A low-energy, high-yield method for synthesizing carbon nanoplatelets, carbon nano-onions (CNOs), and graphene through the electrolytic splitting of CO2 in molten CO32− electrolyte is presented. Resulting CO2 splitting products from the electrolysis comprise highly valuable graphene nanocarbons with unique morphologies. These valuable products create an incentive for climate change mitigation and greenhouse gas removal by utilizing CO2. CNOs, a lesser-known carbon nanomaterial, are made up of nested graphene carbon spheroids. Unlike traditional methods that use transition metal catalysts to grow carbon nanotubes, this process minimizes the use of such catalysts, resulting in a uniform production of CNOs with larger diameters as the growth time increases.