Ultrasonically-assisted surface modified TiO2/rGO/CeO2 heterojunction photocatalysts for conversion of CO2 to methanol and ethanol

Panpailin Seeharaj; Panyata Kongmun; Piyalak Paiplod; Saowanee Prakobmit; Chaval Sriwong; Pattaraporn Kim-Lohsoontorn; Naratip Vittayakorn

doi:10.1016/j.ultsonch.2019.104657

Ultrasonically-assisted surface modified TiO₂/rGO/CeO₂ heterojunction photocatalysts for conversion of CO₂ to methanol and ethanol

Ultrason Sonochem. 2019 Nov:58:104657. doi: 10.1016/j.ultsonch.2019.104657. Epub 2019 Jun 22.

Authors

Panpailin Seeharaj¹, Panyata Kongmun², Piyalak Paiplod², Saowanee Prakobmit², Chaval Sriwong², Pattaraporn Kim-Lohsoontorn³, Naratip Vittayakorn²

Affiliations

¹ Advanced Materials Research Unit, Department of Chemistry, Faculty of Science, King Mongkut's Institute of Technology Ladkrabang, 10520 Ladkrabang, Bangkok, Thailand. Electronic address: panpailin.se@kmitl.ac.th.
² Advanced Materials Research Unit, Department of Chemistry, Faculty of Science, King Mongkut's Institute of Technology Ladkrabang, 10520 Ladkrabang, Bangkok, Thailand.
³ Center of Excellence on Catalysis and Catalytic Reaction Engineering, Department of Chemical Engineering, Faculty of Engineering, Chulalongkorn University, 10330 Pathumwan, Bangkok, Thailand.

PMID: 31450324
DOI: 10.1016/j.ultsonch.2019.104657

Abstract

Converting CO₂ to usable fuel may contribute to lowering of global warming, thus this study developed effective heterojunction photocatalysts for the photoreduction of CO₂ with water into methanol and ethanol fuels. The photocatalysts were prepared from combining surface modified titanium dioxide (TiO₂) nanoparticles with reduced graphene oxide (rGO) and cerium oxide (CeO₂). The TiO₂ surfaces were firstly modified via the sono-assisted exfoliation, with high intensity ultrasonic waves (ultrasonic horn, 20 kHz, 150 W/cm²) in 10 M NaOH for 1 h. Highly reactive nanosheets delaminated from outer surfaces of the primary TiO₂ 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% CeO₂ were incorporated into the surface modified TiO₂ to promote photogenerated charge separation, electron mobility and CO₂ absorptivity. The modified TiO₂/rGO/CeO₂ photocatalysts exhibited superior photocatalytic performance by producing methanol at 641 μmol/g_cath and ethanol at 271 μmol/g_cath, almost 7 times higher than rates from pure TiO₂. The significant improvement in CO₂ photoconversion activity was mainly attributed to the high interfacial contact area and strong connection between the reactive delaminated TiO₂ nanosheets, rGO and CeO₂, 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.

Keywords: CO(2) photoconversion; Photocatalyst; Sono-assisted exfoliation; Titanium dioxide.