Environmentally-safe preparation and testing of electroactive phenazines charge storage

The United Nations (UN) has 17 core sustainable development goals (SDGs). Phenazines are widely utilized in chemistry, material science and physics. We utilized an ultrasonic homogenizer to discover the green, sustainable synthesis and purification of four electroactive phenazines by employing the green solvent for the reaction and purification. The high purity of phenazines was confirmed by the UV-Vis, elemental analysis, 1 H NMR (500 MHz) and 13 C NMR (125 MHz) spectroscopy. The electroactivity and electronic reversibility were investigated through voltammograms (current-voltage curves) that provided data for comparison. These phenazines possess reversible redox behavior in the negative potential range, demonstrating their potential as negative electrode materials for charge storage. Compared to the PAZ-1, 2, and 3, the PAZ-4 showed one-electron ( n = 1e-) electroreduction (O + ne -↔R), higher Δ E p = 0.2 V, and lower i pa /i pc = 0.80; therefore, PAZ-4 is ranked lowest in electrochemical stability/reversibility. This is because the two-electron donating CH 3 groups (EDG) increase the pi-electron density (pi-orbitals), thereby making it more energetically demanding to add electrons. Experimental parameters indicate that PAZ-3 (n = 2e - electro-reduction, E red o = -1.70, Δ E p = 0.07 V, i pa /i pc = 0.96) provides the best opportunity to widen the potential window and fast electron-transfer highly recommended for the charge-storage materials. Among the 4 PAZs, the PAZ-3 and PAZ-2 offer a robust combination of fast electron-transfer and electro-reduction charge storage properties. Hence, this research favors UN-SDGs for the green sustainable processing useful in the chemistry, material science while two-electron reversible electroreduction is highly desirable for the eco-friendly charge storage materials.