Effect of doping, coating and electrolytic environment on the photocatalytic and photoelectrochemical activity of metal oxide semiconducting materials

Student thesis: Doc typesDoctor of Sciences

Abstract

Photocatalytic/photoelectrochemical water splitting under solar light irradiation is considered as a prospective technology to support the sustainable and renewable H2 economy. Extensive efforts have been devoted to the conversion of solar energy into H2 production by PC/PEC water splitting. However, the process of PC/PEC for H2 production is still with low efficiency. The design and optimization of both photocatalyst materials and PC/PEC systems to achieve high efficiency and stability for H2 production under solar light are urgently in need but full of challenge. TiO2 based photocatalysts with high chemical stability and excellent photocatalytic properties have great potential for solar-to-H2 conversion. To conquer the challenges of the large band gap and rapid recombination of photogenerated electron-hole pairs in TiO2, non-metal doping method emerges to be economic, facile and effective on boosting the visible light activity. In this thesis, we firstly synthesized the carbon doped and coated TiO2 by the “one pot” hydrolysis of TiCl4 in glucose solution approach. The synergistic effect of carbon doping and coating of TiO2 to significantly boost textural, optical and electronic properties and photocurrent of TiO2 for high performance visible light H2 production from water splitting has been comprehensively investigated. Carbon doping can significantly inhibit the phase transformation of the Titania material from anatase to rutile, thus increasing its thermal stability while carbon coating can suppress the grain aggregation of TiO2. The synergy of carbon doping and coating however, not only ensures an enhanced narrowing effect of the electronic band gap of TiO2 thus extending the absorbance to the visible or even near-infrared (NIR) regions, but also promotes dramatically the separation of electron-hole pairs. Owing to these synergistic effects, the carbon coated and doped TiO2 shows much superior photocatalytic activity for both degradation of organics and PC/PEC water splitting under solar light illumination. Secondly, the carbon composed TinO2n-1 (2 ≤ n ≤ 9) were obtained in the process of carbon coating and doping TiO2 at high temperature. The influence factors, formation mechanism of the growth of TinO2n-1 and the followed performance of PEC water splitting were further investigated. Except studies on the effects of photocatalysts or photoanode materials on photocatalytic activity, the studies on how electrolytic species in PEC system especially additives such as sacrificial reagents (SRs) and electrolyte cations/anions affect the photocatalytic activity of different photocatalysts including TiO2 are also carried out. The electrolytic parameters are fine-tuned to optimize the efficiency of PEC water splitting. The main target of third part work is to provide the improved understanding of optimizing the electrolytic environments to achieve high efficiency of PEC water splitting over different photocatalysts such as TiO2, WO3, Fe2O3, BiVO4, ZnFe2O4, ZnCr2O4 and LaFeO3.
Date of Award24 Sep 2020
Original languageEnglish
Awarding Institution
  • University of Namur
SponsorsChina Scholarship Council
SupervisorBAO LIAN SU (Supervisor), Olivier DEPARIS (President), Alain KRIEF (Jury), Luca FUSARO (Jury), Alexandru Vlad (Jury) & Yu Jia Zeng (Jury)

Keywords

  • Semiconducting materials
  • photocatalysis
  • Hydrogen production

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