Photocorrosion Of CdS Research Articles

CdS/g-C3N5 for heterogeneous catalytic degradation of hazardous pollutants

CdS, as an important photocatalytic degradation material, exhibits certain limitations. In our study, carbon nitride/cadmium sulfide (C3N5/CdS) nanocomposites were synthesized via an in-situ method, and the crystalline structure, composition, and morphology of the hybrid samples were evaluated using various techniques. The development of the Z-scheme heterojunction in the C3N5/CdS composite photocatalyst facilitated more effective separation of photogenerated charges, resulting in higher photocatalytic degradation efficiency. Under visible light irradiation at 425 nm, the composite with a 1:1 ratio exhibited the best degradation performance, achieving degradation rates of 93.8% for methyl orange solution and 96.8% for rhodamine B solution. Additionally, the introduction of C3N5 significantly reduced the photocorrosion of CdS. These experimental results were confirmed by fluorescence analysis, surface photovoltage (SPV) measurements, electrochemical tests, etc.

In situ proof construction of GDY/NiWO4/CdS double S-scheme heterojunction: Improving charge transfer and promoting photocatalytic activity

In the field of photocatalysis, the inherent properties of catalysts are a hard condition that affects catalytic performance, and constructing heterojunctions is a common method to improve catalyst defects and enhance catalyst performance. This article makes effective use of the outstanding stability and unique electronic structure of graphdiyne, along with its excellent semiconductor properties comparable to silicon. It uses these properties to attach rod-shaped CdS and microspherical NiWO4 onto sheet-like graphdiyne, creating an S-scheme heterojunction. With the construction of S-scheme heterojunctions and the special contact methods between the three, the physical potential barrier and the distance of electron transfer are reduced. Furthermore, the combined impact of NiWO4 and graphdiyne works to inhibit the photo corrosion of CdS, enhance its electron transfer capabilities, decrease electron-hole recombination efficiency, and boost hydrogen evolution sites. This maximizes the redox potential during catalysis, leading to exceptional stability and efficiency of the composite catalyst. This study opens up a new avenue for leveraging the superior properties of graphdiyne and advancing sustainable practices.

Plant-Based Phytochemicals for Synthesis of Z-Scheme In2O3/CdS Heterostructures: DFT Analysis and Photocatalytic CO2 Reduction to HCOOH and CO.

Photocatalytic CO2 reduction shows potential for mitigating industrial emissions. Z-scheme In2O3/CdS(bio) heterostructures (25 nm, 217.0 m2 g-1 surface area) with a more negative conduction band synthesized using phytochemicals present in Aegle marmelos with short microwave irradiation inhibit CdS(bio) photocorrosion forming SO42-. In2O3/CdS(bio) increased the photocurrent density (0.82 μA cm-2) and CO2 adsorption (0.431 mmol g-1) significantly compared to CdS(bio) and In2O3(bio) NPs. Heterostructures increased decay time and reduced PL intensity by 46.28 and 61.80% over those of CdS(bio) and In2O3(bio) NPs. Density functional theory (DFT)-optimized geometry, band structure analysis, and density of states (DOS) studies indicate that the DOS of CdS is modified with In2O3 incorporation, enhancing charge separation. Optimal 0.4In2O3/CdS(bio) heterostructures exhibit remarkable CO2 conversion to HCOOH/CO production of 514.4/162 μmol g-1 h-1 (AQY 4.44/2.45%), surpassing CdS(bio) and In2O3(bio) by 9 and 6.5 times, and retain their morphological and structural stability. This study provides valuable insight for developing bio-based CdS heterostructures for photocatalytic CO2 reduction.

Metal single atom-oxygen modification induced transformation of carbon nitride-based heterojunctions from type-II to S-scheme for efficient photocatalytic overall water splitting

Constructing semiconductor S-scheme hetero-(homo-)junctions (SSHs) is one of the most effective ways to enhance the photocatalytic overall water splitting (POWS) performance, but encumbered by deficiency of efficient water-oxidizing semiconductors. Herein, tungsten single atom-oxygen group (W-O) modified polymeric carbon nitride (WPCN, an example of metal single atom-oxygen group modified PCN) was used as a water-oxidizing semiconductor to construct a CdS/WPCN SSH, for which the W-O modification plays a key role that causes transformation from a PCN/CdS type-II heterojunction to the CdS/WPCN SSH which exhibits remarkably enhanced photoexcited charge separation than single CdS and WPCN. Pt-CdS/WPCN exhibits 2.6 and 7.2 times higher POWS activity than Pt-WPCN and Pt-CdS, respectively, further demonstrating the key role of the SSH, and lower activity than Pt@Cr2O3-CdS/WPCN that exhibits 5.4-fold higher activity than Pt@Cr2O3-PCN/CdS, and especially, higher photochemical stability by suppressing rapid photocorrosion of CdS. The solar-to-hydrogen conversion efficiency of Pt@Cr2O3-CdS/ WPCN reaches 0.014 %, with an external quantum yield of 0.093 % at 420 nm. This work reveals the role of metal single atom-oxygen modification of PCN in SSHs and provides a way to suppress rapid photocorrosion of CdS.

Synergistic promotion for the performance of photocatalytic carbon dioxide reduction by vacancy engineering and N-doped carbon nanotubes

The structural devise of photocatalytic materials are closely related to the separation of photogenerated carriers and the transport of charge, which is crucial to enhance the performance of photocatalytic carbon dioxide reduction reaction (CO2RR). Here, a photocatalyst (CdS-SV@Co@NCNT) has been successfully prepared by growing cadmium sulfide nanoparticles with sulfur vacancies on N-doped carbon nanotubes through a simple solvothermal method. The intrinsic electronic structure is regulated by sulfur vacancies to promote photocatalytic activity. Meanwhile, a larger specific surface area of Co@NCNT could expose more reaction sites and shorten the transfer distance of photogenerated carriers. Furthermore, the combination with Co@NCNT could effectively suppress the photocorrosion of CdS. The possible photocatalytic CO2RR path is further speculated by in-situ infrared test results, in which CO2 molecules adsorbed on sulfur vacancies preferentially generate important intermediate COOH*, which is then reduced to CO and CH4. Therefore, it exhibits a high CO yield of 263.3 μmol·g−1·h−1 and trace of CH4 while showing excellent stability. This research provides a novel idea for designing the photocatalysts with highly active and stability for CO2RR.

Natural Wollastonite-Derived Two-Dimensional Nanosheet Ni3Si2O5(OH)4 as a Novel Carrier of CdS for Efficient Photocatalytic H2 Generation

Ni3Si2O5(OH)4 rods (NS) were synthesized via a hydrothermal method, employing natural wollastonite as a template. The hierarchical Ni3Si2O5(OH)4 rods exhibited vertically oriented nanosheets, resulting in a substantial increase in the specific surface area (from 2.24 m2/g to 178.4 m2/g). Subsequently, a CdS/Ni3Si2O5(OH)4 composite photocatalyst (CdS/NS) was prepared using a chemical deposition method. CdS was uniformly loaded onto the surface of the Ni3Si2O5(OH)4 nanosheets, successfully forming a heterojunction with Ni3Si2O5(OH)4. The CdS/NS photocatalyst in the presence of lactic acid as a sacrificial agent demonstrated an impressive H2 production rate of 4.05 mmol h−1 g−1, around 40 times higher than pure CdS. The photocorrosion of CdS was effectively solved after loading. After four cycles, the performance of CdS/NS remained stable, showing the potential for sustainable applications. After photoexcitation, electrons moved from Ni3Si2O5(OH)4 to the valence band of CdS, where they interacted with the holes via an enhanced interface contact. Simultaneously, electrons in CdS transitioned to its conduction band, facilitating hydrogenation. The enhanced performance was attributed to the improved CdS dispersion by Ni3Si2O5(OH)4 loading and efficient photogenerated carrier separation through the heterojunction formation. This work provides new perspectives for broadening the applications of mineral materials and developing heterojunction photocatalysts with good dispersibility and recyclability.

Simultaneously Regulating charge separation and proton supply-demand in polyphenol amine for hydrogen peroxide photosynthesis

In the H2O2 photosynthesis, apart from the charge separation, the balance of proton supply and demand was also required between the kinetically faster oxygen reduction reaction (ORR) (μs ∼ ms) and the sluggish kinetics of water oxidation reaction (WOR) (s). Faced by this challenge, the article designed the heterojunction photocatalyst formed by in-situ polymerization of polyphenol amine on the surface of CdS under alkaline conditions. As a result, the synthesized CdS-Poly(catechol-hexamethylenediamine) (PCHA) produced 6.1 mM H2O2 after 8 h of visible light irradiation, which is 29 times that of CdS. The experimental results evidenced that the coating of PCHA increased the charge separation and mobility, inhibited the photocorrosion of CdS, and thus enhanced the stability and photoactivity. Moreover, the catechol units of PCHA could function as a proton supplier and regulate local protons concentrations around the catalytic active sites to balance the proton supply–demand in the ORR and WOR at different reaction time scales.

Synergistic effect of Zn-AgIn5S8/CdS Z-scheme heterojunction and S-doped rGO for efficient removal of chromium from contaminated water.

This study aimed to synthesize a Zn-AgIn5S8/CdS/SrGO nanocomposite for Cr(vi) removal from contaminated water under solar irradiation. To prevent photo corrosion of CdS, a Z-scheme heterojunction was formed between CdS and Zn-AgIn5S8. The introduction of Ag2+ plasmonic materials extended the light absorption range and stabilized the photocatalyst. Further, to improve the catalytic surface area, electrical conductivity, and minimize the rate of electron and hole pair recombination, the Zn-AgIn5S8/CdS Z-scheme heterojunction was loaded onto S-doped rGO. The morphological and structural analysis of the synthesized nanomaterials (NMs) was done using various techniques, including XRD, FT-IR, UV-vis DRS, FESEM, TEM, EDAX, photoluminescence, and Raman spectroscopy. Results revealed that the Zn-AgIn5S8/CdS/SrGO nanocomposite removed 85% of Cr(vi) at an initial concentration of 50 mg L-1 in 180 min when exposed to solar irradiation. The simulated first-order kinetic model fitted to the experimental data for Cr(vi) reduction by the nanocomposite exhibits a high correlation coefficient (R 2 ≥ 0.97) and the K app value for Zn-AgIn5S8/CdS/SrGO (K app = 0.0114 min-1) is around 1.6 times larger than that of bare ZnAgIn5S8. Moreover, Zn-AgIn5S8/CdS/SrGO heterojunctions show excellent reusability up to 4 cycles. Further, the possible photocatalytic mechanism of Cr(vi) reduction has been proposed. Therefore, the Zn-AgIn5S8/CdS/SrGO nanocomposite could serve as an alternative photocatalyst system driven by solar light for Cr(vi) reduction.

Nickel-Based Bifunctional Cocatalyst to Enhance CdS Photocatalytic Hydrogen Production.

The design of nanocomposites as a light-capturing system applied in photocatalytic water splitting is an emerging area of research. In our study, a simple in situ photodeposition method was proposed for the synthesis of CdS nanoflowers modified by nickel-based bifunctional, i.e., Ni/Ni(OH)2, cocatalysts. The introduction of cocatalysts has demonstrated a notable enhancement in the photocatalytic hydrogen evolution efficiency of CdS. The quantity of cocatalysts supported on CdS played an important role in governing the light absorption capability and photocatalytic efficacy. Ni-CdS-10 showed the best photocatalytic activity of 30.51 mmol g-1 h-1, which was 1.8 times and 2.6 times higher activity than Pt-CdS-1 wt % and pure CdS, respectively. Mechanism studies with UV-vis DRS, photoluminescence, and Mott-Schottky plots revealed the intrinsic electric field created at the p-n Ni(OH)2/CdS junctions, which can effectively implement the transport and separation of photoinduced carriers. From linear sweep voltammetry, electrochemical impedance spectroscopy, and DFT calculation, both Ni(OH)2 and Ni can effectively decrease the Gibbs free energies of hydrogen adsorption and reduce the overpotential of hydrogen evolution. As a result, the efficiency of generating H2 through photocatalysis experienced significant improvement, and the participation of bifunctional cocatalysts further reduced the photocorrosion of CdS, enhanced stability, improved low price, and efficient photocatalyst production.

Facile in-situ synthesis of solid mediator based CdS-rGO-WO3 Z-scheme photocatalytic system for efficient photocatalytic hydrogen generation

Reduced graphene oxide (rGO) solid state mediator based Z scheme photocatalyst CdS-rGO-WO3 heterojunction comprising of nano-rods of CdS and nanoplates of WO3 was fabricated in-situ by a facile hydrothermal process, characterized and tested for solar hydrogen generation. The systematically designed heterojunction created separated oxidative and reductive sites for photo generated electron hole pairs with enhanced redox ability, improving the charge separation and photo-stability, mitigating the problem of photo-corrosion of CdS. This was evident from an enhanced photocatalytic activity of 11.69 mmolg−1h−1 which was almost 2.3 times than pristine CdS (4.9 mmolg−1h−1), in presence of simulated solar light. Due to the high electron mobility property of graphene sheet, rapid transport of electrons was possible at the interface between CdS and WO3. The charge transfer via Z scheme mechanistic pathway was verified by X-ray Photoelectron Spectroscopy (XPS), Photoluminescence (PL) and photocurrent measurement studies. This research study will provide a newer insight in engineering nano-hetero-structures for enhanced photocatalytic hydrogen evolution, in an attempt to make the process commercially viable.

Rapid charge migration of hierarchical S-Scheme g-C3N4/CdS@C for efficient photocatalytic hydrogen evolution

Photocatalytic H2 evolution as a resultful way to figure out energy problems is still inhibited by carrier separation efficiency and catalyst service life. Here, we report a hierarchical S-Scheme heterostructure of layered graphite carbon nitride and CdS nanoparticles coated with carbon film (g-C3N4/CdS@C) by a simple hydrothermal method for highly efficient visible-light-driven H2 evolution. The S-Scheme, comprising g-C3N4 and CdS, synergistically enhances the efficiency of carrier separation while maintaining the redox capacity of both components. The introduction of carbon film enhances the migration rate of carriers, in the meantime inhibits the photo corrosion of CdS to enhance the stability of catalyst. The g-C3N4/CdS@C achieves the H2 generation rate of 6.4 mmol g−1 h−1 and the apparent quantum yield of 12.7%, superior to most works on g-C3N4. This work provides a delicate S-Scheme photocatalyst and offers a valid strategy for prolonging the lifetime of transition metal sulfide-based materials.

Ternary-role of NiCo-MOFs for boosting the photocatalytic H2-evolution and long term stability of CdS

CdS is a promising candidate for visible-light-driven photocatalytic H2-evolution, but its practical application is still limited by self-photo-corrosion and noble co-catalysts needing. Herein, CdS/NiCo-MOFs (CM) heterojunction was synthesized by an in-situ hydrothermal method, where NiCo-MOFs (BMOFs) acted as platform to inhibit the aggregation of CdS nanoparticles. Furthermore, BMOFs provided dual-reaction sites to improve the photocatalytic H2-evolution speed and suppress the photo-corrosion of CdS by taking its Ni-linker as catalytic active sites for water splitting and Co-linker as hole trapping sites to suppress the self-oxidation between S2− and holes. Therefore, the optimal CM-20% exhibited a remarkable photocatalytic H2-evolution rate of 1.810 mmol g−1 h−1 under sunlight irradiation, which is 4.55 times higher than that of CdS. Moreover, CM-20% maintained this high photocatalytic H2-evolution rate for 100 h reaction, which for CdS is just 50 h. This research provides insight into designing high-efficiency and photo-stable sulfide-based photocatalyst systems for H2-evolution.

Ternary CdS@MoS2-Co3O4 Multiheterojunction Photocatalyst for Boosting Photocatalytic H2 Evolution.

Turning the carrier dynamics in heterojunction photocatalysts is a direct and effective strategy for improving the solar energy conversion efficiency of photocatalysts. Herein, we report a ternary CdS@MoS2-Co3O4 multiheterojunction photocatalyst consisting of the p-n junction of MoS2-Co3O4 and the type-I junction of CdS@MoS2, wherein MoS2 located at the frontier between CdS and Co3O4 acts as an intermediate bridge. The type-I junction allows the directional transfer of photoinduced charge from CdS to MoS2, suppressing the photocorrosion of CdS. Notably, the single-particle photoluminescence technique demonstrates the sequential one-direction hole transfer from MoS2 to Co3O4 aroused by the p-n junction, resulting in a long-lifetime charge separation in the carrier lifetime (54-58 ns). Compared to the bare CdS and type-I CdS@MoS2, the CdS@MoS2-Co3O4 photocatalyst affords a 347-fold and 3.5-fold enhancement of the H2 evolution rate, a quantum efficiency of 28.6% at 450 nm, and a 20 h of long-term stability. This work provides a new understanding of the rational regulation of the charge-transfer mechanism of type-I systems by constructing multiheterojunction photocatalysts.

Enhancement of CdS resistance to photocorrosion and photocatalytic removal of uranyl by complexation with N-deficient g-C3N4under aerobic conditions

The effect of oxygen on the reduction of uranyl and photocorrosion of CdS remains a pressing issue when CdS is used as a photocatalyst for the removal of uranyl in uranium-containing wastewater. In this study, composites (CdS/PCN) were prepared by designing N-deficient g-C3N4 composite with CdS for efficient photocatalytic reduction of uranyl under aerobic condition. Meanwhile, a series of characterizations of the CdS/PCN composites were carried out by XRD, FT-IR, XPS, EDS and UV–vis. Surprisingly, the CdS/PCN not only showed very high photocatalytic reduction activity for uranyl under aerobic condition, but also the photocorrosion of CdS by oxygen and h+ was inhibited. With a starting uranium (VI) concentration of 20 ppm, the uranium (VI) removal efficiency could reach 97.33% (dark: 30 min, light: 10 min). Interestingly, the removal efficiency was better in air condition than in pure nitrogen or 30% oxygen atmosphere, i.e. a proper amount of oxygen has accelerated the reduction reaction, while excess oxygen weakened the reduction. Finally, a new mechanism of reduction of uranyl by CdS/PCN photocatalyst was given under aerobic condit ions. This work presents a novel strategy for reduction of U(VI) by photocatalysis and the inhibition of photocorrosion of photocatalysts under aerobic conditions.

Piezo-potential induced redox of polyaniline and CdS/PANI heterostructures for efficient photoelectrochemical water splitting

Photoelectrode materials with high electron-hole separation efficiency and long-lasting stability are extremely important for photoelectrochemical (PEC) water separation. In this paper, the CdS/PANI composite structure was prepared by a simple hydrothermal method to improve the stability of CdS while maximizing its excellent PEC properties. This system (CdS/PANI) utilizes the redox effect of PANI internal functional groups to accomplish electron-hole migration, which suppresses the photocorrosion of CdS without using any surface sacrificial agent. Meanwhile, the carrier separation is further promoted by the heterojunction structure formed by CdS/PANI under the stimulation of ultrasonic waves. The coordination of the above two effects achieves improved photocatalytic activity and enhanced stability. The electrochemical test results under ultrasonic conditions showed that the PANI composite on CdS increased the photocurrent density (1.23 V vs. RHE) from 1.68 mA/cm−2 to 2.62 mA/cm−2 compared to pure CdS. In addition, the stability of PEC is further enhanced and the photocorrosion rate decreases from 43% to 12%. This strategy provides a promising example for the development of more efficient organic-inorganic piezoelectric photoanode materials.

Radial Nano-Heterojunctions Consisting of CdS Nanorods Wrapped by 2D CN:PDI Polymer with Deep HOMO for Photo-Oxidative Water Splitting, Dye Degradation and Alcohol Oxidation.

Solar energy harvesting using semiconductor photocatalysis offers an enticing solution to two of the biggest societal challenges, energy scarcity and environmental pollution. After decades of effort, no photocatalyst exists which can simultaneously meet the demand for excellent absorption, high quantum efficiency and photochemical resilience/durability. While CdS is an excellent photocatalyst for hydrogen evolution, pollutant degradation and organic synthesis, photocorrosion of CdS leads to the deactivation of the catalyst. Surface passivation of CdS with 2D graphitic carbon nitrides (CN) such as g-C3N4 and C3N5 has been shown to mitigate the photocorrosion problem but the poor oxidizing power of photogenerated holes in CN limits the utility of this approach for photooxidation reactions. We report the synthesis of exfoliated 2D nanosheets of a modified carbon nitride constituted of tris-s-triazine (C6N7) linked pyromellitic dianhydride polydiimide (CN:PDI) with a deep oxidative highest occupied molecular orbital (HOMO) position, which ensures sufficient oxidizing power for photogenerated holes in CN. The heterojunction formed by the wrapping of mono-/few layered CN:PDI on CdS nanorods (CdS/CN:PDI) was determined to be an excellent photocatalyst for oxidation reactions including photoelectrochemical water splitting, dye decolorization and the photocatalytic conversion of benzyl alcohol to benzaldehyde. Extensive structural characterization using HR-TEM, Raman, XPS, etc., confirmed wrapping of few-layered CN:PDI on CdS nanorods. The increased photoactivity in CdS/CN:PDI catalyst was ascribed to facile electron transfer from CdS to CN:PDI in comparison to CdS/g-C3N4, leading to an increased electron density on the surface of the photocatalyst to drive chemical reactions.

Bifunctional S-scheme hybrid heterojunction comprising CdS nanorods and BiOIO3 nanosheets for efficient solar-induced antibiotic degradation and highly-selective CO2 reduction

The development of a bifunctional photocatalyst that can be utilized for both energy conversion and environmental remediation is of great practical significance. In addition, an S-scheme charge transfer process can assist a photocatalyst in efficiently separating photoexcited electrons and holes while maintaining the strong reducibility and oxidizability of the former and the latter, respectively. We developed a bifunctional S-scheme hybrid photocatalyst comprising CdS nanorods and BiOIO3 (BIO) nanosheets for efficient antibiotic degradation and cocatalyst- and sacrificial reagent-free CO2 reduction. The combination of visible-light-responsive one-dimensional (1D) CdS and UV-light-responsive 2D BIO resulted in a CdS/BIO hybrid photocatalyst with effective 1D/2D (line) interfacial contact and a broadened optical absorption range. Notably, the CdS/BIO hybrid exhibited exceptional diclofenac degradation and mineralization as well as outstanding CO2 reduction activity for CO production, with 95.4% CO selectivity over H2 production. The exceptional performance of the hybrid catalyst is primarily attributed to the accelerated photoexcited charge transfer caused by the 1D/2D line interfacial contact and the high charge separation and strong redox power of the separated charges, both of which stem from the effective S-scheme charge transfer process. In addition, photocorrosion of CdS was substantially mitigated, resulting in the high photocatalytic performance of the hybrid catalyst even after repeated test runs. This study provides insight into the rational design of bifunctional S-scheme hybrid photocatalysts for CO2 reduction and pollutant degradation.

A novel loading strategy of Mo-O/Mo-S cocatalysts based on the photocorrosion property of CdS

The promoting role of cocatalysts is not only dependent on their physical and chemical properties, but also closely related to their loading methods and nanostructures. In this study, by converting the disadvantages of CdS photocorrosion into the advantages of cocatalysts loading, a novel cocatalyst loading strategy is adopted to promote the photocatalytic H2 evolution performance of CdS. Using 1D CdS nanorods as primary photocatalyst, a limited amount of Mo-O cocatalyst (e.g. CdMoO4-MoOx) was in-situ deposited on the photocorrosive surface of CdS under intensive irradiation, and further transformed into few-layer Mo-S (e.g. MoS2-CdMoS4) nanofins by a facile ion-exchange method. The as-synthesized CdS@MoS2-CdMoS4 heterojunctions show a surprising “boiling” effect in visible-light-driven H2 evolution process (∼40.3 mmol·h−1·g−1).

Water flow induced piezoelectric polarization and sulfur vacancy boosting photocatalytic hydrogen peroxide evolution of cadmium sulfide nanorods

Piezo-photocatalytic H2O2 production utilizing earth-abundant solar and mechanical energies, oxygen and water is a highly appealing route to produce renewable energy carriers. However, piezoelectric polarization always suffers from high-frequency mechanical vibration, which severely restricts its actual applications. Here, we report prominent piezo-photocatalytic H2O2 evolution from pure water triggered by low-frequency water flow induced mechanical stress over 1D CdS nanorods with sulfur vacancy (CdS NRs). The polar CdS NRs possess benign piezoelectric property and favorable morphology, enabling high sensitivity and respond to weak force of water flow, which contribute to yielding large piezoelectric polarization for photogenerated charges separation. Piezoelectric polarization also shows an inhibition effect on the photocorrosion of CdS to ·SO3-. Besides, DFT calculations demonstrate that sulfur vacancy allows enhanced O2 adsorption and formation of the intermediate *OOH on the surface of CdS. Under simultaneous visible light and high-speed stirring, CdS NRs display a remarkably synergetic piezo-photocatalytic H2O2 production (1631.4 µmol g−1 h−1) without any sacrificial agents, 2.4 and 73.8 times of that under sole visible light and mechanical agitation, respectively. Importantly, it achieves an apparent quantum efficiency (AQY) of 1.32% at wavelength up to 500 nm and a solar-to-chemical (STC) conversion efficiency of 0.05% under one-sun illumination, which far exceeds other reported sulfide-based catalysts. This work integrates well with polarization engineering, defect engineering and morphology engineering to enhance catalytic behavior, providing a feasible strategy for designing efficient piezo-photocatalysts sensitive to weak mechanical forces.

2D/2D covalent organic framework/CdS Z-scheme heterojunction for enhanced photocatalytic H2 evolution: Insights into interfacial charge transfer mechanism

• The 2D/2D COF/CdS Z-scheme heterojunction was first reported. • The Z-scheme charge transfer pathways were first identified by Femtosecond transient absorption. • The excellent photocatalytic hydrogen evolution was achieved. • The improved charge separation and hydrogen-evolution kinetics were confirmed. Covalent organic frameworks (COFs) with high crystallinity and flexible designability have been considered as promising candidates for photocatalytic hydrogen evolution. However, the existence of unpropitious exciton effects in COFs leads to poor charge separation, and thus results in low photocatalytic efficiency. Herein, to improve the photoelectron migration efficiency, we designed a 2D/2D organic/inorganic direct Z-scheme COF-based heterojunction (TpTAP/CdS), by the in-situ growing of CdS nanosheets on the COF copolymerized via 2,4,6-tris(4-aminophenyl)-1,3,5-triazine (TAP) and 1,3,5-triformylphloroglucinol (TP). The femtosecond transient absorption (fs-TAS) decay kinetics of TpTAP-COF and TpTAP/CdS further reveal the processes of shallow electron trapping and the recombination of the free photogenerated electron-hole pairs. In particular, the transient absorption traces for TpTAP-COF and TpTAP/CdS normalized to the photoinduced absorption peak can effectively verify the Z-scheme charge transfer between TpTAP-COF and CdS, which could enhance the charge mobility and separation, thus reducing the photocorrosion of CdS. Additionally, ultraviolet photoelectron spectroscopy (UPS), in-situ X-ray photoelectron spectroscopy (XPS), transient photovoltage measurements, and Electron spin resonance spectroscopy (ESR) further confirm the establishment of the internal electric field (IEF). This work demonstrates the important role of COFs in the construction of 2D/2D organic/inorganic direct Z-scheme heterojunctions and offers a new avenue to explain the criticality of dynamics of the photogenerated carriers for the construction of Z-scheme heterojunctions.