Enhancing the activity and stability of Cu2O nanorods via coupling with a NaNbO3/SnS2 heterostructure for photoelectrochemical water-splitting

Abstract

Fabrication of a NaNbO₃/SnS₂/Cu₂O heterostructure was undertaken for the application of photoelectrochemical water-splitting. A type-II band alignment for charge carrier migration (i.e., electrons and holes) provided a high rate of charge transfer at the interface of the heterostructure, which aided prevention of photocorrosion and broadened the absorption range from the ultraviolet region to the visible region. Type-II band alignment was created in a NaNbO₃/SnS₂ heterojunction. Another type-II band alignment was formed in SnS₂/Cu₂O with a n–p-type heterojunction. Linear sweep voltammetry (LSV) plots of the NaNbO₃/SnS₂/Cu₂O heterostructure showed higher photocurrent density at a low onset potential. Mott–Schottky plots confirmed formation of a n–n–p heterojunction in the composition of NaNbO₃/SnS₂/Cu₂O, which helps to lower the recombination rate of charge carriers. Electrochemical impedance spectroscopy (EIS) suggested a smaller value of charge transfer resistance of the NaNbO₃/SnS₂/Cu₂O heterostructure; these data supported the evidence that migration of charge carriers was much more favorable in the designed heterostructure, which exhibited higher activity towards photoelectrochemical water-splitting.