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Author: search.filters.author.Seeharaj, PanpailinSubject: search.filters.subject.CO2 photoconversion

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    CeO2/CuO/TiO2heterojunction photocatalysts for conversion of CO2to ethanol
    (2021-09-10)
    Seeharaj, Panpailin
    ;
    Vittayakorn, Naratip
    ;
    Morris, John
    ;
    Kim-Lohsoontorn, Pattaraporn
    An attempt to reduce CO2 emissions has led to the development of CeO2/CuO/TiO2 heterojunction photocatalysts for photoconversion of CO2 to useful products, e.g. ethanol. Composite photocatalysts were simply prepared by mixing TiO2 (P25) with different mass ratios of CeO2 (1 wt%) and CuO (2 or 3 wt%) by ball milling. The prepared photocatalysts had uniformly distributed CeO2 and CuO phases, throughout the TiO2 phase. The integration of CeO2 and CuO into TiO2 at 1 wt% CeO2 and 3 wt% CuO produced a composite, with a reduced band gap of 2.88 eV, allowing absorption of lower energy light and a lower electron-hole recombination rate. The 1%CeO2/3%CuO/TiO2 photocatalysts yielded ethanol at 30.5 μmol gcat-1 h-1, almost three times higher than the yield from pure TiO2. This improved CO2 conversion efficiency was due to contributions from properties of both additives: CeO2 increased light absorption, while CuO acted as an electron trap and enhanced CO2 adsorption. In addition, the heterojunction at the interfaces facilitated the photogenerated charge separation, which, in turn, increased the charge participation in the catalyzed conversion reactions.
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    Ultrasonically-assisted surface modified TiO2/rGO/CeO2 heterojunction photocatalysts for conversion of CO2 to methanol and ethanol
    (2019-11-01)
    Seeharaj, Panpailin
    ;
    Kongmun, Panyata
    ;
    Paiplod, Piyalak
    ;
    Prakobmit, Saowanee
    ;
    Sriwong, Chaval
    Converting CO<inf>2</inf> to usable fuel may contribute to lowering of global warming, thus this study developed effective heterojunction photocatalysts for the photoreduction of CO<inf>2</inf> with water into methanol and ethanol fuels. The photocatalysts were prepared from combining surface modified titanium dioxide (TiO<inf>2</inf>) nanoparticles with reduced graphene oxide (rGO) and cerium oxide (CeO<inf>2</inf>). The TiO<inf>2</inf> surfaces were firstly modified via the sono-assisted exfoliation, with high intensity ultrasonic waves (ultrasonic horn, 20 kHz, 150 W/cm<sup>2</sup>) in 10 M NaOH for 1 h. Highly reactive nanosheets delaminated from outer surfaces of the primary TiO<inf>2</inf> crystals leading to an increase in specific surface active area, light absorption and decrease in electron-hole recombination rate, which enhanced photocatalytic activity. Then, 0.75 wt% rGO and 1 wt% CeO<inf>2</inf> were incorporated into the surface modified TiO<inf>2</inf> to promote photogenerated charge separation, electron mobility and CO<inf>2</inf> absorptivity. The modified TiO<inf>2</inf>/rGO/CeO<inf>2</inf> photocatalysts exhibited superior photocatalytic performance by producing methanol at 641 μmol/g<inf>cat</inf>h and ethanol at 271 μmol/g<inf>cat</inf>h, almost 7 times higher than rates from pure TiO<inf>2</inf>. The significant improvement in CO<inf>2</inf> photoconversion activity was mainly attributed to the high interfacial contact area and strong connection between the reactive delaminated TiO<inf>2</inf> nanosheets, rGO and CeO<inf>2</inf>, which, in turn, facilitated the flow of large number of photogenerated charge carriers to react with the absorbed species, and the multi-step charge transportation due to the heterojunction effect that effectively retarded electron-hole recombination.