Anchoring ultrafine Co3O4 grains on reduced oxide graphene by dual-template nanocasting strategy for high-energy solid state supercapacitor

Co3O4-based materials are regarded as superior electrode candidates in various energy storage devices due to their high theoretical capacity. Unfortunately, the poor electronic conductivity and huge volume expansion hamper their widespread applications. Therefore, nano-processing and introducing conductive matrix can view as the necessary methods to make Co3O4-based materials better for an advanced supercapacitor electrode. Herein, a dual-template nanocasting technique is proposed to design the ultrafine Co3O4 grains highly-dispersed on the reduced oxide graphene nanosheets (Co3O4/rGO-C), in which cetyltrimethyl ammonium bromide and silicate species are hired as the ideal soft and hard template, respectively. Co3O4 grains with size \u3c10 nm can expose more active sites and thus exert more redox activities to enhance the capacitive performance. In additional, ∼4 nm moderate pores are obtained in Co3O4/rGO-C after the hard template removing, which provides more diffusion channels for ion/electron rapid transport and also effectively alleviates the volume expansion on cycling. Consequently, the Co3O4/rGO-C electrode exhibits a remarkable specific capacitance (709.1 F g−1 at 1 A g−1) and long-term endurance (91.2% after 6000 cycles). Furthermore, an assembled solid-state asymmetric device of Co3O4/rGO-C||rGO delivers a super-high energy-density of 48.2 Wh kg−1 at 750.5 W kg−1. The high energy-density assists two devices in lightning a red light-emitting diode for 340 s. These results evidence the nanocasting strategy as an efficient method to achieve the advanced electrode materials for energy storage devices

MnO2-introduced-tunnels strategy for the preparation of nanotunnel inserted hierarchical-porous carbon as electrode material for high-performance supercapacitors

Nanotunnels inserted hierarchical-porous carbon (NTHPC) have been synthesized successfully via a MnO2-introduced-tunnels strategy using MnO2 nanorods as template, with agar and β-cyclodextrin serving as hybrid carbon precursors. The as-prepared NTHPC possesses a higher specific surface area of 1441 m2 g−1, a moderate pore volume of 1.23 cm3 g−1, and the hierarchical-porous structure with inserted nanotunnels. Transmission electron microscopy has demonstrated that the width of the nanotunnels is between 20 and 100 nm, and the length ranges from 0.2 to 2.0 μm. Tests in a three-electrode system showed that the NTHPC has high specific capacitance (253.1 F g−1, 5 mV s−1), as well as good rate capability (203.3 F g−1, 100 mV s−1) and excellent cycling stability. More importantly, an assembled symmetric supercapacitor with NTHPC electrodes delivered an outstanding energy density of up to 34.9 Wh kg−1 with power density of 755.2 W kg−1. The remarkable electrochemical performance of the NTHPC is ascribed to the nanotunnels, which act as ion reservoirs and liquid transfer channels that can increase the ion transport rate and shorten the ion transfer distance. This study provides a novel method for the preparation of high-performance hierarchical-porous carbon and guidance for its potential applications in supercapacitors

Chitosan-confined synthesis of N-doped and carbon-coated Li4Ti5O12 nanoparticles with enhanced lithium storage for lithium-ion batteries

Using chitosan as the carbon and nitrogen source, highly-crystalline lithium titanate nanoparticles with N-doped carbon-coating (N-C/LTO) have been successfully synthesized via a facile refluxing and microwave-assisted hydrothermal processes followed by a subsequent calcination step. Due to the effect of chitosan-confined, the fabricated N-C/LTO composites crystallized into well-defined cubic spinel structure with an average size of ∼50 nm, leading to a significantly enhanced specific surface area. The successful doping of nitrogen into the carbon layer of the N-C/LTO has been confirmed by XPS technology. The porous LTO with nitrogen-doped carbon coating fabricated with chitosan exhibits superior electrochemical performance (a high reversible capacity of 194 mAh g−1 was achieved at 1 C). This work therefore reveals that the N-doped carbon coating realized by chitosan confinement is an effective way for enhancing the surface lithium storage capability of LTO as the anode materials for lithium-ion batteries (LIBs)

Molecular Breeding of Water-Saving and Drought-Resistant Rice for Blast and Bacterial Blight Resistance

Rice production is often affected by biotic and abiotic stressors. The breeding of resistant cultivars is a cost-cutting and environmentally friendly strategy to maintain a sustainable high production level. An elite water-saving and drought-resistant rice (WDR), Hanhui3, is susceptible to blast and bacterial blight (BB). This study was conducted to introgress three resistance genes (Pi2, xa5, and Xa23) for blast and BB into Hanhui3, using marker-assisted selection (MAS) for the foreground selection and a whole-genome single-nucleotide polymorphism (SNP) array for the background selection. As revealed by the whole-genome SNP array, the recurrent parent genome (RPG) recovery of the improved NIL was 94.2%. The resistance levels to blast and BB of the improved NIL and its derived hybrids were higher than that of the controls. In addition, the improved NIL and its derived hybrids retained the desired agronomic traits from Hanhui3, such as yield. The improved NIL could be useful to enhance resistance against biotic stressors and produce stable grain yields in Oryza sativa subspecies indica rice breeding programs

Preparation of Lithium Titanate/Reduced Graphene Oxide Composites with Three-Dimensional “Fishnet-Like” Conductive Structure via a Gas-Foaming Method for High-Rate Lithium-Ion Batteries

With use of ammonium chloride (NH₄Cl) as the pore-forming agent, three-dimensional (3D) “fishnet-like” lithium titanate/reduced graphene oxide (LTO/G) composites with hierarchical porous structure are prepared via a gas-foaming method. Scanning electron microscopy and transmission electron microscopy images show that, in the composite prepared with the NH₄Cl concentration of 1 mg mL^–1 (1-LTO/G), LTO particles with sizes of 50–100 nm disperse homogeneously on the 3D “fishnet-like” graphene. The nitrogen-sorption analyses reveal the existence of micro-/mesopores, which is attributed to the introduction of NH₄Cl into the gap between the graphene sheets that further decomposes into gases and produces hierarchical pores during the thermal treatment process. The loose and porous structure of 1-LTO/G composites enables the better penetration of electrolytes, providing more rapid diffusion channels for lithium ion. As a result, the 1-LTO/G electrode delivers an ultrahigh specific capacity of 176.6 mA h g^–1 at a rate of 1 C. Even at 3 and 10 C, the specific capacity can reach 167.5 and 142.9 mA h g^–1, respectively. Moreover, the 1-LTO/G electrode shows excellent cycle performance with 95.4% capacity retention at 10 C after 100 cycles. The results demonstrate that the LTO/G composite with these properties is one of the most promising anode materials for lithium-ion batteries

Preparation of Lithium Titanate/Reduced Graphene Oxide Composites with Three-Dimensional “Fishnet-Like” Conductive Structure via a Gas-Foaming Method for High-Rate Lithium-Ion Batteries

With use of ammonium chloride (NH₄Cl) as the pore-forming agent, three-dimensional (3D) “fishnet-like” lithium titanate/reduced graphene oxide (LTO/G) composites with hierarchical porous structure are prepared via a gas-foaming method. Scanning electron microscopy and transmission electron microscopy images show that, in the composite prepared with the NH₄Cl concentration of 1 mg mL^–1 (1-LTO/G), LTO particles with sizes of 50–100 nm disperse homogeneously on the 3D “fishnet-like” graphene. The nitrogen-sorption analyses reveal the existence of micro-/mesopores, which is attributed to the introduction of NH₄Cl into the gap between the graphene sheets that further decomposes into gases and produces hierarchical pores during the thermal treatment process. The loose and porous structure of 1-LTO/G composites enables the better penetration of electrolytes, providing more rapid diffusion channels for lithium ion. As a result, the 1-LTO/G electrode delivers an ultrahigh specific capacity of 176.6 mA h g^–1 at a rate of 1 C. Even at 3 and 10 C, the specific capacity can reach 167.5 and 142.9 mA h g^–1, respectively. Moreover, the 1-LTO/G electrode shows excellent cycle performance with 95.4% capacity retention at 10 C after 100 cycles. The results demonstrate that the LTO/G composite with these properties is one of the most promising anode materials for lithium-ion batteries