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As a potential alternative to commercial Pt/C, carbon supported Pd nanoparticles (NPs) is powerful in facilitating ORR. However, a strong interaction usually existing between Pd and carbon probably hinders the expression of ORR activity. This work focuses on tuning the interaction between Pd and graphene for architecting high-performance ORR catalyst. The strong interaction between Pd and graphene was confirmed, rendering significant microstructural variation, e.g., the dramatic change of lattice disorder and vibration of surface C-H/C-O bond for the graphene support. Boron (B)-doping enables reversing such structural evolution and suppressing the Pd-C interaction. It literates the Pd from the interaction, increases its electrochemical specific surface area (ECSA) from 68 to 125 m2 g−1 and thereof contributes to the highly efficient ORR performance in alkaline solution with more feasible 4e− pathway on a 2.8 wt% Pd/C catalyst. Moreover, theoretical simulations further proved that B-doping enhances the electron transfer between Pd and the graphene support and probably benefits a 4e− pathway for ORR. Image 1 [ABSTRACT FROM AUTHOR]

The development of functional materials with dual characteristics of microwave absorption and low infrared emissivity is vital for protection against magnetic-wave contamination. Currently, both microwave protection and infrared protection technologies are developing rapidly, but simultaneous integration of both has not been extensively investigated. Herein, a new ternary core-shell CoFe 2 O 4 @SiO 2 @ZAO composite dual-functional material was designed and fabricated. The process consisted of coating CoFe 2 O 4 microspheres with ZAO based on SiO 2 middle layer prepared through hydrolysis and sol-gel methods. The introduction of ZAO and SiO 2 was found conducive to dielectric loss and impedance matching, thereby improving wave absorption. The nano-flower ZAO coating provided low infrared emissivity with a lamellar structure and high carrier concentration in the resulting ternary structure. The rise in ZAO content first enhanced the wave absorption of CoFe 2 O 4 @SiO 2 @ZAO and then decreased while the infrared emissivity declined. Among prepared samples, CoFe 2 O 4 @SiO 2 @ZAO exhibited a minimum reflection loss (RL min) of −59.31 dB at 10.96 GHz, conducive to effective absorption bandwidth (EAB) of 4 GHz at 2 mm thickness with an infrared emissivity of 0.71 in 8–14 μm waveband. In sum, the novel CoFe 2 O 4 @SiO 2 @ZAO core-shell structure showed attractive properties in terms of compatibility of wave absorption and infrared emissivity, promising for future syntheses of dual-functional materials with improved performance. [ABSTRACT FROM AUTHOR]

Photocatalysts for hydrogen evolution reaction (HER) have widely been explored but fine-tuning and engineering multiphase photocatalyst components are still challenging. Among catalysts, ZnIn 2 S 4 has shown promise but maximizing the use of ZnIn 2 S 4 -photogenerated carriers and enhancing quantum yield still require further investigation. One way to achieve this is by enhancing the photon utilization and reducing the recombination of shallow carriers in ZnIn 2 S 4. Accordingly, novel ZnIn 2 S 4 /g-C 3 N 4 /MoS 2 type-II heterojunction composites with 2D/2D/2D structures (abbreviated ZIS/CN/MS) were synthesized in the present work by simple thermal condensation-solvothermal method. The optimized ZIS/CN/MS exhibited a photocatalytic hydrogen evolution rate of 13.6 mmol g−1 h−1 under visible light (λ ≥ 420 nm) irradiation, a value much higher than those of pure-phases ZIS and CN, as well as the binary composite of ZIS/CN. The apparent quantum efficiency of the optimized ZIS/CN/MS at a wavelength of 420 nm reached 27.0 % coupled with excellent cycling stability. The significantly improved photocatalytic performance and the excellent stability can mainly be attributed to the unique 2D/2D/2D arrangement of the ternary components of ZIS, CN, and MS in ZIS/CN/MS photocatalyst, providing a large number of close interfacial contacts between the components for shortened migration distance of photogenerated charges and more pathways for electron separation and transport in type-II heterostructures. Overall, the proposed methodology and ZIS/CN/MS composites with type-II heterojunction and 2D/2D/2D structures have great potential for use in solar-to-hydrogen energy conversion and can be extended to the preparation of other photocatalysts. [Display omitted] • 2D/2D/2D ZnIn 2 S 4 /g-C 3 N 4 /MoS 2 hybrid junction enhances dielectric properties. • New structure provides close interfacial contact and pathway for electron separation. • Unique 2D/2D/2D arrangement improves photocatalytic performance and stability. [ABSTRACT FROM AUTHOR]

Microwave absorbing (MA) materials with yolk-shell structures have been extensively studied in impedance matching. However, the impedance matching achieved by the complementary effect of the core and the shell does not determine the reflection of the microwaves upon the occurrence at the first incidence. The interaction between the outer layer of materials and the electromagnetic waves significantly impacts the MA properties of materials. In this study, the impedance matching improvement method of the shell structure was further explored by preparing CoFe 2 O 4 @HCN (honeycomb carbon with N-doping) through the hydrothermal method followed by hydrolysis, polymerization, etching, and annealing. The resulting structure with heteroatoms doping provided the novel CoFe 2 O 4 @HCN with excellent impedance matching and multiple loss mechanisms contributing to MA process. The absorber with a filler loading of 40% exhibited an RL min of −68.03 dB with a matching thickness of 2.5 mm. The efficient absorbing bandwidth reached 5.92 GHz (a change from 11.92 to 17.84 GHz) at 1.99 mm thickness. Interestingly, these findings look promising for future synthesis and application of yolk-shell structure microwave absorbers. [ABSTRACT FROM AUTHOR]

Due to the harmful influence of electromagnetic waves, electromagnetic absorption materials are being actively pursued. Herein, a one-step hydrothermal method is used to synthesize rGO/Al/CoFe 2 O 4 composites with different amounts of CoFe 2 O 4 , and their electromagnetic properties and infrared emissivity are studied in detail. The results reveal that the rGO/Al/CoFe 2 O 4 composite with a CoFe 2 O 4 content of 0.06 g possesses a minimum reflection loss (RL min) of −68.03 dB at 15.5 GHz at a thickness of 1.38 mm, while the effective absorption broadband (EAB) and infrared emissivity are found to be 3.3 GHz and 0.63, respectively. Hence, the as-designed rGO/Al/CoFe 2 O 4 composites can be used for both wave absorption and low-infrared emissivity fields, and the proposed strategy is an effective solution for designing bifunctional wave absorption materials. [ABSTRACT FROM AUTHOR]

Currently, to solve the problem of electromagnetic radiation, it is imperative to develop a thin, lightweight absorber, with a wide bandwidth and an excellent absorption ability. In this study, SiC and CoFe 2 O 4 were combined on reduced graphene oxide (rGO) with immobilized rGO and SiC nanoparticles and varying amounts of CoFe 2 O 4 nanoparticles. A facile one-pot hydrothermal technique was employed to prepare four rGO/SiC/CoFe 2 O 4 composite samples with varied CoFe 2 O 4 concentrations. The electromagnetic properties of rGO/SiC/CoFe 2 O 4 composites were affected by CoFe 2 O 4 content, and CoFe 2 O 4 content was varied to change the electromagnetic properties of composites. The rGO/SiC/CoFe 2 O 4 composite samples were prepared at a graphene oxide (GO) mass of 0.5 g, SiC mass of 0.25 g, and CoFe 2 O 4 mass of 1.5 g, and this composite sample exhibited the best microwave absorption consumption. At 60 wt% of rGO/SiC/CoFe 2 O 4 composite sample, the RL min at 7.4 GHz with a thickness of 2.43 mm was −62.39 dB, and efficient absorption of broadband (EAB) was 1.4 GHz (6.8–8.2 GHz). The EAB was 3.2 GHz (11.8–15 GHz), and the RL min was −59.77 dB at 13.2 GHz with a thickness of 1.39 mm. The RL min at 17.2 GHz was −65.49 dB, and the EAB was 2.3 GHz (15.7–18 GHz), despite a thickness of only 1.06 mm. The rGO/SiC/CoFe 2 O 4 composite comprised carbon materials, magnetic metals, and semiconductors. High-performance microwave absorption was achieved by the introduction of more than one loss mechanism and coordination and supplementation of multicomponent functions. The proposed carbon/semiconductor/magnetic composite material provides a feasible solution for the preparation of excellent microwave absorbing materials in the future. [ABSTRACT FROM AUTHOR]

High-entropy perovskite oxides (HEPOs) suffer from inferior stability in high-power battery-supercapacitor hybrid (BSH) devices. Therefore, revealing their energy storage mechanism is extremely important for optimizing appliance stability. Herein, La 0.7 Bi 0.3 Mn 0.4 Fe 0.3 Cu 0.3 O 3 nano-HEPO exhibits the dual-ion energy storage mechanism in aqueous alkaline BSH devices. The rapid deintercalation of oxygen anions from the (sub)surface facilitates the intercalation of hydrogen cations into the bulk during charging; however, the deintercalation of hydrogen cations upon the discharge process is hindered because of the surface filling with oxygen vacancies, resulting in an irreversible phase transition and volumetric expansion. Meanwhile, the evolution of surface oxygen species leads to the weak binding between the surface metal-oxygen polyhedron and the bulk, causing severe capacity deterioration due to the active cation leaching and surface inactive La(OH) 3 aggregation. Finally, optimal strategies are presented based on the dual-ion intercalation chemistry of HEPOs for application in high-performance BSH devices with long service life. [Display omitted] [ABSTRACT FROM AUTHOR]

Pure and Pd-loaded SnO 2 cubic nanocages with hierarchically nanoparticle-assembled and porous shells have been successfully fabricated through a straightforward multi-step route. The synthetic step-dependent structure evolution and the formation mechanism have been discussed. Furthermore, the toluene-sensing performances of these Pd-loaded SnO 2 nanocages are elaborated and compared with those of pure SnO 2 . The toluene sensing results demonstrate that Pd-loaded SnO 2 nanocages with the optimal loading amount of 1.0 mol% show a low detection limit (0.1 ppm) with response of 41.4–20 ppm toluene at the working temperature of 230 °C with the fast response time of 0.4 s, and improved selectivity. The improvement of toluene sensing properties is not only attributed to the effective utility of hollow and porous architecture, but also due to the dramatic sensitization of the loaded Pd nanoparticles. [ABSTRACT FROM AUTHOR]

An ideal photocatalyst should have high redox capacity, efficient charge separation, and large reaction surface area. However, it is an extreme challenge to construct a photocatalytic system with above three merits. Herein, the g-C 3 N 4 /Bi@Bi 2 WO 6 composite photocatalyst was prepared by simple wet chemical method. Then the separation pathway of photoinduced charges through the interface was explored by XPS, EPR and active species capture experiments, confirming that the Z-scheme charge transfer route was followed. The optimized composite photocatalyst exhibited the photocatalytic hydrogen production rate of 1219.3 μmol h−1g−1, which is 2.29 times that of pure g-C 3 N 4 (533.4 μmol h−1g−1). Moreover, the photocatalytic degradation rates of RhB and TC were 82.43% and 66.7%, respectively, which were 7.55 times and 1.92 times that of pure Bi 2 WO 6. Ultimately, the enhanced photocatalytic performances were attributed to the synergistic effect of 2D/2D coupling interface and the deposited metal Bi, which not only benefited the efficient charge separation and fast charge migration but also provided the large reaction surface area. In addition, surface plasmon resonance effect of metal Bi can boost the visible light absorption and broaden the light absorption range to the full spectrum. Our study provides a new idea to design high-performance Z-scheme photocatalyst for highly efficient utilization of solar energy. • The idea of construction Z-scheme heterojunction system have high redox capacity, efficient charge separation, and large reaction surface area. • The enhanced photocatalytic performances were attributed to the synergistic effect of 2D/2D coupling interface and the deposited metal Bi. • The SPR effect of metal Bi can promote visible light absorption and broaden the light absorption range. [ABSTRACT FROM AUTHOR]

A new type of nonspherical yolk-shell structures in the case of SnO 2 has been successfully prepared by a simple anneal-etching strategy without employing any additional templates or capping agents. The morphological and structural characterization reveals that SnO 2 yolk-shell particles have a hierarchical architecture with penetrable multi-walled surfaces and cuboctahedral shape, where the secondary building blocks are numerous nanoparticles. The synthetic step-dependent evolution process of SnO 2 yolk-shell cuboctahedra is investigated and the possible formation mechanism is also discussed. To demonstrate the merit of unique structure for the fast mass transfer, sensor based on SnO 2 products has been fabricated and the results exhibit excellent sensing performances for toluene detection. It is found that our SnO 2 yolk-shell structures have a response of 28.6–20 ppm toluene at the optimal working temperature of 250 °C, and the response time and recovery time are within 1.8 and 4.1 s, respectively. [ABSTRACT FROM AUTHOR]

Abstract: Measurements of electron spin resonance (ESR) of La2/3Ca1/3MnO3 (LCMO) in the ferromagnetic and paramagnetic phases were carried out. Phase transition and temperature dependence of the peak-to-peak ESR linewidth were determined. The transition temperature between ferromagnetic and paramagnetic phases was observed at 265K. A prominent increase of the peak-to-peak linewidth with decreasing temperature below T c was observed. Using the dynamic scale theory and block spin transformation in critical phenomenon, the quantitative calculation of peak-to-peak linewidth at near T c was made, which was in good agreement with the experimental data. It was believed that the long interactions between the ferromagnetic microregions for LCMO played a key role in determining the ESR linewidth. [Copyright &y& Elsevier]