A Supercapacitor Diode with High Rectification Ratio Induced by Carbon and Oxygen Vacancies

Supercapacitor-based ionic diode (CAPode) integrates ion-electron dual charge carriers in one device, thus possessing great potential in bioabiotic systems such as intelligent implantable devices and human-computer interfaces. Herein, we present a high-performance CAPode that takes carbon-modified anatase titania (C@TiO_2-<i>x</i>) nanowires with abundant oxygen vacancies as the negative electrode. The modification of the thin carbon layer improves the conductivity and cycling stability of TiO₂ nanowires, and more attractively, introduces a large amount of oxygen vacancies in them, enhancing the electrochemical kinetics and rectification capability of the C@TiO_2-<i>x</i> nanowires. Consequently, the C@TiO_2-<i>x</i> electrode exhibits a high rectification ratio I (<i>RR</i>_I) of 204.6 and a rectification ratio II (<i>RR</i>_II) of 98.3% at 1 mV s^-1. Also, the assembled CAPode exhibits an <i>RR</i>_I of 99.1 at 8 mV s^-1 and a wide operating window of -1.0 to 1.4 V. Therefore, the assembled CAPodes successfully demonstrate the functionality of both "AND" and "OR" gates, revealing the potential to process information. The above results show that the rectification capability of CAPodes can be comparable to that of conventional ionic diodes and highlight the importance of modulating the electrochemical ion storage behavior to improve the rectification performance of CAPodes.