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Tuning the photonic band gap (PBG) to the electronic band gap (EBG) of Au/TiO2 catalysts resulted in considerable enhancement of the photocatalytic water splitting to hydrogen under direct sunlight. Au/TiO2 (PBG-357 nm) photocatalyst exhibited superior photocatalytic performance under both UV and sunlight compared to the Au/TiO2 (PBG-585 nm) photocatalyst and both are higher than Au/TiO2 without the 3 dimensionally ordered macro-porous structure materials. The very high photocatalytic activity is attributed to suppression of a fraction of electron-hole recombination route due to the co-incidence of the PBG with the EBG of TiO2 These materials that maintain their activity with very small amount of sacrificial agents (down to 0.5 vol.% of ethanol) are poised to find direct applications because of their high activity, low cost of the process, simplicity and stability.

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X-ray spectroscopy reveals the presence of inter-band gap electronic states of egsymmetry in M:BiVO4(M = Mo, W) PEC anodes.

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This study systematically re-examines the titania-catalysed photo-oxidation of methylene blue (MB) in aqueous solution at 20°C, placing particular emphasis on the effects of TiO 2 crystallite size, TiO 2 polymorph (anatase, brookite, rutile and combinations thereof) and experimental test conditions on the rate of MB photo-oxidation. For all TiO 2 samples tested, the highest rate of MB photo-oxidation was observed at pH 6, slightly above the isoelectric point of TiO 2 (*5.8 for P25 TiO 2 ). Increasing the ionic strength at pH 6 induced MB dimer formation in solution, and lowered the rate of MB photo-oxidation by TiO 2 . For all TiO 2 polymorphs, the surface area normalised rate increased with crystallite size reflecting the corresponding reduction in surface and bulk defects (electronhole pair recombination sites). The optimum crystallite sizes were *20-25 nm for anatase and *50 nm for brookite. The photocatalytic activity of the different TiO 2 powders followed the general order P25 [ anatase [ brookite ) rutile, with the high activity of P25 TiO 2 providing strong evidence that anatase-rutile heterojunctions act as ''hotspots'' for MB photo-oxidation. Mixed phase anatase-rutile or brookite-rutile powders, each containing *5 wt% rutile, demonstrated superior area normalized photocatalytic activities for MB photo-oxidation compared to pure phase anatase or brookite powders of comparable crystallite size. Finally, deposition of Pd, Pt or Au nanoparticles decreased the activity of P25 TiO 2 for MB photo-oxidation. This paper clarifies long-standing confusion in the scientific literature about the photo-oxidation of aqueous MB over TiO 2 and M/TiO 2 (M = Pd, Pt and Au) photocatalysts.

Transparent thermoelectric materials offer a synergetic performance for energy harvesting as smart windows. Among them, p-type copper iodide (CuI) is preferred due to its low synthesis temperature, moderate conductivity and mobility, and high optical transparency. X-ray absorption spectroscopy results showed a pre-edge feature in the Cu 2p 3/2 spectrum, which suggested the presence of Cu 0 -like defect states in γ-CuI films. Interface and grain boundaries of CuI and Cu 0 act as a potential energy barrier for energy filtering of charge carriers, which along with the decrease in charge carrier density enhanced the Seebeck coefficient, α. The α value increased by 298% upon annealing at 100 °C, α = 789.5 μVK −1 , which resulted in a 480% increase in the power factor (α 2 σ = 740.9 μWm −1 K −2 ). Our results showed that a high Seebeck coefficient resulted from a decrease in charge carrier density and energy filtering of charge carriers at the interface and grain boundaries in optically transparent (T visible ∼ 60−85%) γ-CuI films for energy harvesting as smart windows.