Nanostructured promoted titania photocatalysts

Concern over the economics of accessing fossil fuel and widespread acceptance of the anthropogenic origin of rising CO2 emissions and associated climate change is driving academic and commercial research into new routes to sustainable fuels, to meet the demands of a rapidly rising global population and reduce an impact on the environment. The titania oxide semiconductor has attracted a great interest as a photocatalyst for wide-ranging applications including wastewater depollution, solar fuels via both H2 production and CO2 reduction. Tailoring the physicochemical properties of titania photocatalysts, and their resulting reactivity, in a predictable fashion remains challenging. The thesis explores the impact of thermal processing, macroporosity and metal deposition on the surfactant-templated mesoporous TiO2 and dual soft-hard templated macro-mesoporous TiO2 series and resulting activity in aqueous phase photocatalytic dye degradation, H2 production and CO2 reduction reactions. Control over the structural and photophysical properties of mesoporous titania enables systematic tuning of Methyl Orange photocatalytic depollution and H2 evolution. Hierarchical macro-mesoporous titanias exhibit uniform mesopores with macropore diameters that can be systematically tuned between 140-310 nm, resulting in a close-packed, ordered macropore framework. Hierarchically-structured TiO2 display two fold increase in photoactivity relative to mesoporous counterparts in the H2 production. Ultra-low concentrations (0.02-0.1 wt%) of copper introduced into the mesoporous and macro-mesoporous titania surfaces by wet-impregnation enhance activity for dye degradation by six fold, and for H2 production four fold, through the genesis of isolated Cu (I) species which suppress charge recombination. Furthermore, promotion with Pt increases photocatalytic activity in Methyl Orange degradation by eleven fold, H2 production 16-26 times and are the only series which display activity in the CO2 reduction reaction. Moreover, the impact of the macropore diameter on the activity of the Methyl Orange degradation is observed for Cu and Pt promoted macro-mesoporous TiO2 series. Nanostructured promoted titanias offer an insight into the relative importance of physicochemical and electronic properties upon their associated activity together with significantly enhanced photocatalytic performance

Single atom Cu(I) promoted mesoporous titanias for photocatalytic Methyl Orange depollution and H 2 production

Tailoring the physicochemical properties and hence reactivity of semiconductor photocatalysts in a predictable fashion, remains a challenge to their industrial application. Here we demonstrate the striking promotional effect of incorporating single Cu(I) atoms, on aqueous phase photocatalytic dye degradation and H2 production over surfactant-templated mesoporous TiO2. X-ray absorption spectroscopy reveals that ultra-low concentrations of copper (0.02-0.1 wt%) introduced into the mesoporous TiO2 surface create isolated Cu (I) species which suppress charge recombination, and confer a six-fold photocatalytic promotion of Methyl Orange degradation and four-fold enhancement of H2 evolution. The impact of mesopore structure and photophysical properties on photocatalytic activity is also quantified for the first time: calcination increases mesopore size and nanocrystalline order, and induces an anatase to rutile phase transition that is accompanied by a decrease in the optical band gap, increased charge carrier lifetime, and a concomitant significant activity enhancement

Tailored mesoporous silica supports for Ni catalysed hydrogen production from ethanol steam reforming

Mesoporous silica supported Ni nanoparticles have been investigated for hydrogen production from ethanol steam reforming. Ethanol reforming is structure-sensitive over Ni, and also dependent on support mesostructure; three-dimensional KIT-6 possessing interconnected mesopores offers superior metal dispersion, steam reforming activity, and on-stream stability against deactivation compared with a two-dimensional SBA-15 support

P25@CoAl layered double hydroxide heterojunction nanocomposites for CO2 photocatalytic reduction

Artificial photosynthesis driven by inorganic photocatalysts offers a promising route to renewable solar fuels, however efficient CO2 photoreduction remains a challenge. A family of hierarchical nanocomposites, comprising P25 nanoparticles encapsulated within microporous CoAl-layered double hydroxides (CoAl-LDHs) were prepared via a one-pot hydrothermal synthesis. Heterojunction formation between the visible light absorbing CoAl-LDH and UV light absorbing P25 semiconductors extends utilisation of the solar spectrum, while the solid basicity of the CoAl-LDH increases CO2 availability at photocatalytic surfaces. Matching of the semiconductor band structures and strong donor–acceptor coupling improves photoinduced charge carrier separation and transfer via the heterojunction. Hierarchical P25@CoAl-LDH nanocomposites exhibit good activity and selectivity (>90%) for aqueous CO2 photoreduction to CO, without a sacrificial hole acceptor. This represents a facile and cost-effective strategy for the design and development of LDH-based nanomaterials for efficient photocatalysis for renewable solar fuel production from particularly CO2 and aqueous water