Strategies for developing efficient photocatalysts under visible light

Strategies for developing efficient photocatalysts under visible light 

Although the properties required by photocatalysts for water splitting have been identified (band edge potentials suitable for water splitting, band-gap energy around 2.0-2.2 eV, and stability under reaction conditions), it is 

Several research approaches are pursued in the quest for more efficient and active photocatalysts for water splitting (i) to find new single-phase materials, (ii) to tune the band-gap energy of TJV-active photocatalysts (band-gap engineering), and (iii) to modify the surface of photocatalysts by deposition of cocatalysts to reduce the activation energy for gas evolution. Obviously, the previous strategies must be combined with the control of the s)mthesis of materials to customize the crystallinity, electronic structure, and morphology of materials at nanometric scale, as these properties have a major impact on photoactivity. 

In the development of active photocatalysts imder visible light, it is essential to control their electronic energy structure. The strategies for controlling the energy structure of photocatalysts for water splitting may be classified in three ways (i) cation or anion doping, (ii) use of mixed semiconductor composites, and (iii) use of semiconductor alloys. 

Cation or anion doping Ion doping has been extensively investigated for enhancing the visible-light response of wide band-gap photocatalysts (UV-active). Examples include Sb- or Ta- and Cr-doped Ti02 and SrTiOs (Kato et al., 2002 Ishii et al., 2004), ZnS doped with Cu or Ni (Kudo and Sekizawa, 1999 Kudo and Sekizawa 2000), or C-doped Ti02 (Khan et al., 2002). 

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