Persistent photothermal CO2 methanation without external energy input

Abstract

Photothermal CO₂ methanation is crucial for carbon neutralization and long-term space exploration, but the reliance on sunlight irradiation limits its practical application. Herein, a fluorite two-dimensional solid solution of NiO and CeO₂ (2D Ni₁Ce₁O₃) is synthesized for low-temperature CO₂ methanation, resulting in 80 ± 4 and 2125 ± 43 mmol g⁻¹ h⁻¹ of CH₄ production rates at 200 and 300 °C respectively, with 99.58 ± 0.12% CH₄ selectivity. This is attributed to 2D Ni₁Ce₁O₃ strengthening the CO₂ adsorption and changing the CO₂ methanation paths. When we used a homemade TiC/Cu based device to absorb sunlight to heat the catalyst, 2D Ni₁Ce₁O₃ showed a photothermal CO₂ methanation rate of 2901 mmol g⁻¹ h⁻¹ under weak sunlight irradiation and more interestingly a robust CO₂ methanation rate of ∼830 mmol h⁻¹ in dark environments. Consequently, the outdoor demonstration could drive CO₂ methanation for five continuous outdoor days and nights with a total CH₄ yield of 898 m³ and 10 tons of boiled water, showing the industrial potential of photothermal CO₂ methanation.