Mengting Li,Huiying Mu,Ran Su,Ruihong Liu,Ying Liu,Yilei Li,Fa-tang Li
Although crystal facet engineering is extensively studied in energy and environmental technologies, the in-depth understanding of intrinsic mechanisms governing crystal facet heterojunctions in tuning band alignments is still limited. Here, novel Bi 5 O 7 NO 3 crystals exposing tailor {080} facets are synthesized via NH 4 + -assisted self-confined construction. It has been confirmed that NH 4 + ions selectively adsorb on the {141} facets, inversely inducing the growth of desired {080} crystal facets, while the tailored {080} facets facilitate the generation of oxygen vacancies. The controllable concentration of oxygen vacancies, influenced by different exposed facets, can optimize the relative positions of Fermi levels and shift the photoelectron transfer route between the {141} and {080}-OV facets from type-II to S-scheme, thus triggering rapid charge transport channels and effectively suppressing electron-hole recombination. DFT calculation verifies that the energy barrier for the *COOH formation on Bi 5 O 7 NO 3 -{080}-OV is the lowest, thereby promoting the generation of CO. The well-designed Bi 5 O 7 NO 3 crystals with the optimal {080}/{141} facet ratio exhibit a 3.8-fold enhancement in photocatalytic CO 2 reduction, compared to traditional Bi 5 O 7 NO 3 dominated by the {141} facets. This work offers new insights into the regulation of band alignments at heterointerfaces and the design of high-efficiency photocatalysts.
Ming Li,Tongyan Ren,Yubao Li,Shuang Li,Ping He,Yao Xiao,Jiufu Chen
In this study, a series of promising binary hybrid heterojunction CdIn 2 S 4 /ZnS (CIS/ZnS) were constructed via a facile hydrothermal method . Credible characterization methods including powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and UV–vis diffuse reflectance spectra (DRS) were carried out to investigate the physicochemical properties the as-obtained photocatalysts . Photocatalytic water splitting for hydrogen evolution was performed to evaluate the photocatalytic activity of the photocatalyst. The results indicate that the light-harvesting ability could be markedly enhanced by decorating CdIn 2 S 4 on ZnS microspheres . Compared with the pristine CdIn 2 S 4 and ZnS, the hybrid photocatalysts present more efficient photocatalytic hydrogen production performance. Among composite photocatalysts, the 5% CIS/ZnS sample manifests the highest photocatalytic hydrogen production rate of 10.80 mmol g −1 h −1 , which is 2.6 and 5.4 times higher than that of ZnS and CdIn 2 S 4 , respectively. Moreover, a type-I band alignment mechanism was prudently put forward to interpret the photocatalytic hydrogen generation activity. The boosted photocatalytic hydrogen evolution activities of CIS/ZnS can be attributed to the enhanced light-harvesting ability, efficient separation and transfer of the photo-induced charge carriers, and inhibition of electrons and holes recombination of binary hybrid CIS/ZnS photocatalysts.
Highly efficient all-inorganic perovskite solar cells require a fast charge transfer from CsPbBr3 to TiO2 to reduce the recombination from trap states. Herein, we insert a CdS/CdSe/CdS quantum dot (QD) layer between the TiO2 and CsPbBr3 layers to fabricate all-inorganic perovskite solar cells. By tuning the thicknesses of the CdSe layer of CdS/CdSe/CdS QDs, the conduction band (CB) levels can be adjusted to -3.72~-3.87 eV. After inserting the QD intermediate layer, the energy offset between the CB of TiO2 and CsPbBr3 is reduced, thus leading to a charge transfer rate boost from to . The power conversion efficiency (PCE) of the solar cell with QD intermediate layer achieves 8.64%, which is 20% higher than its counterpart without QDs.
Band alignments of ZnO/CdSe nanocrystal quantum-dots (NQDs) heterojunctions are determined by ultraviolet photoelectron spectroscopy using synchrotron radiation source. To obtain ideal heterojunction interface, 1,2-ethanedithiol was used for CdSe NQDs as a ligand substitute. A type II band alignment of the ZnO/CdSe NQDs heterojunctions with changeable band offsets by varying the sizes of CdSe NQDs is concluded. The tunable band alignment of ZnO/CdSe NQDs heterojunctions is beneficial to the improvement of the design and fabrication of quantum-dot-sensitized solar cells.
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