Enhanced Capacitance and Desalination Performance with Plasma-Activated Biochar Electrodes

Derived from electric double-layer capacitors (EDLCs), capacitive deionization (CDI) using symmetric carbon-based electrodes is an emerging approach to purifying brackish water into drinking water. The deionization performance is mainly determined by the properties of the electrode materials. This work reports a green and efficient plasma treatment for activating raw biochar, which is subsequently used as the electrode material for both EDLCs and CDI. Oxygen plasma activation effectively modulates the surface charge, morphology, and functional groups. Biochar treated with oxygen plasma exhibits pronounced improvement in supercapacitor specific capacitance from 80 to 97.5 F g⁻¹ and 1.2 times higher desalination capacity in comparison with the raw biochar. Plasma activation can be an effective strategy to improving the capacitance and deionization performance of biochar.