Manganese dioxide nanoparticles/reduced graphene oxide nanocomposites for hybrid capacitive desalination

The faradic asymmetric electrodes have recently attracted attention in capacitive deionization (CDI) because of their capability to remove both Na+ and Cl- ions from saline solution to meet the freshwater requirements. However, the fabrication of CDI electrodes that are high-performing and stable remains a challenge. In this work, an asymmetric electrode with highly stable CDIs has been fabricated by using reduced graphene oxide (RGO) as positive electrodes and spherical-like manganese dioxide nanoparticles decorated RGO sheets (MnO2/RGO) as negative electrodes to selectively capture salt ions from saline solution. MnO2/RGO electrodes exhibit a large specific capacitance of about 485 F g(-1) at 10 mV s(-1) in NaCl with lower internal resistance, which is significantly higher than that of recent electrode materials. Due to the superior specific capacitance and lower internal resistance behavior of MnO2/RGO electrodes, asymmetric CDI device has been assembled for the desalination of salt using saline water. Especially, MnO2/RGO//RGO-based asymmetric CDI device shows higher salt uptake capacity (SAC) of 52 mg g(-1) with higher average salt adsorption capacity (ASAR) of 2.7 mg g(-1) min(-1) than recently reported electrode materials. Furthermore, the recycling studies indicate that MnO2/RGO//RGO electrodes are promising electrode materials for prolonged CDI operation. In summary, the studies confirmed that the MnO2/RGO system offers excellent potential for producing portable drinking water by capacitive deionization of seawater.