Highly conversion efficiency of solar water splitting over p-Cu2O/ZnO photocatalyst grown on a metallic substrate

Earth-abundant Cu2O-based photocatalysts are promising light absorbing materials for highly efficient solar hydrogen production through a photoelectrochemical (PEC) water splitting system. However, growth of these structures over incompatible and low conductive substrates hinders the interfacial charge transport kinetics of photo-generated carriers, which severely reduces PEC performance. Herein, we report a Cu2O photocathode directly grown on a metallic Ti coated on Mo-glass substrate with a ZnO protective nanolayer, to reduce the interfacial transport resistance of photo-generated charge carriers (holes) at the electrode-substrate interface, as well as to improve the separation and extraction efficiency at the electrode-electolyte interface, compared to that grown on a conventional FTO substrate. The morphological, structural, and optical characterization of all structures were examined by scanning electron microscopy (SEM), X-ray diffraction (XRD), UV-vis spectroscopy, and X-ray photoelectron spectroscopy (XPS). Bare Cu2O and Cu2O/ZnO photocathodes fabricated on Ti-substrate achieved efficient light harvesting with photocurrent densities (J(ph)) of similar to-3.03 and -7.23 mA cm(-2) at 0 V, and photocurrent onsets over +0.69 and +0.83 V versus the reversible hydrogen electrode (RHE), respectively, which are approximately 10.45 and 24.93 times higher than that of the pristine Cu2O photocathode grown on a FTO substrate (J(ph) similar to-0.29 mA cm(-2)). Interestingly, the Cu2O/ZnO photocathode on Ti-substarte showed an impressive solar conversion efficiency of 1.77% at 0 V vs. RHE. The interfacial transport resistance was also reduced significantly after using this approach, which emphasizes the role of metallic substrate in enhancing the overall PEC performance. (C) 2019 Elsevier Inc. All rights reserved.