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Precious metal oxides exhibit impressive characteristics that caught worldwide attention due to their promising capacitive performance, excellent electrochemical stability and low resistance, and these metal oxides have been extensively employed in supercapacitor application. This type of supercapacitors is known as redox supercapacitors or pseudocapacitors which applied faradaic process in storing energy in their systems. Thus, new materials with impressive electrochemical performance are highly demanded. In this aspect, cobaltite system with spinel structure has been the subject of intense research due to its established applications in electrochemistry. Besides, carbonaceous materials like activated carbons, carbon nanotubes, graphites, graphenes and fullerenes utilize electric double-layer capacitance whereby energy is stored by charge separation at an electrode/electrolyte interface. With greater development conducted on metal oxides and carbonaceous materials for supercapacitor application, introduction of hybrid and composite electrodes comprise of these two types of materials have been well received. [ABSTRACT FROM AUTHOR]

Abstract: NiCo2O4 and NiMn x Co2−x O4−y (x ≤1.0) have been synthesized by a co-precipitation method, and the effects of Mn substitution for Co on the microstructural and electrochemical properties pertaining to the supercapacitor applications have been studied. Spinel structure is retained when a quarter of Co of the spinel is substituted with Mn (i.e., x =0.5), where the Mn ions predominantly occupy the octahedral sites of the spinel lattice. The presence of Mn significantly suppresses crystal growth upon thermal treatment but tends to cause severe crystallite agglomeration. Electrodes of the materials exhibit nearly ideal electrochemical capacitor behavior in neutral electrolyte solution (1M KCl(aq)). Mn substitution greatly enhances the specific capacitance of the spinel, giving gravimetric and superficial specific capacitances of ca. 110Fg−1 and ca. 380μFcm−2, respectively for x =0.5 powder. The capacitance enhancement is attributed to the facile charge-transfer characteristic of the Mn ions, as revealed by in situ X-ray absorption near-edge structure analysis. [Copyright &y& Elsevier]

Silver sulfide (Ag 2 S) attached to ZnO nanorods film has been successfully prepared by a two-step hydrothermal process. The prepared photoelectrodes were characterized by Field Emission Scanning Eletron Microscopy (FESEM), Energy Dispersive Spectroscopy (EDS), X-ray diffractometry (XRD), UV-vis spectrophotometry (UV–vis) and photoelectrochemical measurements (PEC). The results revealed that Ag 2 S deposited onto the surface of ZnO nanorods was under the influence of growth temperature. The absorption in the visible region and efficient transfer of photoelectron between Ag 2 S/ZnO/ITO photoelectrode and the redox species in the electrolyte were significantly enhanced under the illumination intensity of 100 mW cm−2. The band gap values of the five different growth temperatures ranging from 50 °C to 90 °C were found to decrease from 2.93 eV to 1.57 eV. Besides, the photoelectrochemical measurements verified that Ag 2 S/ZnO nanocomposite grown at 60 °C exhibited the highest photocurrent density of 3.97 mA/cm2 at 1.0 V. The findings suggested that Ag 2 S/ZnO nanocomposite is an efficient alternative for photoelectrode applications. [ABSTRACT FROM AUTHOR]

Solar energy is an alternative sustainable energy resource that can be harvested using photoelectrochemical cell comprised of inorganic sensitized nanostructured oxide semiconductor electrode. In this work, pulse electrodeposition was used to deposit CdSe onto titanium dioxide nanotube arrays (TiO 2 NTAs). TiO 2 NTAs are commonly used in the nanostructured photoelectrochemical cells due to their high surface area, fewer interfacial grain boundaries and excellent charge transfer between interfaces. Duty cycle of pulse electrodeposition played an important role in the formation of CdSe nanoparticles. A significant enhancement in the photoelectrochemical performance was observed for the heterostructure of CdSe/TiO 2 NTAs. CdSe/TiO 2 NTAs prepared at 50% duty cycle exhibited maximum photocurrent of 1.94 mA cm −2 and photoconversion efficiency of 1.18% which was 59 times higher than bare TiO 2 NTAs. These results demonstrated that significant enhancement in the photoconversion efficiency could be obtained by incorporating CdSe as sensitizer into the TiO 2 nanotube arrays via pulse electrodeposition technique. [ABSTRACT FROM AUTHOR]

High density and vertically aligned zinc oxide nanorod arrays (ZnO NRs) have been prepared directly on indium-doped tin oxide (ITO) substrates via two-steps preparation: sol-gel spin coating and hydrothermal process. The nanostructured ZnO was characterized for its morphology, crystalline structure and optical properties by using field emission scanning electron microscopy (FESEM), X-ray diffractometry, and ultraviolet-visible spectroscopy respectively. In addition, the photoeletrochemical (PEC) properties were investigated through photocurrent measurements. The ZnO NRs/ITO had wurtzite-structured (hexagonal) ZnO and preferred growth along (0001) direction. When the growth time was 4 h, ZnO NRs/ITO showed impressive photoresponse. The PEC analysis verified that the ZnO NRs gave better photocurrent response and photoconversion efficiency with approximately 42 times greater than seed layer. [ABSTRACT FROM AUTHOR]