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

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 LiCoO 2 electrode into a lithium (Li)‐doped graphitic carbon nitride (g‐C 3 N 4 )/Co 3 O 4 composite photocatalyst through one‐pot in situ thermal reduction. During the thermal process, melamine served as the reductant for LiCoO 2 decomposition and the raw material for g‐C 3 N 4 production. Li was in situ doped in g‐C 3 N 4 and the generated Co 3 O 4 was in situ integrated, forming a Li‐doped g‐C 3 N 4 /Co 3 O 4 composite photocatalyst. This special composite exhibited an enhanced photocatalytic performance, and its photocatalytic H 2 production and RhB degradation rates were 8.7 and 6.8 times higher than those of g‐C 3 N 4 . The experiments combined with DFT calculation revealed that such enhanced photocatalytic efficiency was ascribed to the synergy effect of Li doping and Co 3 O 4 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.