Search

Promoting charge separation is still the main challenge in the rational design of photocatalysts for visible light photocatalytic reduction of CO2. Based on the unique advantages of the Eu3+ single atom and the Type-II heterojunction in the field of photocatalytic reduction, a Eu3+ single atom doped CdS/InVO4 Type-II heterojunction was successfully constructed through the combination of hydrothermal and in situ synthesis. The prepared CdS/InVO4:Eu3+ single atom composite material has excellent photocatalytic CO2 reduction activity under visible light. The XPS test results show that the In 3d, O 1s, V 2p, and Eu 3d peaks of 10-CdS/IVO:Eu3+ move slightly towards a low energy direction, while, the positions of Cd 3d and S 2p peaks are both shifted to the direction of high binding energies, which indicated that the electrons can be transferred from CdS to IVO with the help of Eu3+. The CO yield of CdS/InVO4:Eu3+ was 11.02 μmol g−1 h−1, which was almost 2.4 times that of pure InVO4 and 1.9 times that of pure CdS, and the yield of CH4 of CdS/InVO4:Eu3+ reached 8.24 μmol g−1 h−1, which was 5.3 times and 10.6 times that of InVO4 and CdS, respectively. Both the theoretical and experimental results show that the single atom Eu3+ can not only modify InVO4 and activate CO2 molecules, but can also promote charge separation between the interface and improve the photocatalytic performance. It is expected that the research results of this paper can provide a novel idea for the rational design of rare earth monatomic catalysts.

Only when the interfacial charge separation is enhanced and the CO2 activation is improved, can the heterojunction nanocomposite photocatalyst be brought into full play for the CO2 reduction reaction (CO2RR). Here, Er3+ single atom composite photocatalysts were successfully constructed based on both the special role of Er3+ single atoms and the special advantages of the SrTiO3:Er3+/g-C3N4 heterojunction in the field of photocatalysis for the first time. As we expected, the SrTiO3:Er3+/g-C3N4 (22.35 and 16.90 μmol g−1 h−1 for CO and CH4) exhibits about 5 times enhancement in visible-light photocatalytic activity compared to pure g-C3N4 (4.60 and 3.40 μmol g−1 h−1 for CO and CH4). In particular, the photocatalytic performance of SrTiO3:Er3+/g-C3N4 is more than three times higher than that of SrTiO3/g-C3N4. From Er3+ fluorescence quenching measurements, photoelectrochemical studies, transient PL studies and DFT calculations, it is verified that a small fraction of surface doping of Er3+ formed Er single-atoms on SrTiO3 building an energy transfer bridge between the interface of SrTiO3 and g-C3N4, resulting in enhanced interfacial charge separation. Aberration-corrected high-angle annular dark-field scanning transmission electron microscopy (AC HAADF-STEM) and adsorption energy calculations demonstrated that the exposed Er single-atoms outside the interface on SrTiO3 preferentially activate the adsorbed CO2, leading to the high photoactivity for the CO2RR. A novel enhanced photocatalytic mechanism was proposed, in which Er single-atoms play dual roles of an energy transfer bridge and activating CO2 to promote charge separation. This provides new insights and feasible routes to develop highly efficient photocatalytic materials by engineering rare-earth single-atom doping.