Abstract
In the present piece of research, hydrogen production via the photo-reforming of glycerol (a byproduct from biodiesel generation) is studied. Catalysts consisted of titania modified by Ni (0.5% by weight) obtained through deposition–precipitation or impregnation synthetic methods (labelled as Ni-0.5-DP and Ni-0.5-IMP, respectively). Reactions were performed both under UV and solar irradiation. Activity significantly improved in the presence of Ni, especially under solar irradiation. Moreover, pre-reduced solids exhibited higher catalytic activities than untreated solids, despite the “in-situ” reduction of nickel species and the elimination of surface chlorides under reaction conditions (as evidenced by XPS). It is possible that the catalyst pretreatment at 400 °C under hydrogen resulted in some strong metal–support interactions. In summary, the highest hydrogen production value (ca. 2600 micromole H2·g−1) was achieved with pre-reduced Ni-0.5-DP solid using UV light for an irradiation time of 6 h. This value represents a 15.7-fold increase as compared to Evonik P25.
Highlights
Fossil fuel depletion and environmental concerns have resulted in the search for clean energies, with one alternative being hydrogen [1]
The chemical composition was determined by inductively coupled plasma mass spectrometry (ICP-MS) and the results, presented in Table 1, evidenced a good incorporation of nickel, with values being quite close to the nominal content (0.5% by weight)
Consistent with the small metal loading and the homogeneous nickel dispersion evidenced by Transmission electron microscopy (TEM) micrographs, no signals associated to nickel species are observed
Summary
Fossil fuel depletion and environmental concerns have resulted in the search for clean energies, with one alternative being hydrogen [1]. Its use has two main advantages [2,3]: i) a high chemical energy per mass (120 KJ/g), superior to that of many fossil fuels, and ii) its combustion only results in water; it does not emit any toxic substance or greenhouse gas into the atmosphere. Hydrogen does not exist in nature in its molecular H2 form but combined to other elements; it requires dedicated methods for its production. Whether or not the use of hydrogen as an energy vector can be termed as “fully green” is dependent on its method of production. The most widespread hydrogen production methodologies are hydrocarbon reforming with water vapor and water electrolysis. Hydrocarbon reforming has the disadvantages of being based on raw materials which are taken from non-renewable fossil sources and, the co-generated
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