Rational design of direct Z-scheme heterostructure NiCoP/ZIS for highly efficient photocatalytic hydrogen evolution under visible light irradiation

Advances in the heterostructures for enhanced hydrogen production efficiency: a comprehensive review

The growing global energy demand and heightened environmental consciousness have contributed to the increasing interest in green energy sources, including hydrogen production. However, the efficacy of this technology is contingent upon the efficient separation of charges, high absorption of sunlight, rapid charge transfer rate, abundant active sites and resistance to photodegradation. The utilization of photocatalytic heterostructures coupling two materials has proved to be effective in tackling the aforementioned challenges and delivering exceptional performance in the production of hydrogen. The present article provides a comprehensive overview of operational principles of photocatalysis and the combination of photocatalytic and piezo-catalytic applications with heterostructures, including the transfer behavior and mechanisms of photoexcited non-equilibrium carriers between the materials. Furthermore, the effects of recent advances and state-of-the-art designs of heterostructures on hydrogen production are discussed, offering practical approaches to form heterostructures for efficient hydrogen production.

Interfacial tuning in FeP/ZnIn2S4 Ohm heterojunction: Enhanced photocatalytic hydrogen production via Zn-P charge bridging

Interfacial regulation is key to photocatalytic performance, yet modulating interfacial charge transfer in heterostructures remains challenging. Herein, a novel nanoflower-like FeP/ZnIn2S4 Ohm heterostructure is first designed, with Zn atoms in ZnIn2S4 (ZIS) acting as potential anchoring sites around P atoms, forming liganded Zn-P bonds. Combining 1D FeP nanowires and 2D ZIS nanosheets enhances the mobility of photogenerated electrons. The synergistic chain-type "electron pickup" mechanism of the Ohm heterojunction coupled with the Zn-P bond speeds up electron transport at the interface. The Ohm heterojunction initiates an internal electric field, creating a driving force to further transfer photogenerated electrons through the Zn-P rapid electron transport channel to FeP, which acts as a reservoir for active sites to release H2. The optimized FeP/ZIS demonstrates a remarkable H2 evolution rate at 4.36 mmol h-1 g-1, 3.6 times that of pristine ZIS. This work provides novel insights into optimizing photocarrier dynamics via interfacial microenvironment modulation.

Rational Design of MIL-68(In) Derived Multiple Sulfides with Well Confined Quantum Dots and the Promoted Photocatalytic Hydrogen Generation

Quantum dots (QDs) of metal sulfides were proven to be excellent cocatalysts in visible-light-driven photocatalytic reactions. Metal organic frameworks (MOFs) possess a 3D porous channel that effectively confines small QDs and preserves their high catalytic activity by preventing their aggregation. In order to precisely construct the ternary metal sulfides of ZnS/ZnIn2S4/In2S3 with well-maintained Zn-AgInS2 (ZAIS) QDs, an in situ sulfurization combining a subsequent Zn(II)-exchange strategy was employed in this work. First, the ZAIS QDs were incorporated into MIL-68(In), which were then used as the precursors to precisely construct the ternary metal sulfides of ZnS/ZnIn2S4/In2S3 with well maintained ZAIS QDs through an in situ sulfurization combining subsequent Zn(II)-exchange strategy. When the optimized nanocomposites (QDs@M-t-Zn, where t is the sulfurization time) were applied in visible light-induced photocatalytic hydrogen generation, the resulting QDs@M-24h-Zn showed a significantly improved hydrogen evolution rate of 448.96 μmol g-1 h-1, which values are clearly higher than those of MIL-68(In), QDs@MIL-68(In), and M-24h-Zn without the presence of ZAIS QDs. To elucidate the increased photocatalytic mechanism, the optical patterns and the batch electrochemical investigations were combined. It has been discovered that the matching band potentials and the close contact heterojunction enhance interface charge transfer, which in turn encourages photocatalytic hydrogen production. This study demonstrates the well-thought-out design of the uniform confinement architecture inherited from MOF QD-assisted multinary metal sulfides photocatalysts.

Tunable electronic and optical properties of BAs/WTe2heterostructure for theoretical photoelectric device design

The geometric structure of the BAs/WTe2heterojunction was scrutinized by employingab initiocalculations grounded on density functional theory. Multiple configurations are constructed to determine the equilibrium state of the heterojunction with optimal stability. The results show that the H1-type heterojunction with interlayer distance of 3.92 Å exhibits exceptional stability and showcases a conventional Type-II band alignment, accompanied by a direct band gap measuring 0.33 eV. By applying external electric field and introducing strain, one can efficaciously modulate both the band gap and the quantity of charge transfer in the heterojunction, accompanied by the transition of band alignment from Type-II to Type-I, which makes it expected to achieve broader applications in light-emitting diodes, laser detectors and other fields. Ultimately, the heterojunction undergoes a transformation from a semiconducting to a metallic state. Furthermore, the outstanding optical characteristics inherent to each of the two monolayers are preserved, the BAs/WTe2heterojunction also serves to enhance the absorption coefficient and spectral range of the material, particularly within the ultraviolet spectrum. It merits emphasis that the optical properties of the BAs/WTe2heterojunction are capable of modification through the imposition of external electric fields and mechanical strains, which will expand its applicability and potential for future progression within the domains of nanodevices and optoelectronic apparatus.

In-situ preparation of mossy tile-like ZnIn2S4/Cu2MoS4 S-scheme heterojunction for efficient photocatalytic H2 evolution under visible light

The reasonable design and fabrication of heterojunction could regulate the photocatalytic performance to some extent, yet it is still a great challenge to construct the S-scheme heterostructure with the stable as well as tight interface on the surface of semiconductor photocatalysts. Herein, the ZnIn2S4/Cu2MoS4 (ZIS/CMS) S-scheme heterostructure was fabricated by in-situ assembling ZIS nanosheets on the CMS plates, obtaining a mossy tile-like morphology. Owing to the compact interface resulting from in-situ growth, this unique architecture efficiently facilitated the separation and transfer of light-induced charges, guaranteed the larger interface area, and enriched the active sites for photocatalytic redox reactions. After adjusting the mass ratio of CMS in ZIS/CMS, S-scheme heterostructure exhibited the remarkable performance with an optimal H2 producing rate up to 1298 μmol·h-1 g-1, about 13.8 times than that of pristine ZIS. The mechanism and driving force of charge transfer and separation in S-scheme heterostructure photocatalysts were explained and discussed. This investigation will provide new insight into design and construction of S-scheme heterojunction photocatalysts for H2 evolution.

Insights into the formation of environmentally persistent free radicals during photocatalytic degradation processes of ceftriaxone sodium by ZnO/ZnIn2S4

At present, the researches on photocatalysis were mainly focused on the design, improvement and development of catalysts, and less attention was paid to the existing characteristics of environmentally persistent free radicals (EPFRs) during the process of photocatalytic oxidation. In this study, A flower-like Z-type heterojunction ZnO/ZnIn₂S₄ (ZnO/ZIS) and typical antibiotic ceftriaxone sodium (CS) were taken as study objects, concentrating on the generation characteristics of EPFRs during the degradation of CS by ZnO/ZIS, and clarifying the degradation mechanism of CS in which EPFRs participated. The results showed that the degradation efficiency of 10 mg/L CS by 0.40 g/L ZnO/ZIS reached 85.3% in 150 min under the irradiation of 500 W xenon lamp. It was clear that ·O₂^- and h⁺ play major roles in CS degradation by ZnO/ZIS under visible light, and ·OH plays an auxiliary role. Furthermore, the formation mechanism of EPFRs during photocatalytic degradation processes of CS by ZnO/ZIS were first investigated thoroughly via experimental analysis and density functional theory (DFT) calculations. The concentration level of EPFRs centered on oxygen atoms is 10¹¹ spin/mm³, which were generated in the process of degradation of CS by ZnO/ZIS under visible light. The production of EPFRs chiefly includes two procedures: chemical adsorption and transfer of electrons. The adsorption energy of precursor P8 on ZnIn₂S₄ side is -1.91 eV, the electrons transferred from precursor P8 and P11 to ZnO/ZnIn₂S₄ heterojunction. Surprisingly, EPFRs have little negative effects on the degradation process of CS by ZnO/ZIS. The study was not only a key field in the development of photocatalysis technology, but also a new way to study the removal mechanism of antibiotics.