| Abstract | Velik broj ekoloških problema s kojima se danas susrećemo je posljedica proizvodnje i korištenja tradicionalnih izvora energije. Široka upotreba fosilnih goriva vodi prema energetskoj krizi i jedan je od najvećih uzroka neprekidnom rastu koncentracije CO2 u atmosferi. Fotokatalitička redukcija se, uz primjenu u organskoj sintezi, može koristiti za konverziju CO2 u solarna goriva što istovremeno smanjuje onečišćenje okoliša te daje čisti i obnovljivi izvor energije. Glavni izazov u realizaciji takvog procesa je pronalazak odgovarajućeg fotokatalizatora, a među brojnim materijalima titanijev dioksid je za tu svrhu privukao najviše pažnje. Unatoč brojnim prednostima, njegova učinkovitost za redukciju CO2 nije dovoljna, no uz određene modifikacije njegova redukcijska svojstva mogu biti značajno poboljšana. U ovom je radu, uz čisti TiO2, sol-gel metodom sintetizirano šest njegovih modifikacija dopiranjem bakrovim i natrijevim kationima u različitim koncentracijama, a svi su sintetizirani fotokatalizatori karakterizirani na FTIR-u. Provedena je fotokatalitička redukcija NaHCO3 sa svim sintetiziranim uzorcima. Za vrijeme reakcija, na TOC analizatoru je praćena promjena ukupnog organskog ugljika, a na HPLC-u kvalitativno i kvantitativno je provedena analiza potencijalnih produkata, oksalne, mravlje i octene kiseline. Konačni produkti redukcije analizirani su na FTIR spektrometru. Fotokatalizatori Na(6)-TiO2, Na(6)-Cu(1,5)-TiO2, i Na(12)-Cu(1,5)-TiO2 pokazali su veću konverziju HCO3- u organski ugljik za 60%, 28% odnosno 23% u odnosu na čisti TiO2, fotokatalizator Na(12)-Cu(3)-TiO2 sličnu, a fotokatalizatori Na(6)-Cu(3)-TiO2 i Na(12)-TiO2 slabiju konverziju. Oksalna, mravlja i octena kiselina nisu potvrđene kao produkti redukcije, a kao takvi predloženi su metanal i metanol. Potrebna je daljnja analiza kako bi se otkrili točni uzroci lošijim redukcijskim svojstvima
Na(6)-Cu(3)-TiO2 i Na(12)-TiO2 te potvrdili predloženi redukcijski produkti. |
| Abstract (english) | Many of the environmental problems we face today are caused by production and use of traditional energy sources. The widespread use of fossil fuels is leading to an energy crisis and is one of the biggest causes of the steady increase in CO2 concentrations in the atmosphere. Photocatalytic reduction can be used to convert CO2 into solar fuels, which reduces environmental pollution and at the same time provides a clean and renewable energy source. The main challenge in the realization of such a process is to find a suitable photocatalyst, and of the many materials studied for this purpose, titanium dioxide has attracted the most attention. Despite its many advantages, its efficiency for CO2 reduction is not sufficient, but with certain modifications its reduction properties can be significantly improved. In this work, in addition to pure TiO2, six modifications were synthesized by the
sol-gel method by doping copper and sodium cations in different concentrations, and all synthesized photocatalysts were characterized on FTIR. Photocatalytic reduction of NaHCO3 was performed with all of the synthesized samples. During the reaction, the change in total organic carbon was monitored on a TOC analyzer, and the analysis of potential products, oxalic, formic and acetic acid, was performed qualitatively and quantitatively on HPLC. The final reduction products were analyzed on an FTIR spectrometer. Photocatalysts Na(6)-TiO2, Na(6)-Cu (1,5 -TiO2, and Na(12)-Cu (1,5)-TiO2 showed a higher conversion of HCO3- to organic carbon by 60%, 28 % and 23%, respectively, relative to pure TiO2. Photocatalyst Na(12)-Cu(3)-TiO2 showed similar, and the photocatalysts Na(6)-Cu(3)-TiO2 and
Na(12)-TiO2 weaker conversion. Oxalic, formic and acetic acid have not been confirmed as reduction products, and methanal and methanol have been proposed as such. Further analysis is needed to discover the exact causes of the poorer reducing properties of
Na(6)-Cu(3)-TiO2 and Na(12)-TiO2 and also to confirm the proposed reduction products. |
