Ultrathin MoS2–MoO3 nanosheets functionalized CdS photoanodes for effective charge transfer in photoelectrochemical (PEC) cells

Abstract

The present study focuses on the synthesis of MoS₂–MoO₃ nanostructures via a hydrothermal method and their application in the modification of CdS photoanodes. Structural characterization reveals that with an increase in the hydrothermal reaction time the fraction of the MoS₂ phase increases in the MoS₂–MoO₃ nanostructures, with MoS₂ being dominant in the sample obtained at the maximum reaction time. TEM characterization reveals the formation of ultra thin nanosheets in the MoS₂–MoO₃ system. Correspondingly, the bandgaps estimated from the Tauc plot analysis indicate a bandgap tuning from 2.40 eV to 1.73 eV for these Mo-nanostructures. The surfaces of spray deposited nanostructured CdS thin films were further modified with these Mo-nanostructures via a very simple and economic chemical impregnation method. The CdS photoanodes modified with the MoS₂–MoO₃ nanosheets exhibit the highest PEC performance which is 4 times the photocurrent of bare CdS photoanodes. In addition, the stability of the modified photoanodes is enhanced to more than 8 hours compared to a few minutes for bare and photocorrosive CdS. The improved PEC performance is attributed to the formation of the n-CdS/p-MoS₂ junction that suppresses the undesirable electron–hole recombination process and thus improves the charge transfer process. A solar-to-hydrogen conversion efficiency of 1.9% is reported for the MoS₂–MoO₃ nanosheets modified CdS photoanode.