Carbon nanotubes with CoNi alloy nanoparticles growing on porous carbon substrate as cathode for Li-CO2 batteries.

The over-exploitation of fossil fuels and rapid industrialization has released a large number of carbon dioxide. As a major greenhouse gas, it can induce the increasing global temperature and result in environmental issues. It is an urgent necessity to reduce carbon dioxide emission and increase carbon capture, utilization and storage. Li-CO2 battery can be used for the fixation and conversion of carbon dioxide to electrochemical energy. However, it is necessary to explore and design efficient catalysts, due to the low electronic conductivity and sluggish decomposition kinetics for lithium carbonate as the discharge product. Herein, carbon nanotubes with CoNi alloy nanoparticles growing on porous carbon substrate (PC/CoNi-CNTs) is designed by immersing porous melamine formaldehyde sponge into cobalt nitrate and nickel chloride solution with the subsequent carbonization. The porous structure of carbon substrate facilitates the electrolyte infiltration and carbon dioxide diffusion. The carbon nanotubes and CoNi alloy catalysts can efficiently enhance the reversible deposition and decomposition of lithium carbonate and carbon, taking advantage of their synergistic effect. At a current density of 0.05 mA cm-2, the terminal discharge and charge voltages are 2.76 and 4.23 V with a limited specific capacity of 0.2 mA h cm-2, respectively. These results demonstrat that the design of carbon nanotubes with alloy nanoparticles on porous carbon substrate as cathode can enhance the electrochemical performances of Li-CO2 battery.