Lanthanide promoted nickel catalysts for the integrated capture and conversion of carbon dioxide to methane via metal carbonates†

An integrated CO₂ capture and conversion system utilizing metal hydroxide salts has been developed to capture CO₂ from various sources including air in the form of carbonate salts and convert them directly into a synthetic fuel; methane. Nickel catalysts have previously been shown to convert carbonate salts, such as K₂CO₃ and Na₂CO₃, to methane. However, the productivity of these systems was rather modest in comparison to other catalysts based on ruthenium metal. With the help of lanthanide promoters, the methane productivity of nickel catalysts has been greatly improved. For the most part, the catalytic performance of the lanthanide promoted nickel catalysts followed the lanthanide contraction trend, i.e. the smaller the atomic size of the lanthanide, the higher the methane yield. Furthermore, the lanthanide promoted nickel catalysts are also stable under the alkaline conditions employed, maintaining their activity over five cycles of integrated CO₂ capture and conversion. Lastly, the lanthanide promoted nickel catalysts were demonstrated to be more economical compared to ruthenium- and unpromoted nicked-based catalysts.