Photoelectrolytic oxidation of organic species at mesoporous tungsten trioxide film electrodes under visible light illumination

Operation of a photoelectrolyser fitted with a semitransparent semiconducting WO3 film photoanode is described. Due to its band-gap energy of 2.5eV, the photoresponse of the WO3 electrode extends into the blue part of the visible spectrum up to 500nm. The WO3 photoanode exhibits particularly high incident photon-to-current efficiencies for the oxidation of several organic species with the maximum occurring at ca. 400nm. Experiments conducted under simulated AM 1.5 solar illumination demonstrated efficient photodegradation of a variety of organic chemicals including small organic molecules as well as EDTA and anthraquinonic Acid Blue 80 dye. Although, due to the inherent mass transport limitations, the described device appears best suited to the treatment of industrial wastewater containing from 100ppm to few gL−1 of impurities, almost complete removal of organic carbon was observed in several photoelectrolysis runs. This is apparently associated with the concomitant photooxidation of sulphate-based supporting electrolyte resulting in the formation of a powerful chemical oxidant-persulphat

Synthesis of Novel Double-Layer Nanostructures of SiC–WOxby a Two Step Thermal Evaporation Process

A novel double-layer nanostructure of silicon carbide and tungsten oxide is synthesized by a two-step thermal evaporation process using NiO as the catalyst. First, SiC nanowires are grown on Si substrate and then high density W18O49nanorods are grown on these SiC nanowires to form a double-layer nanostructure. XRD and TEM analysis revealed that the synthesized nanostructures are well crystalline. The growth of W18O49nanorods on SiC nanowires is explained on the basis of vapor–solid (VS) mechanism. The reasonably better turn-on field (5.4 V/μm) measured from the field emission measurements suggest that the synthesized nanostructures could be used as potential field emitters

Analysis of Bonding between Conjugated Organic Molecules and Noble Metal Surfaces Using Orbital Overlap Populations

The electronic structure of metal−organic interfaces is of paramount importance for the properties of organic electronic and single-molecule devices. Here, we use so-called orbital overlap populations derived from slab-type band-structure calculations to analyze the covalent contribution to the bonding between an adsorbate layer and a metal. Using two prototypical molecules, the strong acceptor 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ) on Ag(111) and the strong donor 1H,1′H-[4,4′]bipyridinylidene (HV0) on Au(111), we present overlap populations as particularly versatile tools for describing the metal−organic interaction. Going beyond traditional approaches, in which overlap populations are represented in an atomic orbital basis, we also explore the use of a molecular orbital basis to gain significant additional insight. On the basis of the derived quantities, it is possible to identify the parts of the molecules responsible for the bonding and to analyze which of the molecular orbitals and metal bands most strongly contribute to the interaction and where on the energy scale they interact in bonding or antibonding fashion

Eumelanin electrodes in buffered aqueous media at different pH values

Eumelanin, a quinone-based biomacromolecule, is the most common form of the biopigment melanin in the human body. Eumelanin has attracted great interest due to its physicochemical properties, such as metal-ion chelation, free radical scavenging, hydration-dependent (photo) electrical response and redox activity. Investigating the electron transfer properties of eumelanin is key to exploiting the electrochemical energy storage properties of the pigment. In this work, we investigated the redox behavior of chemically controlled eumelanin in NaCH3COO buffer solutions, at different pH values. For our study we used cyclic voltammetry, electrochemical impedance spectroscopy, and galvanostatic charge and discharge. Eumelanin, in combination with aqueous electrolytes, provides an attractive case study for eco-designed storage devices based on abundant and environmentally benign materials and interfaces

Light-enhanced Electrochemical Energy Storage of Synthetic Melanin on Conductive Glass Substrates

Eumelanin is a redox active, quinone-based biopigment, featuring a broad band absorption in the UV-Vis region. The combination of the redox and optical properties makes eumelanin an interesting candidate to explore light-assisted storage technologies. Electrodes of melanin on indium tin oxide (ITO) current collectors were investigated for their morphological and voltammetric characteristics in aqueous electrolytes. Under solar light, we observed that the capacity and the capacitance of the melanin electrodes significantly increase with respect to the dark conditions (by 63% and 73%, respectively)

Biosourced quinones for high-performance environmentally benign electrochemical capacitors via interface engineering

Biosourced and biodegradable organic electrode materials respond to the need for sustainable storage of renewable energy. Here, we report on electrochemical capacitors based on electrodes made up of quinones, such as Sepia melanin and catechin/tannic acid (Ctn/TA), solution-deposited on carbon paper engineered to create high-performance interfaces. Sepia melanin and Ctn/TA on TCP electrodes exhibit a capacitance as high as 1355 mF cm(-2) (452 F g(-1)) and 898 mF cm(-2) (300 F g(-1)), respectively. Sepia melanin and Ctn/TA symmetric electrochemical capacitors operating in aqueous electrolytes exhibit up to 100% capacitance retention and 100% coulombic efficiency over 50,000 and 10,000 cycles at 150 mA cm(-2) (10 A g(-1)), respectively. Maximum power densities as high as 1274 mW cm(-2) (46 kW kg(-1)) and 727 mW cm(-2) (26 kW kg(-1)) with maximum energy densities of 0.56 mWh cm(-2) (20 Wh kg(-1)) and 0.65 mWh cm(-2) (23 Wh kg(-1)) are obtained for Sepia melanin and Ctn/TA.Biosourced and biodegradable organic electrode materials are investigated for environmentally benign energy storage, but their performance at higher current density is often poor. Here, the authors construct electrodes with quinone-based species from Sepia melanin and tannins on treated carbon paper and observe electrode capacitance as high as 1355 mF cm(-2) at current densities up to 10 A g(-1)