Photoelectrochemical Formation of Polysulfide at PbSQD-Sensitized Plasmonic Electrodes

Effective electron-hole separation is a key to enhance photoenergy conversion of semiconductor-quantum-dots-(QDs) sensitized plasmonic solar cells. However, in contrast to intense studies on electron transfer, hole transfer from QDs and consequent chemical reactions with donors in electrolytes remain unclear. Herein, in-situ electrochemical surface-enhanced Raman scattering (SERS) measurement on a PbS QDs-sensitized TiO2/Au/TiO2 photoelectrode indicated formation of cycloocta-sulfur (α-S8) via tuning the electrochemical potential. A photocurrent density of 100 nA/cm2 was recorded simultaneously even with an extremely low QDs loading. Two-dimensional correlation analysis of the SERS revealed subsequent formation of S8− and S42− at −1.1 ~ −0.1 V (vs. Ag/AgCl), S8 from −0.3 V, and S52− and S62− at ≥0.2 V via complex disproportionation reactions. The sensitive detection is attributed to the enhanced electromagnetic field of localized surface plasmon resonance, which provide a better understanding of charge se...