Determination of Band Alignment in the Synergistic Catalyst of Electronic Structure-Modified Graphitic Carbon Nitride-Integrated Ceria Quantum-Dot Heterojunctions for Rapid Degradation of Organic Pollutants

We engineered novel heterojunction ceria (CeO₂) QDs decorated on the surfaces of graphitic carbon nitride (g-C₃N₄) nanosheets by a facile in situ hydrothermal synthetic route. Using core-level/valence-band X-ray photoelectron spectroscopy (XPS), diffuse reflectance spectroscopy, and work function measurements of the materials, we constructed the energy band alignment at the heterojunction. The band alignment has a Type-II alignment between organic (g-C₃N₄) and inorganic (CeO₂ QDs) semiconductors junction with valence/conduction band offsets (VBO/CBO) of −0.07/–0.31 eV. The calculated band alignment parameters of the heterojunction were compared with the experimental values of g-C₃N₄/CeO₂ QD composite and a new energy band diagram was proposed for the electronic structure-modified g-C₃N₄/CeO₂ QDs heterojunction. The newly constructed heterojunction is formed by carbon-vacancy-promoted g-C₃N₄ coupled to lower defect-mediated (oxygen vacancies) CeO₂, as determined by high-resolution XPS analysis. Moreover, the CeO₂ QD distribution on g-C₃N₄ sheets using HR-TEM and the lattice parameter variations of g-C₃N₄/CeO₂ QDs as compared with those of pristine CeO₂ QDs from Rietveld refinement were investigated. To demonstrate the ability of the proposed heterojunction as a catalyst, we tested the catalytic activity of the composite junction for the degradation of Rhodamine B (RhB) in the presence of NaBH₄ as an example. The band alignment mechanism is useful for promoting the catalytic activity of the graphitic carbon nitride-based organic semiconductor and will attract researchers’ attention for developing new composite heterojunction catalysts for multifunctional applications

Tiny MoO₃ nanocrystals self-assembled on folded molybdenum disulfide nanosheets via a hydrothermal method for supercapacitor

<p>Coupling of two active semiconductors can easily lead to a deterioration of their intrinsic properties. In this work, tiny MoO₃ nanocrystals were deposited on 3D MoS₂ frameworks via a hydrothermal reaction, with heterostructures forming by oxygen-bonding interactions at their interface. When tested as a supercapacitor electrode, the MoS₂/MoO₃ heterostructure exhibited a high specific capacitance of 287.7 F g⁻¹ at a current density of 1 A g⁻¹, and a remarkable cycling stability after 1000 cycles at 1 A g⁻¹ in an aqueous solution compared to pristine MoS₂. The results thus reveal the superior properties of the MoS₂/MoO₃ heterostructure for supercapacitor electrode.</p> <p>We successfully synthesized tiny MoO₃ nanocrystals deposited on 3D MoS₂ frameworks via a self-assembly. The MoS₂/MoO₃ heterostructure exhibited a high specific capacitance and cycling stability compared to pristine MoS₂.</p