Formation of carbon nanoparticles by electrochemical conversion of CO2 in room-temperature ionic liquid

Nanocarbon materials have attracted attention due to their unique properties and wide range of applications; however, their production requires high temperatures and pressures. This study provides a novel method for electrodeposition of carbon nanoparticles onto an Ag substrate from CO2 using a potential-step application in P2225-TFSI at room temperature and medium pressure. Potential-step electrolysis, where − 3.0, − 0.40, and − 1.0 V (vs. Ag+/Ag) were applied for 1 min each, was conducted to reduce CO2 to silver carbonyl ions, which were then electrochemically reduced to carbon nanoparticles. The SEM images and XRD analysis of the electrodeposited material revealed that the carbon nanoparticles formed near the three-phase interface under an 8.0 atm CO2 atmosphere consist of graphite with a defective structure and ca. 13.7 nm in size. As the CO2 pressure increased from 1.0 to 8.0 atm, the size of carbon nanoparticles decreased. Raman spectroscopy revealed that as the CO2 pressure increased, the crystallinity of carbon improved near the three-phase interface of Ag/P2225-TFSI/CO2. Moreover, in electrodeposited carbon obtained at 8.0 atm CO2 atmosphere, the crystallinity difference of approximately 0.1 in the ID/IG ratio was observed between at the three-phase interface and at the two-phase interface of Ag/P2225-TFSI. The reported data demonstrate that nanocarbon can be electrodeposited by injecting medium-pressure CO2 at room temperature, which is expected to broaden the options for nanocarbon production methods and enable the production of functional carbon materials as a new CO2 recycling technology.