A direct dual Z-scheme 3DOM SnS2-ZnS/ZrO2 composite with excellent photocatalytic degradation and hydrogen production performance

A novel direct dual Z-scheme 3DOM (three-dimensional ordered macropores) SnS₂-ZnS/ZrO₂ composite was prepared by the template method combined with the in situ sulfur replacement technology. The composition, structure, morphology, and surface physicochemical properties of the composites were well characterized. The results indicate that it possesses a uniform and periodical macroporous structure, a large surface area (121.1 m² g^-1), broad visible light absorption, and high separation ability of photoinduced electron/hole pairs. 3DOM SnS₂-ZnS/ZrO₂ composite removed 96.8% of methyl orange within 210 min of simulated sunlight irradiation. Moreover, photocatalytic hydrogen production achieved the rate of 928.1 μmol g^-1, which was 66.3 times as high as that of the commercial P25 after 8 h simulated sunlight irradiation. The enhanced photocatalytic performance mainly attributed to the direct dual Z-scheme system, which improves the charge separation efficiency and optimizes the charge transfer pathway. The charge transfer mechanism over the 3DOM SnS₂-ZnS/ZrO₂ is discussed in detail based on the results of radical trapping experiments. Our work paves a new way to design 3DOM materials with direct dual Z-scheme structure.

Can Half-a-Monolayer of Pt Simulate Activity Like That of Bulk Pt? Solar Hydrogen Activity Demonstration with Quasi-artificial Leaf Device

Pt is the best cocatalyst for hydrogen production. It is also well-known that the surface atomic layer is critical for catalysis. To minimize the Pt content as cocatalyst, herein we report on half-a-monolayer of Pt (0.5θ_Pt) decorated on earth-abundant Ni-Cu cocatalyst, which is integrated with a quasi-artificial leaf (QuAL) device (TiO₂/ZnS/CdS) and demonstrated for efficient solar hydrogen production. For the QuAL, TiO₂ is sensitized with ZnS and CdS quantum dots by the SILAR method. The 0.5θ_Pt-decorated Ni-Cu shows an onset potential of 0.05 V vs reversible hydrogen electrode for the hydrogen evolution reaction, which is almost similar to that of commercial Pt/C. Photoactivity of the present QuAL device with either bulk Pt or 0.5θ_Pt-coated Ni-Cu cocatalyst is, surprisingly, equal. Our findings underscore that a fraction of a monolayer of Pt can enhance the activity of the cocatalyst, and it is worth exploring further for the high activity associated with atomic Pt and other noble metals.

Amplification of active sites and porosity for the adsorption of QDs via the induction of the rare-earth element la into TiO2 for enhanced photovoltaic effects in QDSSCs

Schematic representing preparation of TiO₂ and La–TiO₂, QDSSCs device development and mechanism of charge carrier’s migration in device along with IV curve for La–TiO₂.

Improved light-harvesting and suppressed charge recombination by introduction of a nanograss-like SnO2 interlayer for efficient CdS quantum dot sensitized solar cells

Quantum dot sensitized solar cell (QDSSC) performance is primarily limited by the recombination of charges at the interfaces of TiO₂/quantum dot (QD) sensitizer/electrolyte. Hence, blocking or suppressing the charge recombination is an essential requirement to elevate the QDSSC performance to the next level. To retard the charge recombination, herein, we propose the introduction of a SnO₂ nanograss (NG) interlayer on the surface of TiO₂ using the facile chemical bath deposition method. The SnO₂ NG interlayer not only inhibits the interfacial recombination processes in QDSSCs but also enhances the light-harvesting capability in generating more excitons. Hence, the TiO₂/SnO₂ NG/CdS QDSSCs can achieve the power conversion efficiency of 3.15%, which is superior to that of a TiO₂/CdS device (2.16%). Electrochemical impedance spectroscopy, open-circuit voltage decay and dark current analyses confirm that the recombination of charges at the photoanode/electrolyte interface is suppressed and the life time is improved by introducing the SnO₂ NG interlayer between the TiO₂ and CdS QD sensitizer.

ZnSxSe1-x Alloy Passivation Layer for High-Efficiency Quantum-Dot-Sensitized Solar Cells

Interface modification is an important means for improving the performance of almost all optoelectronic devices. In quantum-dot-sensitized solar cells (QDSCs), effective surface modification of photoanode also has a critical impact on photovoltaic performance. At present, ZnS and ZnSe wide band gap semiconductors are the mainstream materials used for photoanode/electrolyte interface passivation in QDSCs. However, the problem with these two materials is that the passivation effect and the lattice match with TiO₂/QD are difficult to be balanced. Although ZnS can form a larger energetic barrier due to the higher conduction band edge, its lattice mismatch with TiO₂ and QD (such as CdSe and CuInSe₂) is large, leading to the formation of additional defect states. On the contrary, ZnSe has a small lattice mismatch with TiO₂ and QD but a relatively lower conduction band edge. Herein, we propose a strategy to employ ZnS_xSe_1-x alloy materials as a passivation layer for the first time to solve the drawbacks of single-component passivation layers. The ZnS_xSe_1-x alloy passivation layer was deposited on the Zn-Cu-In-Se (ZCISe) QD-sensitized TiO₂ film electrode via successive ionic layer adsorption and reaction (SILAR) method. A stable polyselenosulfide/sulfide mixed anions were served as anion precursor for the formation of ZnS_xSe_1-x alloy passivation layer. Experimental results revealed that the alloy passivation layer is more favorable for the suppression of charge recombination at the photoanode/electrolyte interface. In addition, the ZnS_xSe_1-x alloy passivation layer can significantly improve the photogenerated electron extraction efficiency compared to the current classical ZnS passivation layer as confirmed by the transient absorption (TA) measurement. Consequently, the average efficiency of QDSCs was improved from 12.17 to 13.08% with the replacement of traditional ZnS passivation layer by ZnSSe-10 under AM 1.5G one full sun illumination.

Charge recombination control for high efficiency CdS/CdSe quantum dot co-sensitized solar cells with multi-ZnS layers

ZnS as an inorganic passivation agent has been proven to be effective in suppressing charge recombination and enhancing power conversion efficiency (PCE) in quantum dot-sensitized solar cells (QDSCs).

High performance of TiO2/CdS quantum dot sensitized solar cells with a Cu–ZnS passivation layer

A Cu–ZnS passivation layer effectively suppresses the charge recombination and increases the light harvesting in QDSSCs.

Solution-processed CdS quantum dots on TiO2: light-induced electrochemical properties

Schematic of CdS-sensitized mesoporous TiO₂ nanoparticles thin films along with their energy level diagram.

Plasmon resonance energy transfer and hot electron injection induced high photocurrent density in liquid junction Ag@Ag2S sensitized solar cells

Due to plasmon induced absorption enhancement and direct hot electron injection, a high photocurrent density of ∼25.6 mA cm⁻² was demonstrated in an Ag@Ag₂S co-sensitized solar energy conversion device.