Delving into role of palladium nanoparticles-decorated graphene oxide sheets on photoelectrochemical enhancement of porous silicon
Two different photocathodes based on porous silicon (PS) are fabricated and fully characterized in this study and their photoelectrochemical (PEC) performance is compared with bare PS in both dark and illuminated conditions. The former PS-based photocathode is made by spin-coating of reduced graphene oxide-palladium (rGO-Pd) composite on PS surface, named PS/rGO-Pd and in the case of the later, GO is spin-coated on PS followed by coating it with Pd by electroless method to result in PS/GO/Pd photocathode. Linear sweep voltammetry (LSV) results of PS/GO/Pd sample (under illumination) shows that maximum photocurrent density is -57.1 mA/cm2, which is almost tripled compared to that of PS/rGO-Pd (-21 mA/cm2). Electrochemical impedance spectroscopy (EIS) measurements indicate significant lower charge transfer resistance at the PS/GO and rGO/Pd interfaces compared to bare PS, as a reason for photocurrent density improvement observed in PEC. Well-alignment in electron bands (of PS, GO/rGO, and Pd) and the positive synergetic effect between them that further improves efficient utilization of photo-induced charge carriers for the desired reactions are deemed to be responsible for the mechanism of enhancement.