Pressure-dependent CO2 thermolysis on barium titanate nanocatalysts†

Abstract

Rising CO₂ levels pose a significant threat to global warming, extreme weather events, and ecosystem disruption. Mitigating these effects requires a reduction in CO₂ concentration using innovative technologies for CO₂ capture, storage, and utilization. Perovskite-type barium titanate nanocatalysts have the potential for high CO₂ conversion into valuable solid carbon products at low temperatures. In this study, we investigated the pressure-dependent CO₂ conversion activity of barium titanate nanocatalysts at 700 K. A key focus of this study is the impact of pressure on the interaction between CO₂ molecules and barium titanate nanocatalysts to evaluate the CO₂ conversion mechanism. The primary structures of the nanocatalysts remained unchanged after CO₂ thermolysis, whereas carbon was deposited on the nanocatalysts above 0.05 MPa. The reactant carbons after CO₂ conversion at various pressures between 0.01 and 1.0 MPa at 700 K were evaluated by temperature-programmed desorption in an O₂ atmosphere. The desorption peaks observed at approximately 500 K, 800–900 K, and 900–1300 K were the results of desorption of chemisorbed CO₂, less- and high-crystalline graphitic carbons. Chemisorbed CO₂ and less-crystalline graphitic carbon were observed at 0.05 MPa. Highly crystalline graphitic carbons were observed on the nanocatalysts after CO₂ thermolysis at 0.1–1.0 MPa as well as chemisorbed CO₂, although the amount of carbon at 1.0 MPa was smaller than the others. Therefore, the approach of CO₂ thermolysis at a low temperature of 700 K and 0.1–0.5 MPa is promising for producing valuable solid carbon products and mitigating the environmental impact of CO₂ emissions.