Curcumin as a sustainable electrolyte additive for Zn–air batteries: Corrosion inhibition, interfacial dynamics, and enhanced discharge performance

The fast deterioration of zinc anodes in concentrated alkaline electrolytes represents a significant impediment to the commercialization of sustainable Zn-air batteries. While Curcumin is known for its antioxidant properties, its role in stabilizing high-molarity electrochemical interfaces remains poorly understood. This study presents a systematic evaluation of Curcumin as a sustainable corrosion inhibitor for zinc in strongly alkaline media relevant to Zn–air batteries. This study moves beyond traditional inhibition studies by integrating multi-scale surface characterization (XPS, FT-IR, SEM/EDX) with advanced electrochemical modeling to evaluate Curcumin as a sustainable solution. Curcumin achieved a maximum inhibition efficiency of 93% at 200 ppm in 6 M KOH, attributed to the formation of a compact, adherent protective film on the zinc surface. Thermodynamic analysis revealed a ΔG° ads value of −32.29 kJ·mol −1 , confirming spontaneous and high-affinity adsorption. Importantly, the electrochemical response exhibited distinct nonlinear features such as capacitance dispersion, deviation from ideal Langmuir adsorption, and constant-phase-element behavior, reflecting complex interfacial dynamics governing inhibitor–metal interactions. These nonlinear effects are consistent with modern theoretical models describing amplitude-dependent impedance and fractional-order dynamics in electrochemical systems. Incorporation of Curcumin into Zn–air batteries significantly enhanced discharge capacity and operational stability, establishing a direct correlation between corrosion inhibition and improved device performance. Overall, Curcumin emerges as an efficient, eco-friendly inhibitor exhibiting nonlinear mechanistic behavior and practical relevance for sustainable zinc-based technologies.