Novel Cerium-Based Sulfide Nano-Photocatalyst for Highly Efficient CO2 Reduction.

To address the environmental crisis caused by excessive emissions of CO2 , the development of effective photocatalysts for the conversion of CO2 into chemicals has emerged as one of the most promising strategies. Herein, beyond those well-studied materials, a rare-earth sulfide-based nanocrystal NaCeS2 is fabricated and investigated for efficient and selective conversion of CO2 into CO, where the role of Ce ions is crucial. Firstly, the hybridization of Ce 4f and Ce 5d orbitals contributes to the photoresponsive band structure of NaCeS2 . Secondly, due to the charge rearrangement supplied by the incompletely filled 4f orbitals of Ce ions, NaCeS2 exhibits excellent charge separation efficiency and CO2 adsorption affinity, reducing the energy barrier for the conversion from CO2 to CO. Moreover, a NaCeS2 -MoS2 heterostructure is also designed to further boost the electron transfer from the Mo site to the Ce site, which results in an improvement of the catalytic reduction yield from 7.24 to 23.42 µmol g-1 within 9 h (both better than TiO2 controls). This work offers a platform for the development of rare-earth-based photocatalysts for CO2 conversion.

Mechanistic Investigation of Alkali-Treated Photocatalytic CO2 Reduction: The Role of OH- and Metal Cations for Almost 100 % Selectivity of CO.

In this work, the modulation of activity and selectivity via photoreduction of carbon dioxide under simulated sunlight was achieved by treating P25 and P25/Pt NPs with KOH. It found that KOH treatment could significantly improve the overall conversion efficiency and switch the selectivity for CO. Photoelectric characterizations and CO2 -TPD demonstrated that the synergistic effect of K+ and OH- accelerated the separation and migration of photogenerated charges, and also improved CO2 adsorption level. Significantly, the K ions could act as active sites for CO2 adsorption and further activation. In situ FTIR measurements and DFT calculations confirmed that K+ enhanced the charge density of adjacent atoms and stabilize CO* groups, reducing the reaction energy barrier and inducing the switching of original CH4 to CO, which played a selective regulatory role. This study provides insights into the photocatalytic activity and selectivity of alkali-treated photocatalysts and facilitates the design of efficient and product-specific photocatalysis.