Fotokatalytická redukce oxidu uhličitého v přítomnosti fotokatalyzátorů na bázi CdS/g-C3N4

Abstract

This thesis is focused on photocatalytic reduction of carbon dioxide in the presence of CdS and g-C3N4 photocatalysts and CdS/g-C3N4 nanocomposites. The purpose of this thesis is using prepared photocatalysts to convert the most important greenhouse gas, carbon dioxide, into energy-efficient compounds. Pure CdS and g-C3N4 photocatalysts and CdS/g-C3N4 nanocomposites (1-CdS/CN, 2-CdS/CN, 3-CdS/CN, 4-CdS/CN) were prepared. The prepared photocatalysts were characterized by X-ray diffraction analysis, UV-Vis diffraction spectrometry, X-ray photoelectron spectroscopy and transmission electron microscopy. The photocatalytic reduction of carbon dioxide was carried out in a batch stirred photoreactor in the presence of suspended photocatalysts. The radiation source was an 8W Hg lamp providing radiation with a wavelength of 254 nm, which was placed above the quartz glass window in the reactor cover. The photocatalytic reduction of CO2 was studied in the time interval of 0-8 hours. The main gaseous products of the photocatalytic reduction of carbon dioxide were methane and carbon monoxide. Hydrogen, which is formed during the photocatalytic water splitting, has also been observed. Experimental results showed that photocatalysts with CdS/g-C3N4 heterojunction have significantly higher photocatalytic activity than pure g-C3N4 or CdS photocatalysts. The highest yields of methane and hydrogen were obtained in the presence of 1-CdS/CN photocatalyst. By correlating the photocatalytic activity and physicochemical characteristics of the prepared photocatalysts, it was found that the key parameter influencing the photocatalytic reduction of carbon dioxide is the formation of a heterojunction in CdS/g-C3N4 nanocomposites. The formation of a heterojunction in CdS/g-C3N4 photocatalysts enabled better separation of generated electrons and holes, which had positive effect on the formation of the monitored products.