Enhanced Proton Conduction with Low Oxygen Vacancy Concentration and Favorable Hydration for Protonic Ceramic Fuel Cells Cathode.

Protonic ceramic fuel cells (PCFCs), as an efficient energy storage and conversion device, have great potential to solve the serious problems of energy shortage and environmental pollution. Improving the proton conductivity of the promising cathode materials is an effective solution to promote the widespread application of PCFCs at low temperatures (450-650 °C). Herein, considering the high oxygen reduction reaction (ORR) activity of BaCoO3-based perovskite oxide and beneficial proton uptake capacity of Zn-doping, we construct BaCo0.4Fe0.4Zn0.1Y0.1O3-δ (BCFZnY) as the PCFCs cathode, and compare it with the classic triple-conducting cathode BaCo0.4Fe0.4Zr0.1Y0.1O3-δ (BCFZrY). Different from the general strategy of increasing the initial oxygen vacancy concentration of cathode materials, this work unveils that enhancing the hydration of perovskite oxide with low oxygen vacancy concentration is a more effective strategy to accelerate the proton diffusion in the electrode. Therefore, the BCFZnY cathode achieved excellent proton conductivities of 8.05 × 10-3 and 6.38 × 10-3 S cm-1 as obtained by hydrogen permeation measurements and peak power densities of 982 and 320 mW cm-2 in a BaZr0.1Ce0.7Y0.1Yb0.1O3-δ-based anode-supported fuel cell at 600 and 450 °C, respectively.

Realizing Simultaneous Detrimental Reactions Suppression and Multiple Benefits Generation from Nickel Doping toward Improved Protonic Ceramic Fuel Cell Performance.

Anode-supported protonic ceramic fuel cells (PCFCs) are highly promising and efficient energy conversion systems. However, several challenges need to be overcome before these systems are used more widely, including the poor sintering of recently developed proton-conducting oxides and the decreased proton conductivity due to detrimental reactions between the nickel from anode and the electrolyte occurring during high-temperature co-sintering. Herein, a Ni doping strategy to increase the electrolyte sintering, suppress the detrimental phase reactions, and generate stable Ni nanoparticles for enhanced performance is proposed. A nickel-doped perovskite oxide is developed with the nominal composition of Ba(Zr0.1 Ce0.7 Y0.1 Yb0.1 )0.95 Ni0.05 O3- δ . Acting as a sintering aid, such a small amount of nickel effectively improves the sintering of the electrolyte. Concomitantly, reactions between nickel and the Ni-doped ceramic phase are suppressed, turning detrimental phase reactions into benefits. The nickel doping further promotes the formation of Ni nanoparticles, which enhance the electrocatalytic activity of the anode toward the hydrogen oxidation reaction and improve the charge transfer across the anode-electrolyte interface. As a result, highly efficient PCFCs are developed. The innovative anode developed in this work also shows favorable activity toward ammonia decomposition, making it highly promising for use in direct ammonia fuel cells.

Polyphenol-Polysaccharide Complex: Preparation, Characterization, and Potential Utilization in Food and Health.

Polysaccharides and polyphenols coexist in many plant-based food products. Polyphenol-polysaccharide interactions may affect the physicochemical, functional, and physiological properties, such as digestibility, bioavailability, and stability, of plant-based foods. In this review, the interactions (physically or covalently linked) between the selected polysaccharides and polyphenols are summarized. The preparation and structural characterization of the polyphenol-polysaccharide conjugates, their structural-interaction relationships, and the effects of the interactions on functional and physiological properties of the polyphenol and polysaccharide molecules are reviewed. Moreover, potential applications of polyphenol-polysaccharide conjugates are discussed. This review aids in a comprehensive understanding of the synthetic strategy, beneficial bioactivity, and potential application of polyphenol-polysaccharide complexes.

A Direct n-Butane Solid Oxide Fuel Cell Using Ba(Zr0.1Ce0.7Y0.1Yb0.1)0.9Ni0.05Ru0.05O3-δ Perovskite as the Reforming Layer.

Hydrocarbon-fueled solid oxide fuel cells (SOFCs) that can operate in the intermediate temperature range of 500-700 °C represent an attractive SOFC device for combined heat and power applications in the industrial market. One of the ways to realize such a device relies upon exploiting an in situ steam reforming process in the anode catalyzed by an anti-carbon coking catalyst. Here, we report a new Ni and Ru bimetal-doped perovskite catalyst, Ba(Zr0.1Ce0.7Y0.1Yb0.1)0.9Ni0.05Ru0.05O3-δ (BZCYYbNRu), with enhanced catalytic hydrogen production activity on n-butane (C4H10), which can resist carbon coking over extended operation durations. Ru in the perovskite lattice inhibits Ni precipitation from perovskite, and the high water adsorption capacity of proton conducting perovskite improves the coking resistance of BZCYYbNRu. When BZCYYbNRu is used as a steam reforming catalyst layer on a Ni-YSZ-supported anode, the single fuel cell not only achieves a higher power density of 1113 mW cm-2 at 700 °C under a 10 mL min-1 C4H10 continuous feed stream at a steam to carbon (H2O/C) ratio of 0.5 but also shows a much better operational stability for 100 h at 600 °C compared with those reported in the literature.

Thermal-expansion offset for high-performance fuel cell cathodes.

One challenge for the commercial development of solid oxide fuel cells as efficient energy-conversion devices is thermo-mechanical instability. Large internal-strain gradients caused by the mismatch in thermal expansion behaviour between different fuel cell components are the main cause of this instability, which can lead to cell degradation, delamination or fracture1-4. Here we demonstrate an approach to realizing full thermo-mechanical compatibility between the cathode and other cell components by introducing a thermal-expansion offset. We use reactive sintering to combine a cobalt-based perovskite with high electrochemical activity and large thermal-expansion coefficient with a negative-thermal-expansion material, thus forming a composite electrode with a thermal-expansion behaviour that is well matched to that of the electrolyte. A new interphase is formed because of the limited reaction between the two materials in the composite during the calcination process, which also creates A-site deficiencies in the perovskite. As a result, the composite shows both high activity and excellent stability. The introduction of reactive negative-thermal-expansion components may provide a general strategy for the development of fully compatible and highly active electrodes for solid oxide fuel cells.

Infiltrated NiCo Alloy Nanoparticle Decorated Perovskite Oxide: A Highly Active, Stable, and Antisintering Anode for Direct-Ammonia Solid Oxide Fuel Cells.

Direct ammonia solid oxide fuel cell (DA-SOFC) is superior to low-temperature direct ammonia fuel cell using anion exchange membrane because of much improved anode reaction kinetics at elevated temperature. However, significant performance degradation due to severe sintering of conventional nickel cermet anode under operating conditions is a big challenge for realizing its practical use. Herein, a high-performance anode based on La0.55 Sr0.30 TiO3- δ (LST) perovskite substrate with its surface decorated with in situ exsolved and strongly coupled NiCo alloy nanoparticles (NPs) is designed and fabricated for DA-SOFCs, exhibiting superior catalytic activity for NH3 decomposition reaction due to balanced NH3 adsorption and N2 desorption processes. An electrolyte-supported single cell with infiltrated NiCo/LST on Sm0.2 Ce0.8 O1.9 scaffold anode delivers a maximum power density of 361 mW cm-2 at 800 °C in NH3 fuel, superior to similar SOFCs with Ni or Co NP-decorated LST based anodes (161 and 98 mW cm-2 ). Furthermore, the SOFC with this newly developed anode displays favorable operational stability without obvious performance degradation at 700 °C for a test period of ≈120 h, attributed to its high antisintering capability. This study provides some strategies to develop highly active, stable, and antisintering perovskite-based nanocomposite for DA-SOFCs, facilitating the practical use of this technology.

A Cobalt-Free Multi-Phase Nanocomposite as Near-Ideal Cathode of Intermediate-Temperature Solid Oxide Fuel Cells Developed by Smart Self-Assembly.

An ideal solid oxide fuel cell (SOFC) cathode should meet multiple requirements, i.e., high activity for oxygen reduction reaction (ORR), good conductivity, favorable stability, and sound thermo-mechanical/chemical compatibility with electrolyte, while it is very challenging to achieve all these requirements based on a single-phase material. Herein, a cost-effective multi-phase nanocomposite, facilely synthesized through smart self-assembly at high temperature, is developed as a near-ideal cathode of intermediate-temperature SOFCs, showing high ORR activity (an area-specific resistance of ≈0.028 Ω cm2 and a power output of 1208 mW cm-2 at 650 °C), affordable conductivity (21.5 S cm-1 at 650 °C), favorable stability (560 h operation in single cell), excellent chemical compatibility with Sm0.2 Ce0.8 O1.9 electrolyte, and reduced thermal expansion coefficient (≈16.8 × 10-6 K-1 ). Such a nanocomposite (Sr0.9 Ce0.1 Fe0.8 Ni0.2 O3- δ ) is composed of a single perovskite main phase (77.2 wt%), a Ruddlesden-Popper (RP) second phase (13.3 wt%), and surface-decorated NiO (5.8 wt%) and CeO2 (3.7 wt%) minor phases. The RP phase promotes the oxygen bulk diffusion while NiO and CeO2 nanoparticles facilitate the oxygen surface process and O2- migration from the surface to the main phase, respectively. The strong interaction between four phases in nanodomain creates a synergistic effect, leading to the superior ORR activity.

Perovskite Oxide Based Electrodes for High-Performance Photoelectrochemical Water Splitting.

Photoelectrochemical (PEC) water splitting is an attractive strategy for the large-scale production of renewable hydrogen from water. Developing cost-effective, active and stable semiconducting photoelectrodes is extremely important for achieving PEC water splitting with high solar-to-hydrogen efficiency. Perovskite oxides as a large family of semiconducting metal oxides are extensively investigated as electrodes in PEC water splitting owing to their abundance, high (photo)electrochemical stability, compositional and structural flexibility allowing the achievement of high electrocatalytic activity, superior sunlight absorption capability and precise control and tuning of band gaps and band edges. In this review, the research progress in the design, development, and application of perovskite oxides in PEC water splitting is summarized, with a special emphasis placed on understanding the relationship between the composition/structure and (photo)electrochemical activity.

Chlorine-Doped Perovskite Oxide: A Platinum-Free Cathode for Dye-Sensitized Solar Cells.

Triiodide/iodide (I3-/I-) redox couple-mediated solar cells, batteries, and electrochromic devices require highly efficient and stable electrocatalysts for I3- reduction reaction (IRR) to overcome performance limitations, whereas the widely used platinum (Pt) cathode for IRR has limitations of high price and unfavorable durability. In this work, we present a halogen element (chlorine) doping strategy to design low-cost perovskite-type electrocatalysts with enhanced IRR activity and stability. The dye-sensitized solar cell (DSSC) assembled by the LaFeO2.965-δCl0.035 cathode delivers an attractive power conversion efficiency (PCE) of 11.4% with a remarkable PCE enhancement factor of 23% compared with Pt, which is higher than most of the reported non-Pt DSSC cathodes. Attractively, LaFeO2.965-δCl0.035 displays superior IRR activity/stability and structural stability in the I3-/I--based electrolyte compared to pristine LaFeO3 because chlorine doping facilitates the creation of oxygen vacancies (active sites) and enhances surface acidity simultaneously. This study provides a new way for designing outstanding IRR electrocatalysts, which could be applied to many redox couple-mediated photo/electrochemical devices.