Carbon Nanotubes Produced from Ambient Carbon Dioxide for Environmentally Sustainable Lithium-Ion and Sodium-Ion Battery Anodes

[Image: see text] The cost and practicality of greenhouse gas removal processes, which are critical for environmental sustainability, pivot on high-value secondary applications derived from carbon capture and conversion techniques. Using the solar thermal electrochemical process (STEP), ambient CO(2) captured in molten lithiated carbonates leads to the production of carbon nanofibers (CNFs) and carbon nanotubes (CNTs) at high yield through electrolysis using inexpensive steel electrodes. These low-cost CO(2)-derived CNTs and CNFs are demonstrated as high performance energy storage materials in both lithium-ion and sodium-ion batteries. Owing to synthetic control of sp(3) content in the synthesized nanostructures, optimized storage capacities are measured over 370 mAh g(–1) (lithium) and 130 mAh g(–1) (sodium) with no capacity fade under durability tests up to 200 and 600 cycles, respectively. This work demonstrates that ambient CO(2), considered as an environmental pollutant, can be attributed economic value in grid-scale and portable energy storage systems with STEP scale-up practicality in the context of combined cycle natural gas electric power generation.