Solar-charged pseudocapacitors: Simultaneous conversion and storage of solar energy in ZnO@NiO nanorod arrays

In this paper, bias-free solar-driven pseudocapacitors based on ZnO@O nanorod arrays had been reported, which enable the synergistic coupling of light harvesting and electrochemical storage within one single electrode. When solar-charging, ZnO/NiO PN junction served as a driving force to separate the excitons and induce electron-injection through the interface to counter electrode forming charging bias. At this bias, the OH- trapped by photoexcited holes can make redox reaction with NiO and produce electrons. As expected, under a 1-sun illumination and no external electric bias, this ZnO/NiO composite exhibits a good specific capacitance of 44.5 F g(-1) at current densities of 0.5 A g(-1) as well as a good cycling performance (99% capacity retention after 50 cycles). Additionally, the capacitance equation was derived to account for the boosted capacitance as the increased solar-charging time. These findings here suggest the potential of further developing light-induced electrical energy storage and release on demand by a one-component light-charged capacitors. (C) 2018 Elsevier B.V. All rights reserved.