Critical Role of Aromatic C(sp2)-H in Boosting Lithium-Ion Storage.

Exploring high-sloping-capacity carbons is of great significance in the development of high-power lithium-ion batteries/capacitors (LIBs/LICs). Herein, an ion-catalyzed self-template method is utilized to synthesize the hydrogen-rich carbon nanoribbon (HCNR), achieving high specific and rate capacity (1144.2/471.8 mAh g-1 at 0.1/2.5 A g-1). The Li+ storage mechanism of the HCNR is elucidated by in situ spectroscopic techniques. Intriguingly, the protonated aromatic sp2-hybridized carbon (C(sp2)-H) can provide additional active sites for Li+ uptake via reversible rehybridization to sp3-C, which is the origin of the high sloping capacity. The presence of this sloping feature suggests a highly capacitance-dominated storage process, characterized by rapid kinetics that facilitates superior rate performance. For practical usage, the HCNR-based LIC device can deliver high energy/power densities of 198.3 Wh kg-1/17.9 kW kg-1. This work offers mechanistic insights on the crucial role of aromatic C(sp2)-H in boosting Li+ storage and opens up new avenues to develop such sloping-type carbons for high-performance rechargeable batteries/capacitors.

Regulating Oxygen Configuration in Hierarchically Porous Carbon Nanosheets for High-Rate and Durable Na+ Storage.

Surface oxygen functionalities (particularly C-O configuration) in carbon materials have negative influence on their electrical conductivity and Na+ storage performance. Herein, we propose a concept from surface chemistry to regulate the oxygen configuration in hierarchically porous carbon nanosheets (HPCNS). It is demonstrated that the C-O/C=O ratio in HPCNS reduces from 1.49 to 0.43 and its graphitization degree increases by increasing the carbonization temperature under a reduction atmosphere. Remarkably, such high graphitization degree and low C-O content of the HPCNS-800 are favorable for promoting its electron/ion transfer kinetics, thus endowing it with high-rate (323.6 mAh g-1 at 0.05 A g-1 and 138.5 mAh g-1 at 20.0 A g-1 ) and durable (96 % capacity retention over 5700 cycles at 10.0 A g-1 ) Na+ storage performance. This work permits the optimization of heteroatom configurations in carbon for superior Na+ storage.

Porous α-Fe2O3 nanoparticles encapsulated within reduced graphene oxide as superior anode for lithium-ion battery.

A facile route for the controllable synthesis of porous α-Fe2O3 supported by three-dimensional reduced graphene oxide (rGO) is presented. The synergistic effect between α-Fe2O3 and rGO can increase the electrolyte infiltration and improve lithium ion diffusion as well. Moreover, the combination of rGO nanosheets can increase the available surface area to provide more active sites and prevent α-Fe2O3 nanoparticles from agglomeration during the cycling process to ensure its long-term cycle performance. Consequently, the α-Fe2O3/rGO nanocomposites exhibit higher reversible specific capacity (1418.2 mAh g-1 at 0.1 A g-1), better rate capability (kept 804.5 mAh g-1 at 5.0 A g-1) and cycling stability than the α-Fe2O3 nanoparticles. Owing to the superior electrochemical performance, the α-Fe2O3/rGO nanocomposites might have a great potential as anode for lithium-ion batteries.

Ion-catalyzed synthesis of N/O co-doped carbon nanorods with hierarchical pores for high-rate Na-ion storage.

Appropriate heteroatom doping and pore structure optimization are cost-effective technologies to improve the electronic conductivity and ion diffusion kinetics of hard carbons (HCs). Here, we report an ion-catalyzed synthesis of N/O co-doped carbon nanorods (NOCNRs) with abundant hierarchical pores, achieving high-capacity and high-rate Na-ion storage (336 mA h g-1 at 0.1 A g-1 and 196 mA h g-1 at 20.0 A g-1).

Kinetic Analysis of Bio-oil Derived Hierarchically Porous Carbon for Superior Li+/Na+ Storage.

Herein, an efficient biomass utilization is proposed to prepare bio-oil-derived carbon (BODPC) with hierarchical pores and certain H/O/N functionalities for superior Li+/Na+ storage. Kinetic analyses reveal that BODPC has similar behavior in the electrochemical Li+ and Na+ storage processes, in terms of physical adsorption (Stage I), chemical redox reactions with surface functionalities (Stage II), and insertion into the graphitic interlayer (Stage III). Promisingly, BODPC exhibits a high reversible specific capacity (1881.7 mAh g-1 for Li+ and 461.0 mAh g-1 for Na+ at 0.1 A g-1), superior rate capability (674.1 mAh g-1 for Li+ and 125.7 mAh g-1 for Na+ at 5.0 A g-1), and long-term cyclability. More notably, the BODPC with highly capacitive-dominant behavior would hold great promise for the applications of high-power, durable, and safe rechargeable batteries/capacitors.

Operando mechanistic and dynamic studies of N/P co-doped hard carbon nanofibers for efficient sodium storage.

In situ Raman and electrochemical results reveal that Na+ adsorbs on the surface/defective sites of N/P-HCNF and inserts randomly into its turbostratic nanodomains in the dilute state without a staged formation, which can facilitate fast Na+ diffusion kinetics for efficient sodium storage.

Oxygen vacancies boosted the electrochemical kinetics of Nb2O5-x for superior lithium storage.

The introduction of oxygen vacancies (OVs) into Nb2O5 can not only provide more active sites for lithium storage but also change the electronic structure of Nb2O5 to boost electron/ion transport kinetics. Consequently, the defective Nb2O5-x exhibits high lithium storage capacity, superior rate capability, and cycling stability.

Spectroscopic analyses of iron doped protonated polyaniline/graphene oxide system.

Fe3+ and H+ co-doped PANI/GO (graphene oxide) composites with different iron dopant ratio depending on the starting FeCl3 (GOPNI-1, GOPNI-2, GOPNI-3 and GOPNI-4) are prepared. The formations of composite samples are investigated by some characterization techniques such as XRD, ATR-IR, UV-Vis spectrophotometer and thermal properties by TGA. While, the Nitrogen adsorption/desorption isotherm for (GOPNI-3) shows high specific surface area 48.7 m2 g-1 depending on Brunauer-Emmett-Teller (BET) method. Owing to the high surface area as well as the synergistic effect between polyaniline and graphene oxide the electrochemical performance of (GOPNI-3) shows high specific capacitance 1610.09 F g-1 at 1 A g-1 in 1 M H2SO4 acidic aqueous electrolyte. A symmetric supercapacitor device (SCs) with superbly electrochemical performance is fabricated using GOPNI-3 electrodes. The symmetric device exhibits high specific capacitance 810.88 F g-1 at 1 A g-1 in which the maximum energy density and power density of 18.02 Wh Kg-1 and 189.68 W kg-1, respectively. Moreover, the SCs device shows good cycling stability (67.1%) after 1000 cycles at a scan rate 200 mV s-1.

Sonochemical assisted fabrication of 3D hierarchical porous carbon for high-performance symmetric supercapacitor.

A scalable fabrication of 3D hierarchical porous carbon structure (3D-HPC) has been achieved via a simple sonochemical route at different pyrolysis temperatures. It is worth noting that all the 3D-HPC samples possess oxygen-functional groups after activation by KOH and self-doped by nitrogen, which are beneficial to improving their surface wettability as well as increasing the electro-active surface area between the electrode and the surrounding electrolyte, consequently enhancing their electrochemical performance. Remarkably, the resulting carbon sample pyrolyzed at 850 °C (AC-850) possesses a maximum doping level of 2.75 at% and a high surface area of 1376.19 m2 g-1, which exhibits high electrochemical performance with high capacitance up to 269.19 F g-1 at a current density of 2 A g-1. Moreover remarkably, the AC-850-based symmetric supercapacitor delivers a high energy density of 21.4 Wh kg-1 at a power density of 531.2 W kg-1 with excellent rate performance and superior cycling stability (94.7% retention over 5000 cycles). The present approach is very suitable for large scale production of high-quality porous carbon materials at low cost, which can be used in different aspects, such as energy storage, gas storage, environmental remediation, and so on.

Magnetic Graphene Oxide as an Efficient Adsorbent for the Separation and Preconcentration of Cu(II), Pb(II), and Cd(II) from Environmental Samples.

The separation and preconcentration of copper(II), lead(II), and cadmium(II) ions on magnetic graphene oxide (MGO) by solid-phase extraction was carried out. Quantitative recovery was obtained by adsorption of analytes on MGO at pH 6 and elution of 3 M HNO3 in 10% acetone. To optimize the presented method, the effects of various parameters-including pH, eluent conditions, and vortex time-were examined. Matrix effects were also investigated. Mean recoveries of the analytes were between 95 and 105%. The proposed method was validated by applying it to certified reference materials. Addition and recovery tests were also performed. The method was applied to verify the analyte content of several water and food samples.