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

Abstract

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.