RESUMEN
Developing high-efficiency electromagnetic (EM) wave absorbing materials with light weight, thin thickness, and wide absorption bandwidth is highly desirable for ever-developing electronic and telecommunication devices. Herein, hierarchical metal-organic framework (MOF)-derived Co/C@V2 O3 hollow spheres were designed and synthesized through a facile hydrothermal, precipitation, and pyrolysis method. The composite exhibits both excellent impedance matching and light weight due to the rational combination of hollow V2 O3 spheres and porous Co/C. Additionally, multiple components enable a large dielectric and magnetic loss of the composite, giving rise to enhanced EM wave absorption performance with a maximum reflection loss (RL) of -40.1â dB and a broad effective absorption bandwidth (RL < -10â dB) of 4.64â GHz at a small thickness of 1.5â mm. This work provides insights into the design of hierarchical hollow and porous composites as thin and lightweight EM wave absorbers with efficient absorption, which can also be extended to energy storage, catalysis, and sensing.
RESUMEN
A self-templated strategy is developed to fabricate hierarchical TiO2 /SnO2 hollow spheres coated with graphitized carbon (HTSO/GC-HSs) by combined sol-gel processes with hydrothermal treatment and calcination. The as-prepared mesoporous HTSO/GC-HSs present an approximate yolk-double-shell structure, with high specific area and small nanocrystals of TiO2 and SnO2 , and thus exhibit superior electrochemical reactivity and stability when used as anode materials for Li-ion batteries. A high reversible specific capacity of about 310 mAh g-1 at a high current density of 5 A g-1 can be achieved over 500 cycles indicating very good cycle stability and rate performance.
RESUMEN
Developing S-scheme systems with impressive photocatalytic performance is of huge meaning in realizing the long-term conversion of solar energy into hydrogen. Herein, ZnIn2S4 nanoribbons were integrated with hierarchical CeO2 hollow spheres to construct heterostructure using an oil bath approach under mild conditions. The optimized CeO2/ZnIn2S4 presented a superior photocatalytic hydrogen production rate of 69 µmol/h, which is about 4.9 and 11.5 times greater than pristine ZnIn2S4 and CeO2, respectively. In addition, its apparent quantum yield achieved 7.6% at 420 nm. The improved photoactivity of the CeO2/ZnIn2S4 heterojunction can be referable to the cooperative effects of the aligned bandgap structures, strong visible-light-harvesting capacity, and interfacial interactions via the internal electric field. This study provides insights into the protocols for rational design of S-scheme heterojunction catalysts for high-efficiency hydrogen evolution via sustainable photocatalytic water splitting.
RESUMEN
High-performance and low-cost photocatalysts are of significance to artificial photosynthetic systems for converting of CO2 into CO and other value-added products. In this work, we developed a controllable and scalable self-templated approach to fabricate hierarchical Co-base spinel hollow microspheres for visible light-driven CO2 reduction with a Ru-based sensitizer. The hollow microspheres are assembled by ultrathin nanosheets using Ni-Co-hydroxides as the morphology-conserved precursor. A series of characterization techniques were conducted to investigate structural features of the prepared Co-base spinel hollow spheres. Owing to the integration of the specific microstructure, functional Ni/Co species and oxygen vacancies, Co-base spinel hollow spheres possess enhanced CO2 adsorption ability, more active sites, and efficient transfer and separation of photoexcited electrons. The high CO-evolving rate (27.7⯵molâ¯h-1) and selectivity (84.4%) manifest desirable performance of Co-base spinel hollow spheres for CO2 photocatalytic reduction. The findings suggest that such spinel-structured bimetallic oxides hierarchical hollow spheres, facilely synthesized via the proposed self-templated method, are efficient for photocatalytic CO2 reduction.
RESUMEN
Hierarchical self-assembled hollow spheres (HS) of tungsten oxide nanosheets have been synthesized via a template-free hydrothermal method. Morphology evolution of the products is determined by the amount of H2C2O4 (oxalic acid) which serves as chelating agent. Structural features of the products were characterized by X-ray diffraction (XRD), and morphology was investigated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). In addition, the porous structure was analyzed using the Brunauer-Emmett-Teller (BET) approach. The synthesis mechanism of the products with self-assembled hierarchical structures was proposed. The NO2 gas sensing properties of self-assembled hierarchical WO3 HS materials were investigated, the gas sensing properties of WO3 synthesized by a variety of formulations were compared, and the possible gas sensing mechanism was discussed. The obvious enhancement of the gas sensing properties was ascribed to the structure of the hierarchical HS.
RESUMEN
Hierarchical copper silicate hydrate hollow spheres-reduced graphene oxide (RGO) composite is successfully fabricated by a facile hydrothermal method using silica as in situ sacrificing template. The electrochemical performance of the composite as lithium-ion battery anode was studied for the first time. Benefiting from the synergistic effect of the hierarchical hollow structure and conductive RGO matrix, the composite exhibits excellent long-life performance and rate capability. A capacity of 890 mAh/g is achieved after 200 cycles at 200 mA/g and a capacity of 429 mAh/g is retained after 800 cycles at 1000 mA/g. The results indicate that the strategy of combining hierarchical hollow structures with conductive RGO holds the potential in addressing the volume expansion issue of high capacity anode materials.