Due to their tunable multifunctional properties zinc oxide (ZnO) based materials have attracted extensive scientific and technological attention. Since they combine different properties such as electrochemical activities, chemical and photochemical stability, nontoxicity, biocompatibility, etc. ZnO-based materials have been used in electronics, optoelectronics, biosensing, bioimaging, drug and gene delivery, implants, antimicrobial and anticancer agents. Successful application of ZnO as photoelectrocatalysts arises from its wide band gap (3.37 eV) which can be easily adjusted by different approaches such as: metal and non-metal ion doping, hydrogenation, introducing of crystalline defects, modifying particle morphology and surface chemistry. During the years, to synthesize zinc oxide (ZnO) nanoparticles with improved visible light absorption we have used a fast and environmentally-friendly microwave processing of a precipitate which enable formation of crystalline defects. To further enhance photo(electro)catalytic properties we have employed approaches such as: (1) the incorporation of iron ions into the crystal structure (Zn1-xFexO), (2) sensitization of the particles’ surface with cetyltrimethylammonium bromide, Pluronic F127 and polyethylene oxide, and (3) composites with ruthenium oxide (ZnO/RuO2) and graphene oxide (ZnO/GO and ZnO/rGO). To correlate structural and functional properties, prepared materials were characterized using XRD, FTIR, Raman, UV-Vis DRS, and PL spectroscopy, also FESEM; photocatalytic activity of the samples were tested toward decolorization of methylene blue, while their photoelectrochemical activity for water splitting were tested through linear sweep voltammetry in different electrolytes
