Highly Efficient Cu-Porphyrin-Based Metal-Organic Framework Nanosheet as Cathode for High-Rate Li-CO2 Battery

The lithium-carbon dioxide (Li-CO2) battery as a novel metal-air battery has a high specific energy density and unique CO2 conversion ability. However, its further development is limited by incomplete product decomposition resulting in poor cycling and rate performance. In this work, Cu-tetra(4-carboxyphenyl) porphyrin (Cu-TCPP) nanosheets are prepared through the solvothermal method successfully. An efficient Li-CO2 battery with Cu-TCPP as catalyst achieves a high discharge capacity of 20393 mAh g(-1) at 100 mA g(-1), a long-life cycle of 123 at 500 mA g(-1), and a lower overpotential of 1.8 V at 2000 mA g(-1). Density functional theory calculation reveals that Cu-TCPP has higher adsorption energy of CO2 and Li2CO3 compared with TCPP, and a large number of electrons gather near the Cu-N-4 active sites in Cu-TCPP. Therefore, the excellent CO2 capture ability of the porphyrin ligand and the synergic catalytic effect of Cu atom in Cu-TCPP promote the thermodynamics and kinetics of CO2 reduction and evolution processes.