We report a Cu2O/CdS/ZnO photoanode constructed by coupling
Cu2O and CdS nanoparticles on ZnO nanotube arrays (NTAs)
via combining chemical bath deposition with successive ionic-layer
adsorption and reaction. Integrating the merits of the superior ability
of Cu2O and CdS to harvest visible light, dual heterojunctions,
type-II band structure, a p-n junction, and ordered tubular structure,
the photoanode exhibits simultaneous significant improvements in the
visible light absorption, charge separation, hydrogen generation,
and stability. At 0.4 V versus Ag/AgCl under AM 1.5 G irradiation,
the photoanode achieves a photocurrent density of 7 mA/cm2, which is 2.3-fold higher than that of CdS/ZnO heterojunction NTAs.
Furthermore, under AM 1.5 G illumination without bias potential, the
photoanode achieves an average hydrogen generation rate of 134 μmol/h,
which is 1.5 times that of single-heterojunction CdS/ZnO NTAs. The
highest solar-to-hydrogen conversion efficiency of the Cu2O/CdS/ZnO photoanode is 2.8% at 0.6 V vs. RHE, 1.6 times that of
the CdS/ZnO NTAs.