ZnO nanostructured photocatalysts for water treatment applications : diploma thesis

Poluvodički materijali metalnih oksida, dizajnirani za primjenu u fotokatalitičkim sustavima za pročišćavanje vode, moraju imati veliku specifičnu površinu jer se kemijske reakcije inducirane odgovarajućim zračenjem odvijaju na sučelju površine i tekućine. Cinkov oksid poznat je po mnoštvu morfologija na mikro- i nanoskali, koje lako mogu ispuniti ovaj zahtjev pod utjecajem ultraljubičastog zračenja. Neke morfologije na nanoskali čine cinkov oksid funkcionalnim fotokatalizatorom i na suncu. Fotokatalitička degradacija organske boje, kao modelnog onečišćivala, proučavana je u vodenim otopinama korištenjem struktura cinkovog oksida sintetiziranih u obliku prizmi, štapova i vlati (žica). Rasle su iz otopine, a njihova je cjelovita morfologija kontrolirana uvjetima rasta. Njihova morfologija na mikro- i nanoskalidetaljno je karakterizirana pomoću skenirajuće elektronske mikroskopije te difrakcijei raspršenja X-zraka. Sve strukture pokazale su značajnu fotokatalitičku aktivnost. Međutim, izuzetni rezultati postignuti su s nanostrukturama u obliku vlati, koje su pokazale pojačanu fotokatalitičku aktivnost na sunčevom svjetlu. To je pripisano njihovoj specifičnoj morfologiji s defektima i visokim stupnjem mezoporoznosti.Metal oxide semiconductor materials, designed to be applied in photocatalytic systems for water purification, are required to have large specific surface areas, because chemical reactions induced by suitable irradiation take place by contact between their surface and fluid. Zinc oxide is well known as a material that forms various morphologies at the micro- and nanoscale, which can easily fulfill this requirement in the case of ultraviolet irradiation. However, some nanoscaled morphologies can also provide zinc oxide catalysts that are functional in the sunlight. Photocatalytic degradation of an organic dye, as a model pollutant, was studied in aqueous solutions using structures of zinc oxide synthesized in the form of prism, spiky stick and grass blade. They were grown from a solution and their entire morphology was simply controlled by varying the growth conditions. Detailed characterization of their morphology on the micro- and nanoscale was performed by scanning electron microscopy and X-ray diffraction and scattering measurements. All structures exhibited notable photocatalytic activity. However, remarkable results were achieved with nanostructures in the form of grass blade, which exhibited enhanced photocatalytic activity in sunlike light. This was ascribed to their specific morphology characterized with defects and a high degree of mesoporosity