Abstract
A systematic study on the solar photocatalytic hydrogen production (photoreforming) performance of M/TiO2 (M = Au, Ag, Cu or Pt) using glucose as a model substrate, and further extended to lignocellulose hydrolysates and wastewaters, is herein presented. Three metal (M) co-catalyst loading methods were tested. Variation of the type of metal results in significantly dissimilar H2 production rates, albeit the loading method exerts an even greater effect in most cases. Deposition-precipitation (followed by hydrogenation) or photodeposition provided better results than classical impregnation (followed by calcination). Interestingly, copper as a co-catalyst performed satisfactorily as compared to Au, and slightly below Pt, thus representing a realistic inexpensive alternative to noble metals. Hydrolysates of either α-cellulose or rice husks, obtained under mild conditions (short thermal cycles at 160 °C), were rich in saccharides and thus suitable as feedstocks. Nonetheless, the presence of inhibiting byproducts hindered H2 production. A novel photocatalytic UV pre-treatment method was successful to initially remove the most recalcitrant portion of these minor products along with H2 production (17 µmol gcat−1 h−1 on Cu/TiO2). After a short UV step, simulated sunlight photoreforming was orders of magnitude more efficient than without the pre-treatment. Hydrogen production was also directly tested on two different wastewater streams, that is, a municipal influent and samples from operations in a fruit juice producing plant, with remarkable results obtained for the latter (up to 115 µmol gcat−1 h−1 using Au/TiO2).
Highlights
Biomass represents a sustainable alternative to fossil resources as feedstock for the production of H2 [1,2]
The metal co-catalysts in the M/TiO2 materials used in this work were deposited by three different methods, namely: (i) Deposition-precipitation, (ii) impregnation and (iii) photodeposition, in order to systematically study the influence of different synthetic protocols on loadings and on co-catalyst nanoparticles morphology, and on photocatalytic performance for hydrogen generation from biomass or wastewaters
A systematic study on the effect of co-catalyst metal and loading procedure on photocatalytic performance was undertaken using glucose as a model substrate, given that does it represent the structural building block and motif of the major part of lignocellulosic biomass waste, it is one of the possible organic components in wastewaters generated in the food and drink industrial sectors, as considered in this work
Summary
Biomass represents a sustainable alternative to fossil resources as feedstock for the production of H2 [1,2]. The biomass reforming process can be triggered by light in a photocatalytic process known as photoreforming [7,8,9]. This process proceeds at ambient temperatures, and the extent of degradation reactions is negligible, resulting in extremely high H2 selectivities. A different perspective, direct utilization of wastewaters containingof organic matter, containing matter, into which be transformedrepresents into H2 by photoreforming, represents which may organic be transformed. H2 photoreforming can be used for energetic contained in rich the in resulting andthe (b)produced direct solar of either valorization. Industrial or municipal wastewaters rich in organic matter, whereby the produced H2 can be used for energetic valorization
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