The magnetron sputtering technique is the one which is the least cost-intensive of the vacuum-based ones. Most of the research on ZnO materials done by sputtering concerns transparent conductive ZnO-based films . In this technique, a substrate is positioned close to the deposition source, where it catches the arriving particles and enables them to coalesce into a layer. Because the procedure takes place in a vacuum deposition chamber, the particles can move about freely. The coatings produced this way are in most cases textured along the substrate-source line of sight, and are not conforming because the particles have a tendency to travel in straight lines. Magnetron sputtering can be used to deposit metals, alloys, and composites on a variety of materials with thickness in the nanometer and micrometer range. Compared to other vacuum coating processes, it has a number of significant advantages shown in figure . These properties have led to the development of many commercial applications, from the production of microelectronics to simple decorative coatings. Several years ago, our group showed it was surprisingly possible to obtain ZnO nanostructures through magnetron sputtering with post-deposition annealing which opened the way for uniform nano-structural ZnO coatings on large surfaces. Their applicability in surface reaction-based applications will be shown here as electrodes for photocatalytic water purifying. Although ZnO can decompose in strongly basic or acidic environments, its low toxicity and availability makes is one of the materials of choice for photocatalysis. The advantage of our fabrication method is that the material grows in the form of a meso-porous structure which enables unrestricted medium flow to the ZnO nano-crystals, as is opposite to the solution-processed material where the spherical nanocrystallites aggregate, reducing their available surface and thus the photocatalytic activity. This also means that less material is required to achieve the same efficiency. Finally, no wet chemical processing means that no ligands are covering the surface of the nanostructures, make them more available for any surface-bound reactions, such as the ones in photocatalysis. In photocatalysis, the electronic properties of the material play a significant role. ZnO is generally an n-type semiconductor with the presence of defects such as oxygen vacancies (V O ), interstitial zinc ions and zinc vacancies (V Zn ), which affect its optical and electrical properties. In particular, the V O act as donors in ZnO , providing additional free electrons to the system, while the V Zn act as acceptors, quenching the conductivity. We will discuss the influence of the defects observed in the material on the photocatalytic efficiency in further parts of the text. A simplified diagram of the heterogeneous oxidation steps in the photocatalytic reaction proceeding with ZnO NPs are shown in figure . The stages of the entire process can be described as follows: (1) diffusion of organic impurities from the liquid phase onto the ZnO sur-face; (2) adsorption of organic impurities on the ZnO surface;