Beenish Tahir

Photocatalytic carbon dioxide and methane reduction to fuels over la-promoted titanium dioxide nanocatalyst

Selective photocatalytic carbon dioxide (CO2) reforming of methane (CH4) to carbon monoxide (CO) and hydrocarbons over lanthanum loaded titanium dioxide (La/TiO2) nanoparticles has been investigated. TiO2 nanoparticles (NPs) with different La-loadings were synthesised using sol-gel method. The catalysts were characterised using X-ray diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM) and Photoluminescence (PL) spectroscopy. Pure crystallite and anatase phase TiO2 with hindered charge recombination were detected in the La-loaded TiO2 samples. The products obtained were mainly CO, followed by ethane (C2H6) and traces of propane (C3H8). Pure TiO2 was favourable for CO evolution, while La-loaded TiO2 samples promoted hydrocarbons formation. The 2 wt% La/TiO2 photocatalyst conferred the maximum C2H6 yield of 492.8 μmole/g-cat at CO2/CH4 feed ratio 1.0 and irradiation time 2 h. The enhanced photocatalytic performance can be attributed to efficient reactant adsorption with hindered charge recombination rate in the presence of La-metal.

Photocatalytic carbon dioxide reduction to fuels Over Cu- Loaded g-C3N4 nanocatalyst under visible light

Photocatalytic carbon dioxide (CO2) conversion to chemicals and fuels has gained significant consideration in industrial and scientific research. In this study, photocatalytic CO2 reduction to fuels over Cu-loaded graphitic carbon nitride (g-C3N4) under visible light irradiation has been investigated. The photocatalysts, synthesized by pyrolysis and impregnation method, were characterized by X-ray diffraction (XRD) Fourier transform infrared (FTIR) and Scanning electron microscopy (SEM). Interestingly, CO2 was efficiently converted to CH4 and CH3OH with smaller amounts of C2H4 and C2H6 hydrocarbons. The yield of CH4 evolution as the main product over 3 wt. % Cu/g-C3N4 was 217.8 µmole/g.cat under visible light irradiation, significantly higher than the amount of CH4 produced over the pure g-C3N4 catalyst (119 µmole/g.cat). The enhancement was attributed to charge transfer property and suppressed recombination rate by Cu-metal. The Cu-metal loaded into g-C3N4 enhanced CO3 reduction efficiency for CH4 production while the pure g-C3N4 was promising for both CH4 and CH3OH production. The single step conversion of CO2 to CH4 and CH3OH with appreciable amount of hydrocarbons under solar energy registered good photo-activity and selectivity of Cu/g-C3N4 catalyst. A photocatalytic reaction mechanism was proposed to corroborate with the experimental results over the Cu-loaded g-C3N4 photocatalyst.

Photocatalytic CO2 reduction to CO over Fe-loaded TiO2/Nanoclay photocatalyst

Fe-promoted titanium dioxide (TiO2) nanoparticles dispersed in Montmorillonite (MMT) clay for dynamic photocatalytic carbon dioxide (CO2) reduction to carbon monoxide (CO) and hydrocarbons in a monolith photo-reactor has been investigated. MMT-clay supported Fe/TiO2 nanocomposites were prepared by a controlled and direct sol-gel method and were dip-coated over the monolith micro-channels. The performance of Fe-loaded MMT/TiO2 nano-catalyst for CO2 reduction by H2 toward CO evolution was evaluated in a continuous operation of photo-reactor under UV-light irradiation. The photo-Activity of TiO2 catalyst dispersed in MMT and loaded with Fe was significantly enhanced. The maximum yield of CO over 3 wt% Fe - 10 wt% MMT-loaded TiO2 catalyst reached to 289.30 μmole g-cat-1 h-1 at selectivity 99.61 %, is considerably higher than the amount produced over the MMT/TiO2 (25.95 μmole g-cat-1 h-1) and the pure TiO2 (8.52 μmole g-cat-1 h-1) catalyst. The other products observed with adequate amounts were CH4 and C2H6. These results revealed significantly enhanced photo-Activity of TiO2 loaded with Fe and dispersed over MMT. The enhanced CO evolution was evidently due to larger illuminated active surface area, higher adsorption process inside the monolith micro-channels and hindered charges recombination rate by Fe. This development has confirmed higher photoactivity of Fe-MMT/TiO2 photo-catalyst for continuous CO2 photo-reduction to cleaner fuels.

Carbon dioxide reduction with hydrogen in a continuous catalytic monolith photoreactor

Photocatalytic CO2 reduction with H2 as a reductant over gold (Au)-doped TiO2 nanocatalysts in a continuous monolith photoreactor has been investigated. The nanocatalysts were characterized by XRD, SEM, N2 adsorption-desorption and UV-Visible spectroscopy. Crystalline nanoparticles of anatase phase TiO2 were obtained in the Au-doped TiO2 samples. CO was the major product over 0.5 wt. % Au-doped TiO2 with the yield rate of 12,305 ppm g-catal.-1 h-1 , 318 times higher than un-doped TiO2 catalyst. Significantly higher photoactivity of Au-doped TiO2 was obviously due to fast electron transfer with hindered recombination rates and larger illuminated surface area inside the monolith channels. The CO production rate was gradually reduced with increasing the space velocity. The stability of the reused catalysts for CO production sustained at cyclic runs. It is evident Au-doped TiO2 nanocatalyst supported over monolith channels is highly potential for continuous CO2 photoreduction to CO and hydrocarbons.