Re-carbon, up-carbon, de-carbon: Plasma-electrified roll-to-roll cleaner production of vertical graphenes and syngas from greenhouse gas mixes

Abstract

Conversion of CO2 and CH4 greenhouse gases (GHGs) into high-value products using cleaner, sustainable, and renewable-energy-electrified processes is a critical step towards the ultimate decarbonization of our economy and society. Here, we demonstrate an industry-relevant, scalable, plasma-electrified roll-to-roll process to produce vertical graphenes (VGs) for energy storage and syngas from the GHG feedstock with a one-round conversion efficiency of ∼80%. The growth temperature of VGs from an appropriate mixture of CO2 and CH4 is reduced from the expected 700 °C to only 300 °C due to the effective dissociation of CH4 caused by reactive plasma-generated oxygen-containing species. A new pilot-scale process is developed to fabricate highly-branched VGs from CH4 + CO2 gas mixture on a large area (10 × 100 cm2) nickel foil under plasmas generated by a roll-to-roll linear microwave antenna. The analysis of gaseous products and carbon mass flow reveals that most of the GHG mix is effectively converted into the high-value syngas (CO and H2). Our results demonstrate the integrated re-carbon (re-use of GHGs), up-carbon (conversion of GHG into high-value carbon-based products, HVCBPs), and de-carbon (using the electrification to reduce process-related carbon emissions while producing HVCBPs for clean energy storage) approach that is environmentally benign, scalable, and industry-relevant. Widespread adoption of similar re-carbon – up-carbon – de-carbon process cycles at industry-relevant scales will significantly enhance the production of active nanocarbon materials for diverse applications, while contributing to the achievement of the ultimate zero-carbon-emissions global targets.