Graphene oxide (GO) is useful and promising material for graphene based applications in electronic, optics, chemistry, energy storage and biology. At the beginning of graphene history GO was only a simple and cheap step for preparation of single and multilayer graphene films and bulk structures by reduction. The further studies revealed the substantial structure imperfection of graphene oxide derived materials due to the defects in initial graphite and incompletion of reducing process. However, the results of recent research demonstrated a great amount of unique chemical, optical and electronic properties of graphene oxide that allow regarding it as independent nanomaterial possessing a large area of applications. In general, it represents the ultra-large organic molecule containing 2D carbon mesh. Unlike conventional graphene it provides wide range of chemical methods for attachment of various functional groups to its surface for control optical transparency, electrical and thermal conductance. Recently developed methods for preparation of graphene oxide derivatives saturated by carboxyl groups open the new attractive application areas in green technologies including energy storage and utilizing nuclear wastes. The goal of the review is to summarize the results of recent studies of graphene oxide, derivatives and reveal the most promising directions to focus the efforts of researchers.

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Graphene Oxide and Derivatives: The Place in Graphene Family

Progress of reduction of graphene oxide by ascorbic acid

This highlight article focuses on the rapidly emerging area of electrocatalytic metal–organic frameworks (MOFs) with a particular emphasis on those systems displaying intrinsic activity. Three electrocatalytic conversion processes are discussed, including CO2 reduction, the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER), as well as a selection of other relevant examples. The scope of our discussion encompasses aspects of MOF structure that are key to their function, performance characteristics such as stability and selectivity, together with methods for interfacing MOFs with surfaces. Key challenges that have emerged are highlighted in addition to opportunities that are relevant to the field in the design of more stable, selective and robust electrocatalysts for a range of industrial processes.

Perspectives on metal–organic frameworks with intrinsic electrocatalytic activity

Structural, optical, morphological and thermal properties of TiO2–Al and TiO2–Al2O3 composite powders by ball milling

Pt-Ni/rGO counter electrode: electrocatalytic activity for dye-sensitized solar cell

Solar energy is belong to a renewable source of energy that is sustainable, widely available and totally inexhaustible, unlike fossil fuels whose resources are being depleted. It is also a non-polluting source of energy and it does not emit any greenhouse gases during electricity producing [1-3]. The increasing demand for renewable energy due to recent issues like global warming, drastic climatic changes and the largely unexploited potential of the sun as an energy source made it as increasingly important, especially the solar energy conversion technology. Rapid progress in modern industries, including photovoltaics, depended mostly on the capabilities of materials forming and surface engineering [3-11]. A photovoltaic cell converts the energy from light directly into electricity by the photovoltaic effect. Solar cells are generally made from silicon or other semiconductors. When light quantum is absorbed, charge carriers may be generated by photons of energy greater then material band gap. Electrons struck by such photons break their covalent bonds in atoms, leave their positions and electron-hole pairs are generated. In the electric field of junction free electrons in the conduction band migrates toward the front surface and holes to the back surface. Electric current can flow through an external load when connected to cell’s front and back contacts [1, 2, 4-7]. Dye-sensitized solar cells DSSC are an attractive alternative to conventional crystalline silicon solar cells because of its low-cost, relatively high photon-to-current conversion efficiency for low energy consumption and simple fabrication process [12]. The overall efficiency of ~12% [13] placed dyesensitized solar cells as potential inexpensive alternatives to solid state devices. DSSCs are easy to manufacture using well known printing techniques. Moreover, dye-sensitized solar cells can be semi-transparent and semi-flexible, allowing a range of uses that are not applicable to the commonly known silicon-based photovoltaic wafer systems [2, 14]. The working principle of a DSSC (Fig. 1) substantially differs from that of a conventional solar cell based on silicon. Dye-sensitized solar cell are composed of: a nanostructured semiconductor (typically TiO2), a dye to absorb visible light (mostly ruthenium complex), an electrolyte (e.g. containing I-/ I3 redox ions), which forms the interface with the semiconductor and a counter electrode leading an electrocatalyst, which helps the transfer of electrons to the liquid electrolyte [14-22].

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Carbon Nanotubes Counter Electrode for Dye-Sensitized Solar Cells Application

Influence of laser texturization surface and atomic layer deposition on optical properties of polycrystalline silicon

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Nanocrystalline TiO2 Powder Prepared by Sol-Gel Method for Dye-Sensitized Solar Cells

The paper presents the results of the structure investigation of a counter electrode in dye-sensitized solar cells using the carbon nanomaterials. Solar cells were fabricated on the glass with transparent conductive oxide TCO (10Ω/sq). Nanocrystalline titania based photoanode was prepared by spreading TiO2 paste onto TCO glass and subsequently annealed at 450°C for at least 30 min to convert anatase phase and make an interparticle network. After then the nanostructured titania films was immersed into an ethanolic solution of the ruthenium-based dye. As a counter electrodes of dye-sensitized solar cells composite films of carbon nanomaterials and polystyrene sulfonate doped poly (3,4-ethylenedioxythiophene) PEDOT-PSS (Sigma-Aldrich) were deposited onto TCO substrates. Because carbon nanoelements and titanium oxide consist of nano-metric structural units to determine the properties of the cells and their parameters several surface sensitive techniques and methods, i.e. Raman spectroscopy, Scanning Electron Microscopy (SEM), High-Resolution Transmission Electron Microscopy (HRTEM), and electric properties of conductive layers were used.

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M. Prokopiuk vel Prokopowicz

Papers

Carbon Nanotubes Counter Electrode for Dye-Sensitized Solar Cells Application

Influence of laser texturization surface and atomic layer deposition on optical properties of polycrystalline silicon

Nanocrystalline TiO2 Powder Prepared by Sol-Gel Method for Dye-Sensitized Solar Cells

Carbon Nanomaterials Application as a Counter Electrode for Dye-Sensitized Solar Cells

Graphene oxide film as semi-transparent counter electrode for dye-sensitized solar cell