Application of Copper-Sulfur Compound Electrode Materials in Supercapacitors.

Supercapacitors (SCs) are a novel type of energy storage device that exhibit features such as a short charging time, a long service life, excellent temperature characteristics, energy saving, and environmental protection. The capacitance of SCs depends on the electrode materials. Currently, carbon-based materials, transition metal oxides/hydroxides, and conductive polymers are widely used as electrode materials. However, the low specific capacitance of carbon-based materials, high cost of transition metal oxides/hydroxides, and poor cycling performance of conductive polymers as electrodes limit their applications. Copper-sulfur compounds used as electrode materials exhibit excellent electrical conductivity, a wide voltage range, high specific capacitance, diverse structures, and abundant copper reserves, and have been widely studied in catalysis, sensors, supercapacitors, solar cells, and other fields. This review summarizes the application of copper-sulfur compounds in SCs, details the research directions and development strategies of copper-sulfur compounds in SCs, and analyses and summarizes the research hotspots and outlook, so as to provide a reference and guidance for the use of copper-sulfur compounds.

Preparation of an aqueous zinc ion rGH/V2O5 photorechargeable supercapacitor.

A photorechargeable supercapacitor was constructed using vanadium pentoxide (V2O5), reduced graphene oxide hydrogel (rGH), and zinc trifluoromethanesulfonate (Zn(CF3SO3)2) as the photoanode, cathode, and electrolyte, respectively. The phase composition, microstructure, chemical structure, light absorption, and specific surface area of the synthesized products and the electrochemical performance of the rGH/V2O5 supercapacitor were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FT-IR), Raman spectroscopy, UV-Vis spectroscopy, the Brunauer-Emmett-Teller (BET) method, and an electrochemical workstation, respectively. The results show that the device has a specific capacity of 164 F g-1 at 0.5 A g-1 under illumination with 95 mW cm-2 light intensity, which is 20.5% higher than that under normal electrical charging. The supercapacitor has a 75% capacity retention rate and 100% coulombic efficiency, respectively, after 10 000 testing cycles under photoelectric synergistic charging and discharging. The as-constructed rGH/V2O5 photorechargeable supercapacitor exhibits promising application potential in electric vehicles and wearable electronics.

Graphene Film with a Controllable Microstructure for Efficient Electrochemical Energy Storage.

The agglomeration of graphene sheets and undesired pore size distribution usually lead to unsatisfactory electrochemical properties of reduced graphene oxide (RGO) film electrodes. Herein, crumpled exfoliated graphene (EG) sheets are adopted as the microstructure-regulating agent to tune the morphology and micro-/mesopore amounts with the aim of increasing active surface sites and ion transportation paths in electrodes. With the optimum ratio between EG and GO, the resulting 75%-EG/RGO shows significantly improved specific gravimetric capacitance (Cs) and rate capability when compared with pure RGO electrodes in a symmetrical supercapacitor system. Moreover, when coupling the 75%-EG/RGO cathode with a Zn anode to form a Zn ion hybrid supercapacitor (ZHS), the 75%-EG/RGO exhibits a much higher Cs of 327.39 F g-1 at 0.1 A g-1 and can maintain 91.7% capacitance after 8000 cycles. Systematic ex situ X-ray diffraction (XRD) and X-ray photoelectron spectra (XPS) measurements reveal that the charge storage mechanism is based on both reversible physical adsorption and dual ion uptake. Furthermore, the quasi-solid-state flexible ZHS also presents high capacitive performance and can maintain ∼100% capacitance under various bending states, demonstrating potential application in wearable electronics. This strategy opens up a new path for constructing high-performance graphene film electrodes.

Advances in the research of carbon electrodes for perovskite solar cells.

Perovskite solar cells (PSCs) were first proposed in 2009. They have the advantages of low cost, a simple manufacturing process and excellent photoelectric performance. PSC electrodes are mainly made from precious metals such as gold and silver. Still, the cost of precious metals is high and they react with the other components of the PSCs, resulting in the poor stability of the photovoltaic device. Using carbon as an electrode material can both reduce the cost and significantly improve the stability of the photovoltaic device. However, the poor interface contact between the carbon electrode and perovskite and carbon electrode resistance results in poor photovoltaic device photoelectric performance. Finding a way to successfully utilize carbon as an alternative electrode material is a key step toward moving PSCs from the laboratory to industrialization. This paper reviews the application of carbon black, graphite, graphene, carbon nanotubes (CNTs) and composite carbon electrode in PSCs, focusing on progress in the research of doping, structure, interface modification and the production process.

Detection of host-guest interactions in clathrates of heterocyclic molecules adsorbed in a porous MOF with Cu2 cluster nodes via vibration spectra and magnetic properties.

A three-dimensional NbO-type MOF with the formula Cu2(EBTC)(H2O)2·[G] (1) (EBTC(4-) = 1,1'-ethynebenzene-3,3',5,5'-tetracarboxylate; G = guest molecules and represent DMF, DMSO and H2O) was synthesized using a solvothermal method. The sufficient cavity space in 1 can be used to encapsulate the heterocyclic compounds benzopyrrole (C8H7N), benzofuran (C8H6O) and benzothiophene (C8H6S). The guest-free framework (2) was obtained by heating methanol-exchanged 1 at 130 °C under vacuum. The clathrates [Cu2(EBTC)(H2O)2·1.6C8H7N]∞ (3), [Cu2(EBTC)(H2O)2·2.5C8H6O]∞ (4) and [Cu2(EBTC)(H2O)2·2C8H6S]∞ (5) were prepared by soaking 2 in C8H7N, C8H6O and C8H6S at 55 °C for 48 h, respectively. 1-5 showed quite similar PXRD patterns, indicating that they have the same framework structure. The IR and Raman spectra and the variable-temperature magnetic susceptibilities were comparatively studied for 1-5; the results disclosed the existence of weakly intermolecular interactions between the -C≡C- in the organic linkers and guest molecules, whereas an almost complete absence of intermolecular interactions between the paddle-wheel-type dinuclear Cu2 units and large guest molecules owing to steric hindrance. This study suggests the possibility of these rather useful MOF materials in the removal of organosulfur or organonitrogen compounds that are widely known contaminants in petroleum and fuels via their rationally designed organic linkers.

Comparative study of structures, thermal stabilities and dielectric properties for a ferroelectric MOF [Sr(µ-BDC)(DMF)]∞ with its solvent-free framework.

A ferroelectric MOF with a formula [Sr(µ-BDC)(DMF)]∞ (1) was transformed into [Sr(µ-BDC)(CH2Cl2)x]∞ (2) using a solvent exchange approach, where DMF = N,N-dimethylformamide and BDC(2-) = benzene-1,4-dicarboxylate. The lattice solvents, CH2Cl2 molecules, in 2 were removed by heating to give the solvent-free metal-organic framework [Sr(µ-BDC)]∞ (3) and the crystal-to-crystal transformation is reversible between 1 and 3. The release of DMF molecules from 1 results in the metal-organic framework of [Sr(µ-BDC)]∞ expanding a little along the a- and b-axes. The crystal structure optimizations for 1 and 3 disclosed that the lattice expansion is associated with the alternations of the bond distances and angles in the Sr(2+) ion coordination sphere along the a- and b-axes directions. The metal-organic framework 3 collapses at temperatures of more than 600 °C; such an extremely high thermal stability is related to the closed-shell electronic structure of the Sr(2+) ion, namely, the coordinate bond between the closed-shell Sr(2+) ion and the bridged BDC(2-) ligands does not have a preferred direction, which is favored for reducing lattice strains and is responsible for the higher thermal stability. The comparative investigations for the dielectric and ferroelectric behaviors of 1 and 3 confirmed that the motion of the polar DMF molecules, but not the [Sr(µ-BDC)]∞ framework, is responsible for the ferroelectric properties of 1.