ZnO Nanowires as a Promotor of High Photoinduced Efficiency and Voltage Gain for Cathode Battery Recharging

In recent years, intensive efforts have been focused on the conversion and storage of solar energy in a single device. In this work, we report the use of ZnO-based electrodes in the form of monolayer or nanowires as a light inducer for battery recharging. Two transition metal complexes of ruthenium(II) and iron(II) are grafted onto the ZnO-based electrode to tune the efficiency of the system. We explore the influence of both the ZnO morphology and nature of the transition metal complex on the light induced voltage and faradaic efficiency toward electrochemical storage. The resulting ZnO-based electrodes have all been found to be electrochemically photoactive and their functionalized ZnO nanowire counterpart has shown the best results. Once the ruthenium complex has been grafted, a high potential gain between dark and illumination conditions of 1.3 V is reached, which is associated with a modest faradaic efficiency of 50%. However, in the presence of the iron complex, a favorable potential gain of 700 mV is obtained and advantageously combined with a faradic efficiency of 100%. These results undoubtedly highlight the remarkable synergy between photoactive ZnO, especially in the form of nanowires, and a redox center allowing it to be applied for a photorechargeable battery device.
doi.org/10.1021/acsaem.9b00783