Construction of ZnIn2 S4 /CdS/PdS S-Scheme Heterostructure for Efficient Photocatalytic H2 Production

ZnIn2S4-based multi-interface coupled photocatalyst for efficient photothermal synergistic catalytic hydrogen evolution

Photothermal synergistic catalysis is a novel technology that converts energy. In this study, ZnIn2S4 with S-vacancy (ZIS-Vs) is combined with Nickel, Nickle Oxide and Carbon Nanofiber aggregates (Ni-NiO@CNFs) to create a multi-interface coupled photocatalyst with double Schottky barrier, double channel and mixed photothermal conversion effect. Theoretical calculation confirms that the Gibbs free energy (ΔG*H) of the S-scheme heterojunction in the composite material is -0.07 eV, which is close to 0. This promotes the adsorption of H* and accelerates the formation of H2. Internal photothermal catalysis is achieved by visible-near infrared (Vis-NIR, RT) irradiation. The internal photothermal catalytic hydrogen production rate of the best sample (0.9Ni-NiO@CNFs/ZIS-Vs) is as high as 17.24 mmol·g-1·h-1, and its photothermal conversion efficiency (η) is as high as 61.42 %. Its hydrogen production efficiency is 20.52 times that of ZIS-Vs (0.84 mmol·g-1·h-1) under visible light (Vis, RT) conditions. When the Vis-NIR light source is combined with external heating (75 ℃), the hydrogen production efficiency is further improved, and the hydrogen production efficiency (29.16 mmol·g-1·h-1) is 26.75 times that of ZIS-Vs (1.09 mmol·g-1·h-1, Vis-NIR, RT). Further analysis shows that the increase in hydrogen production resulted from the apparent activation energy (Ea) of the catalyst decreasing from 16.7 kJ·mol-1 to 9.28 kJ·mol-1. This study provides a valuable prototype for the design of an efficient photothermal synergistic catalytic system.

Insights into the function of metallic 1T phase tungsten disulfide as cocatalyst decorated zinc indium sulfide for enhanced photocatalytic hydrogen production activity

Improving the separation efficiency of carriers is an important part of enhancing photocatalytic activity. Herein, we successfully decorated metallic 1T phase tungsten disulfide (1T-WS2) on the surface of zinc indium sulfide (ZnIn2S4) and investigated the synergistic effect of 1T-WS2 on ZnIn2S4. The characterization results show that 1T-WS2 improves the light absorption capacity and utilization efficiency, increases the catalytic active site, improves the photogenerated charge separation efficiency, and optimizes the reduction potential of ZnIn2S4. Theoretical calculations show that compared with ZnIn2S4, 1T-WS2/ZnIn2S4 has a smaller adsorption Gibbs free energy of the intermediate state H*, which is conducive to the catalytic reaction. Under simulated solar irradiation, the hydrogen (H2) production rate of 1T-WS2/ZnIn2S4 with a loading of 12 wt% reaches 30.90 mmol h-1 g-1, which is 3.38 times higher than that of single ZnIn2S4 (9.13 mmol h-1 g-1). In addition, the apparent quantum efficiency of 1T-WS2/ZnIn2S4 with a loading of 12 wt% reaches 21.14 % under monochromatic light at a wavelength of λ = 370 nm. This work analyzes the light absorption and carrier separation to the catalytic site, and elucidates the mechanism for the enhancement of the photocatalytic hydrogen production performance.

A general strategy for the enhanced H2 production performance of CdS/noble metal sulfide nanorods photocatalysts by cation exchange

In this work, we report a series of noble metal (Ag, Au, Pt, etc.) sulfides that act as co-catalysts anchoring on CdS nanorods (NRs) obtained via a cation exchange strategy to promote photocatalytic hydrogen evolution. CdS NRs are first generated via a hydrothermal routine, noble metal sulfides are then in-situ grown on CdS NRs by a cation exchange method. CdS/Ag2S, CdS/Au2S and CdS/PtS NRs show improved hydrogen production rates (2506.88, 1513.17 and 1004.54 μmol g-1h-1, respectively), approximately 18, 11 and 7 times higher than CdS NRs (138.27 μmol g-1h-1). Among CdS/noble metal sulfide NRs, CdS/Ag2S NRs present the best H2 production performance. The apparent quantum efficiency (AQE) of CdS/Ag2S NRs achieves 3.11 % at λ = 370 nm. The improved photocatalytic performance of CdS/noble metal sulfide NRs dues to the following points: i) Noble metal sulfides on CdS NRs are beneficial for elevating light-absorbing and light-utilizing capacities, contributing to generating more photoexcited charges; ii) Noble metal sulfides are in-situ grown on CdS NRs as electron acceptors by a cation exchange method, thus the photoexcited electrons generated by CdS NRs rapidly migrate to the surface of noble metal sulfides, successfully accelerating the carriers separation efficiency. This series of noble metal sulfides acting as co-catalysts anchoring on CdS NRs offer new insights into the construction principles of high-performance photocatalytic hydrogen evolution catalysts.

Construction of two-dimensional zinc indium sulfide/bismuth titanate nanoplate with S-scheme heterojunction for enhanced photocatalytic hydrogen evolution

Improving the separation efficiency of photogenerated carriers plays an important role in photocatalysis. In this study, two-dimensional (2D)/2D zinc indium sulfide (ZnIn2S4)/bismuth titanate (Bi4Ti3O12) nanoplate heterojunctions were synthesized to alter the Bi4Ti3O12 morphology, modulate the bandgap of Bi4Ti3O12, and enhance the utilization of light. Meanwhile, the construction of the S-scheme heterojunction establishes an internal electric field at the ZnIn2S4/Bi4Ti3O12 heterojunctions interface and achieves the spatial separation of photogenerated charges. The hydrogen production rate of ZnIn2S4/Bi4Ti3O12 nanoplate with the optimal ratio reaches 27.50 mmol h-1 g-1, which is 1.5 times higher than that of ZnIn2S4/Bi4Ti3O12 nanoflower (18.28 mmol h-1 g-1) and 2.4 times higher than that of ZnIn2S4 (11.69 mmol h-1 g-1). The apparent quantum efficiency of ZnIn2S4/Bi4Ti3O12 nanoplate reached 57.9 % under a single wavelength of light at 370 nm. This work provides insights into the study of new materials for photocatalytic hydrogen production.

In situ Mo-doped ZnIn2S4/Ni-Ni Hofmann-type coordination polymer composites for photocatalytic hydrogen evolution reaction

Solar energy-assisted hydrogen production technology is an essential tool for exploring hydrogen energy. To date, semiconductors have been used as the primary photocatalyst to generate hydrogen via photocatalytic water splitting. However, the high photogenerated electron-hole recombination rate of semiconductor photocatalysts results in a low hydrogen production rate. Herein, the synergistic effect of Mo-ion doping and the incorporation of Ni-based Hofmann-type coordination polymer (Ni-Ni HCP) on the photocatalytic performance of ZnIn2S4 (ZIS) is investigated. The hydrogen production rate of the prepared in-situ Mo doped ZnIn2S4 wrapped Ni-Ni HCP (Ni-Ni HCP/Mo-ZIS) sample under visible-light irradiation is 26.7 mmol g-1h-1, which is 10 times that of pure ZIS. Hydrogen production rate test, microscopic characterization, and density functional theory calculation confirm that the proposed dual modulation approach (combined ion doping and heterogeneous structure construction) could effectively increase the photocatalytic efficiency of ZIS. The stability of prepared samples is also examined by four-cycle photocatalytic hydrogen production tests. The proposed integrated method opens a new route for advancing renewable energy technology towards a sustainable future.

Tailoring the catalytic sites by regulating photogenerated electron/hole pairs separation spatially for simultaneous selective oxidation of benzyl alcohol and hydrogen evolution

Photocatalytic selective oxidation of alcohols into aldehydes and H2 is a green strategy for obtaining both value-added chemicals and clean energy. Herein, a dual-purpose ZnIn2S4@CdS photocatalyst was designed and constructed for efficient catalyzing benzyl alcohol (BA) into benzaldehyde (BAD) with coupled H2 evolution. To address the deep-rooted problems of pure CdS, such as high recombination of photogenerated carriers and severe photo-corrosion, while also preserving its superiority in H2 production, ZnIn2S4 with a suitable band structure and adequate oxidizing capability was chosen to match CdS by constructing a coupled reaction. As designed, the photoexcited holes (electrons) in the CdS (ZnIn2S4) were spatially separated and transferred to the ZnIn2S4 (CdS) by electrostatic pull from the built-in electric field, leading to expected BAD production (12.1 mmol g-1 h-1) at the ZnIn2S4 site and H2 generation (12.2 mmol g-1 h-1) at the CdS site. This composite photocatalyst also exhibited high photostability due to the reasonable hole transfer from CdS to ZnIn2S4. The experimental results suggest that the photocatalytic transform of BA into BAD on ZnIn2S4@CdS is via a carbon-centered radical mechanism. This work may extend the design of advanced photocatalysts for more chemicals by replacing H2 evolution with N2 fixation or CO2 reduction in the coupled reactions.

Artificial Photosynthetic System with Spatial Dual Reduction Site Enabling Enhanced Solar Hydrogen Production

Although S-scheme artificial photosynthesis shows promise for photocatalytic hydrogen production, traditional methods often overly concentrate on a single reduction site. This limitation results in inadequate redox capability and inefficient charge separation, which hampers the efficiency of the photocatalytic hydrogen evolution reaction. To overcome this limitation, a double S-scheme system is proposed that leverages dual reduction sites, thereby preserving energetic photo-electrons and holes to enhance apparent quantum efficiency. The design features a double S-scheme junction consisting of CdS nanospheres decorated with anatase TiO2 nanoparticles coupled with graphitic C3 N4 . The as-prepared catalyst exhibits a hydrogen evolution rate of 26.84 mmol g-1  h-1 and an apparent quantum efficiency of 40.2% at 365 nm. This enhanced photocatalytic hydrogen evolution is ascribed to the efficient charge separation and transport induced by the double S-scheme. Both theoretical calculations and comprehensive spectroscopy tests (both in situ and ex situ) affirm the efficient charge transport across the catalyst interface. Moreover, substituting the reduction-type catalyst CdS with other similar sulfides like ZnIn2 S4 , ZnS, MoS2 and In2 S3 further confirms the feasibility of the proposed double S-scheme configuration. The findings provide a pathway to designing more effective double S-scheme artificial photosynthetic systems, opening up fresh perspectives in enhancing photocatalytic hydrogen evolution performance.

Self-assembled B-doped flower-like graphitic carbon nitride with high specific surface area for enhanced photocatalytic performance

Graphitic carbon nitride (g-C3N4) is a promising nonmetallic photocatalyst. In this manuscript, B-doped 3D flower-like g-C3N4 mesoporous nanospheres (BMNS) were successfully prepared by self-assembly method. The doping of B element promotes the internal growth of hollow flower-like g-C3N4 without changing the surface roughness structure, resulting in a porous floc structure, which enhances the light absorption and light reflection ability, thereby improving the light utilization rate. In addition, B element provides lower band gap, which stimulates the carrier movement and increases the activity of photogenerated carriers. The photocatalytic mechanism and process of BMNS were investigated in depth by structural characterization and performance testing. BMNS-10 % shows good degradation for four different pollutants, among which the degradation effect on Rhodamine B (RhB) reaches 97 % in 30 min. The apparent rate constant of RhB degradation by BMNS-10 % is 0.125 min-1, which is 46 times faster compared to bulk g-C3N4 (BCN). And the photocatalyst also exhibits excellent H2O2 production rate under visible light. Under λ > 420 nm, the H2O2 yield of BMNS-10 % (779.9 μM) in 1 h is 15.9 times higher than that of BCN (48.98 μM). Finally, the photocatalytic mechanism is proposed from the results of free radical trapping experiments.

Self-induced electron attraction center formation with pyrophosphorylation strategy for photocatalytic hydrogen evolution

An integral approach towards augmenting the performance of photocatalytic hydrogen production lies in the induction of charge transfer mediators within the material matrix itself, thereby facilitating swift and efficient charge transfer processes. Here, CoTiO3 is induced to grow its electronic attraction center, CoP3, through a high-temperature phosphatization strategy. CoP3 acts as the active reduction site for the hydrogen evolution reaction and enhances the photocatalytic performance of the pristine catalyst. Compared with pure CoTiO3, the PCTO7 hybrid catalyst with the electronic attraction center CoP3 exhibits a superior photocatalytic performance and good stability. Experimental results show that the hydrogen evolution performance of the PCTO7 hybrid catalyst reaches 56.52 μmol, which is 78 times higher than that of the single catalyst CoTiO3 (0.72 μmol). These results demonstrate that the hybrid catalyst with the self-induced electronic attraction center has a higher light absorption capacity, faster charge carrier dynamics and improved photogenerated charge carrier separation and transfer than pure CoTiO3, resulting in excellent redox capability. DFT calculations provide evidence supporting the topological metal properties of CoP3 as the electron sink center. This study provides a feasible approach for enhancing the photocatalytic performance of a pristine catalyst employing a high-temperature phosphatization-induced electron sink center.

2D/2D MgO/g-C3N4 S-scheme heterogeneous tight with Mg-N bonds for efficient photo-Fenton degradation: Enhancing both oxygen vacancy and charge migration

Construction of S-scheme heterojunction is an efficient strategy to enhance photocatalytic efficiency. Besides the retained redox ability, the wide work function gap and intimate interface contact are essential for efficient degradation. Nontoxic magnesium oxide (MgO) with two dimensional (2D) structures and high work function is a potential material for S-scheme photocatalysts. Herein, MgO was used to in-situ grown on graphitic carbon nitride (g-C3N4) for constructing the strongly connected MgO/g-C3N4 S-scheme photocatalyst with tight Mg-N bonds. Meanwhile, the presence of Mg-N bonds induces the formation of oxygen vacancy in MgO, which enhances the Fenton-like degradation. Furthermore, the Mg-N bond promotes the charge migration between MgO and g-C3N4. Consisting of the enhanced Fenton-like process and photocatalysis, the MgO/g-C3N4 shows a higher photo-Fenton degradation activity (80.01%) for degradation of organic pollutants (Rhodamine B, 100 mg L-1) in water, than g-C3N4 (28.46%) and MgO (55.64%). Therefore, the interfacial chemical bonds in heterojunction photocatalysts provide an efficient strategy for further enhancing the photocatalysis of S-scheme photocatalysts.

Cation Exchange Reaction-Mediated Photothermal and Polarity-Switchable Photoelectrochemical Dual-Readout Biosensor

Cation exchange (CE) is a burgeoning method for controlled crystal synthesis; however, its applications in bioanalysis are still in their infancy. Herein, we explored the transformation of ZnIn2S4 in properties after the CE reaction with Cu2+ ions; furthermore, the discrepancy was employed to design a dual-readout detection system of photothermal and polarity-switchable photoelectrochemical (PEC) immunoassays to realize reliable detection of carcinoembryonic antigen (CEA). In the presence of CEA, the CuO nanoparticles (CuO NPs) employed as dual-signal response probes would bond to the microplates and be acidolyzed by HCl to release Cu2+, which could replace Zn2+ and In3+ via the CE reaction. After the CE reaction is completed, the photocurrent would switch from a weak anodic photocurrent to a cathode one by using a 635 nm laser as a signal amplifier, while the photothermal signal would be enhanced with 808 nm laser illumination. On the basis of the polarity-switchable PEC strategy, CEA could be accurately detected from 0.1 to 50 ng mL-1 with a limit of detection (LOD) of 48 pg mL-1 (S/N = 3). Moreover, the photothermal assay for CEA detection possesses a linear range from 0.5 to 100 ng mL-1 with a LOD of 0.21 ng mL-1. In addition, the designed sensing platform only relies on devices with portability that are permitted for point-of-care detection.

Boosted Photocatalytic Performance for Antibiotics Removal with Ag/PW12/TiO2 Composite: Degradation Pathways and Toxicity Assessment

Photocatalyst is the core of photocatalysis and directly determines photocatalytic performance. However, low quantum efficiency and low utilization of solar energy are important technical problems in the application of photocatalysis. In this work, a series of polyoxometalates (POMs) [H3PW12O40] (PW12)-doped titanium dioxide (TiO2) nanofibers modified with various amount of silver (Ag) nanoparticles (NPs) were prepared by utilizing electrospinning/photoreduction strategy, and were labelled as x wt% Ag/PW12/TiO2 (abbr. x% Ag/PT, x = 5, 10, and 15, respectively). The as-prepared materials were characterized with a series of techniques and exhibited remarkable catalytic activities for visible-light degradation tetracycline (TC), enrofloxacin (ENR), and methyl orange (MO). Particularly, the 10% Ag/PT catalyst with a specific surface area of 155.09 m2/g and an average aperture of 4.61 nm possessed the optimal photodegradation performance, with efficiencies reaching 78.19% for TC, 93.65% for ENR, and 99.29% for MO, which were significantly higher than those of PW12-free Ag/TiO2 and PT nanofibers. Additionally, various parameters (the pH of the solution, catalyst usage, and TC concentration) influencing the degradation process were investigated in detail. The optimal conditions are as follows: catalyst usage: 20 mg; TC: 20 mL of 20 ppm; pH = 7. Furthermore, the photodegradation intermediates and pathways were demonstrated by HPLC-MS measurement. We also investigated the toxicity of products generated during TC removal by employing quantitative structure-activity relationship (QSAR) prediction through a toxicity estimation software tool (T.E.S.T. Version 5.1.2.). The mechanism study showed that the doping of PW12 and the modification of Ag NPs on TiO2 broadened the visible-light absorption, accelerating the effective separation of photogenerated carriers, therefore resulting in an enhanced photocatalytic performance. The research provided some new thoughts for exploiting efficient and durable photocatalysts for environmental remediation.