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Developing efficient anode catalysts for direct ammonia solid oxide fuel cells (NH3-SOFCs) under intermediate-temperatures is of great importance, in support of hydrogen economy via ammonia utilization. In the present work, the pyrochlore-type La2Zr2−xNixO7+δ (LZNx, x = 0, 0.02, 0.05, 0.08, 0.10) oxides were synthesized as potential anode catalysts of NH3-SOFCs due to the abundant Frankel defect that contributes to the good conductivity and oxygen ion mobility capacity. The effects of different content of Ni2+ doping on the crystal structure, surface morphology, thermal matching with YSZ (Yttria-stabilized zirconia), conductivity, and electrochemical performance of pyrochlore oxides were examined using different characterization techniques. The findings indicate that the LZNx oxide behaves as an n-type semiconductor and exhibits an excellent high-temperature chemical compatibility and thermal matching with the YSZ electrolyte. Furthermore, LZN0.05 exhibits the smallest conductive band potential and bandgap, making it have a higher power density as anode material for NH3-SOFCs compared to other anodes. As a result, the maximum power density of the LZN0.05-40YSZ composite anode reaches 100.86 mW/cm2 at 800 °C, which is 1.8 times greater than that of NiO-based NH3-SOFCs (56.75 mW/cm2) under identical flow rate and temperature conditions. The extended durability indicates that the NH3-SOFCs utilizing the LZN0.05-40YSZ composite anode exhibits a negligible voltage degradation following uninterrupted operation at 800 °C for 100 h. [ABSTRACT FROM AUTHOR]

[Display omitted] • Polyaniline (PANi) and Ni particles modified composite electrode was prepared electrochemically on fluorine-doped tin oxide (FTO) • The FTO/PANi-Ni hybrid electrode exhibits high durability and low poisoning effect. • High performance, low cost and easy fabrication make this electrode a promising anode for DMFCs. A metal–organic composite thin film composed of polyaniline (PANI) and Ni was prepared and characterized for methanol electrooxidation reaction. First, PANI thin films were electrodeposited on a fluorine-doped tin oxide (FTO) coated glass support in an aqueous acidic solution. Subsequently, the polymer film was modified with Ni particles (FTO/PANI-Ni) by chronoamperometric (CA) technique. The composite film was characterized by structural, morphological and electrocatalytic analyses. X-ray diffraction (XRD) results confirmed the crystallization of Ni according to the cubic structure. Scanning electron microscopy (SEM) images showed that the Ni nanoparticles were uniformly dispersed on the PANI surface. The electrocatalytic performance of the FTO/PANI-Ni composite electrode for the methanol electrooxidation reaction was investigated in 0.5 M KOH solution containing methanol using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and chronoamperometry (CA) techniques. The effects of temperature and methanol concentration on the methanol electrooxidation performance were also studied. The modified composite catalyst exhibited an electrochemically active surface area of 0.5235 cm2. The presence of Ni nanoparticles on the polymer surface promoted the adsorption of methanol molecules and facilitated the oxidation process, leading to higher current densities and better overall performance. The maximum current density was 14 mA cm-2 and the electrode maintain 68 % of its initial activity even after 200 cycles, indicating that the FTO/PANI-Ni electrode exhibited good stability. The high methanol oxidation performance of the composite electrode was associated with large real surface area, a possible synergistic effect between the polymer moleucles and Ni particles as well as high intrinsic activity of Ni for this process. [ABSTRACT FROM AUTHOR]

Fabrication of transition-metal catalytic materials is regarded as a promising strategy for developing high-performance sodium-selenium (Na-Se) batteries. However, more systematic explorations are further demanded to find out how their bonding interactions and electronic structures can affect the Na storage process. This study finds that lattice-distorted nickel (Ni) structure can form different bonding structures with Na 2 Se 4 , providing high activity to catalyze the electrochemical reactions in Na-Se batteries. Using this Ni structure to prepare electrode (Se@NiSe 2 /Ni/CTs) can realize rapid charge transfer and high cycle stability of the battery. The electrode exhibits high storage performance of Na + ; i.e., 345 mAh g⁻ 1 at 1 C after 400 cycles, and 286.4 mAh g⁻ 1 at 10 C in rate performance test. Further results reveal the existence of a regulated electronic structure with upshifts of the d-band center in the distorted Ni structure. This regulation changes the interaction between Ni and Na 2 Se 4 to form a Ni 3 -Se tetrahedral bonding structure. This bonding structure can provide higher adsorption energy of Ni to Na 2 Se 4 to facilitate the redox reaction of Na 2 Se 4 during the electrochemical process. This study can inspire the design of bonding structure with high performance in conversion-reaction-based batteries., (© 2023 Wiley-VCH GmbH.)

Solvothermal synthesis offers an important approach to prepare nickel particles with high crystallinity and low agglomeration. In this study, submicron nickel particles are prepared by a solvothermal approach involving alcohol reduction with the assistance of different types of organic bases. The influences of the types of organic bases and solvents, and the amount of organic bases on the particle size and morphology of nickel are studied. It is found that an organic base with a stronger alkalinity is able to generate nickel particles with smaller size. Smaller nickel particles are also prone to be obtained from solvents with a stronger reducing ability. Moreover, the formation mechanism of nickel particles is investigated. It is found that the nickel precursor and OH− form nickel layered hydroxide salts at the initial stage, and then the nickel layered hydroxide salts gradually dissolve to form nickel particles. Magnetic measurement reveals the morphology-dependent magnetic properties. Although the sample which has the smallest size exhibits a relatively high coercivity, samples which have a rather large particle size but consist of smaller primary nanoparticles also show relatively high coercivity values. [Display omitted] • Nickel submicron particles are synthesized via a solvothermal approach in alcohols. • Organic bases with stronger alkalinity are found to generate smaller particles. • Nickel particles with a narrow size distribution (182 ± 18 nm) are obtained. • The formation mechanism of nickel particles in solvothermal conditions is revealed. • Morphology-dependent magnetic properties are observed. [ABSTRACT FROM AUTHOR]