogen fuel is contaminated by 3% carbon monoxide.

In an effort to build the solid oxide fuel cell for intermediate temperature operations, the oxide ion conductor member of LAMOX family appears to be an ideal candidate for electrolyte since its parent crystal La 2 Mo 2 O 9 shows a monoclinic-cubic phase transition around 580 °C. Nonetheless, members of the LAMOX family are much less refractory than the conventional electrode compositions which are targeted to coordinate with the electrolyte of yttrium stabilized zirconia. In this work, we study the viability of a cathode composite of Ba 0.5 Sr 05 Co 0.8 Fe 0.2 O 3 (BSCF) and gadolinium doped ceria (GDC) to match the electrolyte La 1.8 Dy 0.2 Mo 2 O 9 (LDM). Severe interfacial reactions between BSCF and LDM require a ceria-based diffusion barrier between them. The iron-doped GDC barrier of high sinterability is a convenient choice to block the unwanted reactions, allowing us to devise a BSCF/GDC composite cathode of gradient GDC content to relieve thermal stresses. The cell, operated in a mixed reactant chamber with flowing methane/air, functions properly at operation temperature 625–700 °C. Its maximum power output is recorded at 675 °C, since the BSCF crystal begins to degrade at 700 °C under the methane/air atmosphere.

Chromium oxide pigment is a promising electrolyte additive to green the aluminum alloy surface with plasma electrolytic oxidation (PEO) because of its opacity, outdoor durability, and hardness. Initial coating efforts reveal that pigment and adsorbed dispersant, with extra negative charges, dramatically raise positive current and cause power fluctuations under the constant-voltage mode. Accordingly, research attention is redirected to a search of proper electrical parameters under constant current with a required amount of pigment and dispersant. The parameters for green coating involve; 92 mA cm− 2 in positive and negative current densities, 10–20% in duty ratio, 500 Hz in frequency, when the electrolyte is formulated with 10 g dm− 3 pigment and 0.8 g dm− 3 dispersant. Microstructure analysis shows that the resultant coating comprises two layers of different compositions; the top layer is a mixture of chromia and alumina, a dense layer underneath involves nearly 100% alumina. Phase analysis indicates that the aluminum oxide crystallizes in γ- and α-alumina both. A small amount of α-alumina exists in solid solution with chromium. Although the as-received pigment is oxygen deficient, similar to Cr2O2.4 in crystal structure, the oxidative plasma of PEO converts it into stoichiometric Cr2O3.

In an effort to color the aluminum alloy surface green via plasma electrolytic oxidation (PEO), two alkaline solutions have been employed with particulate inclusions and sodium aluminate. Electrolyte I comprises a self-made chromia pigment with a mean particle size 69 nm, whereas electrolyte II contains a commercially available pigment, GN-M, with a larger particle size 351 nm. Both pigments are oxygen deficient Cr2O3-δ of corundum-type structure before coating, the oxidative environment of PEO converts them into stoichiometric Cr2O3. In electrolyte I and II, the oxides of chromium and aluminum deposit simultaneously under analogous PEO conditions, yet resulting in very different microstructures. The GN-M inclusion of large size amasses on top of the coating, while the self-made inclusion goes deep, and closely associates with alumina and pores. The oxide coating, grown in electrolyte II, consists of a top Cr2O3-rich layer and a dense alumina layer underneath, delineated by the boundary marked with microd...

It has been recognized that a connection may exist between defects of oxide coating and its corrosion protection. Such a link has not been substantiated. We prepare two coatings of anodized aluminum oxide (AAO) and plasma electrolytic oxidation (PEO), and analyze them with Mott-Schottky plots and potentiodynamic polarization scans. The as-grown and annealed AAO coatings exhibit both p-type and n-type semiconductor behaviors. Polarization resistance of the AAO coating increases from (1.8 &plusmn, 1.7) &times, 108 to (4.3 &plusmn, 0.5) &times, 108 &Omega, &middot, cm2, while corrosion current decreases from (6.1 &plusmn, 3.6) &times, 10&minus, 7 to (2.3 &plusmn, 0.9) &times, 7 A&middot, cm&minus, 2, as annealing temperature increases from room temperature to 400 &deg, C. The parameter analysis on AAO indicates a positive correlation between corrosion current and donor density, a negative correlation between polarization resistance and donor density. The attempt on correlating corrosion potential gives rise to considerable deviation from a linear fit. The results suggest protection of AAO hinges on its donor density, not acceptor. On the PEO coatings, only the n-type behavior is observed. Intriguingly, the donor density of PEO coating is influenced by the annealing temperature of its pre-anodized layer. The most resistant PEO coating, with pre-anodized and 400 &deg, C annealed AAO, exhibits polarization resistance (2.1 &plusmn, 0.4) &times, 109 &Omega, cm2 and corrosion current (1.7 &plusmn, 8 A&middot, 2.

Given that the amphoteric Li3V2(PO4)3 (LVP) crystal exhibits different capacities in the high and low potential regions, we study its asymmetric capacitor and the mass balancing. Both the positive and the negative electrodes are prepared with 50 wt.% LVP balanced by activated carbon which provide battery and double-layer storage mechanisms; respectively. To retain the capacitor power feature with a sizable capacity, a proper internal hybridization is required to keep the battery mechanism functioning at high-rate cycling. The involvement of battery storage is assured if a high-voltage bulge is observed on the galvanostatic discharge curve. To preserve such a feature, the capacitor analysis indicates three factors are vital. A voltage window is wide enough, 4.0 V, such that the plateau of LVP around 3.6 V (vs. Li/Li+) may operate in discharging the positive electrode. The negative electrode is prelithiated to pin down the negative potential and allow the cell to utilize the permissible potential window. A proper mass ratio 2(+):1(−) provides sufficient but not too much battery storage in the positive electrode. Among the five mass ratios being studied, the 2(+):1(−) capacitor shows a respectable combination of specific energy 43 W h kg−1 and power 520 W kg−1 at 0.2 A g−1, with over 80 % capacity retention in 200 cycles.

A nanostructured electrode, denoted as SnO 2 /Cu/CNT, is prepared with tin dioxide and copper coated on the carbon nanotubes (CNT) backbone. Before coating of tin and copper, the CNT surface has been electrochemically oxidized and examined with the C1s photoelectron spectrum to ensure a minimum oxidation level while sufficient for electroless plating. With the prelithiated SnO 2 /Cu/CNT electrode, matching with an activated carbon (AC) electrode, this lithium ion hybrid capacitor taps into the lithium storage aptitude of tin dioxide for reversible capacity. Thus three capacitors, of the same AC loading, are assembled and studied with the AC:SnO 2 /Cu/CNT mass ratio 1:1, 1:0.67, 1:0.33. Their energy storage capacities are similar in magnitude at 0.1 A g −1 , around 90 Wh kg −1 in a 3.8 V window, but the 1:0.67 cell surpasses the other two cells when the charging current increases. Superiority of the 1:0.67 cell on energy and electric charge storage is discussed, considering the SnO 2 /Cu/CNT role in capacitor. The discussion reveals the prelithiated SnO 2 /Cu/CNT has kept the potential at 0% state of charge ( U 0%SOC ) low to constrict the maximum positive potential. But U 0%SOC should avoid forcing the negative potential descends lower than 0.15 V ( vs . Li/Li + ), where the kinetic barrier of SnO 2 /Cu/CNT becomes problematic at high rates.

Researchers study the solid polymer electrolyte (SPE) to raise the safety and capacity of current lithium ion battery technology to a higher level. We opt to work on the polymer host based on acrylonitrile (PAN), since the nitrile group provides an admirable electrochemical stability and a high polarity, which are critical to the polymeric electrolyte. Yet, the nitrile group is also the origin of high glass transition temperature Tg, which requires synthetic efforts to reduce Tg through tuning the SPE composition. The RAFT mediated polymerization technique is employed to decrease the molecular weight and simultaneously incorporate a substantial amount of thiocarbonate moiety in the backbone. The synthesized PAN copolymer, molecular weight ~1600 g mol−1, contains 43.3% (by mole) carbon, 2.1% sulfur, and 8.7% nitrogen. Copolymerization with dodecyl acrylate increases the free volume of host. Substitution of LiFSI for LiTFSI reduces the glass transition temperature effectively since LiFSI is easier to dissociate and more effective in plasticization. The synthesis efforts result in the highest ion conductivity 6.1 × 10−4 S cm−1 at room temperature and 1.1 × 10−3 S cm−1 at 50 °C. This SPE also displays a lithium transference number 0.318, a high stability when interfacing the lithium metal, and tolerates a potential window of 6.0 V. When sandwiched between lithium anode and NMC622 cathode, the cell of SPE reaches 150 mAh g−1 in charge and discharge.

Coloring a dense oxide layer is accomplished during plasma electrolytic oxidation (PEO) with an electrolyte mixed with dye emulsions. We demonstrate this coating technique using the aluminum disks of 6061 alloy and five synthetic dyes of red, yellow, orange, blue, and black color. The prepared dye emulsions are kinetically stable, containing negatively charged oil droplets of ~ 50 nm in size. To avoid color speckles, a barrier oxide layer must be first grown under the normal PEO conditions with an electrolyte without dye, followed by the growth of colored γ-alumina film with a stepwise increasing voltage of positive polarization in the electrolyte containing dye emulsion. Although the presence of surfactant in emulsion causes a large amount of bubbles that obscures the light of electric sparks, the spark sound can be heard clearly on site. These electric discharges can produce an uneven surface with many volcano craters of micrometer size which is the icon of PEO. Fortunately this typical unevenness can be smoothed out by synthetic dyes with proper voltage adjustment, resulting in a glossy surface.

Urea and sodium nitrite are generally viewed as nitridation additives in the electrolyte for plasma electrolytic oxidation (PEO) of aluminum alloys. We study the influences of these two convenient chemicals in presence of sodium aluminate and find very different effects on film growth. Urea addition enhances the nitrogen content of PEO layer, diminishes the layer thickness, increases the porosity, interferes with the α-alumina formation, and promotes precipitation in the electrolyte. Hence, the electrolytic urea content ought to be maintained less than 45 g dm −3 . On the other hand, sodium nitrite behaves like an oxidation additive, more than a nitridation additive. NaNO 2 addition effectively introduces nitrogen in the PEO layer at low concentration, yet the nitrogen content of oxide layer decreases with increasing NaNO 2 concentration. The effects of NaNO 2 , such as increasing layer thickness, reducing porosity, promoting α-alumina formation are attributed to oxidation enhancement, not because of nitridation.

Incorporated as the negative electrode, the LiSn2(PO4)3 (LSP) crystals requires a prelithiation step to decompose LSP partially and yield tin metal for a relatively steadied capacity in cycling the hybrid capacitor of LiPF6 electrolyte. The charge transfer reactions of lithium alloying tin at low potentials offer a substantial amount of electrical capacity. Hence, several capacitors of LSP negative and activated carbon (AC) positive are prepared to understand the effects of prelithiation and LSP:AC mass ratio on how to exploit this electrochemical capacity. Among two prelithiation levels and three mass ratios, the combination of LSP-I (10% tin) and 1:1 (LSP:AC) mass ratio stands out as the best choice over a wide range of specific current. On the other hand, the selection of a specific current low enough to match the charge-transfer reaction kinetics enables the LSP electrode of high prelithiation level, LSP-II (45% tin), to utilize its battery-like capacity thoroughly. The maximum energy of hybrid capacitor LSP-II/AC is measured 28.7 W h kg−1 at a minimum specific current 0.03 A g−1.

The electrode of sol–gel derived Li3VO4 (LVO), which exhibits a capacity of 2 mol lithium between 0.01 and 2.0 V (vs. Li/Li+), is studied as an anode of the capacitor in conjunction with a cathode of activated carbon (AC). Before assembling the hybrid capacitor of AC/LVO, Li3VO4 has been prelithiated. The end potential of prelithiation affects the lithium loading and the resultant cell capacity. The cell, with LVO prelithiation ending at 0.5 V (vs. Li/Li+), displays 34% more capacity than the other with LVO ending at 2.0 V (vs. Li/Li+). The higher capacity is caused by reducing the electrode potential of the hybrid capacitor at 0% state-of-charge, which also depends on the AC : LVO mass ratio and the specific current. We develop a scheme to estimate the optimal mass ratio for the capacitor. The optimal ratio is verified later by galvanostatic charge–discharge experiments, involving four capacitors with AC : LVO mass ratios of 0.5 : 1, 1 : 1, 2 : 1, 3 : 1. The optimal 2 : 1 cell demonstrates a capacity of specific energy 49.1 W h kg−1 at 0.05 A g−1 and 3.5 V, and 81% retention in the voltage hold test persisting for 100 h.

Coatings of plasma electrolytic oxidation (PEO) can be colored during its oxide growth through electrophoretic deposition, with an electrolyte containing dye emulsion or pigment colloid. We perform the coloration in two steps; growing a white barrier layer first, then depositing the colorful layer. Despite the strong similarities in processing, addition of dye or pigment results in different effects on the electrolytic system. The dye emulsion increases the system impedance and reduces the positive current. Conversely, the pigment plus surfactant increase the positive current, since the negatively charged pigment particles enhances the electrolyte conductivity. Often the enhancement effect is so large that we have to operate PEO in the constant current mode.

The proton conductivity of phosphoric acid (PA) doped polybenzimidazole (PBI) membrane is improved through imbibing antimony pentachloride before doping PA. The antimony involvement diminishes the temperature dependence of proton conductivity in the targeted temperature range 160–260 °C. Among the compositions being prepared, the most conductive one exhibits 8.08 × 10−2 S cm−1 at 180 °C, with a small temperature sensitivity 6.3 × 10−5 S cm−1 °C−1. Several membrane-electrode assemblies (MEAs) have been prepared with the Pt/C catalyst layers to evaluate the practicality of co-doped PBI membrane. After proper activation, the hydrogen/air cell generates substantial electric power, denoted by its peak value over 500 mW cm−2 at 180 °C. Impedance analysis indicates carbon monoxide poisoning affects overall MEA kinetics, as evidenced in the rising resistances of electrolyte, cathode, and anode. But the poisoned performance due to 3% CO/H2 fuel can be rejuvenated after the fuel is switched back to pure hydrogen in one or two hours.

To explore plausible applications of 10 mol% Dy-doped La 2 Mo 2 O 9 (LDM), we have prepared membrane-electrode assemblies (MEAs) based on this oxide ion conductor and operated them under single chamber conditions of methane and air. Material selection is centered on matching thermal expansion of the LDM electrolyte, joined with an anode support of nickel and ceria cermet and a graded cathode of samarium strontium cobaltite plus ceria. The performance test results indicate that both open circuit voltage and ohmic loss increase with increasing LDM thickness, leading an optimal LDM thickness 60 μm. This MEA of 60 μm thick LDM generates peak power 330 mW cm −2 at 700 °C, which can be upgraded to 420 mW cm −2 through promoting the anode activity. Impedance analysis indicates the electrode improvements are effective, but have limitations, because the major polarization loss resides in the LDM electrolyte. High electrolyte polarization loss originates from two weaknesses of LDM, excessive thermal expansion and vulnerability to hydrogen reduction.

We have prepared durable catalysts of CoSe 2 /N-carbon using low-cost raw materials, measured their activities, peroxide yields, stabilities in reducing molecular oxygen, and characterized their crystalline phases and morphology. CoSe 2 /N-carbon is featured with an active support, N-carbon, which by itself shows high stability as evidenced in its small activity decay. After 1000 CV cycles, the half-wave potential ( E 1/2 ) of N-carbon decreases from 0.667 V to 0.636 V in 0.5 M H 2 SO 4 . Loading of CoSe 2 enhances the activity of N-carbon, when the samples were synthesized above 385 °C and formulated with the Se/Co ratio higher than 10. The higher activity is attributed to the pyrite phase of CoSe 2 . But the stability of pyrite CoSe 2 is less than that of N-carbon. Corrosion during the stability test exposes the active sites of underlying N-carbon, which sustains the catalyst activity. Consequently the E 1/2 value of the active CoSe 2 /N-carbon decreases moderately, from 0.711 V to 0.644 V after 1000 CV cycles. In contrast, the E 1/2 value of CoSe 2 /C descends much more, from 0.681 V to 0.475 V.

Dah-Shyang Tsai,1 Tzu-Sen Yang,2,3 Yu-Sheng Huang,1 Pei-Wen Peng,2,4 Keng-Liang Ou3,4 1Department of Chemical Engineering, National Taiwan University of Science and Technology, 2School of Dental Technology, 3Graduate Institute of Biomedical Materials and Tissue Engineering, 4Research Center for Biomedical Implants and Microsurgery Devices, Taipei Medical University, Taipei, Taiwan Abstract: Being endowed with an ability of capturing and releasing oxygen, the ceria surface conventionally assumes the role of catalyzing redox reactions in chemistry. This catalytic effect also makes possible its cytotoxicity toward microorganisms at room temperature. To study this cytotoxicity, we synthesized the doped and undoped ceria particles of 8–9 nm in size using an inexpensive precipitation method and evaluated their disinfecting aptitudes with the turbidimetric and plate count methods. Among the samples being analyzed, the silver-doped ceria exhibits the highest sterilization ability, yet the undoped ceria is the most intriguing. The disinfection effect of undoped ceria is moderate in magnitude, demanding a physical contact between the ceria surface and bacteria cell wall, or the redox catalysis that can damage the cell wall and result in the cell killing. Evidently, this effect is short-range and depends strongly on dispersion of the nanoparticles. In contrast, the disinfection effects of silver-doped ceria reach out several millimeters since it releases silver ions to poison the surrounding microorganisms. Additionally, the aliovalent silver substitution creates more ceria defects. The synergetic combination, silver poisoning and heterogeneous redox catalysis, lifts and extends the disinfecting capability of silver-doped ceria to a superior level. Keywords: ceria nanoparticle, antibacterial activity, cytotoxicity, oxygen vacancy, reactive oxygen species

The Ir(111) surface is oxidized with gas-phase oxygen atoms under vacuum condition to achieve an oxidation level beyond its saturation coverage for chemisorption. Two surface oxides, rutile IrO2 of (100) domain and corundum Ir2O3 of (001) domain, have been grown at 550 K with different oxygen exposure of 3.6 × 105 L and 7.2 × 105 L respectively. The temperature programmed desorption (TPD) experiment of rutile IrO2(100) shows its desorption curve (at 4 K s− 1) peaks at 750 K, followed by a long tail of less pronounced desorption features. On the other hand, TPD of corundum Ir2O3(001) displays a symmetric trace, peaking at 880 K. Carbon monoxide titration experiments show that adsorbed CO reduces corundum Ir2O3(001) at 400 K, but CO does not adsorb on rutile IrO2(100) and no reduction reaction occurs. Evidently, among the two surface oxides, corundum Ir2O3(001) involves in catalysis of carbon monoxide oxidation, while rutile IrO2(100) does not. The formation of two surface oxides is also compared, we conclude that the atom arrangement favors Ir2O3(001) at the oxide/metal interface.

Large surface area nanostructural IrOx films were deposited on stainless steel substrates by reactive radio frequency magnetron sputtering using Ir metal target. The structural and spectroscopic properties of the nanostructural IrOx were characterized. The micrographs of field emission scanning electron microscopy showed the formation of folded leaves with chiffon-like structure for the as-deposited samples. X-ray photoelectron spectroscopy analysis provided the information of the oxidation states and the stoichiometry of IrOxNL. Raman spectra revealed the amorphous-like phase of the as-deposited nanostructural IrOx. The chiffon-like structure provides ultra-high surface area for electrical charge storage which makes the IrOxNL as an attractive candidate for the supercapacitor application.

Various anode-supported solid oxide fuel cells (SOFC), based on 10 mol% Dy-doped La2Mo2O9 (LDM) electrolyte, are prepared analytically and operated under single chamber conditions to explore the connections between electrode and power performance. The cathode of tested SOFCs is compositionally graded with three composites of samarium strontium cobaltite and Gd-doped ceria (GDC) to relax the thermal stress, because of sizable thermal expansion differences above 400 °C. We focus the research attention on varying the anode pore structure and composition to promote the power performance in methane/air mixture at 700 °C. For the one-layer support of GDC+NiO+LDM anode, addition of 10 wt% graphite minimizes its mass transport resistance through creating 8–5 μm long and ∼1 μm wide slit-shaped pores. The graphite pore former raises the peak power value by 80 mW cm−2. Adopting a more porous and active outer layer, the double-layer support further enhances the cell power. The peak power was first raised by 48 mW cm−2, using an outer layer that was prepared with 63 wt% NiO. Dosing 3% Pd on this outer layer uplifts another 59 mW cm−2. In this study, with an improved anode, the peak power value reaches 437 mW cm−2.

Two miniature electrochemical capacitors, of high power and sufficient energy capacity, are prepared using photolithography and transferred to a plastic substrate. The preparation procedure involves, inverting a 60 μm thick interdigital pattern of multi-walled carbon nanotubes (CNT) with a Scotch tape, such that the pre-sputtered gold layer at the bottom effectively collects interfacial charge. The equivalent series resistance (ESR) of the symmetric CNT capacitor measures 0.40 Ω cm2, while that of the asymmetric capacitor with a positive α-Co(OH)2/CNT electrode measures 0.45 Ω cm2, much less than the as-grown CNT capacitor. Electrodeposited α-Co(OH)2 enhances the cell capacitance significantly, especially in a wide potential window. When operated at current density 20 A g−1 and window 1.8 V, the cell capacitance of asymmetric capacitor measures 62.6 F g−1, much higher than that of symmetric capacitor 8.7 F g−1. But the symmetric CNT capacitor displays a better power performance because of a lower ESR. At current density 30 A g−1, its power density reaches 20.6 kW kg−1 with energy density 2.2 Wh kg−1. In contrast, the asymmetric capacitor stores more energy, at 30 A g−1, it exhibits power density 11.4 kW kg−1 and energy density 7.8 Wh kg−1.

Ultracapacitors of asymmetric configuration have been prepared with activated carbon (AC) and undoped or Mo-doped manganese oxide (MnO 2 ) in 1.0 M Na 2 SO 4 electrolyte. Phase analysis shows the AC powder, 1–15 μm in size, contains both disordered and graphitic structures, and the undoped and Mo-doped oxide powder, 0.05–0.20 μm in particle size, mainly involves amorphous MnO 2 and MoO 2 . CV results indicate the single electrode of AC plus 10 wt% Mo-doped MnO 2 (A9O M 1) is superior to the electrode with undoped MnO 2 or high content of doped MnO 2 , exhibiting features of double layer capacitance at high scan rate and pseudocapacitance characteristics at low scan rate. When assembled with a negative electrode of AC, the capacitor of positive A9O M 1 electrode demonstrates the least power loss among three asymmetric capacitors. This asymmetric capacitor also shows a higher capacitance than the symmetric AC capacitor when the current density is less than 8.0 A g −1 in 1.8 V potential window. But a higher electrode resistance of A9O M 1, in contrast with AC, compromises its capacitance plus. When the energy density of A9O M 1 asymmetric capacitor is compared with that of symmetric AC capacitor at the same power level, the capacitance benefit on energy density is restricted to current density ≤ 3.0 A g −1 .

We report the deposition and structural characterization of nanostructural RuO2 on rutile (R)-TiO2/sapphire(100) templates by reactive radio frequency magnetron sputtering. The micrographs of field-emission scanning electron microscopy and X-ray diffraction patterns of RuO2/R-TiO2 heteronanostructures indicated the growth of vertically aligned RuO2 (001) nanotubes (NTs) and/or V-shaped RuO2(101) nanowedges (NWs) on top of R-TiO2 nanorods (NRs). Transmission electron microscopy and selected-area electron diffractometry characterizations of the vertically aligned RuO2 NTs showed that the hollow RuO2 NTs with square cross section have open-end morphology with long axis directed along the [0 0 1] direction, while the V-shaped RuO2 NWs revealed that the nanowedges are crystalline RuO2 with twin plane of (101) and twin direction of 1 ¯ 01 at the V-junction. The probable mechanisms for the formation of well-aligned RuO2 nanocrystals on top of R-TiO2 NRs were discussed.

Large surface area IrO x nanofoils (IrO x NF) were deposited on multi-wall carbon nanotube (MWCNT) templates, forming IrO x /MWCNT nanocomposites, by reactive radio frequency magnetron sputtering using Ir metal target. The structural and spectroscopic properties of IrO x NF were characterized. The micrographs of field emission scanning electron microscopy showed the formation of foil-like structure for the as-deposited samples. Transmission electron microscopy analysis revealed the contiguous presence of glassy iridium oxide, iridium metal, and iridium dioxide nanocrystals in the foil. X-ray photoelectron spectroscopy analysis provided the information of the oxidation states and the stoichiometry of IrO x NF. Raman spectra revealed the amorphous-like phase of the as-deposited IrO x NF. The nanofoil structure provided ultra-high surface area for electrical charge storage which made the IrO x /MWCNT nanocomposites as an attractive candidate for the supercapacitor applications.

MnO2 and carbon nanotubes (CNT) composite electrodes have been built on the interdigital stack layers of Fe–Al/SiO2 and Fe–Al/Au/Ti/SiO2 for the electrochemical micro-capacitors, using photolithography and thin-film technologies. The electrode properties and the performance of micro-cells are measured and analyzed with cyclic voltammetry (CV), impedance spectroscopy, and galvanostatic charge/discharge test in 0.1 M Na2SO4 electrolyte. The vertically aligned CNT, grown on Fe–Al/SiO2, is more suitable for supporting the pseudocapacitive MnO2 than the random CNT on Fe–Al/Au/Ti/SiO2, but ohmic resistance of the former electrode is higher. We have prepared three cells on each stack layer with different electrode materials. The Ragone plot shows systematic variations in power and energy performance, reflecting their differences in electrode structure and polarization loss. The asymmetric cell of a pseudocapacitive positive electrode, loaded with MnO2 and CNT, exhibits a small IR drop and a high specific energy during discharge. Built on Fe–Al/SiO2, this asymmetric cell discharges at specific power 0.96 kW kg−1 with specific energy 10.3 Wh kg−1; while on Fe–Al/Au/Ti/SiO2, the asymmetric cell discharges at power 1.16 kW kg−1 with energy 5.71 Wh kg−1.

a b s t r a c t The crystal structure and proton conductivity of cerium pyrophosphate are investigated to explore its potential electrolyte applications for intermediate temperature fuel cell. Among the CeP2O7 thin plates, which are sintered at 300-900 ◦ C, the 450 ◦ C CeP2O7 sample exhibits superior proton conduc- tivity under humidified conditions. Its conductivity, measured with impedance spectroscopy, is higher than 10 −2 S cm −1 in the intermediate temperature range, with a maximum value 3.0 × 10 −2 S cm −1 at 180 ◦C. When 10 mol% Mg is doped on the Ce site of CeP2O7, the maximum conductivity is raised to 4.0 × 10 −2 S cm −1 at 200 ◦ C. The Mg doping not only raises the conductivity, but also shifts and widens its temperature window for electrolyte applications. Ce0.9Mg0.1P2O7 is considered a more appropriate composition, with conductivity >10 −2 S cm −1 between 160 and 280 ◦ C. Accordingly, a hydrogen-air cell is built with the Ce0.9Mg0.1P2O7 electrolyte and its performance is measured. The fuel cell generates electricity up to 122 mA cm−2 at 0.33 V using 50% H2 at 240 ◦C.

Nitrogen-doped (N-doped) carbon, denoted as Fe–UF–CNx, is synthesized through nitridation of an iron-doped gel precursor on the Vulcan support. It exhibits a legitimate activity on catalyzing oxygen reduction reaction (ORR). Its polarization curve, measured with a rotating disk electrode in O2-saturated H2SO4, indicates Fe–UF–CNx has a widely distributed ORR activity and a high onset potential 0.859 V. The widely distributed activity originates from its complex nitrogen sites on the graphitic sheet, evidenced by the broad N1s spectrum of Fe–UF–CNx, which is featured with twin peaks of nearly equal intensity for pyridinic and pyrrolic nitrogens. The high onset potential suggests, despite an overall mediocre activity, the Fe–UF–CNx activity involves a small fraction of very active sites. When properly joining with the RuSe2 pyrite nanoparticles, the high potential active sites of Fe–UF–CNx uplift the ORR activity to the level of carbon-supported Pt catalyst. The platinum–level activity is manifested by a small half-wave potential difference 0.03–0.04 V between the joint catalyst of RuSe2–Fe–UF–CNx and the commercially available Pt/C catalyst. Additional merits of RuSe2–Fe–UF–CNx, such as high stability, methanol tolerance, low peroxide yield, are also measured and discussed.

We report the growth of well-aligned RuO2/R-TiO2 heteronanostructures on sapphire (100) substrates by reactive magnetron sputtering using Ti and Ru metal targets under different conditions. The surface morphology and structural properties of the as-deposited heteronanostructures were characterized using field-emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), transmission electron microscopy (TEM) and selected-area electron diffractometry (SAED). The FESEM micrographs and XRD patterns indicated the growth of vertically aligned RuO2(001) nanotubes and twinned V-shaped RuO2(101) nanowedges (NWs) on top of R-TiO2 nanorods under different sputtering pressures. TEM and SAED characterizations of the V-shaped RuO2 NWs showed that the NWs are crystalline RuO2 with twin planes of (101) and twin direction of [ 01] at the V-junction.

We demonstrate the applicability of LAMOX as an electrolyte for solid oxide fuel cells (SOFC) by preparing two anode-supported cells based on La0.9Dy0.1Mo2O9 and La0.9Dy0.1Mo1W1O9, and operating at 625°–700°C under single chamber conditions. The two cells, supported by a composite of NiO and Gd-doped ceria (GDC), are initialized with a porous Ni+GDC disk to catalyze the partial oxidation reaction of methane. The partially oxidized methane reduces NiO to Ni catalyst and activates the cell at 650°C. A typical membrane electrode assembly of the single chamber SOFC cell consists of a 60-μm-thick La0.9Dy0.1Mo2O9 electrolyte, an anode of Ni+GDC, and a cathode of lanthanum strontium cobalt ferrite. Its peak power measures 220 mW/cm2 at 700°C in a tubular chamber of 15 mm in diameter, with the total methane/air flow rate of 350 mL/min and CH4:O2=2:1.

IrO2 nanocrystals (NCs) were grown on vertically aligned carbon nanotube (CNT) templates, forming IrO2/CNT nanocomposites, by metal organic chemical vapour deposition using (C6H7)(C8H12)Ir as a source reagent. The surface morphology, structural and spectroscopic properties of the nanocomposites were characterized using field-emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and Raman scattering. IrO2 varied from particle- to tube-like NCs as the deposition time increased from 5 to 60 min. The particle-like IrO2 NCs may be used as a protective layer on CNTs, providing stable and uniform field emission application. The tube-like structure may increase the surface-to-volume ratio which makes the IrO2/CNT nanocomposites as an attractive candidate for the supercapacitor application.

Planar ultracapacitors of miniature interdigital electrode are prepared, using the standard technologies of photolithography and reactive sputtering. The ultracapacitor is denoted by its deposition sequence, for example, hRuO 2 NRGT indicates pseudocapacitive hydrous RuO 2 (hRuO 2 ) and RuO 2 nanorods (NR) are grown on an interdigital stack layer of gold (G) and titania (T). The connection between structure and performance is studied through contrasting the hRuO 2 NRGT capacitor with other capacitors built on a less conducting stack layer or without hydrous RuO 2 filling the gaps between the nanorods. The stack layer can be a major source of cell resistance. For instance, a buffer layer of titania could be utilized between the capacitive RuO 2 and the Au current collector to overcome the delamination problem. But the less conductive titania also makes its cyclic voltammograms (CV) elliptical and tilted, and causes a pronounced IR drop during the cell discharging. In contrast, CV of the hRuO 2 NRGT capacitor on a conductive stack layer takes the shape of horizontal rectangle, and its discharge curve shows no sign of IR drop. Filling hydrous RuO 2 into the gap reduces the cell resistance between nanorods, improves the discharge performance as well. The power output of hRuO 2 NRGT, with the two resistances minimized, is 30.6 μW at 75 μA and 1.23 μW at 5 μA.

Structure, activity, and stability of the Ru1−xFexSey/C (x = 0.0–0.46, y = 0.4–1.9) catalysts, synthesized via hydrogen annealing of carbonyl precursors, are analyzed using X-ray diffraction, transmission electron microscopy, rotating (ring) disk electrode voltammetry, and cyclic voltammetry. Hydrogen annealing at 400 °C enables nucleation of the pyrite phase, which strengthens the catalyst stability for oxygen reduction reaction (ORR) in the acidic electrolyte. Evaluation on the stable Ru1−xFexSey/C catalysts indicates that the ORR activity increases with increasing iron content and Se content. Substitution of base metal Fe enhances the activity and reduces the material cost, but it also increases the H2O2 yield, which is measured less than 3.0% between 0.7 and 0.9 V in contrast to 1.0% of the catalyst without iron. The high activity of Ru0.54Fe0.46Se1.9/C decays more rapidly than that of RuSe2.0/C in the stability test, probably because Fe and Se are preferentially leached in the potential cycling up to 1.2 V. Still the two catalysts with pyrite structure exhibit much higher durability than the cluster-type catalyst of RuSecluster/C (Ru:Se = 1:0.3) that was not annealed.

Well-aligned densely-packed rutile phase TiO 2 nanocrystals (NCs) have been grown on sapphire (100) and (012) substrates by reactive magnetron sputtering using Ti metal target. The surface morphology, structural and spectroscopic properties of the as-deposited NCs were characterized using field-emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and micro-Raman spectroscopy. FESEM micrographs reveal the growth of vertically aligned NCs on sapphire (100), whereas the NCs on sapphire (012) were grown with a tilt angle of ∼ 33° from the normal to substrate. The XRD results reveal TiO 2 NCs with either (002) orientation on sapphire (100) substrate or (101) orientation on sapphire (012) substrate. A strong substrate effect on the alignment of the TiO 2 NCs growth has been demonstrated and the probable mechanism for the formation of these NCs has been discussed. XPS analyses show the oxygen vs. titanium ratio of 2.0 ± 0.1 for the as-grown TiO 2 NCs. Raman spectra of NCs exhibit a slight redshift in the peak position and a small broadening in linewidth with respect to that of the bulk counterpart. The results indicate the formation of good quality of nanocrystalline rutile phase TiO 2 .

Electrochemical activities and structural features of Pt/Sn catalysts supported by hydrogen-reduced SnO2 nanowires (SnO2NW) are studied, using cyclic voltammetry, CO stripping voltammetry, scanning electron microscopy, and X-ray diffraction analysis. The SnO2NW supports have been grown on a carbon paper which is commercially available for gas diffusion purposes. Partial reduction of SnO2NW raises the CO tolerance of the Pt/Sn catalyst considerably. The zero-valence tin plays a significant role in lowering the oxidation potential of COads. For a carbon paper electrode loaded with 0.1 mg cm−2 Pt and 0.4 mg cm−2 SnO2NW, a conversion of 54% SnO2NW into Sn metal (0.17 mg cm−2) initiates the COads oxidation reaction at 0.08 V (vs. Ag/AgCl), shifts the peak position by 0.21 V, and maximizes the CO tolerance. Further reduction damages the support structure, reduces the surface area, and deteriorates the catalytic activity. The presence of Sn metal enhances the activities of both methanol and ethanol oxidation, with a more pronounced effect on the oxidation current of ethanol whose optimal value is analogous to those of PtSn/C catalysts reported in literature. In comparison with a commercial PtRu/C catalyst, the optimal Pt/Sn/SnO2NW/CP exhibits a somewhat inferior activity toward methanol, and a superior activity toward ethanol oxidation.

Deoxygenation of the IrO 2 (1 1 0) surface is investigated at 403–493 K, using the core-level spectroscopy and density functional theory (DFT) calculation. The Ir-4f 7/2 signals of 1f-cus-Ir with and without on-top oxygen (O top ) emerge as surface features of the baked-out surface, whose positive and negative shifts in binding energy are in line with the DFT computation results. Progressively increasing the reduction temperature, the 1f-cus-Ir feature quickly disappears and the signal of 2f-cus-Ir emerges at 403 K. Meanwhile the feature of 1f-cus-Ir + O top diminishes but persists when the Ir metal signal is evident. The intriguing coexistence of 1f-cus-Ir + O top and Ir metal at 433–443 K is elucidated in the theoretical pathway study. DFT calculation reveals that O 2 desorption via pairing two neighboring O top atoms is the rate-determining step of surface deoxygenation. Under the UHV conditions, O top is replenished via migration of the surface oxygen species, including the threefold coordinated oxygen (O 3f ) of a reduced surface. Hence the O top atom is an active and long-lived surface species, which does not vanish until O 3f is consumed and surface Ir begins to cluster. Under the realistic pressure conditions, O top can also be refreshed via the dissociative adsorption of gas-phase oxygen. In either pathway, O top is a critical intermediary of IrO 2 (1 1 0) oxidation catalysis.

We report the growth and characterization of coexistence of vertically aligned and twinned V-shaped RuO2 nanorods (NRs). The well-aligned RuO2 NRs were grown on top of rutile (R) phase TiO2 NRs sitting on sapphire (SA) (1 0 0) substrate via metal-organic chemical vapor deposition (MOCVD) by using bis(ethylcyclopentadienyl) ruthenium (II) and titanium-tetraisopropoxide (TTIP, Ti[OCH(CH3)2]4) as source reagents. The surface morphology, structural, and spectroscopic properties of the as-deposited nanocrystals (NCs) were characterized by field-emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), micro-Raman spectroscopy, transmission electron microscopy (TEM) and selected-area electron diffractometry (SAED). The FESEM images and XRD patterns indicated growth of vertically aligned RuO2(0 0 1) and V-shaped RuO2(1 0 1) NRs on top of R-TiO2 NRs. The Raman spectrum indicated the formation of high quality RuO2 NCs on rutile phase of TiO2 NRs. TEM and SAED characterizations of V-shaped RuO2 NRs showed that the nanorods were crystalline RuO2 with a twin plane of (1 0 1) and twin direction of [ 1 ¯ 0 1 ] at the V-junction. The probable mechanisms for the formation of well-aligned RuO2 NRs are discussed.

Nanostructural (3 0 1) and (1 0 1) twins of RuO2 were grown on top of rutile phase TiO2 nanorods (NRs) sitting on LiNbO3(1 0 0) substrate. The surface morphology, structural and spectroscopic properties of the as-deposited nanocrystals (NCs) were characterized by field-emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), micro-Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and selected-area electron diffractometry (SAED). The FESEM images and XRD patterns indicated growth of V-shaped RuO2 (3 0 1) and (1 0 1) twins with angles of 51° and 110° between two arms, respectively. The Raman spectrum showed the nanosize induced redshift and peak broadening of the RuO2 and rutile phase of TiO2 signatures with respect to that of the bulk counterparts. XPS spectra indicated the existence of higher oxidation states of ruthenium in RuO2 NCs. TEM and SAED characterizations of the V-shaped RuO2 NCs showed that the nanorods were crystalline RuO2 with twin planes of (3 0 1)/(1 0 1) and twin directions of [ 1 ¯ 0 3 ] / [ 1 ¯ 0 1 ] at the V-junction. The probable formation mechanisms of the twins are discussed.

We have used density functional theory (DFT) calculations to investigate the oxidation of ammonia (NH 3 ) on a RuO 2 (110) surface. We characterized the possible reaction pathways for the dehydrogenation of NH x species (x = 1-3) and the formation of the oxidation products N 2 , NO, and H 2 O. The presence of oxygen atoms on coordinatively unsaturated sites (O cus ) promoted the oxidation of NH 3 on the surface. The oxidation of N H 3 is possible on both stoichiometric and oxygen-rich RuO 2 (110) surfaces; in the absence of O cus (stoichiometric surface), however, NH 3 molecules prefer desorption over oxidation. Moreover, the O cus , atoms are the major oxidants in this process; the formations of H 2 O and NO from bridge oxygen atoms (O br ) are both unfavorable reactions. According to our energetic analysis, in the NH x dehydrogenation pathways, H atom migration from NH 2-cus , to O br , has the highest barrier by 0.86 eV; it is much lower than the interaction energy of NH 3 on the RuO 2 (110) surface. In terms of nitrogen-atom-containing products, NO, N 2 , and N 2 O are all possible products of the oxidation of NH 3 . The formation of the gaseous oxidation products H 2 O and NO is determined by their binding energies, whereas that of N 2 is controlled by the diffusion of N cus atoms on the surface. In addition, the selectivity toward the nitrogen-atom-containing products N 2 and NO is dominated by the coverage of O cus atoms on the surface; a higher coverage of O cus atoms results in greater production of NO.

Tilted SnO2 nanowires (SnO2NW) have been grown and aligned on the sapphire (SA) substrate of orientation (100) or (110). Their structural and spectroscopic features are studied using scanning elect...

We report the preparation of well-aligned RuO2 nanorods (NRs) on LiNbO3(1 0 0) by metal–organic chemical vapor deposition using bis(ethylcyclopentadienyl) ruthenium (II) as the source reagent. The surface morphology and structural properties of the as-grown NRs were characterized by using field emission scanning electron microscopy and X-ray diffractometry. The growth pattern initiated with nucleation of both (0 0 1) and (3 0 1) planes at the substrate surface, but eventually NRs with (0 0 1) growth plane outgrew and formed vertically aligned NRs on top of the mixed alignments at the interface. The observed epitaxial growth patterns are explained in terms of the relationship between the atomic arrangements of the substrate and the NRs and the c-directional growth mechanism.