Page 237 - Multifunctional Photocatalytic Materials for Energy

220 Multifunctional Photocatalytic Materials for Energy

Fig. 10.4 (A) The solar-to-hydrogen conversion efficiency for UV to IR region of the
electromagnetic spectrum establishing that the conversion efficiency is higher for low band
gap (~2 eV) materials. (B) Relationship between band structure of semiconductor and redox
potentials of water splitting [7,8].
(A) Reproduced from J. Li, N. Wu, Semiconductor-based phototcatalysts and
petrochemical cells for solar fuel generation: a review, Catal. Sci. Technol. 5 (2015)
1360–1384, with permission of the Royal Society of Chemistry. http://pubs.rsc.org/
en/content/articlelanding/2015/cy/c4cy00974f#!divAbstract; (B) A. Kudo, Y. Miseki,
Heterogeneous photocatalyst materials for water splitting, Chem. Soc. Rev. 38 (2009)
253–278, with permission of the Royal Society of Chemistry. http://pubs.rsc.org/en/content/
articlelanding/2009/cs/b800489g#!divAbstract.

the semiconducting particles has another favorable effect in that the band gap also
can be tuned by employing particles of different sizes. In nano-dimensional semi-
conductors, the exciton (or bound electron-hole pair) lifetime can be modified by
designing heterostructures with different energy band gap offsets, which is discussed
in the next section. Fig. 10.5 depicts the various pathways by which the charges can
recombine or their transfer can take place.