Efficient recycling of Co3O4 from spent lithium-ion batteries and its application as an electrochemical sensor and photocatalyst

Green recycling of spent lithium-ion batteries (LIBs) is a fundamental step toward environmental preservation and increased recovery of raw materials. In this study, lactic acid was used to leach the cathode active material of LIBs. The recycled material (Co3O4) was obtained by selective precipitation of the leachate with KOH, followed by calcination for 4.5 h at 450 degrees C. The composition and microstructure of the recycled material were confirmed by X-ray diffraction, Raman spectroscopy, scanning electron microscopy, and energy dispersive spectroscopy. Co3O4 was applied as a non-enzymatic electrochemical sensor for determination of ascorbic acid and as a photocatalyst in the degradation of methylene blue. The electrochemical sensor consisted of a printed electrode of carbon nanotubes modified with an 85:10:5 (w/w/w) mixture of recycled material, carbon black, and polyvinylidene fluoride (PVDF), respectively. Linear sweep voltammetry was used to measure the oxidation of ascorbic acid at 0.10 V. The analytical curve of the sensor had a coefficient of determination of 0.9915, sensitivity of 0.0498 +/- 0.0023 mu A mol L-1, and detection limit of 0.0245 mol L-1 in the concentration range of 0.166 to 1.0 mmol L-1. Co3O4 applied as a photocatalyst reached an efficiency of 61.47% in the decolorization of methylene blue after 120 min of reaction in the presence of H2O2 and UV light. Co3O4 recycled from spent LIBs is a promising source of raw materials for the development of non-enzymatic electrochemical sensors and photocatalysts via a sustainable and environmentally friendly route.