Hierarchical 3D ZnIn2S4/graphene (ZnIn2S4/Gr) nano-heterostructures were successfully synthesized using an in-situ hydrothermal method. The dual functionality of these nano-heterostructures i.e. for solar hydrogen production and lithium ion batteries has been demonstrated for the first time. The ZnIn2S4/Gr nano-heterostructures were optimized by varying the concentrations of graphene for utmost hydrogen production. An inspection of the structure shows the existence of layered hexagonal ZnIn2S4 wrapped in graphene. The reduction of graphene oxide (GO) to graphene was confirmed by Raman and XPS analyses. The morphological analysis demonstrated that ultrathin ZnIn2S4 nanopetals are dispersed on graphene sheets. The optical study reveals the extended absorption edge to the visible region due to the presence of graphene and hence is used as a photocatalyst to transform H2S into eco-friendly hydrogen using solar light. The ZnIn2S4/Gr nano-heterostructure that is comprised of graphene and ZnIn2S4 in a weight ratio of 1 : 99 exhibits enhanced photocatalytically stable hydrogen production i.e. ∼6365 μmole h(-1) under visible light irradiation using just 0.2 g of nano-heterostructure, which is much higher as compared to bare hierarchical 3D ZnIn2S4. The heightened photocatalytic activity is attributed to the enhanced charge carrier separation due to graphene which acts as an excellent electron collector and transporter. Furthermore, the usage of nano-heterostructures and pristine ZnIn2S4 as anodes in lithium ion batteries confers the charge capacities of 590 and 320 mA h g(-1) after 220 cycles as compared to their initial reversible capacities of 645 and 523 mA h g(-1), respectively. These nano-heterostructures show high reversible capacity, excellent cycling stability, and high-rate capability indicating their potential as promising anode materials for LIBs. The excellent performance is due to the nanostructuring of ZnIn2S4 and the presence of a graphene layer, which works as a channel for the supply of electrons during the charge-discharge process. More significantly, their dual functionality in energy generation and storage is quite unique and commendable.

The evolution of electric vehicles and advanced wearable flexible devices is closely bound with battery safety. Herein, we report, a synthesis of thermally stable, flame-retardant, and flexible solid polymer electrolyte using eco-friendly materials such as cellulose triacetate, PEGMA, and ionic liquid PYR14TFSI. PYR14TFSI and salt LiTFSI were added to the polymer to make a solid polymer electrolyte (PCIL). The conductivity of PCIL at normal temperatures is observed to be 5.24 × 10 −3 S cm −1 , which further increased to 1.03 × 10 −2 S cm −1 at 70 °C. An average transference number (t+) of about 0.43 has been observed for PCIL, which is much better than that for the liquid electrolyte. Moreover, PCIL, being highly stable up to 5 V, can be employed in high-voltage applications. The half cell with LFP as cathode displays the 1st discharge capacity of 125 mAh g −1 at room temperature. It's interesting to note that, after 50 cycles, the cell retains an initial discharge capacity of 76% at room temperature. Additionally, electrospun derived carbon exhibits first discharge capacity at 340 mAh g −1 which reduced to 216 mAh g −1 after 40 cycles. It should be noted that these cycling studies were carried out at ambient temperature, and it was also noted that the synergic effect of polymeric and ionic liquid systems at higher temperatures leads to an increase in mobility of charge carriers, which ultimately confers easier ionic transport and improved storage capacity. The present SPE PCIL may have potential in high-voltage LIBs.

Currently, the limited availability of lithium sources is escalating the cost of lithium-ion batteries (LIBs). Considering the fluctuating economics of LIBs, sodium-ion batteries (SIBs) have now drawn attention because sodium is an earth-abundant, low-cost element that exhibits similar chemistry to that of LIBs. Despite developments in different anode materials, there still remain several challenges in SIBs, including lighter cell design for SIBs. The presented work designs a facile strategy to prepare nitrogen-doped free-standing pseudo-graphitic nanofibers via electrospinning. A structural and morphological study implies highly disordered graphitic structured nanofibers having diameters of ∼120−170 nm, with a smooth surface. X-ray photoelectron spectroscopy analysis showed that nitrogen was successfully doped in carbon nanofibers (CNFs). When served as an anode material for SIBs, the resultant material exhibits excellent sodium-ion storage properties in terms of long-term cycling stability and high rate capability. Notably, a binder-free self-standing CNF without a current collector was used as an anode for SIBs that delivered capacities of 210 and 87 mA h g −1 at 20 and 1600 mA g −1 , respectively, retaining a capacity of 177 mA h g −1 when retained at 20 mA g −1 . The as-synthesized CNFs demonstrate a long cycle life with a relatively high Columbic efficiency of 98.6% for the 900th cycle, with a stable and excellent rate capacity. The sodium storage mechanisms of the CNFs were examined with various nitrogen concentrations and carbonization temperatures. Furthermore, the diffusion coefficients of the sodium ions based on the electrochemical impedance spectra measurement have been calculated in the range of 10 −15 −10 −12 cm 2 s −1 , revealing excellent diffusion mobility for Na atoms in the CNFs. This study demonstrates that optimum nitrogen doping and carbonization temperature demonstrated a lower Warburg coefficient and a higher Na-ion diffusion coefficient leads to enhanced stable electrochemical performance. Thus, our study shows that the nitrogen-doped CNFs will have potential for SIBs.

The multi-functionality of the hierarchical CdIn2S4/graphene nano-heterostructure prepared using a single step process, as an active photocatalyst for hydrogen production and as an anode for Li-ion batteries has been demonstrated.

Nitrogen enriched carbon nanofibers have been obtained by one-step carbonization/activation of PAN-based nanofibers with various concentrations of melamine at 800 °C under a N2 atmosphere.