Efficient Visible-light Photocatalytic Hydrogen Research Articles

Benzodithiophene-4,8-dione-Based Conjugated Microporous Polymers for Efficient Visible-light Photocatalytic Hydrogen Evolution from Water

Benzodithiophene-4,8-dione-Based Conjugated Microporous Polymers for Efficient Visible-light Photocatalytic Hydrogen Evolution from Water

CdS-based Schottky junctions for efficient visible light photocatalytic hydrogen evolution

Heterojunctions photocatalysts play a crucial role in achieving high solar-hydrogen conversion efficiency. In this work, we mainly focus on the charge transfer dynamics and pathways for sulfides-based Schottky junctions in the photocatalytic water splitting process to clarify the mechanism of heterostructures photocatalysis. Sulfides-based Schottky junctions (CdS/CoP and CdS/1T-MoS2) were successfully constructed for photocatalytic water splitting. Because of the higher work function of CdS than that of CoP and 1T-MoS2, the direction of the built-in electric field is from CoP or 1T-MoS2 to semiconductor. Therefore, CoP and 1T-MoS2 can act as electrons acceptors to accelerate the transfer of photo-generated electron on the surface of CdS, thus improving the charge utilization efficiency. Meanwhile, CoP and 1T-MoS2 as active sites can also promote the water dissociation and lower the H+ reduction overpotential, thus contributing to the excellent photocatalytic hydrogen production activity (23.59 mmol·h−1·g−1 and 1195.8 mol·h−1·g−1 for CdS/CoP and CdS/1T-MoS2).

Au NPs-incorporated NiS/RGO hybrid composites for efficient visible light photocatalytic hydrogen evolution

Au NPs-incorporated NiS/RGO hybrid composites for efficient visible light photocatalytic hydrogen evolution

Boosting photocatalytic H2 production performance over perovskite/CdS quantum dots S-scheme photocatalyst

Layered perovskite materials are thought to be excellent photocatalysts. However, which always fails to absorb visible light. In this paper, CdS quantum dots and Ni2+ were incorporated into the interlayer of layered calcium niobate perovskite KCa2Nb3O10 to achieve an efficient visible-light photocatalytic hydrogen production, which was prepared by direct cation exchange reaction and a sulfurization process. The X-ray photoelectron spectroscopy and HRTEM mapping confirmed that the substituted CdS QDs and Ni2+ are mainly located at the interlayer edges and interlamination. The performance was increased with the increase of the interlayered Ni content. The obtained sample KCNO/CdS-Ni-50 exhibited a photocatalytic H2 evolution rate of 5.21 mmol•h−1•g−1 without noble metals as co-catalysts, about 670 times higher than that of pristine KCa2Nb3O10. The highly efficient photocatalytic activity and stability can be ascribed to the S-scheme heterojunction structure, in which the sites for redox reaction were separated in space to inhibit the photo-generated electron-hole recombination.

In-doped Sn3O4 flower-like nanosheets for efficient visible-light photocatalytic hydrogen production

Improving photocatalytic activity is crucial for promoting photocatalytic hydrogen production. Element doping is a feasible strategy to accelerate carrier separation and migration rate. Herein, a simple one-pot hydrothermal process was used to create In doped Sn3O4 composite photocatalyst. It was demonstrated that the addition of In considerably raises the concentration of oxygen vacancy, which provides more unsaturated active sites, thus regulating the photocatalyst's electronic structure and surface properties, and promoting the carrier migration efficiency. Meanwhile, the light absorption range of samples after doping is redshifted, and the light absorption capacity is enhanced, which effectively improves the photocatalytic activity. Due to this, the optimal sample's average hydrogen production under visible light reached 22.83 μmol g−1 h−1, 4.5 folds more than that of Sn3O4, and shown good stability. This research presents a novel approach for the development of metal oxide photocatalyst with excellent activity and durability.

Highly efficient visible-light photocatalytic hydrogen production using ZIF-derived Co9S8/N, S-CNTs-ZnIn2S4 composite

A hierarchical Co9S8/N, S-CNTs-ZnIn2S4 (CSCNs-ZIS) composite was reasonably constructed by grafting ZnIn2S4 nanosheets on the ZIF (67) derived Co9S8/N, S-doped carbon nanotubes for effective photocatalytic hydrogen production. The aggregated ZnIn2S4 nanosheets were uniformly wrapped on the surface of CSCNs, forming a hierarchical core–shell configuration, which effective inhibition of charge-carrier recombination. The CSCNs was adopted as an effective multi-component co-catalyst and further promoted photocatalytic hydrogen production performance. The H2 production rate of optimized CSCNs-ZIS composite reached 2409.2 μmol·h−1·g−1 and has high stability after three cycles. This work may inspire the design of a new noble-metal-free multi-component co-catalyst for sustainable H2 production.

Allochroic platinum/carbon nitride with photoactivated ohmic contact for efficient visible-light photocatalytic hydrogen evolution

The direct hybridization of Pt and g-C3N4 generally forms a Schottky barrier between the two components, which unavoidably hinders the migration of photogenerated electrons from g-C3N4 to the Pt cocatalyst. Herein, we report the first efficient allochroic Pt/g-C3N4 photocatalyst that can form an ohmic contact through photoconversion of semiconducting g-C3N4 to metalloid, accompanied with the charge carrier storage and photocatalyst color change, which is proved experimentally and theoretically. Through intermittent exposure of Pt/g-C3N4 photocatalyst to air for a few minutes during photocatalysis, the photocatalyst shows the highest hydrogen evolution performances. The ohmic contacts greatly promote the electron transfer from the semiconducting g-C3N4 to the Pt cocatalyst driven by the built-in electric field. In addition, the mechanism for the photocatalyst deactivation and activation is presented. The compositional tuning of the allochroic g-C3N4 through light irradiation and exposure to air can control over the photocatalytic activity and long-term stability for hydrogen evolution. This report for the first time unveils the deactivation and regeneration mechanisms of SCN.

Surface-assisted synthesis of biomass carbon-decorated polymer carbon nitride for efficient visible light photocatalytic hydrogen evolution

Template is frequently studied as a structure-directing agent to tune the nanomorphology of photocatalysts. However, the influences of template on the polymerization of precursors and compositions of the resulting samples are rarely considered. Herein, a biomass carbon-modified graphitic carbon nitride (CCNx) with a thin-layer morphology is synthesized via one-pot surface-assisted polymerization of melamine precursor on organic yeast. The formation of the hydrogen bond between melamine and yeast induces a strong interfacial confinement, giving rise to small-sized CCNx. In addition, the carbon materials derived from yeast dramatically broaden n → π* visible light harvesting, improve electron delocalization, and greatly enhance charge carrier separation. The optimized CCNx presents a much higher photocatalytic hydrogen production rate of 2704 μmol g-1h−1 under visible light irradiation (λ ≥ 420 nm), which is nearly 11-fold that of its pristine counterpart. This work realizes the synergistic effect between morphology tunning and composition tailoring by using biomass template, which shows a great potential in developing efficient metal-free photocatalysts.

Hydrophilic hydrogen-bonded organic frameworks/g-C3N4 all-organic Z-scheme heterojunction for efficient visible-light photocatalytic hydrogen production and dye degradation

Herein, a novel all-organic Z-scheme hydrogen-bonded organic frameworks (HOFs)/g-C3N4 nanosheets (CNNS) heterojunction photocatalyst is synthesized through an in-situ electrostatic method. Characterization and density functional theory studies together verify that the band structures with staggered alignment between HOFs and CNNS can induce a rapid Z-scheme interfacial charge-transfer pathway. Combing the complementary advantages of HOFs and CNNS, the fabricated Z-scheme HOFs/CNNS heterojunction inhibits photoinduced electron-hole recombination and more charge carriers are accumulated to produce highly reactive substances (•O2–, •OH and h+). In addition, the superior hydrophilicity of HOFs can enhance the interaction of HOFs/CNNS heterojunction with water molecules and methyl orange pollutant, which is beneficial to boosting photocatalytic activity. Therefore, in contrast to inactive pure HOFs, the novel Z-scheme HOFs/CNNS heterojunction exhibits a high photocatalytic hydrogen evolution rate of 4450 μmol h-1g−1 with an apparent quantum efficiency (AQY) of 22 % at 450 nm, which is approximately 11 times higher than that of pure CNNS. Additionally, such heterojunction enables 100 % degradation of methyl orange within 60 min.

Diaza-substitution on dibenzothiophene sulfone-based linear conjugated polymers for highly efficient visible-light photo-catalytic hydrogen evolution via substituted-position optimization

Two linear conjugated polymers (FSO-TPmT and FSO-TPzT) were synthesized based on dibenzothiophene sulfone and diaza-substituted thiophene-benzene-thiophene with different substituted positions (1,3-diaza-substitution and 1,4-diaza-substitution) for photo-catalytic hydrogen evolution. The 1,2-diaza-substituted polymer (FSO-TPaT) reported from previous work was also used for comparison. The diaza-substitution significantly affected the optical properties, exciton lifetime, charge transport resistance, photo-current response, and thus photo-catalytic performances. Conjugated polymers with 1,3-diaza-substitution exhibited the best photo-catalytic performances with the hydrogen evolution rates (HERs) of 7645 μmol g−1 h−1 and 7280 μmol g−1 h−1 under UV–Vis (>295 nm) and visible light (>420 nm) irradiation, respectively. Moreover, the photo-catalytic performance was further optimized by loading 3 wt% Pt with a HER of 9828 μmol g−1 h−1. The apparent quantum yields were 5.8% and 3.9% at 420 nm and 500 nm, respectively. These results indicated that the conjugated polymer with 1,3-diaza-substitution was mainly active under visible light and should be an excellent visible-light photo-catalyst for hydrogen evolution from water.

Ni2P–Ni2P4O12 enhanced CdS nanowires for efficient visible light photocatalytic hydrogen production

Intrinsic charge carrier recombination, narrow visible light absorption and poor durability restrain the photoactivity for solar-to-H2 production. Here, noble-metal-free binary co-catalyst Ni2P–Ni2P4O12 was synthesized by a simple one-step thermal phosphorylation method for enhancing CdS nanowires in visible-light-driven hydrogen generation, where the CdS nanowires are uniformly dispersed on the surface of Ni2P–Ni2P4O12 through in-situ solvothermal strategy. The photocatalytic hydrogen production rate of 5 ​wt% Ni2P–Ni2P4O12/CdS nanowires can reach 5093 ​μmol ​g−1 ​h−1 using Na2S–Na2SO3 as sacrificial agent under the irradiation of visible light (λ ​> ​420 ​nm), which is about 16 times for CdS nanowires (316 ​μmol ​g−1 ​h−1). In the cycling experiments, the composite catalyst shows good stability and the hydrogen production rate remains about 83% of the initial value. The interface structure construction between CdS nanowires and Ni2P–Ni2P4O12 result in the excellent photocatalytic activity, broaded visible light absorption and stability. Specifically, Ni2P–Ni2P4O12 can effectively promote the separation of electron hole pairs in space, in which Ni2P4O12 can accept H+ ions and Ni2P can reduce the over potential of H+ reduction, resulting in the synergically promotion in the photocatalytic activity. The cost-effective ternary photocatalyst exhibits great potential for sustainable and high-efficiency photocatalytic water splitting, and Ni2P–Ni2P4O12 may be suitable to modify a wider variety of semiconductor photocatalysts.

Hydrophilic Hydrogen-Bonded Organic Frameworks/G-C3n4 All-Organic Z-Scheme Heterojunction for Efficient Visible-Light Photocatalytic Hydrogen Production and Dye Degradation

Hydrophilic Hydrogen-Bonded Organic Frameworks/G-C3n4 All-Organic Z-Scheme Heterojunction for Efficient Visible-Light Photocatalytic Hydrogen Production and Dye Degradation

Fabrication of novel Cu2WS4/NiTiO3 heterostructures for efficient visible-light photocatalytic hydrogen evolution and pollutant degradation

The design and development of efficient and durable catalysts with visible-light response for photocatalytic hydrogen production and pollutants degradation is considered as one of the most challenging tasks. In present work, a novel Cu2WS4/NiTiO3 (abbreviated as × CWS/NTO; x = 0.25, 0.50, 0.75 and 1.00) composite was prepared via a facile electrospinning/calcination technique along with a convenient hydrothermal method. The as-prepared CWS/NTOcomposite was composed of 2D CWS nanosheets and 1D NTO nanofibers manifested by SEM and TEM images. The results of XPS verified the interfacial interaction between CWS and NTO, confirming the heterojunction formation in CWS/NTOcomposite. Photocatalytic tests demonstrated as-prepared CWS/NTO catalysts exhibited outstanding and stable photocatalytic performances for H2 production and pollutants degradation under visible light (λ > 420 nm) irradiation. Specially, 0.50 CWS/NTO sample displayed the highest H2-evolution activity of 810 μmol·g−1·h−1 with the apparent quantum efficiency (AQE) value of 1.65 % at 420 nm. Additionally, it also exhibited the optimal photodegradation properties with the rate constants of 0.030, 0.413 and 0.028 min−1 for TC, RhB and Cr(VI), respectively. The excellent catalytic activities could be attributed to the enhanced visible-light adsorption, high specific surface area and efficient separation of photogenerated charge carriers. The ESR tests and free radicals capturing experiments confirmed that ·O2– and h+ were primary active species for TC/RhB degradation. Eventually, the probable catalytic mechanism was put forward and detailly analysed. The present work provides perspectives of rational design on NiTiO3-based catalysts with superior photocatalytic performance for energy regeneration and environmental remediation.

Well-designed three-dimensional hierarchical hollow tubular g-C3N4/ZnIn2S4 nanosheets heterostructure for achieving efficient visible-light photocatalytic hydrogen evolution

Photocatalytic water splitting for hydrogen production is an important strategy to achieve clean energy development. In this report, a novel three-dimensional (3D) hierarchical hollow tubular g-C3N4/ZnIn2S4 nanosheets (HTCN/ZIS) type-Ⅱ heterojunction photocatalyst was successfully prepared and applied for photocatalytic hydrogen production under visible light irradiation. The experimental results reveal that the optimal proportion of HTCN/ZIS with the remarkable photocatalytic H2 evolution rate of 20738 μmol h−1 g−1 was obtained. The main reasons for the improvement of hydrogen production activity are as follows: (i) this unique tubular hollow structure can effectively enhances the light capturing ability by the multiple light scattering/reflection of incident light in the inner cavity; (ii) the shorten the phase plane transmission distance could reduce the path of charge transfer; (iii) the surface coated a large number of scaly ZnIn2S4 nanosheets can provide abundant reactive sites. Combining the various characterization tests, the enhanced spatial segregation of charge carriers could owning to the intimately interfacial contact and well-matched band gaps structure between g-C3N4 and ZnIn2S4 through the type-II heterojunction. This work provides a new prospect for the construction of a novel 3D hierarchical type-II heterojunction photocatalyst for highly efficient photocatalytic hydrogen production.

Construction of LaFeO3/g-C3N4 nanosheet-graphene heterojunction with built-in electric field for efficient visible-light photocatalytic hydrogen production

Photocatalytic hydrogen desorption from water has been considered to be a more effective way to solve energy shortages. However, the relatively high charge recombination rate and poor recyclability are the principal factors restricting the realistic utilization of photocatalysts. Herein, in order to improve the utilization of photogenerated carriers and the response range of visible light, a ternary composite material LaFeO3/g-C3N4 nanosheets-graphene had been successfully prepared. A series of systematic studies on the structure, microscopic morphology, magnetic properties and photocatalytic hydrogen evolution activity have been carried out. The combination of CNNS, LaFeO3 and graphene in the composites was confirmed by XRD and XPS. SEM and TEM results show that LaFeO3 micro-particles grow uniformly on the CNNS flaps and the graphene is observed to cover the surface of the LaFeO3/CNNS. The optical properties indicate that the absorption edge of the composite material extends to the visible light region. The excellent photocatalytic performance of LFO/CNNS-0.25G composite (1326.5 μmol h−1 g−1) is mainly result in the improved redox capacity and carrier separation due to the tight C–O–Fe bond of Z-scheme heterojunction, meanwhile, the introduction of graphene also broadens the visible light response and accelerates the carrier transport. This research can provide a novel strategy for designing artificial photocatalytic systems with high charge transfer efficiency.

Cuboidal Cu 2 O nanoparticles dispersed granular Mn 0. 05 Cd 0 . 95 S form a p‐n heterojunction for efficient photocatalytic hydrogen evolution

In this work, n-type semiconductor Mn0.05Cd0.95S (MCS) nanoparticles are closely glued to the surface of p-type semiconductor Cu2O nanocubes, which increasing the contact area between them and presenting a more uniform distribution. And a Cu2O/Mn0.05Cd0.95S p-n heterojunction was formed, thus, a p-n interface is constructed at the surface of MCS nanoparticles and Cu2O nanocubes, where the internal electric field drives the transfer of photogenerated electrons, so that high-efficiency prevents the combination of photogenerated electron-hole pairs. Here, under the premise that Na2S/Na2SO3 (0.35 M/0.25 M) solution is used as a sacrificive reagent, Hydrogen production experiments have confirmed this 5%Cu2O/Mn0.05Cd0.95S photocatalyst exhibits the highest photocatalytic hydrogen production activity of 468.3 μmol, which is approximate 2.8 times higher than that of pure MCS nanoparticles. Moreover, a high photostability was also obtained over 5%Cu2O/Mn0.05Cd0.95S photocatalyst. This discovery proves a facile method to construct Cu2O/Mn0.05Cd0.95S p-n heterojunction for highly efficient visible-light photocatalytic hydrogen evolution.

One-step synthesis of Mo and S co-doped porous g-C3N4 nanosheets for efficient visible-light photocatalytic hydrogen evolution

Herein, the doping effect of Mo and S on photocatalytic H2 generation activity of g-C3N4 under visible light irradiation is investigated. By using a simple one-step heating technology, Mo and S co-dopedporous g-C3N4nanosheets were successfully prepared. The sublimation of sulfur powders promotes the formation of porous g-C3N4 nanosheets with large specific surface area. The Mo and S co-doped g-C3N4 exhibits efficient visible-light water splitting hydrogen evolution with the noble metallic cocatalyst free. The optimized Mo/S/g-C3N4-10 photocatalyst exhibits an extraordinary photocatalytic H2 evolution rate of 294 μmol g-1h−1 under visible light irradiation (λ > 420 nm). The co-doping of S and Mo extends the optical response range of g-C3N4. The doping process and electron transport path are analyzed in details. Mo and S co-dopedporous g-C3N4catalysts also exhibit outstanding cycling stability. This work may inspire the facile synthesis of photocatalyst for efficient visible-light water splitting hydrogen evolution.

CuS-modified ZnO rod/reduced graphene oxide/CdS heterostructure for efficient visible-light photocatalytic hydrogen generation

Solar energy utilization is a promising strategy for the photocatalytic generation of H2 from water. Herein, a CuS-modified ZnO rod/reduced graphene oxide (rGO)/CdS heterostructure was fabricated via Cu-induced electrochemical growth with Zn powder at room temperature. The resulting powder revealed good interfacial bonding and promoted photoexcited carrier transport. The CuS nanoparticles played a pivotal role in enhancing visible-light responses and demonstrated excellent catalytic performance. A high visible-light photocatalytic H2 generation rate of 1073 μmol h−1 g−1 was obtained from the CuS–ZnO/rGO/CdS heterostructure containing 0.23% CuS and 1.62% CdS. Increased photoexcited electron lifetimes, improved carrier transport rates, and decreased fluorescence intensities confirmed the synergistic effects of each of the components of the heterostructure. This study provides an innovative strategy for constructing multi-component heterostructures to achieve efficient visible-light H2 evolution.

Coralline-like Ni2P decorated novel tetrapod-bundle Cd0.9Zn0.1S ZB/WZ homojunctions for highly efficient visible-light photocatalytic hydrogen evolution

In this study, Ni2P-Cd0.9Zn0.1S (NPCZS) composites were synthesized by coupling tetrapod bundle Cd0.9Zn0.1S (CZS) and coralline-like Ni2P (NP) via a simple calcination method. CZS shows outstanding activity in photocatalytic hydrogen evolution (1.31 mmol h−1), owing to its unique morphology and heterophase homojunctions (ZB/WZ), which accelerate the separation and transfer of photogenerated charges. After coupling with NP, the photoactivity of NPCZS was enhanced, and the maximum hydrogen evolution rate of 1.88 mmol h−1 was reached at a NP content of 12 wt%, which was 1.43 times higher than that of pure CZS. The experimental results of the photocatalytic activity, viz. photoluminescence spectra, surface photovoltage spectra, and electrochemical test showed that the enhanced photoactivity of NPCZS should be attributed to the synergistic effects of the novel tetrapod-bundle morphology, heterophase homojunctions, and decoration of the NP co-catalyst. Moreover, the as-prepared NPCZS composites exhibited excellent photostability and recyclability. Herein, we propose a possible mechanism for the enhanced photocatalytic activity.

MoS2@SnO2 core-shell sub-microspheres for high efficient visible-light photodegradation and photocatalytic hydrogen production

Two-step hydrothermal processes have been used to synthesize MoS2@SnO2 core-shell sub-microspheres. The effect of the different weight of citric acid for MoS2@SnO2 core-shell sub-microspheres on the microstructural and photocatalytic properties was studied. The results indicate that MoS2@SnO2 core-shell sub-microspheres can reveal the highly efficient photocatalytic water splitting and degradation of rhodamine B solution under visible-light irradiation. The enhanced photocatalytic performance was ascribed to MoS2 sub-microspheres decorated with SnO2 nanoparticles, improving their surface-to-volume ratio and photoinduced electron-hole pairs separation.