•Bi0.5Sr0.5Fe0.8Cu0.2O3−δ cathode materials are studied for applications in SOFCs.•Cathode material gave the lowest polarization resistance of 0.13 Ω cm2 at 700 °C.•Three main oxygen reduction reaction (ORR) processes are identified.A cobalt-free perovskite oxide Bi0.5Sr0.5Fe0.8Cu0.2O3−δ (BSFC) has been investigated as novel cathode for intermediate-temperature solid oxide fuel cells (IT-SOFCs). The BSFC cathode exhibits good thermal stability and chemical compatibility with Ce0.9Gd0.1O1.95 (CGO) electrolyte below 950 °C. The average thermal expansion coefficient (TEC) of BSFC is 13.1 × 10−6 K−1 within a temperature range of 50–800 °C in air, which is close to that of CGO electrolyte. Meanwhile, the polarization resistant values (RP) of BSFC cathode on CGO electrolyte are 0.13, 0.32 and 0.76 Ω cm2 at 700, 650 and 600 °C, respectively; the lowest cathode overpotential is 37 mV at a current density of 125 mA cm−2 at 700 °C in air. The CGO electrolyte-supported single cell with BSFC cathode exhibits maximum power density of 290 mW cm−2 at 700 °C using dry H2 as the fuel. The rate-limiting step for oxygen reduction reaction (ORR) on BSFC cathode is oxygen surface adsorption-dissociation process. The attractive electrochemical performance demonstrates that BSFC oxide is a promising cathode material for IT-SOFCs.Download high-res image (117KB)Download full-size image

•Bi0.5Sr0.5Fe1−xNbxO3−δ oxides are evaluated as cathode for IT-SOFCs.•BSFN0.10 cathode exhibits a low polarization resistance of 0.038 Ω cm2 at 700 °C.•The rate-limiting step of ORR is oxygen adsorption-dissociation process.•The maximum power density reaches 1.54 W cm−2 at 700 °C with BSFN0.10 cathode.Cobalt-free provskite oxides Bi0.5Sr0.5Fe1−xNbxO3−δ (BSFNx, x = 0.05, 0.10 and 0.15) were prepared and evaluated as cathode materials for intermediate temperature solid oxide fuel cells (IT-SOFCs). In particular, the effects of Nb substitution on phase evolution, thermal expansion behavior and electrochemical performance were systematically investigated. The average thermal expansion coefficient (TEC) of BSFNx decreases from 13.3 × 10−6 K−1 at x = 0.05 to 12.6 × 10−6 K−1 at x = 0.15 within a temperature range of 50–800 °C. Among the BSFNx materials, Bi0.5Sr0.5Fe0.9Nb0.1O3−δ (BSFN0.10) oxide shows the best electrochemical performance. The polarization resistances (Rp) of BSFN0.10 cathode on CGO electrolyte are 0.038, 0.075 and 0.156 Ω cm2 at 700, 650 and 600 °C, respectively. Meanwhile the maximum power densities of the anode-supported single cells are 1.28, 1.54 and 1.34 W cm−2 at 700 °C for BSFNx cathodes with x = 0.05, 0.10, and 0.15, respectively. Furthermore, the relationship study of oxygen partial pressure dependence on Rp indicates that the oxygen reduction reaction (ORR) rate-limiting step is the oxygen adsorption-dissociation on the electrode surface. The desirable electrochemical performance demonstrates that BSFNx oxides are potential cathode materials for IT-SOFCs.Download high-res image (477KB)Download full-size image

•BaFe0.85Cu0.15O3-δ cathode materials are studied for applications in SOFCs.•Cathode material gave the lowest polarization resistance of 0.35 Ω cm2 at 700 °C.•Two main oxygen reduction reaction (ORR) processes are identified.A cobalt-free cubic perovskite oxide, BaFe0.85Cu0.15O3-δ (BFC), is successfully prepared and evaluated as a novel cathode for intermediate-temperature solid oxide fuel cells (IT-SOFCs). The X-ray diffraction (XRD) results show that BFC cathode is chemically compatible with the electrolyte Ce0.9Gd0.1O1.95 (CGO) even 950 °C. The DC conductivity measurements demonstrate that BFC possesses the modest electrical conductivity of 7.5–16.0 S cm−1 in air. The electrode performance of the BFC is measured under different oxygen partial pressures at various temperatures. The polarization resistances (RP) of the BFC cathode on CGO electrolyte is 0.35, 0.73 and 1.90 Ω cm2 at 700, 650, 600 °C in air, respectively. Two main oxygen reduction reaction (ORR) processes are identified at the BFC interface. The rate-limiting step for the ORR is determined to be the oxygen adsorption-desorption process. The excellent electrochemical performance indicates that BFC can be used as a promising cathode material for IT-SOFCs.

Cuprous(I) oxide (Cu2O) carries high theoretical specific capacitance (2247.6 F g−1), however, the amount of research about the supercapacitive performance of Cu2O is relatively small compared with other transition metal oxides. A composite of metal and metal oxide could improve the electrochemical performance efficiently. In this work, the results of XRD and XPS demonstrate that CuO/Cu2O/Cu is prepared successfully via a facile, eco-friendly, one-step template-free growth process. SEM figures show that cubic CuO/Cu2O/Cu uniformly and densely covers a skeleton of nickel foam. The binder-free CuO/Cu2O/Cu electrode exhibits excellent supercapacitive performance with a high specific capacitance of 878 F g−1 at a current density of 5 mA cm−2 (1.67 A g−1), when the current density is enlarged ten times (50 mA cm−2 (16.7 A g−1)), the specific capacitance still remains at 545 F g−1. Furthermore, we have first successfully constructed a CuO/Cu2O/Cu//AC asymmetric supercapacitor, which can achieve an energy density of 42 W h kg−1 at a power density of 0.44 kW kg−1. The good electrochemical performance and simple accessibility prove that the as-prepared CuO/Cu2O/Cu/NF electrode has a potential application in electrochemical capacitors.

•3D honeycomb-like NiS2/NiO were prepared via a green hydrothermal process.•The NiS2 reduces the electrochemical impedance of NiO.•The NiS2/NiO electrode exhibits exceptional electrochemical performance.Three dimensional (3D) honeycomb-like NiS2/NiO nano-multiple materials were successfully prepared by fabricating cribrate NiS2 on the surface of NiO nanosheets through simple hydrothermal process on nickel foam. The morphology and phase structure of the NiS2/NiO are characterized by scanning electron microscopy equipped with energy dispersive X-ray spectrometer, transmission electron microscope, X-ray diffractometer and the electrochemical properties are tested by cyclic voltammetry, galvanostatic charge/discharge and electrochemical impedance spectroscopy. The NiS2/NiO electrode owns lower electrochemical impedance compared with bare NiO substrate and exhibits exceptional capacitance performance with a high specific capacitance of 2251 F g−1 delivered at current density of 1 A g−1, while 1192 F g−1 retained at 20 A g−1. What's more, after 2000 cycles, the specific capacitance remains 1275 F g−1 (at 5 A g−1) with a capacitance retention of 78%. Therefore, the NiS2/NiO electrode shows remarkable electrochemical performance and has a promising future for electrochemical supercapacitors.

In this work, RGO is decorated on MnO2 nanoflakes, which are electrochemically deposited on preformed C/TiO2 shell/core nanowire arrays to form a RGO/MnO2/C/TiO2 shell/core array electrode. Their structure and surface morphology are studied using X-ray diffraction analysis, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, Raman microscopy, scanning electron microscopy and transmission electron microscopy. The results suggest that a RGO layer was coated on the MnO2 nanoflakes, and the MnO2 nanoflakes have a well-distributed coverage on the surface of the C/TiO2 shell/core nanowire arrays. The RGO/MnO2/C/TiO2 shell/core arrays are evaluated as a supercapacitor electrode material, which exhibits a high specific capacitance of 822.3 F g−1 at a charge/discharge current density of 1 A g−1 and 87.4% specific capacitance retention after 5000 cycles. The superior pseudo-capacitive properties may be due to the unique shell/core structure and the decoration of RGO. The RGO decorated on MnO2 can provide partial double-layer capacitance; on the other hand, the RGO can improve the electrical conductivity of the electrode and alleviate the volume change of MnO2 during charge/discharge processes given its mechanical flexibility. Our results show that the RGO/MnO2/C/TiO2 electrode can be regarded as advantageous for electrochemical energy applications.

•A novel 3D Au nanoparticles electrode with good electron conductivity and high surface area is successfully fabricated.•Au nanoparticles are uniformly distributed on the surface of C@TiO2 nanowire array.•The electrode exhibits high performance and good stability for NaBH4 oxidation.In this work, Au nanoparticles directly grown on the surface of TiO2 core-C shell (Au/C@TiO2) has prepared by a simple electrodeposition method for the first time. The morphology is characterized by scanning electron microscope, and its structure is investigated by X-ray diffraction. Au nanoparticles are uniformly distributed on the surface of C@TiO2 nanowire array. Its catalytic performance for NaBH4 oxidation is evaluated by cyclic voltammetry and chronoamperometry measurement. The results indicate that Au/C@TiO2 shows a good and stable catalytic performance. In 2 mol cm−3 NaOH and 0.2 mol cm−3 NaBH4 the oxidation current density for the electrooxidation of BH4− can reach 475 mA cm−2 at 0 V. The electrons transfer number released by BH4− electrooxidation on Au/C@TiO2 electrode has been found to be a 6-electron process. The high performance is mainly attributed to its 3D structure which can promote the mass transport of NaBH4, electronic conductivity and Au utilization.

•The in-situ etched Cu(OH)2 nanowire core structure efficiently shortened the pathway for electrons transport.•The novel shell materials NiOOH uniformly wraps each Cu(OH)2 nanowire.•The hybrid Cu(OH)2@ NiOOH/copper-foil electrode displays excellent specific capacity of 1300 C g−1.The 1D nanowire is prepared by in-situ etching current collector displaying faster electron transportation and better connection, plusing the directional charge transport properties, which could enable it become one of the most appropriate core of 3D core@shell structure. We apply novel nanowire-like Cu(OH)2, which is synthesized by etching copper foil, as core structure to be coated by novel NiOOH with high theoretical capacity. The fast electronic conductive core structure and promising faradic electrode material candidate material enable the Cu(OH)2@NiOOH/copper-foil electrode deliver high specific capacity of 1300 C g−1 at current density of 10 mA cm−2 and outstanding cycling stability of capacity retention of 88% after 10000 charge-discharge cycles, indicating the as-prepared Cu(OH)2@NiOOH/copper-foil electrode has potential application in electrochemical capacitors.