Fig. 1.

Traditional and selective light absorber-assisted photothermal systems. a Photograph of the Ni/Y₂O₃ nanosheets powder. b Normalized UV–Vis–IR absorption spectrum of the Ni/Y₂O₃ nanosheets. c Solar energy absorption and thermal radiation diagram for the Ni/Y₂O₃ nanosheets at 200 °C. The ambient solar flux of 1 kW m⁻² is not enough to sustain the thermal radiation; thus, an equilibrium temperature of 200 °C cannot be obtained. d Cross-sectional SEM image and e normalized UV–Vis–IR absorption spectrum of the selective light absorber (AlN_x/Al foil). f Solar energy absorption and thermal radiation diagram of the selective light absorber at 200 °C. The thermal radiation was far below the absorbed energy from ambient solar flux. g Schematic of the new photothermal system used for photothermal CO₂ methanation with the selective absorber and the catalysts. h, i The light-driven temperature and CO₂ conversion rates of the Ni/Y₂O₃ nanosheets with (Ni/Y₂O₃ + S red) and without (Ni/Y₂O₃ green) the selective light absorber-assisted photothermal system, respectively, under different intensities of sunlight irradiation. The scale bar in d is 2000 nm