Manganese-doped zinc oxide recycled from spent alkaline batteries for photocatalysis and supercapacitor applications

Official URL: https://dx.doi.org/10.1016/j.est.2024.113419

In a sustainable future, recycling e-waste will offer an adequate solution to control the raw materials and energy crisis. Our study aims to obtain ZnO-based materials by recycling the alkaline batteries using mild and cost-effective methods. Manganese-doped ZnO materials were obtained through anodic paste annealing at different temperatures. In terms of morphology and structure, particles with rod shape, high crystallinity, and hexagonal symmetry were obtained. The annealing provides an atomic rearrangement ensuring the presence of isolated Mn2+ ions in the ZnO lattice, as evidenced by EPR spectroscopy. The sample defect evolution with the annealing temperature was highlighted by photoluminescence spectroscopy. The photocatalytic and energy storage applications of the obtained sample were investigated. The photocatalytic activity was tested on Rhodamine B and Oxytetracycline under visible light irradiation. The highest photocatalytic efficiency was obtained for Mn-doped ZnO annealed at 700 °C, and the proposed mechanism was based on reactive oxygen species generation correlated with scavengers’ tests, defect's structure, and pores diameter. Additionally, the samples were used to design symmetric supercapacitors and tested using different electrochemical techniques to prove their energy storage features. As a result, the Mn-doped ZnO particles annealed at 800 °C showed increased specific capacitance of 182 F/g, energy density of 25.2 Wh/kg, and power density of 38.7 kW/Kg without the use of booster materials.