The inhibitory effect of graphene oxide on photocatalytic hydrogenation from organic fatty acids

Wen Zhang, Yang Li, Changqing Liu, Taha Marhaba

Research output: Contribution to journalArticlepeer-review

1 Scopus citations

Abstract

Two catalysts, carbon doped TiO 2 (C-TiO 2 ) and C-TiO 2 conjugated with reduced graphene oxide (rGO)–C-TiO 2 /rGO were synthesized and compared with respect to the photocatalytic hydrogen (H 2 ) production using three organic fatty acids (OFAs) as electron donors under visible light irradiation. Our results show that the hybridization between C-TiO 2 and rGO did not subtaintially improve the production of H 2 but instead elicited inhibitory effects compared to C-TiO 2 . For instance, the specific H 2 production on C-TiO 2 was 214 and 336 μmol·h −1 ·g −1 for acetic and propionic acids, respectively, whereas C-TiO 2 /rGO only achieved 155 and 161 μmol·h −1 ·g −1 , respectively. With butyric and lactic acids as electron donors, C-TiO 2 and C-TiO 2 /rGO led to almost the same H 2 production rates (233 and 155 μmol·h −1 ·g −1 , respectively). The inhibitory effect of rGO on photocatalytic activity could be due to the potential deposition of OFAs on graphene sheets that may reduce the mobility and accessibility of OFAs toward catalytic reactions with C-TiO 2 . The electron spin resonance spectrometry (ESR) tests revealed that O - 2 and CH 3 • were the major radicals responsible for OFA degradation. Moreover, the produced concentration of CH 3 • was consistently higher in C-TiO 2 suspension than that in C-TiO 2 /rGO suspension. The estimated aqueous/solid mass transfer rate constant (s −1 ) was lower on the catalyst surface of C-TiO 2 /rGO than C-TiO 2 . Consequently, the decoration of rGO sheets on C-TiO 2 may not always promote photocatalytic H 2 production especially when using OFAs as electron donors. The results demonstrated hereby aim to provide new evidence on potential drawbacks of graphene-based photocatalysis.

Original languageEnglish (US)
Pages (from-to)410-416
Number of pages7
JournalEnvironmental Progress and Sustainable Energy
Volume38
Issue number2
DOIs
StatePublished - Mar 1 2019

All Science Journal Classification (ASJC) codes

  • Environmental Engineering
  • Environmental Chemistry
  • Chemical Engineering(all)
  • Renewable Energy, Sustainability and the Environment
  • Water Science and Technology
  • Waste Management and Disposal
  • Environmental Science(all)

Keywords

  • acetic acid
  • hydrogen production
  • hydroxyl radicals
  • materials science
  • photocatalysis

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