Excellent energy efficiency and pseudocapacitve adsorption in superior microporous electrodes derived from macadamia...

Membrane capacitive deionization (MCDI) is a promising desalination technology that has attracted significant attention in recent years. Identifying novel, sustainable materials with high salt adsorption capacity (SAC) for MCDI electrodes has been a major research focus. In this study, MCDI electrodes were fabricated for the first time from macadamia seed shell-derived activated carbon (MSS-AC) under optimal preparation conditions determined using response surface methodology (RSM). The results indicate that the MSS-AC electrode possesses a high specific surface area (808.27 m² g^-1) and excellent microporosity (81.69%), with a specific capacitance reaching 1004.65 F g^-1 (at 1.0 mV s^-1), maintaining 96.44% capacitance retention after 3000 galvanostatic charge-discharge (GCD) cycles. It also exhibits outstanding electrochemical performance, achieving a high energy density (Ed) of 167.98 Wh·kg^-1 and a power density (Pd) of 7199.99 W kg^-1 with a low diffusion resistance of only 0.10 Ω. Furthermore, the MSS-AC electrode shows pronounced pseudocapacitive behavior resulting from ion insertion and surface redox reactions, contributing up to 48.16% (at 1.0 mV s^-1), and achieves a salt adsorption capacity of 34.49 mg g^-1 at an initial salt concentration of 476.46 mg L^-1. These results suggest that MSS-AC is a promising electrode material for MCDI applications.