###### Abstract  
Graphene, graphene oxide, reduced graphene oxide and their composites with various compounds/materials have high potential for substantial impact as cheap photocatalysts, which is essential to meet the demands of global activity, offering the advantage of utilizing \"green\" solar energy. Accordingly, graphene-based materials might help to reduce reliance on fossil fuel supplies and facile remediation routes to achieve clean environment and pure water. This review presents recent developments of graphene-based semiconductor photocatalysts, including novel composites with faceted particles, photonic crystals, and nanotubes/nanowires, where the enhancement of activity mechanism is associated with a synergistic effect resulting from the presence of graphene structure. Moreover, antimicrobial potential (highly needed these days), and facile recovery/reuse of photocatalysts by magnetic field have been addresses as very important issue for future commercialization. It is believed that graphene materials should be available soon in the market, especially because of constantly decreasing prices of graphene, vis response, excellent charge transfer ability, and thus high and broad photocatalytic activity against both organic pollutants and microorganisms. graphene; heterogeneous photocatalysis; antimicrobial properties; photonic crystals; magnetic particles; vis response; catalyst recovery; environmental purification; composite photocatalysts address +
Footnote †: journal: Applied Sciences  
electrodes, optoelectronics, quantum dots), light processing, energy conversion (fuel and solar cells), energy storage (supercapacitor, batteries), sensors, environmental purification (filter, adsorbent), plasmonics, catalysis, and photocatalysis. Recently, the research on photocatalysis has been highly exploring due to the possibility to use \"green energy\" (the sun) to drive many photochemical reactions, e.g., water splitting, photocurrent generation, water and air purification, wastewater treatment, disinfections, self-cleaning and synthesis of organic compounds. Among various semiconductor photocatalysts, titania (titanium(IV) oxide, TiO\({}_{2}\)) is probably the most widely investigated due to high activity, stability, abundance, and low toxicity [1,2], but its application is limited due to charge carriers' recombination and inability of visible light (vis) absorption. In this regard, titania has been modified with different elements and species, including doping, surface modification and coupling [3]. Accordingly, G/GO/rGO has also been proposed for surface modification of titania (and other wide-bandgap semiconductors), due to large specific surface area (efficient reagents adsorption), high conductivity (inhibited charge carriers' recombination), flexible structure and high stability [4, 5, 6]. For example, hydrothermally prepared composites have shown to be quite efficient for photocatalytic decomposition of organic compounds, e.g., bisphenol A under both UV and vis irradiation (TiO\({}_{2}\)-rGO) [7], 4-chlorophenol under solar radiation (TiO\({}_{2}\)-G) [8], and buttene in the gas phase (TiO\({}_{2}\)-GO) [9]. TiO\({}_{2}\)-rGO, synthesized by ionothermal [10] method and laser synthesis [11], is able to generate hydrogen under UV irradiation, indicating that graphene might work as co-catalyst on titania surface similar to well-known noble metals for hydrogen evolution. ZnO-G, synthesized by combined method of Hummers, Offeman and hydrothermal treatment, is efficient for degradation of cyanide in water under UV, vis, solar and even NIR irradiation due to plasmonic properties of graphene [12]. Moreover, CO\({}_{2}\) fixation and conversion into CH\({}_{3}\)OH under vis irradiation is possible on \(\alpha\)-Fe\({}_{2}\)O\({}_{3}\)-ZnO/rGO, prepared by the Hummer/redox replacement/electrochemical process [13].