Advanced Hollow Cubic FeCo-N-C Cathode Electrocatalyst for Ultrahigh-Power Aluminum-Air Battery.

The exploration of electrocatalysts toward oxygen reduction reaction (ORR) is pivotal in the development of diverse batteries and fuel cells that rely on ORR. Here, a FeCo-N-C electrocatalyst (FeCo-HNC) featuring with atomically dispersed dual metal sites (Fe-Co) and hollow cubic structure is reported, which exhibits high activity for electrocatalysis of ORR in alkaline electrolyte, as evidenced by a half-wave potential of 0.907 V, outperforming that of the commercial Pt/C catalyst. The practicality of such FeCo-HNC catalyst is demonstrated by integrating it as the cathode catalyst into an alkaline aluminum-air battery (AAB) paring with an aluminum plate serving as the anode. This AAB demonstrates an unprecedented power density of 804 mW cm-2 in ambient air and an impressive 1200 mW cm-2 in an oxygen-rich environment. These results not only establish a new benchmark but also set a groundbreaking record for the highest power density among all AABs reported to date. Moreover, they stand shoulder to shoulder with state-of-the-art H2-O2 fuel cells. This AAB exhibits robust stability with continuous operation for an impressive 200 h. This groundbreaking achievement underscores the immense potential and forward strides that the present work brings to the field.

Facile Preparation of SrZr1-xTixO3 and SrTi1-xZrxO3 Fine Particles Assisted by Dehydration of Zr4+ and Ti4+ Gels under Hydrothermal Conditions.

In recent decades, perovskite-type compounds (ABB'O3) have been exhaustively studied due to their unique ferroelectric properties. In this work, a systematic study aiming to prepare fine particles in the binary system SrZrO3-SrTiO3 was conducted under hydrothermal conditions in a KOH (5 M) solution at 200 °C for 4 h under a constant stirring speed of 130 rpm. The precursors employed were SrSO4 powder (<38 µm size) and coprecipitated hydrous gels of Zr(OH)4•9.64 H2O (Zr-gel) and Ti(OH)4•4.5H2O (Ti-gel), which were mixed according to the stoichiometry of the SrZr1-xTixO3 in the compositional range of 0.0 > x > 100.0 mol% Ti4+. The XRD results revealed the formation of two crystalline phases rich in Zr4+, an orthorhombic structured SrZr0.93Ti0.07O3 and a cubic structured SrZr0.75Ti0.25O3 within the compositional range of 0.1-0.5 mol of Ti4+. A cubic perovskite structured solid solution, SrTi1-xZrxO3, was preferentially formed within the compositional range of 0.5 > x > 0.1 mol% Ti4+. The SrZrO3 and SrZr0.93Ti0.07O3-rich phases had particle sizes averaging 3 µm with a cubic morphology. However, a remarkable reduction in the particle size occurred on solid solutions prepared with hydrous Ti-gel over contents of 15 mol% Ti4+ in the reaction media, resulting in the formation of nanosized particle agglomerates with a cuboidal shape self-assembled via a 3D hierarchical architecture, and the sizes of these particles varied in the range between 141.0 and 175.5 nm. The limited coarsening of the particles is discussed based on the Zr-gel and Ti-gel dehydration capability differences that occurred under hydrothermal processing.

Preparation and characterization of single perovskite microplates and its sunlight assisted photodecolorization activity, validated by response surface methodology.

Perovskites overtaking simple metal oxides as solar light harvesting material due to their excellent photocatalytic efficiency and superior stability. An efficient visible light responsive, K2Ba0.3Cu0.7O3 single perovskites oxides (SPOs) photocatalyst was fabricated by a facile hydrothermal method. The fabricated SPOs was characterized by various techniques. SEM analysis confirm the cubic morphology of SPOs, the average length and diameter of SPOs were 27.84 and 10.06 µm calculated from SEM images. FT-IR analysis confirmed the presence of M-M and M - O bonds. EDX showed prominent peaks of the constituent elements. The average crystallite size of SPOs calculated by Scherrer and Williamson-Hall equation was 14.08 and 18.47 nm respectively. The optical band gap value lies in visible region of spectrum (2.0 eV) determined from the Tauce's plot. The fabricated SPOs was applied for photocatalytic degradation of methylene blue (MB) dye. Maximum degradation 98.09% of MB was achieved at 40 min irradiation time, 0.01 g catalyst dose, 60 mg L-1 MB concentration and pH 9. The photocatalytic degradation of MB follows first order kinetic. RSM modeling of MB removal was also caried out. Reduce quadratic model was best fitted model having F-value = 300.65, P-value = < 0.0001,R2 = 0.9897, predicted R2 = 0.9850 and adjusted R2 = 0.9864.

Annealing temperature effect on cobalt ferrite nanoparticles for photocatalytic degradation.

In this work, cobalt ferrite nanomaterials was prepared employing simple co-precipitation technique and annealed at 300, 400 and 600 °C. XRD study revealed the formation of cubic structure of CoFe2O4 nanoparticles and confirmed by high intense peak at 2θ value of 35.3°. The creation of ferrite phase was further confirmed by the studies such as FTIR, Raman and PL spectra. FTIR spectra confirmed the occurrence of Fe-O and Co-O metal oxygen vibrations and the lattice defects and oxygen vacancies of the CoFe2O4 nanoparticles were explored by PL spectra. No other signals were detected in Raman spectra, which explored pure spinal ferrites. The energy band gap values are obtained by using Tauc plot and the obtained band gap values for all the cobalt ferrite nanoparticles were 2.84, 2.75 and 2.89 eV respectively. The morphology of synthesized cobalt ferrite nanomaterials were observed from the SEM and TEM images. The product annealed at 400 °C showed the better morphology with least amount of agglomeration in comparison to other SEM images. In addition, SAED pattern of magnetic nanoparticles confirmed the existence of polycrystalline nature of the CoFe2O4 nanoparticles. The obtained surface area of CF2 sample was 5.082 m2 g-1 and pore volume and diameter of CF2 sample was found to be 0.013 cc/g and 3.937 nm respectively. Then, the product annealed at 400 °C exhibited most excellent activity and degraded 74% of cationic dye in 80 min, and it also exhibited excellent stability even maintain in three cycles.

Identification of silver cubic structures during ultrasonication of chitosan AgNO3 solution.

During ultrasonication of chitosan AgNO3 solution (10mM), silver cubic structures were identified along with other dispersed silver nanoparticles. Temperature influenced the formation of the cubic structures. Formation of the silver cubic structures occurred via initial formation of 'four petal flower-like' structures that underwent transformation to the "cubic morphology" in the latter stages. Aging of the reaction mixture led to formation of complete dendrites. These dendrites comprised a large quantity of silver nanoparticles. Upon repetition of the experiment with starch instead of chitosan, the identified silver cubic structures were completely absent, indicating that formation of the 'silver cubic structures' is dependent on the polysaccharide used. It is believed that the structural features of chitosan facilitate the formation of 'silver cubic structures' under ultrasonic conditions. The phenomena occurring during the experiments were evaluated via scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS), ultraviolet-visible (UV-vis) spectra, transmission electron microscopy (TEM), and selected area electron diffraction (SAED) analysis.