A Dual-Heterojunction Cu2O/CdS/ZnO Nanotube Array Photoanode for Highly Efficient Photoelectrochemical Solar-Driven Hydrogen Production with 2.8% Efficiency

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/cm(2), 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 mu mol/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.