Uniform Decoration of CdS Nanoparticles on TiO2 Inverse Opals for Visible Light Photoelectrochemical Cell

We present a CdS nanoparticle-decorated TiO2 inverse opal (IO) for use as an electrode for visible-light photoelectrochemical cells. A facile, low-temperature deposition of CdS nanoparticles is achieved via a sonochemical method. The use of TiO2 IO structures enable the uniform deposition of CdS nanoparticles throughout the film. The quantity of deposited CdS nanoparticles is controlled by the concentration of the CdS precursor solution. The deposited layer of CdS nanoparticles sensitizes the TiO2 surface to visible light; CdS-sensitized TiO2 IO films demonstrate absorption of up to approximately 550 nm light, with enhanced absorption for increased CdS deposits. The CdS-sensitized TiO2 IO film is employed as a photoanode for the PEC cell. We obtain a maximum photocurrent of 7.29 mA/cm2 at the optimum CdS deposition of 39.33 ms%. The optimum amount of deposited CdS is defined by balancing the light harvesting rate against the charge recombination rate, both of which increase with increasing CdS deposition. The CdS-sensitized TiO2 IO electrodes are compared with mesoporous TiO2 nanoparticulate electrodes; higher photocurrent is obtained with the IO, due to the uniform pores of the IO structures.