Plasmonic effect in Au(core)-CdS(shell) quantum dot-sensitized photoelectrochemical cell for hydrogen generation from water

Abstract

UV-light irradiation of Au nanoparticle (NP)-loaded mesoporous TiO2 nanocrystalline films in an ethanol solution of Cd(NO3)2 and S8 at 298 K gives rise to selective CdS deposition on Au NPs to yield Au(core)-CdS(shell) hybrid quantum dots (Au@CdS/mp-TiO2). Two-electrode quantum dot-sensitized photoelectrochemical cells with the structure of photoanode|0.25 M Na2S, 0.35 M Na2SO3 (solvent = water)|cathode were fabricated. The Au@CdS/mp-TiO2 photoanode cell yields hydrogen (H2) with a rate of 0.18 ml h−1 [solar-to-current efficiency (STCE) = 0.028%] without external bias far surpassing the rate of 0.028 ml h−1 (solar-to-current efficiency = 0.006%) for the CdS/mp-TiO2 photoanode cell under illumination of simulated sunlight (λ > 430 nm, AM 1.5, one sun). The 3D finite-difference time-domain calculations for a model Au@CdS/TiO2 system indicate that an intense local electric field with an enhancement factor of ∼103 is generated at the Au-CdS-TiO2 three-phase interface. The striking effect of the Au core stems from the enhancement of the excitation of the CdS shell and subsequent charge separation by the intense local electric field.