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To obtain BaZrO 3 -based electrolyte materials with both good sinterability and high proton conductivity, a Cu-doped B-site BaZr 0.5 Ce 0.3 Y 0.2- x Cu x O 3- δ (BZCYCu x ; x = 0, 0.05, 0.1) system is designed and synthesized. The effects of Cu doping on the crystal structure, sintering and electrical properties of BZCYCu x are systematically investigated. The BZCYCu 0.05 sample demonstrates the highest sintering density and total conductivity among the studied materials. BZCYCu 0.05 can be densified at 1250 °C, which is 300 °C lower than that for unmodified BZCY. The calculated results suggest that the increased conductivity in BZCYCu 0.05 benefits from a high apparent specific grain-boundary conductivity, which originates from a small space-charge potential and a large clean part of impurities in the electrolyte. A synthetic analysis based on impedance spectroscopy and distribution of relaxation time further confirms that BZCYCu 0.05 is more conductive. A single cell built using the BZCYCu 0.05 (∼46 μm) electrolyte shows an excellent power density of 258 mW cm−2 at 700 °C. These results indicate that BZCYCu 0.05 is a potential proton conductor for use in protonic ceramic fuel cells. [Display omitted] [ABSTRACT FROM AUTHOR]

A triple-conducting Ba 0.95 La 0.05 Fe 0.8 Zn 0.2 O 3−δ (BLFZ) cobalt-free perovskite was evaluated as cathode for proton-conducting solid oxide fuel cells based on BaZr 0.1 Ce 0.7 Y 0.1 Yb 0.1 O 3−δ (BZCYYb) electrolyte. BLFZ had a cubic perovskite structure and good chemical compatibility with BZCYYb electrolyte at temperatures below 1100 °C. The average thermal expansion coefficient of BLFZ is 20.4 × 10−6 K−1 at 30 °C-1000 °C. The polarization resistance (R p) of BLFZ decreased from 2.072 Ω cm2 in air to 1.334 Ω cm2 in wet air (3% H 2 O) at 600 °C due to the introduction of water. The single-cell power density with BLFZ–30 wt%BZCYYb composite cathode reached 329 mW cm2 at 750 °C, and the corresponding R p is 0.083 Ω cm2. Based on the impedance and distribution of relaxation time analyses, proton diffusion and incorporation to the electrolyte lattice (H a d + (N i) → H + (s u r f a c e , e l e c t r o l y t e) and H + (s u r f a c e , e l e c t r o l y t e) → H + (b u l k , e l e c t r o l y t e)) were the rate-limiting steps above 650 °C, whereas the oxygen incorporated into the lattice (O 2 − (B L F Z) → O 2 − (b u l k , e l e c t r o l y t e)) and proton bulk diffusion to the triple-phase boundary (H + (b u l k , e l e c t r o l y t e) → H + (T P B)) were the rate-limiting steps below 650 °C. The single cell with BLFZ–30 wt% BZCYYb composite cathode showed good stability at 700 °C during a 100-h test. [ABSTRACT FROM AUTHOR]

Developing a new strategy to effectively prevent the restacking of MXene nanosheets will have significant impacts on designing flexible supercapacitor electrodes. Herein, a novel Ti 3 C 2 T x /polyvinyl alcohol (PVA) porous sponge with 3D interconnected structures is prepared by sol-gel and freeze-dried methods. This Ti 3 C 2 T x /PVA porous sponge is used as the template of in-situ polyaniline (PANI) polymerization, and the fabricated PANI@Ti 3 C 2 T x /PVA hydrogel composite is applied as flexible supercapacitors electrodes. 1D conductive polymer chains PVA could increase the interlayer spacing of Ti 3 C 2 T x nanosheets, which is beneficial to expose more electrochemical active sites. The supercapacitor based on PANI@Ti 3 C 2 T x /PVA hydrogel composite exhibits the coexistence of double-layer capacitance and pseudocapacitance behavior. This supercapacitor shows a maximum areal specific capacitance of 103.8 mF cm−2 at 2 A m−2, and it also exhibits a maximum energy density of 9.2 μWh·cm−2 and an optimum power density of 800 μW cm−2. The capacitance of this supercapacitor is almost not change under different bending angles. Moreover, 99% capacitance retention is achieved after 10 000 charge/discharge cycles of the supercapacitor. The synergistic effect between PANI and Ti 3 C 2 T x /PVA composite may improve the number of reactive sites and provide efficient channels for ion diffusion/electron transport. [ABSTRACT FROM AUTHOR]