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For the first time, proton conductors BaZr0.1Ce0.7Y0.1Yb0.1O3−δ (BZCYYb) and La2Ce2O7 (LCO) are combined to create an interface active and steam-tolerant electrolyte for high-performance proton-con...

Triple-conducting materials have been proved to improve the performance of popular protonic ceramic electrolysis cells. However, partially because of the complexity of the water-splitting reaction involving three charge carriers, that is, oxygen (O2-), proton (H+), and electron (e-), the triple-conducting reaction mechanism was not clear, and the reaction conducting pathways have seldom been addressed. In this study, the triple-conducting Ruddlesden-Popper phase Pr1.75Ba0.25NiO4+δ as an anode on the BaCe0.7Zr0.1Y0.1Yb0.1O3-δ electrolyte was fabricated and its electroresponses were characterized by electrochemical impedance spectroscopy with various atmospheres and temperatures. The impedance spectra are deconvoluted by means of the distribution of the relaxation time method. The surface exchange rate and chemical diffusivity of H+ and O2- are characterized by electrical conductivity relaxation. The physical locations of electrochemical processes are also identified by atomic layer deposition with a surface inhibitor. A microkinetics model is proposed toward conductivities, triple-conducting pathways, reactant dependency, surface exchange and bulk diffusion capabilities, and other relevant properties. Finally, the rate-limiting steps and suggestions for further improvement of electrode performance are presented.

The role of molybdenum in the interaction of the composed phases of 2205 duplex stainless steel (DSS) in the 3.5-wt% NaCl solution was investigated, by comparing the untreated 2205 DSS sample with two single-austenite and single-ferrite samples prepared via selective dissolution. The results demonstrate that, the interaction is beneficial to the whole passive film properties of 2205 DSS by promoting both the γ-phase and α-phase. The passivity of 2205 DSS at high potential strongly depends on the protective ability of Mo species. Compared with α-phase and γ-phase, Mo species of the 2205 DSS are more capable of keeping stable and being beneficial to passive film recovery, which make 2205 DSS show enhanced performance in pitting resistance and repassivation.

Electron, proton and oxygen-triple-conducting materials are becoming the dominant steam electrode candidate to break the rate limit on the water-splitting reaction that throttles the performance of protonic ceramic electrolysis cells (PCECs). In this study, based on Pr2NiO4+δ Ruddlesden-Popper phase, we manipulate these conductivities by Pr-site Ba substitution to probe the correlation of each conductivity with the kinetics of the elementary reaction steps. It is found that the proton conductivity is vital to sustain an extended active surface area for faster adsorption of reactants and desorption of products. The effect of oxygen conductivity is surprisingly found insignificant in the water-splitting reaction. On the contrary, surface oxygen removal is discovered as the most rate-limiting process. The electronic conductivity is not a direct limiting factor. However, an electron transfer process between the current collector and the electrode junction could introduce extra resistance that is perceptible at a high operating temperature range. The best water-splitting activity is obtained on a proton conductivity/oxygen surface desorption capability well-balanced sample after Ba substitution. As a result, a water-splitting reaction resistance of 0.022 Ωcm2, a current density of 1.96 A/cm2 at 700 °C is achieved on Pr1.7Ba0.3NiO4+δ, one of the best performances for PCECs.

In this study, we report a high performance and redox-stable symmetrical solid oxide fuel cell (SOFC) based on (Ba0.5Sr0.5) (Mo0.1Fe0.9)O3-δ (BSMF) electrode and La0.8Sr0.2Ga0.8Mg0.2O3-δ (LSGM) electrolyte. BSMF is able to operate both as anode and cathode. Excellent electrocatalytic activity has been achieved on BSMF towards hydrogen oxidation and oxygen reduction. Due to its closely matched lattice parameter to LSGM electrolyte, a unique diffuse interface is formed between BSMF and LSGM. Compared to a clean interface, e.g. BSMF/gadolinium doped ceria interface, this diffuse interface promotes the performance of BSMF electrode 1–1.8 times in 600–800 °C. Polarization resistance of the BSMF/LSGM specimen is as low as 0.047 and 0.007 Ωcm2 in humidified H2 and in air at 800 °C, respectively. On the BSMF/LSGM/BSMF symmetrical cell, a maximum power density of 2.28 W/cm2 is achieved at 800 °C, the highest among with redox-stable ceramic electrodes to the best of our knowledge. Redox stability of this cell is confirmed. The role of anode and cathode is reversed back and forth in different operation modes. No apparent degradation is observed through 4 cycles within a 110 h operation period. These findings demonstrate that (Ba0.5Sr0.5) (Mo0.1Fe0.9)O3-δ coupled with LSGM electrolyte is an excellent choice to build a high performance, redox-stable SOFC.

The rechargeable aqueous zinc-ion batteries (ZIBs) based on the Zn/MnO2 couple and mildly acidic electrolyte have emerged as promising large-scale energy storage systems. This work reports an in situ electrochemical activation approach to oxidizing MnS into an electrochemically derived oxide (MnS-EDO), which unlocks its potential as high-performance cathodes for ZIBs. MnS-EDO contains fragmented layers with abundant defects and thus demonstrates large electrochemically active surface areas, high electrochemical reactivity, fast ion diffusion kinetics, accelerated charge transfer and exceptional structural robustness during cycling compared to α-MnO2. MnS-EDO exhibits a specific capacity of 335.7 mAh g−1 with ~100% capacity retention after 100 cycles at 0.3 A g−1, outstanding rate capability and long-term stability retaining 104 mAh g−1 after 4000 cycles at 3 A g−1. This work elucidates the underlying electrochemical insights and a hybrid discharge mechanism involving homogeneous Zn2+ intercalation at ~1.4 V and subsequent heterogeneous reactions of insertion of both H+ and Zn2+ at ~1.25 V. The ambiguities among Zn buserite, birnessite and zinc hydroxide sulfate are clarified. This work provides a simple and low-cost approach to unlocking the potential of MnS-EDO cathode for promising aqueous rechargeable ZIBs and sheds light on a mechanistic understanding of manganese oxide-based cathodes.

uIn situ exsolution of nanoparticles is widely considered as an efficient and cost-effective method for increasing the number of active sites and consequently the catalytic activity on ceramic anodes in solid oxide fuel cells (SOFCs). In this study, by doping on the A-site of Sr2Fe1.5Mo0.5O6-delta (SF1.5 M), evenly distributed Fe nanoparticles (similar to 100 nm) were exsolved on the La0.5Sr1.5Fe1.5Mo0.5O6- delta (LSFM) surface under a typical anode operating environment (humidified H-2, 800 degrees C). In addition, the exsolution-dissolution reversibility of the exsolved Fe nanoparticles was observed during a redox cycle. Electrical conductivity relaxation (ECR) analysis demonstrated that the surface reaction kinetics on the LSFM anode is enhanced by in situ exsolution. Based on electrochemical impedance spectroscopy (EIS) and distribution of relaxation time (DRT) analysis, the perovskite structure was not damaged by the exsolution or the surface phase transition. During exsolution, the ionic conductivity increased. The higher surface catalytic activity and faster oxygen transportation led to enhanced electrochemical performance.