Construction of Active and Stable Photoelectrodes via Complementary Coupling of Two-Dimensional Narrow- and Wide-Bandgap Nanosheets

Heteroassembly of chemically exfoliated nanosheets (NSs) has been explored to produce functional two-dimensional materials for a wide range of applications in electronic and energy devices. In this study, the molecular-scale assembly approach is extended to construct visible light-active and stable photoelectrodes consisting of narrow- and wide-bandgap semiconductor units, i.e., MoS2 and Ti0.87O2 NSs, which contribute with complementary roles to the performance of the photoelectrodes. As a visible light response element, 2H phase MoS2 NSs possessing high crystallinity were electrochemically exfoliated from a MoS2 crystal and functionalized via interface modification, yielding an absorbed photon-to-electron conversion efficiency that was 2 orders of magnitude higher than that of previously studied defective MoS2 NSs synthesized via Li intercalation. Furthermore, the controlled interfacial coupling between corrodible MoS2 NSs and a chemically stable, visible light-transparent Ti0.87O2 NS coating resulted in the enhanced photoelectrode durability due to the hole tunneling ability inherent to ultrathin insulating oxide layers. Therefore, the visible light responsivity of MoS2 and the chemical stability of Ti0.87O2 NSs were complementary and combined in the interface-engineered heteroassembly system. This photoelectrode design can be expected to be applicable to other combinations of visible light-active narrow-bandgap and corrosion-protective wide-bandgap NS units compatible with various reaction systems.