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