Metallized semiconductor powder electron-hole separation

Figure 2. Electron-hole separation on a metallized (M) semiconductor (SC) powder.

Similar to the molecular photosensitizers described above, solid semiconductor materials can absorb photons and convert light into electrical energy capable of reducing C02. In solution, a semiconductor will absorb light, and the electric field created at the solid-liquid interface effects the separation of photo-excited electron-hole pairs. The electrons can then carry out an interfacial reduction reaction at one site, while the holes can perform an interfacial oxidation at a separate site. In the following sections, details will be provided of the reduction of C02 at both bulk semiconductor electrodes that resemble their metal electrode counterparts, and semiconductor powders and colloids that approach the molecular length scale. Further information on semiconductor systems for C02 reduction is available in several excellent reviews [8, 44, 104, 105],... 

Y. Nosaka Y. Ishizuka H. Miyama, Separation mechanism of a photo-induced electron-hole pair in metal-loaded semiconductor powders. Ber. Bunsenges. Phys. Chem. 1986, 90, 1199-1204. 

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