Synthesis and characterisation of materials for photoelectrochemical applications
Abstract
The preparation of visible light driven photocatalysts for photocatalytic water splitting
has been achieved by a CO₂ free, low cost and simple novel method. Combination of
peroxide based route with organic free solvent and titanium nitride, carbon free
precursor and air and moisture stable, would be useful. Clear red-brown solution of
titanium peroxo species was obtained by dissolution of TiN in H₂O₂ and HNO₃ acid at
room temperature without stirring. The resultant red brown solution is then used as a
titanium solution precursor for yellow amorphous and yellow crystalline TiO₂
synthesis. Visible light photoactivity of the samples was evaluated by photooxidation
of methylene blue and photoreduction producing hydrogen from water splitting.
The high surface area of yellow amorphous TiO₂ exhibits an interesting property of
being both surface adsorbent and photoactive under visible light for
photodecolourisation of aqueous solution of methylene blue. However, it might not
appropriate for hydrogen production.
Nanoparticulate yellow crystalline TiO₂ with defect disorder of Ti³⁺ and oxygen
vacancies depending upon synthesis conditions has been characterised by ESR, XPS,
CHN analysis and SQUID. Single phase rutile can be produced at low temperature. It
is stable at high temperature and the red shift of absorption edge increases with the
treatment temperature. Yellow crystalline TiO₂ exhibits an interesting property of
being photoactive under visible light. The best photocatalytic performance was
observed for 600°C calcination, probably reflecting a compromise between red shift and surface area with changing temperature. Moreover, overall water splitting into hydrogen and oxygen might be obtained by using this material even in air atmosphere.
Photoactivity can be improved by testing under anaerobic atmosphere and/or adding
sacrificial agent. Quantum efficiency under visible light is still low but comparable to
other reports. The maximum efficiency varies from 0.03 % to 0.37 % for hydrogen
production and from 0.03 % to 0.12 % for oxygen production, depending on photon
energy and sacrificial agents.
Type
Thesis, PhD Doctor of Philosophy
Collections
Items in the St Andrews Research Repository are protected by copyright, with all rights reserved, unless otherwise indicated.