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The photoreforming of organic molecules is a growingly interesting technology to achieve faster hydrogen production than with water splitting, while simultaneously mineralising organic pollutants in water. This paper investigates the possibility to produce hydrogen or gaseous fuel mixtures by using simulated wastewaters of the pulping industry. Glucose was first used as model molecule for carbohydrate-containing wastewaters, while tartaric acid was the model for those rich of carboxylic acids. Different titania catalysts were prepared starting form the P25 commercial material and monometallic Pt or Au, or bi-metallic Au x Pt y formulations were prepared in form of surface-decorated nanomaterials. The effect of pH and co-catalysts addition was explored, achieving after 5 h of irradiation the highest glucose conversion (15.2%) and H 2 productivity (4.1 mol H 2 kg cat −1 h irr −1) with sample 1.0 wt%Au 6 Pt 4 /P25. This result competes with the best ones reported in the literature. Testing of tartaric acid showed much faster conversion of the substrate, but limited hydrogen productivity, ethane and CO 2 being the main products, anyway leading to a valorisable gaseous fuel mixture. The best performing materials were also tested for the photoreforming of simulated wastewaters representative of pulping industry effluents, according to the two pulp processing technologies, the Kraft and sulphite ones. Similar results than tartaric acid were obtained when testing the Kraft spent liquor, mainly composed of hydroxycarboxylic acids. By contrast, the Sulphite spent liquor was mainly composed of carbohydrates, acetic and gluconic acids and led to methane as main product, possibly coming from the decarboxylation of acetic acid. The results overall testify the interest of photoreforming to valorise wastewaters into gaseous fuels in a circular economy concept. • The photoreforming of glucose has been investigated over metal-promoted titania. • Effects of cocatalysts are discussed on the products distribution and conversion. • Bimetallic Pt–Au formulations allowed the highest productivity. • Simulated pulping industry waste liquors were tested. • Different mechanisms of reaction are discussed, leading to different products distribution. [ABSTRACT FROM AUTHOR]

Highlights • The feasibility of different photocatalytic processes is studied for energy storage. • Calculated productivity of H 2 evaluated for solar light harvesting at different latitudes. • H 2 productivity by photoreforming is insufficient for practical exploitation. • Photoreduction of CO 2 to different products is considered as solar energy storage process. • Feasible productivity was demonstrated for formaldehyde (13% solar energy storage efficiency) Abstract The experimental results of testing with different irradiation power are compared and used as a basis for the feasibility assessment and conceptual design of a photoreforming reactor. The highest H 2 productivity (0.276 mol H 2 /h kg cat) was achieved with 1 g/L of 1 wt% Au/TiO 2 P25 catalyst by using a 113 W/m2 UVA irradiation. Insufficient hydrogen productivity for practical deployment was achieved, following reactor design. However, the comparison with the state of the art evidenced that also the energy storage potential of the literature photocatalysts do not allow a short term feasibility of the proposed technology. The potential productivity of hydrogen, as well as solar energy storage efficiency are discussed both for the present experimental values and for the best results in the literature. On the other hand, solar energy can be used to artificially fix CO 2 , e.g. captured and stored from combustion processes that can be converted back to chemicals or regenerated fuels. The production of H 2 , HCOOH, HCHO and CH 3 OH by photoreduction of CO 2 has been evaluated as for daily production potential. CO 2 photoconversion to formaldehyde can be envisaged as solar energy storage mean with 13.3% efficiency, whereas for the other products the solar energy storage efficiency was below 1%. [ABSTRACT FROM AUTHOR]

Abstract: In this paper we describe the production and investigation of two supported gold catalyst systems prepared by magnetron sputtering: Au on WO3 and Au on activated carbon. The magnetron sputtering technique entails using an argon plasma to sputter a high purity gold target producing a flux of gold atoms which are deposited onto a constantly tumbling support material. This technique offers a number of advantages over conventional chemical preparation methods. One advantage is the ability to create gold nanoparticles (diameters <3nm) on unusual support materials, such as WO3 and carbon, which are generally not accessible using the ubiquitous deposition-precipitation technique. We present data demonstrating the formation of catalytic gold nanoparticles with average diameters of 1.7nm (Au/C) and 2.1nm (Au/WO3), as well as a substantial number of single atom species on the Au/C sample. Prototypical carbon monoxide oxidation (Au/WO3) and glycerol oxidation (Au/C) reactions were performed in order to gauge the activity of these catalysts. The WO3 supported catalyst exhibits substantial catalytic activity from room temperature to 135°C (0.0018–0.082mol CO/mol Aus) with an activation energy near 23kJ/mol. The activity of the Au/C catalyst was compared to a Au/C catalyst prepared from a poly(vinyl alcohol) (PVA) sol. The smaller catalysts prepared by sputtering are more active than the large gold particles prepared using the PVA sol, however the larger gold nanoparticles are substantially more selective towards the production of intermediate products from the oxidation of glycerol. [Copyright &y& Elsevier]