Novel Cerium‐Based Sulfide Nano‐Photocatalyst for Highly Efficient CO₂Reduction

Abstract

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.

Constructing Heteroatom-Doped Transition-Metal Sulfide Heterostructures for Hydrogen Evolution Reaction

“…The information of remaining elements (C, N, O, and Na) is displayed in Table S3. These results acquired by XPS spectra prove that the residual oxygen would drop into the lattice of MoS 2 and Ce 2 S 3 , which can increase the electronegativity for activating the catalytic sites; there are the polyvalent states of metallic elements (e.g., Ce 3+ , Ce 4+ , Mo 4+ , and Mo 6+ ), which would be beneficial to boost the electron transfer from Mo sites to Ce sites …”

“…According to the above analysis, the homogeneously distributed initial precursors and weak interactions of HAs@MoS 2 /Ce 2 S 3 deliver outstanding electroactive sites by reducing the aggregation; , the heterostructures present in HAs@MoS 2 /Ce 2 S 3 favor to improve the electrical conductivity by synergistic effects; the defects and localized disorders would provide additional active sites and enhance the adsorption of H atoms for increasing the catalytic activity of the HAs@MoS 2 /Ce 2 S 3 surface; ,, the doped heteroatoms (C, N, O, and Na) would enhance the inherent activity of the original active sites by boosting the densities of S–Mo–S in the MoS 2 edge molecular layer and exposed metal actives of Ce 2 S 3 , respectively; ,, and the high content of ordered/amorphous carbon in HAs@MoS 2 /Ce 2 S 3 would also heighten the catalytic activity by prompting charge transfer during the electrochemical catalytic process …”

“…The expectations of cost and effective electrocatalytic materials for the HER are also growing, such as excellent conductivity and highly efficient and large catalytic areas . Among all transition-metal compounds, transition-metal sulfides (TMSs), divided into two-distinct classes (layered MS 2 and nonlayered M x S y , M = transition metals), which possess the advantages in low-cost, abundant reserves, and sustainability, are thus regarded as promising substitutes for noble metal catalysts (e.g., Pt and Pd). , Additionally, different TMSs can emerge as different catalytic active sites: the S–M–S sites located on the edge of the MS 2 structure mainly present outstanding in-plane electrical conductivity; ,, some undercoordinated surface cations and the ligands (S adsorbing H atoms to form S–H bands) of M x S y are regarded as the excellent catalytic active sites for the HER. , However, the catalytic performances of TMS are still enormously hindered by the following factors: inert catalytic active sites of the basal plane-MS 2 , , low loading amounts of active centers (M) in M x S y , and serious aggregation during the reactions of M x S y . Addressing the issues, various strategies have been developed, including heteroatomic dropping, heterojunction constructing, , and defective introducing .…”

“…Heteroatom-doped carbon materials with TMS can effectively shorten the diffusion paths of electrons/ions, generating an amazing catalytic performance (η = 86 mV) . The heteroatoms (e.g., O and Ce) not only activate the catalytic sites but also reduce the catalytic energy barriers to exhibit the outstanding catalytic performances with excellent charge separation/transfer. , In addition, the structure defects will also improve the catalytic performances of MoS 2 by the following paths: producing excess electrons, facilitating the charge transfer, and enhancing the adsorption of H atoms . However, it is still a huge challenge to develop TMSs as heterostructures with excellent catalytic performance with a flexible approach. ,, …”

“…Herein, we utilized the interaction between urea and transition metal ions to construct a heterostructure (3R–MoS 2 and Ce 2 S 3 ) with heteroatoms (carbon, nitrogen, oxygen, and sodium) at a high-temperature nitrogen atmosphere. The chemical state of the active sites would intrinsically boost HER kinetics by reconstructing the chemical state of active sites after the incorporation of heteroatoms. , What is more, the charge transfer/mass transport will be accelerated by synergistic effects of ordered/amorphous carbon formed in the pyrolysis process, the presence of Ce, and heterojunctions. ,,, Also, the heterojunctions of 3R–MoS 2 and Ce 2 S 3 will further increase the basically catalytic active sites by increasing the number of edge Mo–S sites and the undercoordinated surface cation/ligand number of M x S y . As a result, HAs@MoS 2 /Ce 2 S 3 exhibits excellent properties in the HER: lower overpotential in acidic (147.0 mV) and alkaline (160.5 mV) environments.…”