Direct Thermochemical CO₂ Reduction to Reduced Graphene Oxide-like Nanomaterials: Implications for Environmental and Energy Storage and Conversion Applications

CO2 capture and conversion to value-added products have seen continued advancement in recent years through electrochemical and thermochemical routes. In this work, we have adapted a facile and potentially scalable thermochemical reduction technique that directly reduces CO2 to different-quality reduced graphene oxide (rGO) solids. Several characterization techniques have been undertaken to investigate the role of two- and three-dimensional copper catalytic substrates, reaction time, and CO2 humidity content on the characteristics of the prepared rGO. Growth for 1 h at 550 °C atop a uniform two-dimensional (2D) catalytic copper substrate under a humidified CO2 environment (0.14 gH2O/gCO2) attained rGO with low defect densities (0.36 × 1011 cm–2) and high domain (31.9 nm) and crystallite (3.32 nm) sizes. Detailed statistical Raman analyses over large areas confirm that the mean defect distance of the synthesized rGO samples is 16–20 nm, indicative of the intrinsic high quality attained. The degree of reduction in rGO based on C/O ratios from 4 to 8 suggests that operating conditions can be fine-tuned to attain different-quality rGO with different attributable macroproperties such as conductivity and hydrophilicity. The developed method of direct CO2 reduction to rGO can be further tuned to produce different quality, morphology, and yield of other high-value solid carbon-based materials for emerging and existing applications.