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The transition metal oxides with multiple oxidation states and large electrical conductivity have been extensively studied in energy storage capacitors. Herein, the core-shell cobalt sulfide/manganese molybdate composites grown on reduced graphene oxide/Ni foam (CoS/MMO/rGO/NF) have been successfully prepared via hydrothermal and followed by electrodeposition methods. It is found that the deposition mass of CoS has a significant effect on the morphologies and electrochemical properties of CoS/MMO/rGO/NF electrodes. When the mass of CoS is 0.4 mg cm−2 (CoS-0.4/MMO/rGO/NF), the composite yields a remarkable specific capacitance of 3074.5 F g−1 (1 A g−1) and a good cycling performance of 87% through 5000 cycles. Moreover, an asymmetric device based on the CoS-0.4/MMO/rGO/NF composite shows a maximum energy density (50.3 W h kg−1 at 415.8 W kg−1) and a good long-term stability (retention 96% even after 8000 cycles). These characteristics of CoS-0.4/MMO/rGO/NF are mainly attributed to the high conductivity of reduced graphene oxide and the synergistic effects of MnMoO4 and CoS, as well as its unique morphology. These superior properties of CoS-0.4/MMO/rGO/NF demonstrate its potential application as electrode material in energy storage capacitors.

Herein, zinc cobalt layered double hydroxide (ZnCo-LDH) hybrid composites with different Zn/Co molar ratios are in-suit grown onto Ni foam by a simple and cost-effective hydrothermal approach. It is found that the Zn/Co molar ratios have an important influence on the morphology and electrochemical performance of the ZnCo-LDH composites. An interconnected nanowires structure and the highest specific capacitance were achieved when the Zn/Co molar ratio is 1: 2 (Zn1Co2-LDH).Moreover, interconnected Zn1Co2-LDH is further combined with reduced graphene oxide stuck onto Ni foam (Zn1Co2-LDH@rGO/NF) to improve its electrochemical properties. Benefiting from its unique structural feature and excellent electrical conductance ability, the as-prepared material exhibits an enhanced specific capacitance of 2142.0 F g−1 as supercapacitor electrode. Remarkably, the assembled asymmetric supercapacitor device based on Zn1Co2-LDH@rGO/NF and active carbon delivers a high specific capacitance (149.6 F g−1), high energy density (53.2 Wh kg−1), and excellent long cycling stability (90.9% capacitance retention after 6000 cycles at 3 A g−1), which holds huge potential for practical application in energy conversion and storage fields.

Ternary metal sulfides such as manganese-cobalt-sulfide (MCS) with the unique physical, chemical properties and high specific capacity can be used as energy storage material for supercapacitor. Herein, we prepared a MCS nanosheet array stick onto reduced graphene oxide (rGO)/Ni foam (MCS/rGO/NF) by a carefully controlled sulfurization time process. As the reaction time increased, the thickness of MCS/rGO/NF nanosheet arrays charged from thin to thick. After 3 h of sulfurization reaction (MCS/rGO/NF-3h), the nanosheets became rough due to the formation of some small sheets, and the composite showed the best electrochemical performance. The MCS/rGO/NF-3h composite exhibited a large specific capacity of 1356 C g−1 at a current density of 1 A g−1, and a long-term cyclic stability of 92.9% at a current density of 10 A g−1 through 3000 cycles. Moreover, a hybrid supercapacitor (HSC) device was assembled using MCS/rGO/NF-3h and rGO as the positive and negative electrodes, respectively. The MCS/rGO/NF-3h//rGO HSC exhibited a high energy density of 45.4 W h kg−1 at a power density of 850.2 W kg−1. The prominent electrochemical performance suggests that MCS/rGO/NF composites are promising electrode materials for energy storage applications.

Decorated graphite-like carbon nitride (g-C3N4) exhibits high photo-catalytic activity and is a central research area in the field of energy shortage. In this reported study, g-C3N4 was used as a precursor from which six kinds of metal sulfides (Ce, Zn, Ni, Cu, Bi, In) were produced with varying atomic ratios. This library of thousands of catalysts was applied (MySx/g-C3N4) to a semiconductor chip using ink-jet printing and the active catalysts were selected employing high throughput screening. Using visible blue light, the high throughput technique revealed four very active catalysts (Ce0.06Ni0.19Bi0.08Zn0.04Cu0.13In0.50)S/g-C3N4, (Ce0.03Ni0.52Bi0.38Zn0.01Cu0.04In0.03)S/g-C3N4, (Ce0.19Ni0.10Bi0.08Zn0.11Cu0.22In0.28) S/g-C3N4, (Ce0.21Ni0.10Bi0.08Zn0.11Cu0.22In0.28)S/g-C3N4 and one catalyst with low catalytic activity (Ce0.05Ni0.08Bi0.17Zn0.33Cu0.24In0.12)S/g-C3N4.

The hierarchical core-shell ZnCo2O4@Ni-Co-S nanosheets with microsphere structures for supercapacitors were prepared through a facile three-step method including hydrothermal reaction, subsequent annealing and electrodeposition process. The influences of deposition cycles on its structure and electrochemical performances were studied in detail. On account of a synergistic effect of the ZnCo2O4 and Ni-Co-S composite and its unique core-shell nanostructure, the as-prepared electrode reveals excellent supercapacitor properties. The ZnCo2O4@Ni-Co-S with 6 electrodeposition cycles (ZCO@NCS-6) shows high specific capacitance values of 1762.6 F g−1 at 1 A g−1, outstanding rate performance with 81.3% at 50 A g−1, and remarkable long-term stability of 18.6% capacity loss through 5000 cycles. Moreover, the asymmetric supercapacitor (ASC) device was further constructed by using of ZCO@NCS-6 and active carbon to evaluate the practical values of the fabricated composite materials. The assembled ASC device shows the maximum voltage window up to 1.7 V, high energy density of 37.1 W h kg−1 and the excellent cycling life-span (only 9.71% capacitance loss after 8000 cycles). All these results suggest that ZnCo2O4@Ni-Co-S could be the hopeful electrode materials for energy storage devices.

Orthophosphoric acid (H3PO4), pyrophosphoric acid (H4P2O7), polyphosphoric acid (H6P4O13) and phytic acid (C6H18O24P6) were specially employed as activating agents to produce activated carbons from mushroom roots (MR). Thermogravimetric studies of MR after these phosphorus oxyacids (POA) impregnation indicated the thermal degradation of MR was greatly influenced by different polycondensed POA. The prepared activated carbons were characterized by N2 adsorption/desorption isotherms, Fourier-transform infrared spectroscopy (FTIR) and Boehm's titration. The surface area of the carbons was similar but the characteristics of pore volume were different. MRAC-C6H16O24P6 owned the largest surface area and micropore volume. MRAC-H3PO4, MRAC-H4P2O7 and MRAC-H6P4O13 presented a similar micropore volume. MRAC-H6P4O13 exhibited a comparatively narrow mesopore distribution around 4 nm. Boehm's titration results indicated that MRAC-C6H16O24P6, MRAC-H6P4O13 and MRAC-H4P2O7 had much more acidic functionalities than MRAC-H3PO4. MRAC-C6H18O24P6 had the highest amount of total acidic surface groups (4.02 mmol/g). Batched sorption studies were also performed to compare adsorptive properties of the carbons toward methylene blue (MB). The sorption capacity of MB follows an order of MRAC-C6H16O24P6 ≈ MRAC-H6P4O13 > MRAC-H4P2O7 > MRAC-H3PO4, which may be assigned to the different pore structures and chemical properties.