Anti-Site Defect-Induced\nCascaded Sub-Band Transition\nin CuInS<sub>2</sub> Enables Infrared Light-Driven CO<sub>2</sub> Reduction

Photocatalytic\nCO<sub>2</sub> conversion is a promising\napproach\nto simultaneously mitigate climate change and alleviate the energy\ncrisis. However, infrared light, which constitutes nearly half of\nthe solar energy, has not been effectively utilized yet. In this work,\nwe discover a photogenerated charge transition mechanism in CuInS<sub>2</sub> with intrinsic In<sub>Cu</sub> antisite defects for synergistic\nutilization of full-spectrum photons. Femtosecond transient absorption\nspectroscopy and DFT calculation unveil an intermediate band induced\nby the intrinsic antisite defects, where cascaded sub-band transition\ncould be realized by high-energy photons (UV–vis) and low-energy\n(IR), thus improving the absorption range of infrared light as well\nas the utilization efficiency of photogenerated carriers. <i>In situ</i> Kelvin probe force microscopy demonstrates that\nthe generation of photoexcited electrons could be greatly enhanced\nthrough this synergistic utilization of full spectrum light. Moreover, <i>in situ</i> X-ray photoelectron spectroscopy and <i>in\nsitu</i> diffuse reflectance infrared Fourier transform spectroscopy\nreveal that infrared photons could also enhance the adsorption and\nactivation of CO<sub>2</sub> and H<sub>2</sub>O on the catalyst surface.\nAs a result, the CO production rate under full spectrum light reaches\n19.9 μmol g<sup>–1</sup> h<sup>–1</sup>, which\nis more than a 7-fold increase over that under UV–vis irradiation.