An amino-functionalized metal-organic framework achieving efficient capture-diffusion-conversion of CO2 towards ultrafast Li-CO2 batteries

Li-CO2 batteries provide a promising solution towards global sustainability since they are not only an energy storage device but also a recycling system of CO2 gas. However, Li-CO2 batteries suffer from sluggish diffusion of CO2 and poor electrode kinetics which gives rise to a large charge/discharge overpotential and low energy conversion efficiency. Herein, we design a composite of amino-group functionalized metal-organic framework encapsulated RuO2 nanoparticles (NH2-Cu-MOFs@RuO2). The amino groups on the pore wall help achieve high capture efficiency of CO2 and the ordered pores in the MOFs provide efficient transport channels for CO2/Li+ diffusion. Meanwhile, the synergistic catalytic effect of Cu nodes and RuO2 enables fast conversion of CO2 molecules. Benefitting from the capture-diffusion-conversion synergetic effects, the NH2-Cu-MOFs@RuO2 cathode exhibits a low cut-off overpotential of 1.21 V within a limiting capacity of 100 mu A h cm(-2) and a high capacity of 2903 mu A h cm(-2) at a current density of 50 mu A cm(-2). The rate performance improves significantly when using the NH2-Cu-MOFs@RuO2 as the cathode, where the battery presents a tardy decrease of discharge voltage and a slight increase of charge voltage from a current density of 20 to 1000 mu A cm(-2) and even retains similar to 2.6 V discharge voltage at a high current density of 1000 mu A cm(-2). Such a functionalized MOF-supported structure suggests a new way to produce efficient catalysts that improve the performance of diffusion-limited applications.