Magnetron sputtering of platinum on nitrogen-doped polypyrrole carbon nanotubes as an efficient and stable cathode for lithium–carbon dioxide batteries

As an emerging green energy storage and conversion system, rechargeable Li–CO2 batteries have undergone extensive research due to their ultra-high energy density and their significant role in greenhouse gas CO2 conversion. However, current Li–CO2 batteries have some shortcomings that severely limit their large-scale application. The most critical problems involve the insulation of the discharge product Li2CO3 and the slow decomposition kinetics, meaning that the battery generates a large overpotential and has a low cycle life, so the rational design of an efficient cathode catalyst is imperative. Here, we prepared a composite material via the magnetron sputtering of Pt onto nitrogen-doped polypyrrole carbon nanotubes (NPPy-CNTs) as a high-efficiency cathode catalyst for Li–CO2 batteries. The three-dimensional hollow tubular NPPy-CNTs can provide efficient channels for CO2 diffusion and enough space for the uniform deposition and decomposition of Li2CO3. Benefiting from the doping of nitrogen, more defects and active sites are introduced into the polypyrrole carbon nanotubes. Furthermore, the introduction of a small amount of the precious metal Pt effectively improves the catalytic activity of the CO2 reduction reaction (CO2RR) and the CO2 release reaction (CO2ER), greatly improving the cycle life of the battery. The Pt–NPPy-CNT-based battery shows a much improved electrochemical performance. The overpotential of the battery is reduced to 0.75 V, and the battery shows a specific discharge capacity of up to 29 614 mA h g−1.