Recycling Spent LiCoO2 Battery as a High-efficient Lithium-doped Graphitic Carbon Nitride/Co3O4 Composite Photocatalyst and Its Synergistic Photocatalytic Mechanism

Abstract

The ever-increasing quantity of spent lithium-ion batteries (LIBs) is both a potential environmental pollutant and a valuable resource. The spent LIBs recycling mainly aimed at the separation of valuable elements. Some issues still exist in these processes such as high energy consumption and complex separation procedures. This study avoided element separation and proposed a facile approach to transform spent LiCoO2 electrode into a lithium (Li)-doped graphitic carbon nitride (g-C3N4)/Co3O4 composite photocatalyst through one-pot in situ thermal reduction. During the thermal process, melamine served as the reductant for LiCoO2 decomposition and the raw material for g-C3N4 production. Li was in situ doped in g-C3N4 and the generated Co3O4 was in situ integrated, forming a Li-doped g-C3N4/Co3O4 composite photocatalyst. This special composite exhibited an enhanced photocatalytic performance, and its photocatalytic H2 production and RhB degradation rates were 8.7 and 6.8 times higher than those of g-C3N4. The experiments combined with DFT calculation revealed that such enhanced photocatalytic efficiency was ascribed to the synergy effect of Li doping and Co3O4 integrating, which extended the visible light absorption (450–900 nm) and facilitated the charge transfer and separation. This study transforms waste into a high-efficient catalyst, realizing high-valued utilization of waste and environmental protection.