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

Abstract

Li-CO<inf>2</inf> batteries provide a promising solution towards global sustainability since they are not only an energy storage device but also a recycling system of CO<inf>2</inf> gas. However, Li-CO<inf>2</inf> batteries suffer from sluggish diffusion of CO<inf>2</inf> 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 RuO<inf>2</inf> nanoparticles (NH<inf>2</inf>-Cu-MOFs@RuO<inf>2</inf>). The amino groups on the pore wall help achieve high capture efficiency of CO<inf>2</inf> and the ordered pores in the MOFs provide efficient transport channels for CO<inf>2</inf>/Li⁺ diffusion. Meanwhile, the synergistic catalytic effect of Cu nodes and RuO<inf>2</inf> enables fast conversion of CO<inf>2</inf> molecules. Benefitting from the capture-diffusion-conversion synergetic effects, the NH<inf>2</inf>-Cu-MOFs@RuO<inf>2</inf> cathode exhibits a low cut-off overpotential of 1.21 V within a limiting capacity of 100 μA h cm⁻² and a high capacity of 2903 μA h cm⁻² at a current density of 50 μA cm⁻². The rate performance improves significantly when using the NH<inf>2</inf>-Cu-MOFs@RuO<inf>2</inf> 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 μA cm⁻² and even retains ∼2.6 V discharge voltage at a high current density of 1000 μA cm⁻². Such a functionalized MOF-supported structure suggests a new way to produce efficient catalysts that improve the performance of diffusion-limited applications.