Visible-light Photocatalytic H2 Research Articles

Metallic plasmons significantly boosted visible-light photocatalytic hydrogen evolution from water splitting

Surface plasmon resonance (SPR) of Ni nanoparticles has been studied to promote the generation of hot electrons, charge transfer and separation over g-C3N4/Ni@C plasmonic photocatalysts, resulting in boosted visible-light photocatalytic H2 evolution from water splitting.

In Situ Fabrication of N-Doped ZnS/ZnO Composition for Enhanced Visible-Light Photocatalytic H2 Evolution Activity.

For achieving the goal of peaking carbon dioxide emissions and achieving carbon neutrality, developing hydrogen energy, the green and clean energy, shows a promising perspective for solving the energy and ecological issues. Herein, firstly, we used the hydrothermal method to synthesize the ZnS(en)0.5 as the precursor. Then, ZnS/ZnO composite was obtained by the in situ transformation of ZnS(en)0.5 with heat treatment under air atmosphere. The composition, optical property, morphology, and structural properties of the composite were characterized by X-ray photoemission spectroscopy (XPS), Ultraviolet-visible absorption spectra (Uv-vis Abs), Scanning electron microscopy (SEM) and Transmission electron microscopy image (TEM). Moreover, the content of ZnO in ZnS/ZnO was controlled via adjustment of the calcination times. The visible-light response of ZnS/ZnO originated from the in situ doping of N during the transformation of ZnS(en)0.5 to ZnS/ZnO under heat treatment, which was verified well by XPS. Photocatalytic hydrogen evolution experiments demonstrated that the sample of ZnS/ZnO-0.5 h with 6.9 wt% of ZnO had the best H2 evolution activity (1790 μmol/h/g) under visible light irradiation (λ > 400 nm), about 7.0 and 12.3 times that of the pure ZnS and ZnO, respectively. The enhanced activities of the ZnS/ZnO composites were ascribed to the intimated hetero-interface between components and efficient transfer of photo-generated electrons from ZnS to ZnO.

Cobalt clusters on g-C3N4 nanosheets for enhanced H2/H2O2 generation and NO removal

A one-step thermal polymerization method was developed to create homogeneous metallic cobalt (Co) clusters on graphitic carbon nitride (g-C3N4) nanosheets. The size (less than 3 nm) and distribution of Co clusters were controlled by a subsequent acid treatment. Because of the nanofluidic channels, efficient charge transfer, and enhanced light harvesting ability, optimized Co/g-C3N4 nanoarchitectonics by acid treatment revealed excellent photocatalytic activities. The visible-light photocatalytic H2 generation, H2O2 evolution and NO removal rate of the nanoarchitectonics were 82, 4, and 2 times of those of g-C3N4 nanosheets, respectively, suggesting that integrating transition metal clusters on g-C3N4 nanosheets is a novel strategy for NO removal and water splitting. Interestingly, Co/g-C3N4 nanoarchitectonics were further heat-treated at high temperature to create Co clusters decorated N-doped carbon nanosheets, in which ideal performance in hydrogen evolution reaction, oxygen evolution reaction, and oxygen reduction reaction in alkaline solution were observed. This result supplied an efficient route to construct non-noble metal multifunctional catalysts.

(Invited) Towards Broadband Solar Fuel Production

Combining nanomaterials of different properties into nanohybrids can potentially lead to improved properties/performance or multiple functions. In particular, forming nanomaterials junctions and using plasmons represent two important, promising strategies for realizing broadband photocalysis in strategically important applications such as solar fuels and photocatalytic degradation of pollutants in our environments. In this talk, I will present some of our recent work on the rational design and realization of nanohybrid materials as well as their applications in solar fuel and photocatalysis. For instance, the construction of homojunctions of nanoplates made of metal–organic frameworks (MOF) led to broadened light absorption and increased photoactivity. The well-defined MOF homojunction was prepared by a facile one-pot synthesis route directed by hollow transition metal nanoparticles. The homojunction is enabled by two concentric stacked nanoplates with slightly different crystal phases. The enhanced charge separation in the homojunction was visualized by in-situ surface photovoltage microscopy. The as-prepared nanostacks displayed a visible-light-driven carbon dioxide reduction with very high carbon monooxide selectivity, and excellent stability. Another example is about the in situ synthesis of plasmonic Ag nanoparticles (AgNPs) and Ag-MOM (metal organic matrix) using one-step facile approach. The intimate and stable interface between the AgNPs and Ag-MOM and hot electron transfer from the plasmonic AgNPs to MOM led to highly efficient visible-light photocatalytic H2 generation in aqueous solution, which surpasses most of reported MOF-based photocatalytic systems. This work sheds light on effective electronic and energy bridging between plasmonic NPs and metal organic matrix.Related

Mo-/O-deficient Bi2Mo3(S,O)12 oxysulfide for enhanced visible-light photocatalytic H2 evolution and pollutant reduction via in-situ generated protons: A case of material design in converting an oxidative Bi2Mo3O12 catalyst for the reduction

The Mo-nonstoichiometry, oxygen vacancy, and S incorporation into Bi-Mo bimetallic oxide enhance the activity by creating defects that improve charge carrier separation efficiency and narrow bandgap energy. Oxygen vacancies synergistically attired nonstoichiometric and Mo-deficient and O-deficient Bi2Mo3-x(S,O)12-y oxysulfide (Mo-/O-deficient Bi2Mo3(S,O)12) is found by a one-pot facile method to enhance the photocatalytic H2 evolution and pollutant reduction via in-situ generated protons. The best Mo-/O-deficient Bi2Mo3(S,O)12 catalyst with x = 0.75 and oxygen vacancy content of 27.6 % produced 480.87 µmol/h H2 with 25 mg catalyst and achieved AQE of 14.26 % at λ = 420 nm, whereas reduced 88.9 % 4-NP and 91.6 % RhB by in-situ generated protons. Bi-non-stoichiometry leads to Mo4+ and oxygen vacancy formation and creates active reaction sites of oxygen vacancy and active surface oxygen. These enhancements benefit photogenerated carrier separation efficiency and fast electron transfer and achieve Mo-/O-deficient Bi2Mo3(S,O)12 with superb PHER. Therefore, non-stoichiometry and sulfur doping into Bi2Mo3O12 bimetallic oxide is a promising approach for designing novel and synergistically defect-attired oxysulfide photocatalysts.

Construction and performance of CdS/MoO2@Mo2C-MXene photocatalyst for H2 production

Nowadays, photocatalytic technologies are regarded as promising strategies to solve energy problems, and various photocatalysts have been synthesized and explored. In this paper, a novel CdS/MoO2@Mo2C-MXene photocatalyst for H2 production was constructed by a two-step hydrothermal method, where MoO2@Mo2C-MXene acted as a binary co-catalyst. In the first hydrothermal step, MoO2 crystals with an egged shape grew on the surface of two-dimensional (2D) Mo2C MXene via an oxidation process in HCl aqueous solution. In the second hydrothermal step, CdS nanorods were uniformly assembled on the surface of MoO2@Mo2C-MXene in ethylenediamine with an inorganic cadmium source and organic sulfur source. The CdS/MoO2@Mo2C-MXene composite with MoO2@Mo2C-MXene of 5 wt% exhibits an ultrahigh visible-light photocatalytic H2 production activity of 22,672 µmol/(g·h), which is ∼21% higher than that of CdS/Mo2C-MXene. In the CdS/MoO2@Mo2C-MXene composite, the MoO2 with metallic nature separates CdS and Mo2C MXene, which acts as an electron-transport bridge between CdS and Mo2C MXene to accelerate the photoinduced electron transferring. Moreover, the energy band structure of CdS was changed by MoO2@Mo2C-MXene to suppress the recombination of photogenerated carriers. This novel compound delivers upgraded photocatalytic H2 evolution performance and a new pathway of preparing the low-cost photocatalyst to solve energy problems in the future.

Carbon dots incorporated in hierarchical macro/mesoporous g-C3N4/TiO2 as an all-solid-state Z-scheme heterojunction for enhancement of photocatalytic H2 evolution under visible light

In recent years, coupling TiO2 with other narrow bandgap semiconductors to improve photocatalytic hydrogen generation rate has attracted widespread attention. Herein, carbon dots (C dots) decorated g-C3N4/TiO2 all-solid-state Z-scheme heterojunction photocatalysts with hierarchical macro/mesoporous structure have been fabricated via a facile solvothermal and calcination method. The dosage of C dots greatly influences the microstructure and the visible-light photocatalytic H2 evolution rate (HER). Under the optimal condition, the ternary composites consisting of C dots, g-C3N4 and TiO2 exhibited the highest HER of 580 μmol g−1 h−1, exceed the pure TiO2, pure g-C3N4 and the binary g-C3N4/TiO2 hybrid photocatalyst by a fact of 6.6 times, 2.1 times and 1.6 times, respectively. The excellent photocatalytic performance for hydrogen evolution is ascribed to the stronger light absorption, higher specific surface area and faster charge transportation. An all-solid-state Z-scheme heterojunction mechanism was proposed in which C dots serve as a mediator to improve the separation and transportation of photo-excited charge carriers.

Selectively constructing sandwich-like heterostructure of CdS/PbTiO3/TiO2 to improve visible-light photocatalytic H2 evolution

Fast migration and efficient spatial separation of photogenerated charges in photocatalytic materials are indispensable to efficient solar water splitting reactions. Here, we construct a three-phase heterostructure of CdS/PbTiO3/TiO2 by selectively depositing CdS and TiO2 at oppositely poled crystal facets of PbTiO3 using single-domain ferroelectric PbTiO3. The heterostructure has matching band edge alignments and strong interfacial connections at different moieties. The heterostructure combines the interfacial electrical and ferroelectric fields because of their peculiar microstructures, which provide a strong driving force throughout the whole bulk to separate photogenerated charges. Almost two orders of magnitude improvement of visible-light-driven photocatalytic H2 production has been realized in CdS/PbTiO3/TiO2 compared with bare PbTiO3/TiO2, showing the efficiency of charge separation in the heterostructure. The idea of combining ferroelectrics with potential light capture semiconductor provides a paradigm to accurately design charge migration pathways, bringing a step closer to efficient solar water splitting.

Realizing high-efficiency carrier separation in 3D hierarchical carbon nitride nanosheets via intramolecular donor-acceptor motifs strategy

The insufficient visible light responsive region and fast charge recombination probability are still the key obstacles for designing high-performance photocatalytic system. Herein, a “One Stone, Two Birds” strategy was reported in three-dimensional (3D) hierarchical graphitic carbon nitride (g-C3N4) nanosheet with intramolecular donor-acceptor (D-A) motifs (3D CN) photocatalyst, which solved two urgent problems simultaneously. The 3D hierarchical nanosheets structure endowed 3D CN with abundantly exposed reaction active sites and cross-plane diffusion channels. The formation of internal D-A system facilitated the light absorption and accelerated the transfer and separation of charge carriers. Furthermore, the introducing of D-A motifs optimized the bandgap of g-C3N4 and negative-shifted conduction band position. The as-prepared 3D CN showed excellent visible-light photocatalytic H2 performance, with H2 evolution rate of 2521.2 μmol h−1/g, which was six times higher than the pristine CN. This outstanding performance was ascribed to the synergistic effect of 3D hierarchical nanosheets structure and intramolecular D-A motifs. This current work provides a novel insight to design and construct of 3D hierarchical CN nanostructures with D-A motifs simultaneously, which can be further promising applications for clean and sustainable energy conversion.

Insight into NiCo-based nanosheets modified MnS/Mn0·2Cd0·8S hybrids for enhanced visible-light photocatalytic H2 evolution

Bimetallic compounds nanocrystals exhibited great potential in catalysis due to the synergistic effects and encouraging performance. Herein, a series of NiCo-based nanosheets, including NiCo LDH/NiCo(OH) 2 , NiCo, and NiCo 2 O 4 , have been developed to modify MnS/Mn 0·2 Cd 0·8 S (MMCS) nanoparticles for photocatalytic H 2 production under visible light (λ > 420 nm). The two-dimensional (2D) NiCo 2 O 4 and NiCo were derived from the oxidation and reduction process of the as-prepared NiCo LDH/NiCo(OH) 2 nanosheets, respectively. MMCS nanoparticles were prepared using a one-pot solvothermal method and then integrated into three different NiCo-based nanosheets through a simple hybridization approach. Compared to pure MMCS, the resultant NiCo-based nanosheets/MMCS hybrids show dramatically improved visible-light photocatalytic activities. Moreover, among the three types of composites, NiCo 2 O 4 -MMCS (7%NiCo 2 O 4 -MMCS) displays the highest H 2 production rate of 3.31 mmol g −1 h −1 with the apparent quantum efficiency of 6.42% at 420 nm, approximately 22 and 5 times that of pure MMCS (0.15 mmol g −1 h −1 ) and Pt/MMCS (0.67 mmol g −1 h −1 ), respectively. The remarkably enhanced photocatalytic activities of the NiCo LDH/NiCo(OH) 2 -MMCS, NiCo-MMCS, and NiCo 2 O 4 -MMCS are mainly ascribed to the formed type-II, Schottky, and p-n heterojunctions, respectively, which efficiently boost photogenerated charge carrier separation and migration. In this paper, we intensively investigate the roles of three different NiCo-based nanosheets in the Mn x Cd 1-x S-based system. This work provides an effective strategy to design and construct the innovative 2D bimetallic compounds-based catalysts for high-efficiency photocatalytic H 2 production. The existence of type-II, Schottky, and p-n heterojunctions for NiCo LDH/NiCo(OH) 2 -MMCS, NiCo-MMCS, and NiCo 2 O 4 -MMCS boosted the transfer of photogenerated carriers. This work provides important insights into the various heterojunctions based on the NiCo-based nanosheets and suitable visible-light-responsive semiconductors toward high-efficiency photocatalytic water splitting. • MnS/Mn 0·2 Cd 0·8 S (MMCS) were prepared via a one-pot solvothermal approach. • NiCo-based nanosheets modified MMCS exhibited enhanced photocatalytic activity. • NiCo 2 O 4 -MMCS composite exhibited the highest photocatalytic H 2 production rate. • The heterojunctions of three different MMCS-based composites were investigated.

Well-designed NiS/CdS nanoparticles heterojunction for efficient visible-light photocatalytic H2 evolution

Heterojunction photocatalysts based on semiconducting nanoparticles show excellent performance in many photocatalytic reactions. In this study, 0D/0D heterojunction photocatalysts containing CdS and NiS nanoparticles (NPs) were successfully synthesized by a chemical precipitation method. The NiS NPs were grown in situ on CdS NPs, ensuring intimate contact between the semiconductors and improving the separation efficiency of hole-electron pairs. The obtained NiS/CdS composite delivered a photocatalytic H 2 evolution rate (7.49 mmol h −1 g −1 ), which was 39.42 times as high as that of pure CdS (0.19 mmol h −1 g −1 ). This study demonstrates the advantages of 0D/0D heterojunction photocatalysts for visible light-driven photocatalytic hydrogen production. • 0D/0D NiS/CdS heterojunction were successfully synthesized by a novel method. • Photocatalytic activity of NiS/CdS-X was related to the crystallization time of CdS. • NiS/CdS-90 showed high catalytic activity and stability for hydrogen evolution. • The possible mechanism for enhanced photocatalytic activity was proposed.

ZnO-based heterostructure constructed using HKUST-1 for enhanced visible-light photocatalytic hydrogen evolution

ZnO is a promising candidate for photocatalysts, whereas suffered from low activity due to the insufficient visible-light absorption and rapid recombination of photogenerated charges. In order to improve the visible-light catalytic activity of unmodified ZnO, a ZnO/Cu2O/CuO (ZCC) heterostructure photocatalyst constructed from in-situ growth of Cu-based MOF (HKUST-1) on ZnO nanosheets by in-situ growth was designed for photocatalytic H2 evolution, which exhibited excellent visible-light H2 production rate of 467.1 μmol h−1 g−1. It was confirmed that the enhanced photoactivity was mainly attributed to the wide visible-light absorption range and improvement of active sites. The construction of heterostructure promoted the migration and separation of photogenerated charges and enhanced the synergistic effect between the multicomponent hybrid semiconductor materials. This work highlights the design of using MOFs as precursor to construct metal oxide heterostructures with ZnO nanosheets for visible-light photocatalytic H2 production.

Robust visible-light photocatalytic H2 evolution on 2D RGO/Cd0.15Zn0.85In2S4–Ni2P hierarchitectures

Unique 2D ternary hierarchitectures constructed from reduced graphene oxide nanosheets grown with ultrathin Cd0.15Zn0.85In2S4 nanosheets and Ni2P nanoparticles exhibited an outstanding capability for visible-light photocatalytic H2 production.

Enhanced H2 evolution of visible light active SnO2@Mg nanoflower

Developing a catalyst with a highly effective composite for hydrogen (H2) evolution has been recognised as a promising path toward evidence in modern energy and environmental remediation solutions. Herein, tin oxide (SnO2) based nanoflower photocatalysts were developed using the Sol-Gel process and then decorated with magnesium (Mg). These Mg interactions improve photogenerated charge carrier mobility, transfer, and separation, hence increasing visible light H2 evolution performance. As an outcome, the photocatalytic SnO2@Mg (10 wt%) nanocomposite had much better visible-light photocatalytic H2 evolution activity (26 µmol g−1/h−1) than pure SnO2 (3 µmol g−1/h−1). Besides, photocurrent density has increased to 38 µA cm−2, which is nearly 12 times higher than bare SnO2 (3 µA cm−2).

Unique Cd0.5Zn0.5S/WO3-x direct Z-scheme heterojunction with S, O vacancies and twinning superlattices for efficient photocatalytic water-splitting.

Photocatalytic water-splitting employing the Z-scheme semiconductor systems mimicking natural photosynthesis is regarded as a promising way to achieve efficient soalr-to-H2 conversion. Nevertheless, it still remains a big challenge to design high-performance direct Z-scheme photocatalysts without the use of noble metals as electron mediators. Herein, a unique Cd0.5Zn0.5S/WO3-x direct Z-scheme heterojunction was constructed for the first time, which consisted of smaller O-vacancy-decorated WO3-x nanocrystals anchoring on Cd0.5Zn0.5S nanocrystals with S vacancies and zinc blende/wurtzite (ZB/WZ) twinning superlattices. Under visible-light (λ > 420 nm) irradiation, the Cd0.5Zn0.5S/WO3-x composites exhibited an outstanding H2 evolution reaction (HER) activity of 20.50 mmol h-1 g-1 (corresponding to the apparent quantum efficiency of 18.0% at 420 nm), which is much superior to that of WO3-x, Cd0.5Zn0.5S, and Cd0.5Zn0.5S loaded with Pt. Interestingly, the introduced O and S vacancies contributed to improving the HER activity of Cd0.5Zn0.5S/WO3-x significantly. Moreover, the cycling and long-term HER measurements confirmed the robust photocatalytic stability of Cd0.5Zn0.5S/WO3-x for H2 production. The excellent light harvesting and efficient spatial charge separation induced by the ZB/WZ twinning homojunctions and defect-promoted direct Z-scheme charge-transfer pathway are responsible for the exceptional HER capability. Our study could enlighten the rational engineering and optimization of semiconductor nanostructures for energy and environmental applications.

Enhancing interfacial charge transfer in mesoporous MoS2/CdS nanojunction architectures for highly efficient visible-light photocatalytic water splitting

Mesoporous MoS2-modified CdS nanojunction networks possessing advantageous electronic connectivity and charge transfer behavior at the interfaces deliver highly efficient visible-light photocatalytic H2 production activity from water splitting.

Metal–organic framework with atomically dispersed Ni–N4 sites for greatly-raised visible-light photocatalytic H2 production

The depletion of traditional fossil fuels and related environmental issues have increased the demand for clean and sustainable energy resources to achieve carbon neutrality. Active, robust and cheap photocatalysts are required for large-scale photocatalytic H2 evolution reaction (p-HER), which transforms solar energy into chemical energy. Here we report the decoration of Ni-imidazole framework (NiIm) with CdS nanorods for p–HER. The p–HER rate of CdS/NiIm hybrid sharply increased by about 14.23 times to 21,712 µmol h−1 g–1 when compared with that of CdS alone. Physicochemical characterizations and theoretical calculations reveal strong interactions at the CdS/NiIm interface and the presence of numerous Ni–N4 active sites on NiIm leading to the significant performance enhancement. This work demonstrates that NiIm acts as an affordable and abundant co-catalyst that remarkably enhances the p–HER, and enlightens the further development in the design and preparation of metal−organic framework-based materials for various applications in photocatalysis and related subjects.

In situ construction of 0D CoWO4 modified 1D Mn0.47Cd0.53S for boosted visible-light photocatalytic H2 activity and photostability

To enhance the photocatalytic activity, loading proper semiconductor with high efficiency and low cost is one of the most valid approaches. Herein, various amounts of CoWO4 as a novel metal-free material were loaded on Mn0.47Cd0.53S (MCS) nanorods for photocatalytic hydrogen production reaction. The CoWO4/Mn0.47Cd0.53S-25 (CW/MCS-25) exhibits the highest hydrogen production rate of 41.53 mmol·h−1·g−1 in the Na2S/Na2SO3 system, which is about 2.68 times higher than that of pristine MCS. The Mapping and HRTEM reveals the deposited of CoWO4 on the MCS. The detailed analyses of XPS, EIS, TRPL spectra and transient photocurrent responses indicate that CoWO4 and MCS interacted closely and the photogenerated electrons of CoWO4 can be transferred into MCS. In particular, the introduction of CoWO4 can further transfer the photogenerated holes of MCS, thereby inhibiting the photocorrosion of MCS and improving photocatalytic activity. This work provides a reference for the exploration of noble metal-free composite material and shows great potential in the photocatalytic application.

Efficient Electronic Modulation of g-C 3 N 4 Photocatalyst by Implanting Atomically Dispersed Ag 1 -N 3 for Extremely High Hydrogen Evolution Rates

Efficient Electronic Modulation of g-C ₃ N ₄ Photocatalyst by Implanting Atomically Dispersed Ag ₁ -N ₃ for Extremely High Hydrogen Evolution Rates

Bimetallic Ni–Co nanoparticles confined within nitrogen defective carbon nitride nanotubes for enhanced photocatalytic hydrogen production

This work for the first time reports bimetallic Ni–Co and monometallic (Ni and Co) nanoparticles (NPs)-engineered carbon nitride nanotubes with nitrogen vacancies (V-CNNTs) for visible-light photocatalytic H2 generation application. The bimetallic Ni–Co NPs have an average size of less than 5 nm and are homogenously dispersed along the nanochannels of V-CNNTs. The composition of the bimetallic NPs plays an essential role to maximize photocatalytic activity. With the optimal Ni/Co atom ratio of 3:1, Ni–Co/V-CNNTs nanohybrids yielded a H2 production rate of 4.19 μmol/h, which is higher than those of monometallic counterparts and V-CNNTs. The intimately loaded Ni–Co NPs and incorporated nitrogen vacancies enhance the photocatalytic performance through extended light absorption, abundant active sites, strong metal-support interaction, and efficient charge carrier transfer along the axial direction. This study presents a stable and highly efficient hybrid as a promising photocatalyst for visible light photocatalytic H2 production through water splitting.