A solid photothermal reservoir is designed to implement solar-steam generation in the absence of bulk water. The photothermal reservoir is composed of a water absorbing core encapsulated by a photothermal reduced graphene oxide based aerogel sheet which absorbs light and converts it into heat thus evaporating the stored water. The photothermal reservoir is able to store 6.5 times its own weight in water, which is sufficient for one day solar evaporation, thus no external water supplement is required. During solar-steam generation, since no bulk water is involved, the photothermal reservoir minimizes heat conduction loss, and maximizes both of the exposed evaporation surface area and net energy gain from the environment, leading to an energy efficiency beyond the theoretical limit. An extremely high water evaporation rate of 4.0 kg m À2 h À1 (normalized to projection area) is achieved in laboratory studies over a cylinder photothermal reservoir with a diameter of 5.2 cm and a height of 15 cm under 1.0 sun irradiation. Practical evaluation of the photothermal reservoir outdoors as part of a desalination device demonstrates a similar evaporation rate where the salinity of the clean water produced is lower than 24 ppb. Thus the photothermal reservoir shows great potential for real world applications in portable solarthermal desalination.

Au–Ag alloy nanoparticles on titania exhibit superior photocatalytic performance in selective oxidation of methanol to methyl formate.

Hydrogen-rich organic molecules such as alcohols are widely used as hydrogen donors in transfer hydrogenation. Nevertheless, water as a more abundant and eco-friendly hydrogen source has hardly been used due to the high difficulty in splitting water molecules. Herein, we designed a photocatalytic water-donating transfer hydrogenation (PWDTH) technique, in which hydrogen was extracted from water under light illumination and then in situ added to different unsaturated bonds (C=C, C=O, N=O) for chemical synthesis. Platinum loaded carbon nitride (Pt/CN) was used as the model catalyst for this cascade reaction, which is beyond its normal applications for water splitting. This approach was highly accessible to efficiency optimization, either by modifying CN for extended light absorption and enhanced charge transfer, or by alloying Pt with another metal for better catalytic activities. Remarkably, a quantum efficiency up to 21.8% was achieved for nitrobenzene hydrogenation under 380 nm irradiation which is 3 times higher than that obtained in a single water splitting reaction, indicating the PWDTH can be more rewarding than hydrogen evolution for solar energy harvesting. Deep insights into the underlying mechanism was provided by detailed measurements and interpretations of femtosecond transient absorption spectra, action spectra (quantum efficiency as a function of excitation wavelength) and reaction kinetic profiles under varied conditions including the variation of light intensities, temperatures and water isotopes. The mild Page 1 of 22 ACS Paragon Plus Environment ACS Catalysis 2 reaction conditions, simple processing and broad substituent group tolerance endow this approach a high potential toward a general solar to chemical conversion technique.

Direct hydrogenation of C=C double bonds is a basic transformation in organic chemistry which is vanishing from simple practice because of the need for pressurized hydrogen. Ammonia borane (AB) has emerged as a hydrogen source through its safety and high hydrogen content. However, in conventional systems the hydrogen liberated from the high-cost AB cannot be fully utilized. Herein, we develop a novel Pd/g-C N stabilized Pickering emulsion microreactor, in which alkenes are hydrogenated in the oil phase with hydrogen originating from AB in the water phase, catalysed by the Pd nanoparticles at the interfaces. This approach is advantageous for more economical hydrogen utilization over conventional systems. The emulsion microreactor can be applied to a range of alkene substrates, with the conversion rates achieving >95 % by a simple modification.

No abstract