Semiconductor Photocatalysis: Effect of Light Intensity on Nanoscale CdS-Catalyzed Photolysis of Organic Substrates

Article abstract of DOI:10.1021/j100151a041

The relationship between light intensity and product distribution in semiconductor photocatalysis was investigated by using nanoscale CdS microcrystallites (CdS-0) as photocatalysts, triethylamine (TEA) as the electron donor, and either aromatic ketones, electron-deficient alkenes, or 1-benzylnicotinamide (BNA⁺) as substrates.In the case of the ketones and BNA⁺, the yield of their respective one-electron reduction products, pinacols and the dimer, (BNA)₂, increases with decreasing light intensity.When alkenes are employed in the CdS-0 system, cis-trans photoisomerization always occur regardless of the light intensity.The kinetics for the photocatalysis of the alkanes and the measuement of the inital formation rate of active lattice Cd atoms (Cd⁰) (which act as catalytic sites for two-electron-transfer reductions) reveal that Cd⁰ formation is proportional to the square of the relative light intensity, I_r².The chemoselectivity in the photocatalysis using nanoscale CdS should be affected by the quantity of the Cd⁰, whose formation strongly depends on the light intensity.