Experimental screening of transition metal-doped TiO2 for hydrogen production through photoreforming of methanol Ruiman Ma 1, Serigo Vernuccio 2 1 University of Sheffield, China, 2 University of Sheffield, Italy Environmental pollution, consumption of fossil fuels, and shortage of clean energy are some of the most serious issues facing the world today. Thus, hydrogen is receiving special attention from the research community as the next generation energy carrier (Schneider et al. , 2014). The use of solar energy, as a clean and renewable source is particularly promising to achieve photocatalytic hydrogen production using materials such as titanium dioxide as a photocatalyst which has the advantages of low cost, wide availability, and stability (Ni et al. , 2007). However, the band gap width of the pristine titanium dioxide (3.2 eV) is not suitable for absorbing visible light radiations, and only UV light can be utilized (Fresno et al. , 2014). Since UV light accounts for only a small fraction of the solar radiation, the inability to utilize the contribution of visible light strongly limits the efficiency of solar photocatalytic hydrogen production. To overcome this problem, novel materials need to be designed to improve the efficiency of hydrogen production. In this work we synthesized, characterized and tested in the hydrogen production from photoreforming several materials obtained from photodeposition of transition metals (e.g., Cu, Ag, Pt, Au, Pd) on titanium dioxide. We used methanol as a hole scavenger, to limit the recombination rate of electrons and holes, thus improving the hydrogen production rate. Photocatalytic tests were performed in an annular glass batch reactor (V = 280 ml; H = 40 cm), equipped with a high-pressure mercury vapor lamp located in a quartz jacket. The photocatalytic activity of several different metal dopants (Pt, Pd, Cu, Ag, Au) was tested under both UV and visible light radiation and the effect of different dopant amounts (in the range 0-10% mol) and different sacrificial agent concentrations (in the range 0-3 M) on the hydrogen production rate were examined. The results showed that the Pt-doped titanium dioxide (with a Pt loading of 0.5% mol) exhibits the best performance with a hydrogen production rate of about 180 mmol h -1 . The catalyst activity shows the following order Pt >Pd >Au >Cu >Ag under UV light radiation and Pd >Au >Pt >Cu >Ag under visible light radiation suggesting that the hydrogen production is governed by a different photocatalytic mechanism depending on the frequency of the radiations. The photocatalytic activity is enhanced as result of an increased methanol concentration up to a value of 2.5M. Further increase in the sacrificial agent concentrations do not result in any additional change in the hydrogen production rate. References 1. Fresno, F. et al. (2014), Journal of Materials Chemistry A , 2(9), pp. 2863–2884. doi: 10.1039/c3ta13793g. 2. Ni, M. et al. (2007), Renewable and Sustainable Energy Reviews , 11(3), pp. 401–425. doi: 10.1016/j.rser.2005.01.009. 3. Schneider, J. et al. (2014), Chem. Rev. , 114(9), p. 9919−9986.
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