H2 Evolution Rate Research Articles

Improved Plasmonic Hot-Electron Capture in Au Nanoparticle/Polymeric Carbon Nitride by Pt Single Atoms for Broad-Spectrum Photocatalytic H2 Evolution

HighlightsA hybrid co-catalysts system comprising Au nanoparticles (NPs) and PtSAs with different functions was constructed on the polymeric carbon nitride (PCN) surface by double-solvent method.For the dual co-catalysts, the Au NPs absorb relatively long-wavelength light to produce plasmonic hot-electrons, and the adjacent Pt single atoms (PtSAs) can trap the plasmonic hot-electrons effectively for H2 evolution.The PtSAs–Au2.5/PCN exhibits excellent broad-spectrum photocatalytic H2 evolution activity with the H2 evolution rate of 8.8 mmol g−1 h−1 at 420 nm and 264 μmol g−1 h−1 at 550 nm, respectively.

Tailoring Advanced N-Defective and S-Doped g-C3 N4 for Photocatalytic H2 Evolution.

Although challenges remain, synergistic adjusting various microstructures and photo/electrochemical parameters of graphitic carbon nitride (g-C3 N4 ) in photocatalytic hydrogen evolution reaction (HER) are the keys to alleviating the energy crisis and environmental pollution. In this work, a novel nitrogen-defective and sulfur-doped g-C3 N4 (S-g-C3 N4 -D) is designed elaborately. Subsequent physical and chemical characterization proved that the developed S-g-C3 N4 -D not only displays well-defined 2D lamellar morphology with a large porosity and a high specific surface area but also has an efficient light utilization and carriers-separation and transfer. Moreover, the calculated optimal Gibbs free energy of adsorbed hydrogen (ΔGH* ) for S-g-C3 N4 -D at the S active sites is close to zero (≈0.24eV) on the basis of first-principle density functional theory (DFT). Accordingly, the developed S-g-C3 N4 -D catalyst shows a high H2 evolution rate of 5651.5µmolg-1 h-1 . Both DFT calculations and experimental results reveal that a memorable defective g-C3 N4 /S-doped g-C3 N4 step-scheme heterojunction is constructed between S-doped domains and N-defective domains in the structural configuration of S-g-C3 N4 -D. This work exhibits a significant guidance for the design and fabrication of high-efficiency photocatalysts.

α-Fe2O3/CeO2 S-scheme heterojunction photocatalyst for enhanced photocatalytic H2 evolution

High photo-stability and effective charge separation are pivotal for hydrogen production over the photocatalysts through solar energy. Here mesoporous CeO2 nanorods were hydrothermally synthesized using cetyltrimethyl ammonium bromide and tetrapropylammonium hydroxide as the template to construct the novel S-scheme heterojunction α-Fe2O3/CeO2 photocatalyst. The obtained heterojunction Fe2O3/CeO2 photocatalyst exhibited outstanding enhanced H2 evolution under visible illumination. The XRD results indicated that the Fe2O3/CeO2 nanocomposites revealed rhombohedral α-Fe2O3 and cubic CeO2 structures without impurities. TEM images revealed the formation of CeO2 nanorods with 400 nm length and 20 nm width decorated with Fe2O3 NPs (10 nm). The optimized S-scheme Fe2O3/CeO2 nanocomposites displayed a superior photocatalytic H2 evolution rate of 2973.2 µmolg−1h−1, which was promoted 5.43 folds greater than that of CeO2 nanorods (547.05 µmolg−1h−1). The electron transport channels in S-scheme Fe2O3/CeO2 nanocomposites interfacial junctions facilitated the directional migration spatial and separation of photocarriers. The H2 evolution rate over the obtained Fe2O3/CeO2 photocatalyst was significantly promoted due to its synergistic effect, porous architecture, oxygen vacancies, small particle size and high visible light absorption ability. There was no decrease in the H2 evolution rate after five cycles of photocatalytic H2 evolution, which could verify the durability and stability of the Fe2O3/CeO2 nanocomposite. The photoluminescence (PL) and electrophotochemical responses were conducted to determine the charge carriers separation rate and understand the photocatalytic mechanism.

Construction of S-scheme CdS/g-C3N4 heterojunctions with enhanced photocatalytic H2 evolution and Cr(VI) reduction performance

Construction of heterojunctions is one of the most attractive approaches to synthesize highly active photocatalysts. In this work, we prepared CdS/g-C3N4 (CSCN) heterojunctions with different molar ratio of CdS/g-C3N4 via ball milling for photocatalytic hydrogen production and removal of Cr(VI). The successful construction of CSCN heterojunctions was proved by the various characterization methods. Formation of CSCN heterojunctions not only generates more vacancies to act as active site, but also accelerates the separation of photoinduced charge carriers, endowing with more electrons to participate in the photocatalytic reduction reaction. 2%CSCN sample was confirmed to hold the highest separation and transfer performance of photoinduced e−/h+ pairs by photoelectric tests. 2%CSCN samples exhibit the highest photocatalytic H2 evolution rate (680.04 μmol/g/h), which is 3.63-fold higher than that of the bare g-C3N4 (146.83 μmol/g/h). The activity of photocatalyst was further examined by removal of Cr(VI) experiment. The results show that the reduction efficiency of Cr(VI) on 2%CSCN is 2.46-fold of that of on the single g-C3N4, and the elimination rate of Cr(VI) on 2%CSCN can reach 64% after 1 h under simulated sunlight illumination. The improved photocatalytic performance can be ascribed to the creation of appropriate C vacancies and the widened light absorption range induced by CdS. A rational mechanism for enhanced photocatalytic activity was proposed to further understand the separation and transfer of photogenerated carriers produced by heterojunctions.

Co3O4 Nanosheet/g-C3N4 Hybrid Photocatalysts for Promoted H2 Evolution

Co3O4 is an attractive semiconductor in the photocatalytic field due to its proper band gap; however, its energy level structure is mismatched for H2 evolution. Herein, the Co3O4-based photocatalysts, Co3O4 nanosheet/g-C3N4 hybrids, were successfully prepared by an ultrasonic self-assembly method for enhanced photocatalytic H2 evolution. The optimized hybrid with 20 wt % g-C3N4, 20-CNCo, displayed the best photocatalytic performances, and the average H2 evolution rate was 134.6 μmol·g–1·h–1. The enhanced photocatalytic H2 evolution activities of 20-CNCo were due to the formation of heterojunctions between Co3O4 nanosheets and g-C3N4, which can increase the optical absorption ability, promote the separation of photogenerated charges, accelerate the electron transfer, and prolong the lifetime of the excited electrons. Moreover, following the unique step-scheme (S-scheme) charge transfer mechanism, the strong redox ability of the Co3O4 nanosheet/ g-C3N4 hybrid was retained, which was beneficial to the H2 evolution. This work provides strategies for designing active catalysts for photocatalytic reactions.

Testing of Sr-Doped ZnO/CNT Photocatalysts for Hydrogen Evolution from Water Splitting under Atmospheric Dielectric Barrier Plasma Exposure.

Nonthermal plasma is a well-recognized environmentally advantageous method for producing green fuels. This work used different photocatalysts, including PZO, SxZO, and SxZCx for hydrogen production using an atmospheric argon coaxial dielectric barrier discharge (DBD)-based light source. The photocatalysts were produced using a sol-gel route. The DBD discharge column was filled with water, methanol, and the catalyst to run the reaction under argon plasma. The DBD reactor was operated with a 10 kV AC source to sustain plasma for water splitting. The light absorption study of the tested catalysts revealed a decrease in the band gap with an increase in the concentration of Sr and carbon nanotubes (CNTs) in the Sr/ZnO/CNTs series. The photocatalyst S25ZC2 demonstrated the lowest photoluminescence (PL) intensity, implying the most quenched recombination of charge carriers. The highest H2 evolution rate of 2760 μmol h-1 g-1 was possible with the S25ZC2 catalyst, and the lowest evolution rate of 56 μmol h-1 g-1 was observed with the PZO catalyst. The photocatalytic activity of S25ZC2 was initially high, which decreased slightly over time due to the deactivation of the photocatalyst. The photocatalytic activity decreased from 2760 to 1670 μmol h-1 g-1 at the end of the process.

Highly efficient twinned MnxCd1-xS homojunction photocatalyst modified by noble metal-free Ni12P5 for H2 evolution under visible light

A series of twin-phase MnxCd1-xS solid solutions with zinc blende (ZB) and wurtzite (WZ) structures were prepared by an alkaline hydrothermal method in this work. When using 0.35 M Na2SO3/0.25 M Na2S solution as a sacrificial agent under visible light (λ ≥ 420 nm), the H2 production activity of T-Mn0.5Cd0.5S is 33.4 mmol h−1 g−1, significantly higher than that of ZB-Mn0.5Cd0.5S (15.4 mmol h−1 g−1) or WZ-Mn0.5Cd0.5S (18.2 mmol h−1 g−1). The photocatalytic activity of T-Mn0.5Cd0.5S is further enhanced by introducing Ni12P5 as a cocatalyst, in which the H2 evolution rate of 0.2% Ni12P5/T-Mn0.5Cd0.5S can reach 96.5 mmol h−1 g−1, 2.89 and 1.77 times than that of pure T-Mn0.5Cd0.5S and 0.5% Pt/T-Mn0.5Cd0.5S (54.6 mmol h−1 g−1), respectively. The crystalline phase, microstructure, elemental composition, optical and optoelectronic properties of the samples were characterized by XRD, SEM, TEM, HRTEM, XPS, UV–vis, PL and electrochemical workstation. The results show that the formation of a homojunction with interlaced energy band inhibits carrier recombination in the bulk phase of T-Mn0.5Cd0.5S. In addition, Ni12P5 can substitute for the noble metal as a cocatalyst to reduce the overpotential and improve the separation rate of electrons and holes to enhance H2 evolution. This work provides reference for building homojunction photocatalysts and loading inexpensive transition metal phosphides instead of noble metals.

Microwave-assisted synthesis of edge-grafted carbon nitride by triazole rings for efficient photocatalytic hydrogen evolution

Copolymerization of conjugated nitrogen heterocycles within carbon nitride nowadays is proven to be a successful strategy to promote charge separation. Here, a novel edge-grafted carbon nitride nanosheets by triazole rings were synthesized from the copolymerization of dicyandiamide and 3-amino-1, 2, 4-triazole via microwave-assisted heating with improved yield. Based on the building of a feasible donor-acceptor (D-A) system by such edge grafting, the rapid charge transfer pathways were formed. Benefiting from the thin-layer structure of carbon nitride via microwave-assisted heating and abundant π electrons by intramolecular doping, the system showed enhanced visible light absorption from n-π∗ electrons transition, facile charge separation and transfer, and then an increased H2 evolution rate (637.58 μmol h−1 g−1), which is 17.43 times than the triazole modified sample from conventional thermal condensation method. This work enlightens an innovative pathway for the regulation of carbon nitride photocatalysts by conjugated nitrogen heterocycles for efficient solar energy conversion applications.

Visible-Light-Driven GO/Rh-SrTiO3 Photocatalyst for Efficient Overall Water Splitting

The combining of the heterostructure construction and active sites modification to remodel the traditional wide-band-gap semiconductor SrTiO3 for improving visible light absorption capacity and enhancing photocatalytic performance is greatly desired. Herein, we research a novel GO/Rh-SrTiO3 nanocomposite via a facile hydrothermal method. The champion GO/Rh-SrTiO3 nanocomposite exhibits the superior photocatalytic overall water splitting performance with an H2 evolution rate of 55.83 μmol∙g−1∙h−1 and O2 production rate of 23.26 μmol∙g−1∙h−1, realizing a breakthrough from zero with respect to the single-phased STO under visible light (λ ≥ 420 nm). More importantly, a series of characterizations results showed that significantly improving photocatalytic performance originated mainly from the construction of heterostructure and more active sites rooted in Rh metal. In addition, the possible photocatalytic reaction mechanisms and the transport behavior of photogenerated carriers have been revealed in deeper detail. This work provides an effective strategy for heterostructure construction to improve solar utilization through vastly expanding visible light response ranges from traditional UV photocatalysts.

Activities in photocatalytic hydrogen evolution of In2O3/In2S3 heterostructure and In2O3/In2S3@PAN nanofibers

Fabrication of flexible photocatalysts with the heterostructure is one of promising approaches to improve the photocatalytic activity and reusability. In the present work, the In2O3/In2S3 heterostructures were synthesized by the solvothermal reactions. And the In2O3/In2S3@PAN nanofibers were synthesized by loading In2O3/In2S3 nanoparticles on the surface of PAN nanofibers. The SEM, TEM and elemental mapping images exhibit the homogeneous distribution of the In2O3/In2S3 nanoparticles over the whole surface of nanofibers. The increased photocurrent density and decreased radius of EIS curve indicate that higher effective separation for photogenerated electron-hole pairs and charge transfer were obtained by the In2O3/In2S3 heterostructures. The loading on the surface of PAN nanofibers gives a larger number of photoactive sites to the H2 evolution reactions. And the H2 evolution rate in the photocatalytic process with the presence of the In2O3/In2S3-3@PAN photocatalyst is ∼10.32 and ∼5.33 times higher than the rates of pure In2O3 and In2S3.

Construction of porous Ni2P cocatalyst and its promotion effect on photocatalytic H2 production reaction and CO2 reduction

Due to superior light absorption abilities, porous materials are suitable to be served in photocatalytic reactions. In this study, porous Ni2P is target-constructed from porous Ni(OH)2 nanoflower. Promotion effect of the porous Ni2P as cocatalyst is confirmed on photocatalytic performance of Ni2P/CdS composite. The constructed porous Ni2P/CdS photocatalyst shows much higher photocatalytic H2 evolution rate (111.3 mmol h−1 g−1) from water and much higher CO (178.0 μmol h−1 g−1) and CH4 (61.2 μmol h−1 g−1) evolution rates from CO2 reduction than non-porous Ni2P/CdS photocatalyst. Characterizations including UV-Vis diffuse reflectance, photoluminescence, transient photocurrent response, electrochemical impedance and electron paramagnetic resonance are conducted to verify the role of porous Ni2P cocatalyst. The slow photon effect derived from porous structure Ni2P is found to improve light path and increase the absorption utilization of light. The enhanced photocurrent intensity and the lowered resistance of porous Ni2P/CdS due to the formed heterojunctions indicate much rapid isolation of photogenerated electron-hole pairs and rapid charge transfer of electrons. The higher signal of ⋅O2- radicals is detected in porous Ni2P/CdS than non-porous Ni2P/CdS, which result in the remarkable photocatalyst activities of porous Ni2P/CdS. Reaction mechanisms over Ni2P/CdS photocatalyst are illustrated with a Z-scheme charge transfer path.

WS2–TiO2 hetero-photocatalysts for efficient hydrogen evolution via plasmon-induced resonance energy transfer

Lowering the cost and increasing the efficiency of photocatalysts for hydrogen (H2) evolution remain challenging, especially with eco-friendly materials. With these goals in mind, in this study we adopted tungsten disulfide (WS2) nanosheets, a nonmetallic surface plasmon resonance (SPR) material covering P25 TiO2, for plasmon-induced resonance energy transfer (PIRET) to improve the photocarrier response of H2 evolution. Under simulated solar light irradiation, the optimized 2.4W heterostructure provided a durable and outstanding H2 evolution rate (321 μmol g−1 h−1) that was approximately 55.3 times higher than that of TiO2. Raman spectra revealed the presence of dipole–dipole interactions within the WS2–TiO2 heterostructure, while UV–Vis optical absorption spectra indicated that the WS2 absorption range overlaid the band gap of TiO2. Under irradiation with light, the SPR of the WS2 nanosheets underwent near-field dipole-dipole coupling with the excitons of TiO2 to increase the number of excitons and inhibit charge recombination. This study suggests the possibility of using nonmetallic SPR materials for efficient solar energy conversion.

Synergism of sulfur vacancy and Schottky junction in Ni/ZnIn2S4 nanosheet assembly for efficient charge separation and photocatalytic hydrogen evolution

Surface and interface engineering play vital roles on improving the photocatalytic hydrogen evolution. Herein, Ni/ZnIn2S4 nanosheet assembly with sulfur vacancy and Schottky junction (Ni/DZIS) is fabricated through facile ethanediol-assisted solvothermal method. Density functional theory (DFT) calculation reveals that the Ni is absorbed at the hollow site of three S atoms next to sulfur vacancy on the ZnIn2S4 (006) face due to the formation of sulfur vacancy. The resultant Ni/DZIS Schottky junction exhibits high photocatalytic H2 evolution rate of 703 μmol g−1h−1 without any noble metal cocatalysts, which is 2.6 times higher than that of pristine ZnIn2S4 nanosheets. The improved photocatalytic performance is mainly attributed to the synergism of sulfur vacancy and Schottky junction accelerating the photogenerated charge transfer and thus inhibiting the charge recombination. Moreover, the photocatalytic performance of Ni/DZIS nearly keeps constant even after six recycles, indicating the high stability and potential applications in field of energy. This work provides a convenient strategy for constructing efficient defective heterojunction assembly photocatalysts via surface and interface engineering.

Biochars from Olive Stones as Carbonaceous Support in Pt/TiO2-Carbon Photocatalysts and Application in Hydrogen Production from Aqueous Glycerol Photoreforming.

Several biochars were synthesized from olive stones and used as supports for TiO2, as an active semiconductor, and Pt as a co-catalyst (Pt/TiO2-PyCF and Pt/TiO2-AC). A third carbon-supported photocatalyst was prepared from commercial mesoporous carbon (Pt/TiO2-MCF). Moreover, a Pt/TiO2 solid based on Evonik P25 was used as a reference. The biochars used as supports transferred, to a large extent, their physical and chemical properties to the final photocatalysts. The synthesized catalysts were tested for hydrogen production from aqueous glycerol photoreforming. The results indicated that a mesoporous nature and small particle size of the photocatalyst lead to better H2 production. The analysis of the operational reaction conditions revealed that the H2 evolution rate was not proportional to the mass of the photocatalyst used, since, at high photocatalyst loading, the hydrogen production decreased because of the light scattering and reflection phenomena that caused a reduction in the light penetration depth. When expressed per gram of TiO2, the activity of Pt/TiO2-PyCF is almost 4-times higher than that of Pt/TiO2 (1079 and 273 mmol H2/gTiO2, respectively), which points to the positive effect of an adequate dispersion of a TiO2 phase on a carbonaceous support, forming a highly dispersed and homogeneously distributed titanium dioxide phase. Throughout a 12 h reaction period, the H2 production rate progressively decreases, while the CO2 production rate increases continuously. This behavior is compatible with an initial period when glycerol dehydrogenation to glyceraldehyde and/or dihydroxyacetone and hydrogen predominates, followed by a period in which comparatively slower C-C cleavage reactions begin to occur, thus generating both H2 and CO2.

Kinetic Evidence for Type-II Heterojunction and Z-Scheme Interactions in g-C3N4/TiO2 Nanotube-Based Photocatalysts in Photocatalytic Hydrogen Evolution

Composite materials based on g-C3N4 and TiO2 nanotubes have been synthesized as environmentally friendly photocatalysts with heterojunctions suitable for enhanced photocatalytic hydrogen production. Composites were prepared with various ratios (x = 0–1) of g-C3N4 and after chemical modification and exfoliation of bulk g-C3N4. Contact formation between g-C3N4 and TiO2 generally enhanced photoactivity, which caused the x-dependent changes in the photocatalytic hydrogen evolution rates of the g-C3N4/TiO2 compounds to vary following a volcano-shaped curve with the maximum rate at x ∼ 0.6 for all the compounds regardless of the pretreatment (bulk or modified) of g-C3N4. The modified g-C3N4-based composites showed higher photoactivities than the unmodified bulk g-C3N4 due to the high surface area. The major reason for the enhanced photoactivity with the volcano shape was attributed to the Z-scheme interaction at the heterojunction. Interestingly, detailed analysis of the kinetic H2 evolution rates of the composites with Pt cocatalysts only on TiO2 nanotubes further showed that the dominant type of interaction at the heterojunctions changed from the type-II heterojunction to the Z-scheme at x ∼ 0.1. It is inferred that structural diversity at the g-C3N4/TiO2 interfaces is the origin of the changes in the dominant type of interaction in the composites with increasing ratios of g-C3N4.

Fabrication of optimal oxygen vacancy amount in P/Ag/Ag2O/Ag3PO4/TiO2 through a green photoreduction process for sustainable H2 evolution under solar light

Defects engineering on photocatalysts such as oxygen vacancies (OVs) is an effective approach for improving photocatalytic hydrogen (H2) evolution efficiency. In this study, OVs modified P/Ag/Ag2O/Ag3PO4/TiO2 (PAgT) composite was successfully fabricated via a photoreduction process by controlling the ratio of PAgT to ethanol (16, 12, 8, 6 and 4 g·L-1) under simulated solar light irradiation for the first time. Characterization methods confirmed the presence of OVs in the modified catalysts. Meanwhile, the OVs amount and their effects on the light absorption ability, charge transfer rate, conduction band and H2 evolution efficiency of the catalysts were also investigated. The results indicated that the optimal OVs amount endowed OVs-PAgT-12 with the strongest light absorption, the fastest electron transfer rate and suitable band gap for H2 evolution, leading to the highest H2 yield (863 μmol·h−1·g−1) under solar light irradiation. Moreover, OVs-PAgT-12 exhibited a superior stability during cyclic experiment, indicating its great potential for practical application. Furthermore, a sustainable H2 evolution process was proposed based on a combination of sustainable bio-ethanol resource, stable OVs-PAgT, abundant solar energy and recyclable methanol. This study would provide new insights into the design of defects modified composite photocatalyst for enhanced solar-to-hydrogen conversion.

Mesostructured ellipsoidal capsules barium stannate based perovskite photocatalysts anchored PtO nanoparticles for hydrogen evolution

Background: The separation and transportation of photocarriers are considered significant factors in photocatalytic H2 evolution. Method: Mesoporous BaSnO3, with superior electron mobility with a large surface area, was chosen to integrate PtO nanoparticles (NPs) to obtain a highly effective photocatalytic system. PtO NPs (5–10 nm) are uniformly hosted with high crystallinity on the mesoporous BaSnO3 networks by impregnation-calcination approach. Significant Findings: TEM images of BaSnO3 exhibited ellipsoidal capsules with lengths of 200 ± 10 nm and a diameter of 50 nm. The construction PtO/BaSnO3 heterojunction system with better electron transport ability was modulated to achieve better photocatalytic ability than BaSnO3. The H2 evolution over 1.2% PtO/BaSnO3 nanocomposite was about 21,550 μmol·g−1 after 9 h visible illumination, while bare BaSnO3 was produced only 3750 μmol·g−1. The optimal 1.2% PtO/BaSnO3 nanocomposite revealed the largest H2 evolution, and it was promoted 5.75 times larger than BaSnO3. The H2 evolution rate over-optimized 1.2% PtO/BaSnO3 photocatalyst was about 2380 μmolg−1h−1, 6 times larger than that of bare BaSnO3 (397.37 μmolg−1h−1). The obtained PtO/BaSnO3 nanocomposites could facilitate the photoinduced electrons transfer from BaSnO3 to PtO, indicating the efficient photoinduced carriers separation for the enhanced H2 evolution rate. The PtO/BaSnO3 nanocomposite displayed high photostability and recyclability even after 45 h of illumination. This work provides a novel approach for perovskites with mesoporous structures and tunable bandgap with low PtO content utilized in energy applications and photocatalytic reactions.

High-efficiency of novel hierarchical 3D macroporous g-C3N4 material on solar-driven photocatalytic water-splitting for hydrogen evolution

The use of multi-pore nanostructured g-C3N4 photocatalysts is an efficient approach to separate photogenerated charge carriers and increase visible light photocatalytic performance. Recent progress has yielded nanostructured material through hard templating, which limits potential applications. Integrating the 2D building block into multidimensional porous structures remains a significant challenge in scalable production. Herein, a novel technique based on P407 bubble clusters templating and fixation by freezing is described for the first time to fabricate a 3D opened-up macroporous g-C3N4 nanostructures for photocatalytic H2 evolution. Three-dimensional hierarchical nanostructures provide more contact active sites and synergistically promote the creation of heterogeneous catalytic interfaces. This feature is very useful for understanding the transfer path of photoinduced charges as well as the origins of the high charge separation efficiency in photocatalytic reactions, thus yielding a remarkable visible light-induced H2 evolution rate of 4213.6 μmol h−1 g−1, which is nearly 5.6 times (716 μmol h−1 g−1) higher than that of lamellar bulk g-C3N4. This newly developed approach offers a promising alternative to synthesize broad-spectral response 3D hierarchal g-C3N4 nanostructures and can be extended to assemble other functional nanomaterials as building blocks into macroscopic configurations coupled with electronic modulation strategy simultaneously.

Stable Immobilization of Nickel Ions on Covalent Organic Frameworks for Panchromatic Photocatalytic Hydrogen Evolution.

Post-coordination design on covalent organic frameworks (COFs) is an efficient strategy for elevating the photocatalytic activity of organic moiety. However, the rigid skeletons and densely layered stacking of two-dimensional (2D) COFs cannot be flexibly adapted for specific conformations of metal complexes, thereby impairing the metal-COF cooperation. Here, we adopt a solvothermal method to immobilize nickel(II) ions into a 2,2'-bipyridine-containing 2D COF, forming a stable coordination motif. Such the complex remarkably enhances the photocatalytic performance, giving an optimized H2 evolution rate of as high as 51 300 μmol h-1 g-1 , 2.5 times higher than the pristine COF. The evolved hydrogen gas can also be detected upon 700-nm light irradiation, while its analog synthesized by the traditional coordination method is photo-catalytically inert. This work provides a strategy for optimizing the metal-COF coordination system and strengthening a synergy for electronic regulation in photocatalysis.

Stable Immobilization of Nickel Ions on Covalent Organic Frameworks for Panchromatic Photocatalytic Hydrogen Evolution

AbstractPost‐coordination design on covalent organic frameworks (COFs) is an efficient strategy for elevating the photocatalytic activity of organic moiety. However, the rigid skeletons and densely layered stacking of two‐dimensional (2D) COFs cannot be flexibly adapted for specific conformations of metal complexes, thereby impairing the metal‐COF cooperation. Here, we adopt a solvothermal method to immobilize nickel(II) ions into a 2,2′‐bipyridine‐containing 2D COF, forming a stable coordination motif. Such the complex remarkably enhances the photocatalytic performance, giving an optimized H2 evolution rate of as high as 51 300 μmol h−1 g−1, 2.5 times higher than the pristine COF. The evolved hydrogen gas can also be detected upon 700‐nm light irradiation, while its analog synthesized by the traditional coordination method is photo‐catalytically inert. This work provides a strategy for optimizing the metal‐COF coordination system and strengthening a synergy for electronic regulation in photocatalysis.