Solar Energy Conversion and Electron Storage by a Cu₂O/CuO Photocapacitive Electrode

Solar conversion devices are generally connected with energy storage systems to overcome the influence of sunlight variability. Developing an integrated solar energy conversion and storage device is an attractive approach to compensate for the energy loss of directly connecting these separate devices. In this work, a photocapacitive device is developed based on the Cu2O/CuO heterostructure, with Cu2O as a light absorber and CuO providing a platform for electron and ion storage. The coupling of Cu2O and CuO leads to a high specific capacitance of 135 mF/cm2 under bias and an open-circuit potential of 0.62 VRHE. A photo-charge and dark-discharge ability of Cu2O/CuO system under zero-bias is also discovered and explained based on the concept of Faradaic junction. This work presents an avenue for the investigation of high-performance Cu2O-based solar energy storage devices.