Metallic AgInS2 nanocrystals with sulfur vacancies boost atmospheric CO2 photoreduction under near-infrared light illumination

Unraveling the function of vacancy engineering in influencing the intrinsic CO2 photoreduction with low photon energy directly from air remains a significant challenge. Here, a metallic photocatalyst, ultrafine AgInS2 nanocrystals with sulfur vacancies (VS-AgInS2) is designed to exhibit superior atmospheric CO2 reduction performance under near-infrared (NIR) light. Theoretical calculations reveal that the presence of sulfur vacancies and metallic characteristics result in extended spectrum absorption to the NIR region and efficient separation of charge carriers. As evidenced by In situ Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) experiment and theoretical calculations, the unique properties of charge delocalization around the vacancy-induced dual sites at AgInS2 nanocrystals contribute to COOH* intermediates for CO production while simultaneously inhibiting the formation of CHO* intermediates. Consequently, the metallic VS-AgInS2 nanocrystals demonstrate nearly 100% selective CO production with a rate of 8.04 μmol g−1 h−1 under NIR irradiation, even directly from atmospheric CO2 in the air.