Doping with heteroatoms has become a significant strategy for modifying the electronic properties and enhancing the electrochemical properties of graphene (GN).

Three-dimensional (3D) nanostructures have attracted considerable attention because of their high surface areas and unique properties which gives outstanding performance in catalysis and energy storage applications. This paper proposes the growth mechanism of 3D flower-like β-Ni(OH)2 constructed through a two dimensional sheet framework using a one-step oleylamine-assisted solvothermal approach, where oleylamine acts as the surfactant, co-solvent, stabilizer, and reducing agent. A detailed examination of the product morphology after various reaction times suggested that the self-assembly of flower occurs through a mechanism involving nucleation, Ostwald ripening, and recrystallization. The associated characterization revealed it to be pure β-Ni(OH)2 without any sign of contamination. The effect of the morphology (sheet to 3D flower-like β-Ni(OH)2) on the electrochemical supercapacitive behavior was assessed by cyclic voltammetry and galvanostatic charge-discharge tests. The results showed that 3D flower-like β-Ni(OH)2 exhibited better specific capacitance of ~1567 F g−1 at a current density of 1 A g−1 and retained ~25% capacitance at a high current density of 10 A g−1 compared to the other reference materials. The superior electrochemical properties of the 3D flower-like β-Ni(OH)2 originate from their large specific surface area and unique structure.

SnS 2 is an emerging candidate for an electrode material because of the considerable interlayer spaces in its crystal structures and the large surface area. SnS 2 as a photocatalyst and in lithium ion batteries has been reported. On the other hand, there are only a few reports of their supercapacitor applications. In this study, sheetlike SnS 2 (SL-SnS 2 ), flowerlike SnS 2 (FL-SnS 2 ), and ellipsoid-like SnS 2 (EL-SnS 2 ) were fabricated via a facile solvothermal route using different types of solvents. The results suggested that the FL-SnS 2 exhibited better capacitive performance than the SL-SnS 2 and EL-SnS 2 , which means that the morphology has a significant effect on the electrochemical reaction. The FL-SnS 2 displayed higher supercapacitor performance with a high capacity of approximately ∼431.82 F/g at a current density of 1 A/g. The remarkable electrochemical performance of the FL-SnS 2 could be attributed to the large specific surface area and better average pore size. These results suggest that a suitable solvent is appropriate for the large-scale construction of SnS 2 with different morphologies and also has huge potential in the practical applications of high-performance supercapacitors.

Fibrous Pani-MnO2 nanocomposite were prepared using a one-step and scalable in situ chemical oxidative polymerization method. The formation, structural and morphological properties were investigated using a range of characterization techniques. The electrochemical capacitive behavior of the fibrous Pani-MnO2 nanocomposite was examined by cyclic voltammetry and galvanostatic charge-discharge measurements using a three-electrode experimental setup in an aqueous electrolyte. The fibrous Pani-MnO2 nanocomposite achieved high capacitance (525 F g(-1) at a current density of 2 A g(-1)) and excellent cycling stability of 76.9% after 1000 cycles at 10 A g(-1). Furthermore, the microbial fuel cell constructed with the fibrous Pani-MnO2 cathode catalyst showed an improved power density of 0.0588 W m(-2), which was higher than that of pure Pani and carbon paper, respectively. The improved electrochemical supercapacitive performance and cathode catalyst performance in microbial fuel cells were attributed mainly to the synergistic effect of Pani and MnO2 in fibrous Pani-MnO2, which provides high surface area for the electrode/electrolyte contact as well as electronic conductive channels and exhibits pseudocapacitance behavior.

Layered Sn-based chalcogenides and heterostructures are widely used in batteries and photocatalysis, but its utilizations in a supercapacitor is limited by its structural instability and low conductivity. Here, SnS x thin films are directly and conformally deposited on a three-dimensional (3D) Ni-foam (NF) substrate by atomic layer deposition (ALD), using tetrakis(dimethylamino)tin [TDMASn, ((CH 3 ) 2 N) 4 Sn] and H 2 S that serves as an electrode for supercapacitor without any additional treatment. Two kinds of ALD-SnS x films grown at 160 °C and 180 °C are investigated systematically by X-ray diffractometry, Raman spectroscopy, X-ray photoelectron spectroscopy, and transmission electron microscopy (TEM). All of the characterization results indicate that the films deposited at 160 °C and 180 °C predominantly consist of hexagonal structured-SnS 2 and orthorhombic-SnS phases, respectively. Moreover, the high-resolution TEM analyses (HRTEM) reveals the (001) oriented polycrystalline hexagonal-SnS 2 layered structure for the films grown at 160 °C. The double layer capacitance with the composite electrode of SnS x @NF grown at 160 °C is higher than that of SnS x @NF at 180 °C, while pseudocapacitive Faradaic reactions are evident for both SnS x @NF electrodes. The superior performance as an electrode is directly linked to the layered structure of SnS 2 . Further, the optimal thickness of ALD-SnS x thin film is found to be 60 nm for the composite electrode of SnS x @NF grown at 160 °C by controlling the number of ALD cycles. The optimized SnS x @NF electrode delivers an areal capacitance of 805.5 mF/cm 2 at a current density of 0.5 mA/cm 2 and excellent cyclic stability over 5000 charge/discharge cycles.