Evaluation of the Specific Capacitance of High-Entropy Oxide-Based Electrode Materials in View of Their Use for Water Desalination via Capacitive Method

Water pollution and scarcity are serious concerns for the growing world population. To meet the ever-pressing demand of fresh water, a variety of desalting techniques of seawater have been developed. Due to its environmental friendliness, high efficiency, easy regeneration of the electrodes, ambient operating pressure, and low operating potential suitable for the use in remote areas, the capacitive deionization (CDI) method is one of the most sustainable among them. This work focuses on the preparation of high-entropy oxides (HEOs) and carbon/HEO composites and the evaluation of their specific capacitance in view of their possible use as CDI electrode materials. CrMnFeCoNi-HEO, having spinel structure (sHEO), is obtained in the form of nanoparticles (NPs) and nanofibers (NFs) by the sol-gel method and electrospinning, respectively. Composite NFs with embedded sHEO NPs or MgCoNiCuZn-HEO NPs with rock-salt structure (rHEO) are also produced. In the 5-100 mV s(-1) scan rate range, the specific capacitance improves in the order C/rHEO NFs (8-32 F g(-1)) approximately equal to sHEO NPs (9-32 F g(-1)) < sHEO NFs (8-43 F g(-1)) < C/sHEO NFs (12-66 F g(-1)). The highest capacitance is obtained when the beneficial contributions of the carbon matrix and smaller-sized HEO NPs are synergistically coupled.

Automated summary

Water pollution and scarcity pose significant challenges for the growing world population. Capacitive deionization (CDI) emerges as one of the most sustainable desalting techniques due to its environmental friendliness and efficiency. This study focuses on the preparation and evaluation of high-entropy oxides (HEOs) and carbon/HEO composites as potential CDI electrode materials. The results show that the specific capacitance increases when the carbon matrix and smaller-sized HEO nanoparticles are synergistically coupled.