Fabrication of Hierarchical Two-Dimensional MoS₂ Nanoflowers Decorated upon Cubic CaIn₂S₄ Microflowers: Facile Approach To Construct Novel Metal-Free p–n Heterojunction Semiconductors with Superior Charge Separation Efficiency

Abstract

Due to the enormous demand for effective conversion of solar energy and large-scale hydrogen production, cost-effective and long-lasting photocatalysts are believed to be necessary for global production of sustainable and clean hydrogen fuel. Robust and highly efficient p-n heterojunction photocatalysts have a striking ability to enhance light-harvesting capacity and retard the recombination of photoexcitons. A series of p-MoS/n-CaInS heterojunction composites with different MoS contents have been synthesized via a facile two-step hydrothermal technique in which rose-like p-MoS nanoflowers are decorated upon n-type cubic CIS microflowers. In the synthesis protocol highly dispersed MoS nanoflowers provided more active edge sites for the growth of c-CIS nuclei, leading to a hierarchical architecture with intimate interfacial contact. The formation of a hierarchical flower-like morphology of the photocatalyst has been established by an HRTEM and FESEM study. Electrochemical characterization, especially the slope of the curve from Mott-Schottky analysis and nature of the current from LSV, reveals the p-n heterojunction nature of the composite photocatalyst. The fabricated heterojunction photocatalysts were further examined for visible light photocatalytic H evolution. Far exceeding those for the neat c-CIS and MoS, it is seen that the p-MoS/n-CIS heterojunction photocatalyst with an optimum content of MoS exhibited enhanced H evolution using a 0.025 M NaS/NaSO solution as hole quenching agent under visible light illumination. The 0.5 wt % p-MoS/n-CIS photocatalyst presents a higher H production rate of 602.35 μmol h with 0.743 mA cm photocurrent density, 19 times and 8 times higher than those of neat c-CIS, respectively. This superior photocatalyic activity is due to the efficient separation of electron-hole charge carriers at the interface, as supported by a photoluminescence study and EIS measurements.

Visible‐Light‐Driven p–n Type BiMSbO6(M=Ti, Sn)/BiOBr Heterojunction Photocatalyst toward Degradation of Levofloxacin

“…Compared with the flat band potential of pure BiOBr (‐0.825 eV), the flat band potential of the BiMSbO 6 (M=Ti, Sn)/BiOBr heterojunction exhibited a negative shift, indicating that the Fermi level of the p‐type semiconductor BiMSbO 6 (M=Ti, Sn) moved downward in the BiMSbO 6 (M=Ti, Sn)/BiOBr heterojunction, while the Fermi level of the n‐type semiconductor BiOBr moved upward in the BiMSbO 6 (M=Ti, Sn)/BiOBr heterojunction . Furthermore, the carrier density of the electrode material was inversely proportional to the slope of the Mott‐Schottky plot . The slope of 20 wt% BiTiSbO 6 /BiOBr heterojunction (3.02) or the slope of 10 wt% BiSnSbO 6 /BiOBr heterojunction (3.84) was much smaller than the slope of pure BiOBr (8.66), confirming that the BiMSbO 6 (M=Ti, Sn)/BiOBr heterojunction had a much higher donor density capacity.…”

Fabrication of interlayer β-CD/g-C3N4@MoS2 for highly enhanced photodegradation of glyphosate under simulated sunlight irradiation

“…where the values of X for MoS 2 and g-C 3 N 4 are 5.323 and 4.72, respectively, E 0 is the energy of free electrons on the hydrogen scale ($4.5 eV), and E g is the band gap. 32 On the basis of the above equations, the calculated positions of the CB and VB of MoS 2 are À0.097 eV and 1.743 eV, respectively, and the calculated positions of the CB and VB of g-C 3 N 4 are À1.13 eV and 1.57 eV, respectively. Aer doping with oxygen atoms and the formation of a composite with MoS 2 , the absorption edge of O-C 3 N 4 /MoS 2 -5 underwent a red shi, which led to a wider absorption edge that reached about 537 nm.…”

Inside‐and‐Out Semiconductor Engineering for CO2 Photoreduction: From Recent Advances to New Trends

“…Photocatalysts with 3D structure, such as nanosheets‐assembled flowers, [ 227–233 ] hollow spheres, [ 234–243 ] and hierarchical NW arrays, [ 244–252 ] have been widely developed. Due to their special features, including high specific surface area and high light utilization, they always demonstrate excellent photocatalytic CO 2 reduction performance.…”