A highly active three-dimensional Z-scheme ZnO/Au/g-C3N4 photocathode for efficient photoelectrochemical water splitting

Abstract

All-solid-state Z-scheme photocatalyts have been widely used in solar water splitting, but most of the previous applications are achieved through powder systems. Herein, a Z-scheme ZnO/Au/graphitic carbon nitride (g-C3N4) composite heterojunction with three-dimensional (3D) urchin-like micro/nanostructure has been successfully fabricated and applied as an excellent photocathode for PEC H2 evolution. The 3D urchin-like ZnO/Au/g-C3N4 heterostructure provides a rapid Z-scheme charge-carrier transport and collection channel. The characterization of electrochemical impedance and time-resolved photoluminescence confirm that the incorporated Au nanoparticles act as an electron mediator to promote vectorial electron transfer in direct Z-scheme ZnO/g-C3N4 heterojunction. With a bias of 0 V vs. RHE in neutral electrolyte (0.2 M Na2SO4), the Pt co-catalysts loaded Z-scheme ZnO/Au/g-C3N4 photocathode shows a stable photocurrent as high as -0.29 mA cm−2 over 36,000 s. This work delivers a new insight to the future development of novel all-solid-state Z-scheme photoelectrodes for efficiently converting solar energy into hydrogen fuels.