In this paper, we describe new strategies to reduce the resistances related to cathode reactions and interfacial proton transfer in protonic solid oxide fuel cells (H+-SOFCs) based on ...proton-conducting BaZrxCe0.8−xM0.2O3−δ (M = Y, Yb, Sc etc.) by means of material and cell-structure design changes. First, an extension of the effective cathode reaction areas by employing the H+/O2−/e− triple-conducting cathode is described. Cubic La0.7Sr0.3Mn1−xNixO3−δ (x = 0–0.3) can be hydrated under fuel cell conditions due to its large hydration enthalpy (∼100 kJ mol−1), whereas rhombohedral La0.7Sr0.3Mn1−xNixO3−δ does not exhibit hydration capabilities; hence, the porous anode cermet support fuel cells (PAFCs), which use the former as a cathode, possess significantly smaller cathode polarization resistances than the PAFCs that use the latter. Second, we describe a new thermodynamic mechanism for reducing the electrolyte and cathode reaction resistances in a hydrogen-permeable metal-support fuel cell (HMFC), which involves the blocking of the oxide ion minor conduction in the BaZrxCe0.8−xM0.2O3−δ electrolyte at metal/oxide heterointerfaces. The BaZrxCe0.8−xM0.2O3−δ membrane of HMFCs is forced to gain extra protons to compensate for the charge from the oxide ions accumulating near the heterointerfaces via blocking, resulting in extremely high proton conductivity. This promotes significant interfacial proton diffusion for cathode reactions.
Graphene-covering is a promising approach for achieving an acid-stable, non-noble-metal-catalysed hydrogen evolution reaction (HER). Optimization of the number of graphene-covering layers and the ...density of defects generated by chemical doping is crucial for achieving a balance between corrosion resistance and catalytic activity. Here, we investigate the influence of charge transfer and proton penetration through the graphene layers on the HER mechanisms of the non-noble metals Ni and Cu in an acidic electrolyte. We find that increasing the number of graphene-covering layers significantly alters the HER performances of Ni and Cu. The proton penetration explored through electrochemical experiments and simulations reveals that the HER activity of the graphene-covered catalysts is governed by the degree of proton penetration, as determined by the number of graphene-covering layers.
The preparation of porous carbon from biomass flour as high-performance electrocatalysts for oxygen reduction reaction (ORR) was reported in this paper. The fast and vigorous pyrolysis of flour was ...induced in the presence of magnesium nitrate, by which MgO nanoparticles were introduced as nano-template to create numerous nanopores and to increase the specific surface area (SSA). The pore structure, SSA and elemental dopant were influenced by the ratio of biomass to magnesium nitrate and calcination temperature. A highly hierarchical micro-meso-macroporous carbon, which was calcined at 1000 °C and had a high SSA of 1880 m
2
g
−1
, exhibited the best ORR performance in terms of fast ORR kinetic, superior stability and excellent methanol tolerance.
Graphical Abstract
•Chemical composition of anodic porous film depends on index number of iron facet.•The electrochemical thermodynamics of anodic nanopores/nanotubes formation is dependent on crystallographic ...structure of Fe.•Faster kinetics of oxygen evolution is observed for anodizing of Fe (100) single crystal comparing with Fe (110) and Fe (111).
Anodizing of iron (100), (110) and (111) single crystals in mono-ethylene-glycol electrolyte containing 1.5 mol dm−3 water and 0.1 mol dm−3 ammonium fluoride leads to formation of anodic iron nanopores/nanotubes where the nanopores are essentially composed of oxide nanotubes separated by iron fluoride matrix. It was found that electrochemical thermodynamics for nanoporous/nanotubular film formation apparently depends on the index number of facet on which the anodic film is formed. The film formation on (100) facet is associated with extended gas evolution upon anodizing and consequently corresponds to a shift of current-time curve towards higher current density values comparing with those formed on higher index number facets. The nanotubes formed on (100) facet have a general chemical formula of Fe2O3.FeF2, whereas those formed on higher index number are composed of Fe3O4.FeF2. The anodic films formed on Fe (110) and Fe (111) are essentially amorphous whereas the one formed on (100) facet shows high degree of crystallinity. The results are discussed in view of anisotropic properties of iron.
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Among several types of low‐temperature solid oxide fuel cells, hydrogen‐permeable metal‐supported fuel cells (HMFCs) are devices that can achieve outputs of approximately 1.0 W cm−2 at 400 °C. This ...work clarifies the mechanism for promoting the cathode reaction on proton‐conducting ceramics at such low temperatures. Combined numerical and electrochemical analyses demonstrate that blocking minor oxide ion conduction at metal/oxide heterojunctions promotes proton transfer at the cathode/electrolyte interfaces, thereby enhancing the turnover frequency of the cathode reaction at the triple‐phase boundary. The electrolyte membrane in HMFCs is forced to gain extra protons to compensate for the charge of oxide ions that accumulate because of the blocking, resulting in an increment of the proton concentration gradients near the cathode/electrolyte interfaces so as to eject the excess amount of proton. The interfacial proton concentration gradient increases and thus the cathode polarization resistance of HMFCs decrease with the cell bias. An HMFC with a highly oxygen‐deficient BaZr0.5Sc0.5O3−δ electrolyte accumulates a large amount of oxide ions, thereby developing large concentration gradients. Thus, it achieves a cathode reaction resistance of 0.54 Ω cm2 at 400 °C with conventional cathode materials, La0.6Sr0.4Co0.2Fe0.8O3−δ. These findings demonstrate that HMFCs can efficiently utilize overpotential.
A new mechanism to accelerate fuel cell cathode reactions at low temperatures below 400 °C is presented. Combined simulation and experimental studies elucidate that metal/oxide heterojunctions in hydrogen‐permeable metal‐supported cells accelerate proton diffusion at the cathode interfaces and triggers changes in the cathode reaction pathway, allowing bias‐dependent polarization resistance and significantly reduced activation energies.
Rechargeable aqueous zinc (Zn)‐ion batteries (RAZIBs), which use non‐flammable aqueous electrolytes and low‐cost electrode materials, show great potential to boost the development of safe, ...cost‐effective, and highly efficient energy storage systems. The adoption of lightweight and inexpensive aluminum (Al) as current collectors seems to be a good vision, but Al exhibits an easily‐corroded nature and a high impedance in aqueous electrolytes, making it a challenge to realize the utilization of Al current collector in RAZIBs. In this study, through the direct current magnetron sputtering, niobium (Nb) coated Al (Al‐Nb) foils are prepared, which shows superior corrosion‐resistance in an aqueous solution, while maintaining a satisfying electronic conductivity. Moreover, the Al‐Nb foils can be adopted to both anode and cathode current collectors while exhibiting high coulombic efficiency and good cycling stability even when they are tested under a condition that can meet the real‐world application demands, e.g., the Zn||Al‐Nb half‐cell shows an average coulombic efficiency of 99.17% in 320 cycles under a current density of 25 mA cm−2 and a galvanizing capacity of 6.25 mAh cm−2. The superior performance of the modified Al current collectors may mark a significant step toward the development of high‐energy‐density aqueous batteries.
A layer of nano‐scaled Nb metal is coated onto the surface of Al by magnetron sputtering, and the passivation layer formed spontaneously on Nb surface is an effective barrier that can act against the attack from aggressive species in the aqueous electrolyte. Hence, the Al‐Nb foil can serve as a dual‐purpose current collector for both anode and cathode in rechargeable aqueous Zn batteries.
Purpose
Postoperative delirium is one of the most common complications after cardiovascular surgery in older adults. Benzodiazepines are a reported risk factor for delirium; however, there are no ...studies investigating remimazolam, a novel anesthetic agent. Therefore, we prospectively investigated the effect of remimazolam on postoperative delirium.
Methods
We included elective cardiovascular surgery patients aged ≥ 65 years at Hamamatsu University Hospital between August 2020 and February 2022. Patients who received general anesthesia with remimazolam were compared with those who received other anesthetics (control group). The primary outcome was delirium within 5 days after surgery. Secondary outcomes were delirium during intensive care unit stay and hospitalization, total duration of delirium, subsyndromal delirium, and differences in the Mini-Mental State Examination scores from preoperative to postoperative days 2 and 5. To adjust for differences in the groups’ baseline covariates, we used stabilized inverse probability weighting as the primary analysis and propensity score matching as the sensitivity analysis.
Results
We enrolled 200 patients; 78 in the remimazolam group and 122 in the control group. After stabilized inverse probability weighting, 30.3% of the remimazolam group patients and 26.6% of the control group patients developed delirium within 5 days (risk difference, 3.8%; 95% confidence interval −11.5% to 19.1%;
p
= 0.63). The secondary outcomes did not differ significantly between the groups, and the sensitivity analysis results were similar to those for the primary analysis.
Conclusion
Remimazolam was not significantly associated with postoperative delirium when compared with other anesthetic agents.
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