Visible-light Hydrogen Evolution Research Articles

Photodeposition of NiS thin film enhanced the visible light hydrogen evolution performance of CdS nanoflowers

The use of loaded co-catalysts has been found to be effective in addressing the issue of rapid recombination of photogenerated carriers, which can limit photocatalytic efficiency. Herein, we report on the adsorption of Ni2+ on the surface of CdS by photodeposition to obtain NiS/CdS composites. It improves visible light response while providing abundant active sites for photocatalytic reaction. NiS/CdS exhibits a superior photocatalytic H2 evolution rate of up to 7557 μmol·g−1·h−1, which is approximately 4.9 times higher than that of CdS. The corresponding AQE is 19.6% at 420 nm. XPS and photoelectrochemical testing provide a possible mechanism, indicating that the heterojunction between NiS and CdS promotes the transfer and separation of interfacial charge, thus accelerating the water decomposition reaction. This work demonstrates the effectiveness of loading two-dimensional thin film co-catalysts to design high-performance and low-cost composites for promoting the photocatalytic reaction.

A recyclable ZnIn2S4/PAN photocatalytic nanofiber membrane for boosting visible light hydrogen evolution in seawater without cocatalyst

Using seawater for photocatalytic hydrogen production is always a highly promising direction. However, traditional powdered photocatalysts encounter challenges like ion interference and difficulty in reuse. To address these issues, we have combined the photocatalyst ZnIn2S4 (ZIS) with a polymer (PAN) using electrospinning technology to produce a composite photocatalytic ZIS/PAN nanofiber membrane. In aqueous solution, the ZIS/PAN nanofiber membrane achieves a maximum hydrogen evolution rate of approximately 1836 μmol/g/h, which is 3.37 times that of ZIS particles. Additionally, cyanide groups on PAN fibers can capture a small portion of photogenerated electrons, which then adsorb ions from seawater, reducing their impact on the photocatalyst and demonstrating excellent seawater hydrogen production performance. At specific ion concentrations, the membrane's activity is 20 % higher than in aqueous solution. Moreover, it overcomes the limitations of powdered photocatalyst structures, enabling device integration that facilitates easy recovery and reuse.

Construction of nanorod-shaped TiO2/Cu3N p–n heterojunction for efficient visible-light hydrogen evolution

p-Type Cu3N was deposited onto n-type TiO2 nanorod arrays to form p–n heterojunction and achieve an efficient visible-light hydrogen evolution.

Nitrogen defects and porous self-supporting structure carbon nitride for visible light hydrogen evolution

Porous self-supporting carbon nitride with nitrogen defects not only optimizes the surface electronic structure of a catalyst but also provides an abundance of reactive sites for the photocatalytic hydrogen evolution reaction.

Efficient Visible Light Hydrogen Evolution Catalyst Composed of Non-noble Metal Nitride (Ni3N) Cocatalyst and Zn0.5Cd0.5S Solid Solution

Efficient Visible Light Hydrogen Evolution Catalyst Composed of Non-noble Metal Nitride (Ni3N) Cocatalyst and Zn0.5Cd0.5S Solid Solution

Controlled photoinduced electron transfer from g-C3N4 to CuCdCe-LDH for efficient visible light hydrogen evolution reaction

Ample visible-light response and efficient charge transfers in semiconductor heterojunction are still enslaved to the limited photocatalytic water splitting. In most cases, the rational design of hybrid composites tune in atomic level interaction led to remarkable stability and superior activity. Here, this work is a systematic investigation of metal ion substitution in the LDH and LDH/g-C3N4 hybrid composites for hydrogen evolution reaction (HER) under visible light. The construction of heterostructure not only facilitates the charge separation and transfer owing to the formed heterojunction through band gap engineering and tunable optical properties which are inherited from morphology of as grown CuCdCe-LDH over the exfoliated g-C3N4 but also provides plenty of surface active sites due the increased surface area photostability. The CuCdCe-LDH/g-C3N4 exhibits superior HER rate of 3.5 mmolg−1h−1 with AQY of 5.78% over their binary counterparts. The density functional theory calculations also suggest that the HER activity of CuCdCe-LDH is substantially enhanced by coupling with g-C3N4 the electrochemical results leading to high photocurrent response. The high photocatalytic activity of the composite was due to efficient photoexcited charge transfer process and the synergistic effect between CuCdCe-LDH and g-C3N4. These finding will open scopes for designing inexpensive high performance materials for broad applications of photocatalytic energy conversion.

Carbohydrate-regulated synthesis of ultrathin porous nitrogen-vacancy polymeric carbon nitride for highly efficient Visible-light hydrogen evolution

Morphologies and electronic structures of the photocatalysts play a critical role in governing their photocatalytic actives via providing large specific surface area (more active sites) and suitable band structure. To achieve high visible-light photocatalytic activity, herein, an ultrathin porous nitrogen-vacancy polymeric carbon nitride (PCN) was synthesized by high-temperature thermal polymerization using melamine with a biomass derived carbohydrate aqueous solution, offering a flexible nature to finely tune the vacant and porous structures through properly changing the carbohydrate. The ultrathin porous structure could significantly enhance the specific surface area of PCN and improve the mobility of charges. Moreover, the induced vacancies structures could largely expand the light absorption range and reduce the recombination rate of photogenerated carriers. These led to an excellent photocatalytic activity for H2 production, with the optimal hydrogen evolution rate 17.2 times (5.5 mmol h−1 g−1, 1 wt.% Pt as a co-catalyst) higher than that of the unmodified PCN (0.32 mmol h−1 g−1). These results provide a simple, effective, and cost-effective strategy for the synthesis of novel photocatalysts using biomass-based raw materials to obtain a highly active photocatalyst with simultaneous adjusting the vacancies and porous structures.

Extraordinary Promotion of Visible-Light Hydrogen Evolution for Graphitic Carbon Nitride by Introduction of Accumulated Electron Sites (BN2)

The application of accumulated electron sites on the catalyst surface for photocatalytic hydrogen production represents a prospective strategy for efficient utilization of solar energy. Herein, the accumulated electron sites (BN2) loaded on graphitic carbon nitride (G-CN) were prepared without effort by a two-step calcination method in which melamine was calcined and then heat-treated with NaBH4. When compared with that of the bulk G-CN, the rate toward water splitting to produce H2 of the represented catalyst (CN-B0.05) greatly increased by 2.3 times under illumination (λ ≥ 420 nm). The improved activity could be attributed to the decrease in interlayer distance and the potential barrier of interlayers which was beneficial to readily transfer electrons in the Z direction, improve the adsorption and activation of water, and decline the Gibbs free energies for H* adsorption. The increase in π–π conjugation facilitated enhancement of the separation efficiency of photogenerated electron–hole pairs and light-capturing capabilities in the visible region with the introduction of BN2 sites. An approach for efficient H2 production is demonstrated in this work.

Construction of S-scheme heterojunction consisting of Zn0.5Cd0.5S with sulfur vacancies and Ni Co1-(OH)2 for highly efficient photocatalytic H2 evolution

• Vs-ZCS/Ni 0.6 Co 0.4 (OH) 2 heterojunction was fabricated for water splitting. • Sulfur vacancies in the photocatalyst provide abundant reaction sites. • The charge separation was significantly enhanced by the S-scheme mechanism. • Synergistic effects render an outstanding H 2 evolution rate of 64.6 mmol·h −1 ·g −1 . Efficient spatial charge separation under visible light irradiation plays a vital role in improving the photocatalytic performance of semiconductors. It is a promising approach to construct S-scheme charge transfer mechanism to meet this demand. In this research, a hybrid nanomaterial, which consists of zinc cadmium sulfide (ZCS) with appropriate surface sulfur vacancy (Vs-ZCS) and bimetallic hydroxides Ni x Co 1- x (OH) 2 (0 ≤ x ≤ 1), is successfully fabricated via a facile in-suit hydrothermal method. Among the prepared materials, the Vs-ZCS/5%-Ni 0.6 Co 0.4 (OH) 2 hybrid nanomaterial delivers a superior visible-light hydrogen evolution rate of 64.6 mmol·h −1 ·g −1 in Na 2 S/Na 2 SO 3 solution, which is about 11.1 and 3.5 times as much as those of ZCS (5.8 mmol·h −1 ·g −1 ) and Vs-ZCS (18.5 mmol·h −1 ·g −1 ), respectively. The significantly boosted photocatalytic performance over Vs-ZCS/Ni x Co 1- x (OH) 2 hybrids is ascribed to the abundant active sites caused by sulfur vacancy and efficient interfacial charge separation induced by S-scheme charge transfer mechanism. This work highlights the critical role of sulfur defects and bimetallic hydroxides modification in construction of S-scheme system and provides a new strategy for the design of highly efficient photocatalyst.

Boosting visible-light hydrogen evolution on CdS hollow nanospheres with CoN as cocatalyst

The photocatalytic water splitting to produce hydrogen is of great significance to solve the energy crisis, so the development and research of the visible-light-driven energy conversion have the priority in the progress of photocatalytic technology. Herein, we synthesized CdS with hollow sphere (CdS-HS) structure and combined it with CoN to form CoN/CdS-HS photocatalytic system. The particular hollow sphere structure and cocatalyst CoN in the CoN/CdS-HS system increase the utilization of visible light and promote the separation and transfer of photo-generated carriers for photocatalysts, which greatly improves photocatalytic performance of materials. The time‐resolved photoluminescence spectra shows that the carrier lifetime of 15%CoN/CdS-HS is 7.52 ns, which is much larger than that of CdS (4.26 ns). In addition, the hydrogen output of the optimized 15%CoN/CdS-HS is 4.57 times superior to that of pristine CdS-HS under the same conditions. The photocatalytic hydrogen evolution rate of 15%CoN/CdS-HS reaches 58.80 mmol/g.h under visible light with an apparent quantum efficiency (AQE) of 23.53% at 405 nm monochromatic light. After 25 h of photocatalytic reaction, the 15%CoN/CdS-HS can still maintain excellent overall stability. This work provides an idea for the design and development of efficient visible-light-driven photocatalysts in the future.

Integration of 2D layered CdS/WO3 S-scheme heterojunctions and metallic Ti3C2 MXene-based Ohmic junctions for effective photocatalytic H2 generation

The rapid recombination of photo-generated electron-hole pairs, insufficient active sites, and strong photocorrosion have considerably restricted the practical application of CdS in photocatalytic fields. Herein, we designed and constructed a 2D/2D/2D layered heterojunction photocatalyst with cascaded 2D coupling interfaces. Experiments using electron spin resonance spectroscopy, ultraviolet photoelectron spectroscopy, and in-situ irradiation X-ray photoelectron spectroscopy were conducted to confirm the 2D layered CdS/WO3 step-scheme (S-scheme) heterojunctions and CdS/MX ohmic junctions. Impressively, it was found that the strong interfacial electric fields in the S-scheme heterojunction photocatalysts could effectively promote spatially directional charge separation and transport between CdS and WO3 nanosheets. In addition, 2D Ti3C2 MXene nanosheets with a smaller work function and excellent metal conductivity when used as a co-catalyst could build ohmic junctions with CdS nanosheets, thus providing a greater number of electron transfer pathways and hydrogen evolution sites. Results showed that the highest visible-light hydrogen evolution rate of the optimized MX-CdS/WO3 layered multi-heterostructures could reach as high as 27.5 mmol/g/h, which was 11.0 times higher than that of pure CdS nanosheets. Notably, the apparent quantum efficiency reached 12.0% at 450 nm. It is hoped that this study offers a reliable approach for developing multifunctional photocatalysts by integrating S-scheme and ohmic-junction built-in electric fields and rationally designing a 2D/2D interface for efficient light-to-hydrogen fuel production.

A novel microwave induced preparation of CuFe2O4/g-C3N4-based efficient photocatalyst for enhanced visible-light hydrogen evolution

A novel microwave induced preparation of CuFe2O4/g-C3N4-based efficient photocatalyst for enhanced visible-light hydrogen evolution

MOF-mediated fabrication of coralloid Ni2P@CdS for enhanced visible-light hydrogen evolution

Ni2P is an efficient cocatalyst to improve the photoelectric properties of CdS. In consideration of this, we designed a coralloid Ni2P@CdS photocatalyst (C-Ni2P@CdS) via a MOF-mediated tandem pyrolysis strategy for enhanced photocatalytic hydrogen evolution. Benefiting from the unique synergistic effect between coralloid Ni2P and CdS, C-Ni2P@CdS shown a high photocatalytic H2 production rate of 28 391 μmol h−1 g−1, nearly 11 times higher than CdS. Compared with CdS, the absorption intensity of C-Ni2P@CdS was drastically extended in the visible-light region (λ > 540 nm). Meanwhile, PL spectra, EPR and photoelectric responsiveness etc. were further employed to study the synergistic effect between Ni2P and CdS. From Density Functional Theory (DFT), strong electronic coupling effect induced electrons to accumulate on adsorbed H2O and the most energetically favorable configuration indicated that Ni-P bridges were the active sites for water dissociation. Lastly, a viable mechanism of C-Ni2P@CdS heterojunction for photocatalytic hydrogen evolution was proposed.

A novel noble-metal-free binary and ternary In2S3 photocatalyst with WC and “W-Mo auxiliary pairs” for highly-efficient visible-light hydrogen evolution

Herein, noble-metal-free In2S3-WC and In2S3-based photocatalysts with dual cocatalysts of flower-like MoS2 and bulk WC were synthesized through a facile solvothermal reaction. Electrochemical results indicated WC increased the interface conductance of photocatalyst and boosted the transference of photogenerated carriers. The optimal In2S3-WC show a hydrogen production rate of 128.11 μmol·h−1·g−1, which is around 6 times higher than In2S3-1%Pt (20.73 μmol·h−1·g−1). The above results demonstrate commercial WC has a crucial impact of replacing precious metal and separating carriers. Morphology characterization exhibited hydrangea In2S3 and flower-like MoS2 were attached to bulk WC. Gratifyingly, photocurrent, impedance and photoluminescence results demonstrated MoS2 further effectively separated the photogenerated carriers. Remarkably, the higher hydrogen generation rate of 390.52 μmol·h−1·g−1 obtained by the optimal ternary In2S3-WC-MoS2 composite was around 3 and 18 times higher than the optimal In2S3-WC and In2S3-1% Pt. The photocatalytic results demonstrated that "W-Mo auxiliary pairs" was a great efficient synergistic cocatalyst for In2S3 to increase active sites and improve e--h+ pairs separation for H2 generation. Furthermore, a probable reaction mechanism of the enhanced photocatalytic H2 generation was also proposed. This presented research provides an effective concept to design novel and efficient noble-metal-free photocatalyst with "W-Mo auxiliary pairs" for prominent H2 generation activity.

Crystalline carbon nitride anchored on MXene as an ordered Schottky heterojunction photocatalyst for enhanced visible-light hydrogen evolution

Carbon nitride (CN) polymer is considered as a potential material for photocatalysis, but surfers from the low photoconversion efficiency due to its high defect density. Although the defects can be limited through the crystallization of CN, the photocatalytic activity of single-component photocatalyst is still restricted by the recombination of photoexcited carriers. In our work, the ordered Schottky heterojunction of heptazine-based crystalline carbon nitride (HCN) and Ti3C2 MXene was successfully prepared through ionothermal method. The HCN/Ti3C2 composites exhibit higher photocatalytic performance than pristine HCN. Particularly, the HCNT20 sample exhibits the highest photocatalytic H2 evolution activity, which is about 8 and 2 times higher than that of bulk CN and pristine HCN, respectively. The results of charge transfer dynamics and DFT calculation reveal that the photocatalytic enhancement mechanism is primarily attributed to the synergistic effects of crystallization of CN, excellent conductivity of Ti3C2 and well-constructed Schottky heterojunction.

All-solid-state direct Z-scheme NiTiO3/Cd0.5Zn0.5S heterostructures for photocatalytic hydrogen evolution with visible light

All-solid-state direct NiTiO3/Cd0.5Zn0.5S Z-scheme heterostructures enabled the visible-light hydrogen evolution at an optimal H2-releasing rate of 26.45 mmol h−1 g−1.

Excited Carrier Dynamics in a Dye-Sensitized Niobate Nanosheet Photocatalyst for Visible-Light Hydrogen Evolution

Dye-sensitized photocatalysts that consist of a light-absorbing dye and a wide-gap oxide semiconductor have been studied extensively as components of solar energy conversion systems. Although surfa...

Triptycene-based discontinuously-conjugated covalent organic polymer photocatalysts for visible-light-driven hydrogen evolution from water

Effective photocatalytic systems that are capable of converting solar energy into chemical fuels have recently attracted significant attention. Covalent organic polymers (COPs) have been explored as promising photocatalysts for visible-light-driven hydrogen evolution from water. Herein, a series of triptycene (TP)-based discontinuously conjugated COP photocatalysts are described for the first-time using TP with monothiophene (MT), trithiophene (TT), dithiophene benzothiadiazole (DTBT), and diphenyl benzothiadiazole (DPBT), denoted as MT-TP, TT-TP, DTBT-TP, and DPBT-TP, respectively. Difference photophysical, morphological, and photocatalytic properties can be tuned by introducing different types of linkers of the TP-based COPs. DPBT-TP shows a significant enhancement of the hydrogen evolution rate (HER) in comparison to those using other polymer photocatalysts at identical conditions. The transmission electron microscopy/scanning electron microscopy data show that the tube-like polymer photocatalysts afford higher HERs than those observed with the particle-like polymer photocatalysts. This report describes the first demonstration that the polymer photocatalysts constructed by the disconuiously conjugated system (conjugation length: less than 5 aromatic rings) is sufficient for an efficient visible-light-driven hydrogen evolution. It provides an alternative material design strategy for polymer photocatalysts to achieve efficient visible light hydrogen evolution.

Construction of p-n type heterojunction for effective photo-generated electron separation and visible light hydrogen evolution

With the development of research on the photocatalytic water splitting and hydrogen (H2) precipitation, cobalt ferrite and molybdate have begun to appear as catalysts for the study of photocatalytic hydrogen precipitation. In this paper, the p-n heterojunction CoFe2O4/NiMoO4 (CFO/NMO) is prepared by hydrothermal method. The constructed p-n type (type Ⅱ) heterojunction CFO/NMO has the highest hydrogen evolution (Eosin Y as a sensitizer), which is 7.39 times and 1.95 times that of elemental CFO and NMO, respectively. After the CFO and NMO form a heterojunction, a built-in electric field is formed inside to effectively separate the photogenerated carriers. At the same time, the dense interface of the heterojunction also promotes the transfer of photogenerated carriers and promotes the reduction of H+ protons on this catalyst surface. In short, this work provides more possibilities for the field of photocatalytic hydrogen evolution from molybdate and cobalt ferrite compounds.

Tailored Coupling of Biomineralized CdS Quantum Dots to rGO to Realize Ambient Aqueous Synthesis of a High-Performance Hydrogen Evolution Photocatalyst.

Nanocomposite photocatalysts offer a promising route to efficient and clean hydrogen production. However, the multistep, high-temperature, solvent-based syntheses typically utilized to prepare these photocatalysts can limit their scalability and sustainability. Biosynthetic routes to produce functional nanomaterials occur at room temperature and in aqueous conditions, but typically do not produce high-performance materials. We have developed a method to produce a highly efficient hydrogen evolution photocatalyst consisting of CdS quantum dots (QDs) supported on reduced graphene oxide (rGO) via enzyme-based syntheses combined with tuned ligand exchange-mediated self-assembly. All preparation steps are carried out in an aqueous environment at ambient temperature. Size-controlled CdS QDs and rGO are prepared through enzyme-mediated turnover of l-cysteine to HS- in aqueous solutions of Cd-acetate and graphene oxide, respectively. Exchange of cysteamine for the native l-cysteine ligand capping the CdS QDs drives self-assembly of the now positively charged cysteamine-capped CdS (CdS/CA) onto negatively charged rGO. The use of this short linker molecule additionally enables efficient charge transfer from CdS to rGO, increasing exciton lifetime and, subsequently, photocatalytic activity. The visible-light hydrogen evolution rate of the resulting CdS/CA/rGO photocatalyst is 3300 μmol h-1 g-1. This represents, to our knowledge, one of the highest reported rates for a CdS/rGO nanocomposite photocatalyst, irrespective of the synthesis method.