Efficient hydrogen (H 2 ) production from renewable energy source is the most important requirement to produce clean fuels. Developing materials systems with high activity and good stability for solar energy conversion has become one of the most prominent and challenging research fields in the interdisciplinary scientific community. Recently, metal-free and graphite-like carbon nitiride (g-C 3 N 4 ) based on tri-s-triazine (heptazine) units has received much attention in the photocatalysis research due to its low cost, good stability and excellent optical and electronic properties.

Supported Pd, Au, and Pd−Au alloy catalysts are characterized with in situ diffuse reflectance infrared Fourier transform spectroscopy of CO adsorption (DRIFTS), quantitative powder X-ray diffraction, and X-ray photoelectron spectroscopy. The spectroscopic results presented in the paper demonstrate the existence of electron density transfer between Pd and Au atoms in alloy surfaces. In particular, the modification of the Pd electronic structure by the addition of Au is confirmed probably for the first time by the DRIFT spectra. The relationship between surface composition and catalyst performance in the synthesis of hydrogen peroxide directly from hydrogen and oxygen was established. Preliminary results indicate that the activity and selectivity of Pd−Au alloy catalysts can be significantly enhanced through adjusting the surface structures by changing the Au content in alloys.

Highly crystalline pure brookite and two-phase anatase/brookite TiO 2 nanostructures were synthesized via a simple hydrothermal method with titanium sulfide as the precursors in sodium hydroxide solutions. The control of the phase composition has been demonstrated via solution concentration and reaction time, and the phase transformation mechanism has been elucidated. Photocatalytic activities of the assynthesized two-phase anatase/brookite TiO 2 , pure anatase nanoparticles, and pure brookite nanoplates were appraised via photocatalytic hydrogen evolution in aqueous methanol solution. Results have shown that the photocatalytic activity is higher for the two-phase anatase/brookite TiO 2 and brookite nanoplates as compared to pure anatase nanoparticles despite the lower surface areas of the two-phase anatase/brookite TiO 2 and brookite nanoplates. From the Mott−Schottky analysis, brookite phase is shown to have a more cathodic conduction band edge potential than anatase phase, which leads to more energetically favorable hydrogen reduction. Moreover, femtosecond transient absorption spectroscopy measurements suggests that the photoexcited electrons transfer from brookite to anatase phaseleading to further enhancement of the photocatalytic activity. In comparison with the highly active two-phase commercial benchmark P25, our synthesized two-phase anatase/brookite TiO 2 is 220% more active when measured by the H 2 yield per unit area of the photocatalyst surface.

For the purpose of efficiently utilizing the renewable solar energy, it is of vital importance to understand the key factors that contribute to the performance merits for photocatalysis applications. In this work, we find that anatase titania nanostructures with high efficiency in photoelectrochemical cell (PEC) do not necessarily retain the same good performance when used in direct heterogeneous reaction (DHR). Investigation is carried out to elucidate how the electronic properties of the different nanostructures are correlated with the PEC and DHR efficiencies. Good PEC cell performance is identified to be related to topotactically formed samples with intimately connected particles that facilitate easy charge transfer. Additional benefit for PEC cell is found to be achieved from the vectorial conduction pathway in the pseudo one dimensional structure. On the other hand, high activity of DHR photocatalysis is attributed mainly to the exposed high reactivity crystal facets. The presence of anatase TiO2 {010} facets is identified to enhance electron‐hole separation and create specific surface states that facilitate interactions across the semiconductor/electrolyte interfaces.