Preparation of Cu2O/rGO for photocatalytic reduction of CO2

  • 呂 俊昇

Student thesis: Master's Thesis

Abstract

In the past decades the global warming which causes the serous global climate change problem and ocean acidification tends to be more and more severe with increasing of greenhouse gases such as methane nitrous oxide and especially carbon dioxide A global agreement to reduce greenhouse gases has been reached on the COP21 in Paris in December 2015 Hence reduction of CO2 emission is a big and global issue In order to reduce CO2 emission there are two main technologies developed; one is carbon capture and storage and the other is CO2 conversion There is a problem for carbon capture and storage i e very limited sites for CO2 storage in the world CO2 conversion has a potential to reduce CO2 to hydrocarbon However the extra energy is required for reduction of CO2 because of a positive ΔG value Therefore CO2 conversion by using photocatalytic reactions via solar energy is one of potential and eco-friendly attractive technology Cuprous oxide (Cu2O) a p-type semiconductor with a narrow band gap (2 0-2 2 eV) is low cost nontoxicity and environmental friendliness It is suitable to be used as photocatalysts in the photoreduction of CO2 but the rate of electron-hole pairs recombination is high due to the narrow band gap Therefore the incorporation of graphene onto Cu2O may reduce the rate of electron-hole recombination and enhance the performance of photocatalysts In this study Cu2O was chosen to photocatalytic reduction of CO2 under visible light (λ>420) Different amounts of reduced graphene oxide (rGO) were decorated onto Cu2O to enhance the photocatalytic activity After visible irradiation for 20 hours CO2 can be converted into methanol by Cu2O and Cu2O/x%rGO (x = 1 5 10) The yields of methanol are 9 76 47 91 335 26 and 12 41 μmole/g-cat observed for Cu2O Cu2O/1%rGO Cu2O/5%rGO and Cu2O/10%rGO composites respectively Among all the prepared samples Cu2O/5%rGO has the superior activity of CO2 photoreduction because the proper amounts of incorporated rGO could decrease electron-hole recombination and avoid block of light to reach surface of Cu2O nanocrystals The effect of facets on photocatalytic activity of photocatalysts were also studied The yields of methanol are 4 35 26 81 and 355 26 μmole/g-cat after 20 hours under visible irradiation which corresponding to cubic Cu2O/5%rGO nanocrystals with (100) facets octahedral Cu2O/5%rGO nanocrystals with (111) facets and rhombic dodecahedra Cu2O/5%rGO nanocrystals with (110) facets respectively The rhombic dodecahedra Cu2O/5%rGO shows surpassing photocatalytic performance due to the positive charged (110) surface of particles Moreover different oxidation states of copper decorated with rGO were discussed in this study
Date of Award2017 Aug 30
Original languageEnglish
SupervisorShou-Heng Liu (Supervisor)

Cite this

Preparation of Cu2O/rGO for photocatalytic reduction of CO2
俊昇, 呂. (Author). 2017 Aug 30

Student thesis: Master's Thesis