Photoelectrochemical Activity of CdS/CdSe-deposited onto TiO_2 Photoanodes: Comparing Performance with vs. without Sacrificial Reagents

摘要

The photocurrent density of CdS/CdSe-modified TiO_2 photoanodes measured under standard test conditions were 0.94 mAcm~(-2) and 7.4 mAcm~(-2) at 1.23 V_(RHE) using 1 M NaOH electrolyte (no reagents) and Na_2S/Na_2SO_3-added electrolyte (with reagents), respectively. The actual current contribution in the case of the aqueous alkaline electrolyte was due to water oxidation while the 8-fold photocurrent enhancement using the latter electrolyte was due to sulfite oxidation. A maximum Solar-To-Hydrogen (STH) efficiency of 0.71% and water splitting efficiency of 12.4% at 1.23 V_(RHE) were determined for the photoelectrochemical cell. The incident photon-to-current conversion efficiency spectrum measured for the photoanode revealed that the current conversion efficiency is lower (≤17%) when absorption occurs solely from the external CdSe layers, indicating higher recombination possibly due to unsaturated localized trap states and interfacial recombination during charge transport in the intermediate CdS layer. The photocurrent and onset potential for the CdS/CdSe-modified Li:TiO_2 photoanodes were found to improve under acidic conditions, showing a slightly increased PEC activity and faster reaction kinetics.