Visible-light Photocatalytic Hydrogen Evolution Research Articles

Solvated Electrons Generated on the Surface of Na-SPHI for Boosting Visible Light Photocatalytic Hydrogen Evolution with Ultra-High AQE.

Enhancing the utilization of visible-light-active semiconductors with an excellent apparent quantum efficiency (AQE) remains a significant and challenging goal in the realm of photocatalytic water splitting. In this study, a fully condensed sulfur-doped poly(heptazine imide) metalized with Na (Na-SPHI) is synthesized by an ionothermal method by using eutectic NaCl/LiCl mixture as the ionic solvent. Comprehensive characterizations of the obtained Na-SPHI reveal several advantageous features, including heightened light absorption, facilitated exciton dissociation, and expedited charge transfer. More importantly, solvated electron, powerful reducing agents, can be generated on the surface of Na-SPHI upon irradiation with visible light. Benefiting from above advantage, the Na-SPHI exhibits an excellent H2 evolution rate of 571.8 µmol·h-1 under visible light illumination and a super-high AQE of 61.7% at 420nm. This research emphasizes the significance of the solvated electron on the surface of photocatalyst in overcoming the challenges associated with visible light-driven photocatalysis, showcasing its potential application in photocatalytic water splitting.

Reconstructing delocalized π electron structure of C3N4 nanosheets for enhanced visible light photocatalytic hydrogen evolution

For improving the essential photocatalytic H2 evolution activity of C3N4, strategies via simultaneously modulating the delocalized π electron structure and defects are feasible but challenging. Herein, a C3N4 nanosheets material defined as C3N4-NS-RN with expansive delocalized π electron structure and enriched N vacancies was synthesized successfully via a facile post heat treatment. Firstly, a precursor of C3N4 nanosheets defined as C3N4-NS-PN with corrugate tri-s-triazine basal plane and abundant NHx groups in aromatic conjugate system was prepared. Fourier transform infrared spectra, X-ray photoelectron spectroscopy and nuclear magnetic resonance demonstrated C3N4-NS-PN had an enhanced delocalized π electron configuration via van der Waals coupling effect. However, the delocalization of π electrons across the basal plane was disturbed due to the corrugate conjugate plane. For further reconstructing delocalized π electron structure of C3N4-NS-PN, C3N4-NS-RN was synthesized via eliminating NHx groups and introducing enriched N vacancies in the conjugate system. Photoluminescence spectroscopy and electron paramagnetic resonance verified C3N4-NS-RN had an enhanced delocalized π electrons structure than C3N4-NS-PN. The photocatalytic H2 evolution activity of C3N4-NS-RN was steady and was about 1.8 and 6.1 times of C3N4-NS-PN and the bulk C3N4, respectively.

Activating 2D MoS2 by loading 2D Cu–S nanoplatelets for improved visible light photocatalytic hydrogen evolution, drug degradation, and CO2 reduction

Finding reliable photocatalysts capable of driving reactions using only sunlight is more needed than ever. A variety of strategies to harvest sunlight and convert it into chemical energy have been successfully utilized such as synthesizing nanostructures, using metal nanoparticles, doping, and others. In this work, we discover a facile way to anchor CuS nanoplatelets on 2D MoS2 by the solvothermal method using ethylene glycol (EG) as both a reduction agent and an exfoliating agent of bulk MoS2. Using CuS as a co-catalysis on MoS2 with their huge surface areas, led to improved photocatalytic activity for three different applications including H2 evolution, CO2 reduction, and endosulfan degradation. Specifically, Cu–S@MoS2 3% nanocomposite produced 9.86 μmol g−1 h−1 of H2, 0.48 μmol g−1 h−1 of CO and full decomposition of endosulfan within 6 h. The Cu-loaded MoS2 nanocomposites were thoroughly characterized by spectroscopic (including synchrotron-based spectroscopy) and microscopic methods to understand the formation of Cu–S during the solvothermal process. Moreover, the role of the EG during the synthetic procedure was revealed experimentally and studied theoretically via DFT simulations.

Fabrication of graphene-incorporated tin-niobate-doped zinc oxide for highly enhanced photocatalytic hydrogen evolution and degradation

This study focuses on designing, synthesizing, and characterizing an innovative graphene-based Sn2Nb2O7-ZnO. Ternary Sn2Nb2O7-ZnO with graphene is added to a catalyst, enhancing the efficiency of visible-light photocatalytic hydrogen (H2) evolution and ciprofloxacin (CIP) degradation in an aqueous solution. It also facilitates easier charge transfer and control over electron-hole recombination between light-harvesting processes. Additionally, the UV–vis shows that rGO doping can be used to tune significant visible light absorption in addition to the effective charge transmission channel of Sn2Nb2O7-rGO-ZnO nanorods. Under visible light, Sn2Nb2O7-rGO-ZnO nanorods demonstrate expected photocatalytic hydrogen evolution and CIP degradation of 1240 μmol·h−1·g−1, a 96% increase over pure catalysts. Photocatalytic H2 production over Sn2Nb2O7-rGO-ZnO is assessed using transient photocurrent response, suggesting a possible mechanism. Owing to the type II process ability, more electrons can participate in the H2 evolution reduction and CIP degradation. Furthermore, it has the potential to completely replace the present base metal as an incredibly powerful and long-standing light radiation-based photocatalyst. In this study, we prepared catalysts that are more stable and highly efficient up to a six-cycle test, non-toxic, low-cost catalysts for H2 production and CIP degradation.

Ni7S6 decorated g-C3N4/graphene oxide composites for enhanced visible light photocatalytic hydrogen evolution

Rationally designing high-efficient g-C3N4 based photocatalysts still remains a big challenge. Herein, Ni7S6 decorated K-doped g-C3N4/graphene oxide photocatalyst was synthesized. Interestingly, amorphous conductive carbon black and urea are simultaneously transferred to graphene oxide and K-doped g-C3N4, which achieves in-situ coupled K-g-C3N4/graphene oxide composite. The in-situ fabricated graphene oxide acts as a charge transfer substrate for the rapid photocarriers migration. Ni7S6 forms Schottky heterojunction with K-g-C3N4 photocatalyst, promoting photocarriers separation. The Ni7S6/K-g-C3N4/graphene oxide composite achieves a visible light hydrogen production rate of 487.59 μmol·g−1·h−1, which is about 7.5 times higher than that of K-g-C3N4 (65.4 μmol·g−1·h−1). This work provides a novel strategy for preparing high-efficient g-C3N4 based photocatalysts.

2D Metal–Organic Framework Nanosheets based on Pd‐TCPP as Photocatalysts for Highly Improved Hydrogen Evolution

AbstractIn this report, a 2D MOF nanosheet derived Pd single‐atom catalyst, denoted as Pd‐MOF, was fabricated and examined for visible light photocatalytic hydrogen evolution reaction (HER). This Pd‐MOF can provide a remarkable photocatalytic activity (a H2 production rate of 21.3 mmol/gh in the visible range), which outperforms recently reported Pt‐MOFs (with a H2 production rate of 6.6 mmol/gh) with a similar noble metal loading. Notably, this high efficiency of Pd‐MOF is not due to different chemical environment of the metal center, nor by changes in the spectral light absorption. The higher performance of the Pd‐MOF in comparison to the analogue Pt‐MOF is attributed to the longer lifetime of the photogenerated electron‐hole pairs and higher charge transfer efficiency.

Facile fabrication of AgBr/HCCN hybrids with Z-scheme heterojunction for efficient photocatalytic hydrogen evolution

Constructing a Z-scheme heterojunction with enhanced photocatalytic hydrogen evolution for graphitic carbon nitride-based (g-C3N4) composites is challenging because integrating g-C3N4 with other semiconductors, without specific band structure design, typically results in type I or type II heterojunctions. These heterojunctions have lower redox ability and limited enhancement in photocatalysis. Herein, we select highly crystalline carbon nitride (HCCN) as a proof-of-concept substrate. For the first time, we develop a AgBr nanosphere/HCCN composite photocatalyst that features an all-solid-state direct Z-scheme heterojunction for visible-light photocatalytic hydrogen evolution. The electron transfer mechanism is initially studied from the band structures and Fermi levels of HCCN and AgBr. It is subsequently confirmed by X-ray photoelectron spectroscopy (XPS), and electron microscopy. The close heterojunction contact and the built-in electron field of the Z-scheme heterojunction promote the migration and separation of photogenerated electrons and holes in the composite photocatalyst. Due to the redistribution of charge carriers, the photocatalyst shows superior redox capability and a markedly enhanced hydrogen evolution performance compared to its individual components. Combining all the advantages, AgBr nanosphere/HCCN reached an apparent quantum efficiency (AQE) of 6 % under the illumination of 410 nm, which is 4 times higher than that of the single HCCN component.

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

Rational design of pyrene and thienyltriazine-based conjugated microporous polymers for high-performance energy storage and visible-light photocatalytic hydrogen evolution from water

Conjugated microporous polymers (CMPs) have found extensive applications in various fields such as optoelectronics, CO2 capture, and catalysis. However, their potential in electrochemical supercapacitors as energy storage and H2 production systems remains relatively unexplored. This limited exploration can be attributed to certain challenges, including issues related to structural and electrochemical stability, as well as the relatively modest specific capacitance. Additionally, many of the CMPs discovered thus far have exhibited lower energy densities, further contributing to this underexplored aspect of their utility. In this study, we prepared two different CMPs [TPET-TTh and PyT-TTh CMPs] containing thienyltriazine units (TTh) for the redox mechanism and constructed electrodes for supercapacitor applications. The synthesized TPET-TTh and PyT-TTh CMPs displayed exceptionally high specific surface areas of 545 and 528 m² g⁻¹, respectively. Furthermore, their pore sizes were very similar, centered at approximately 0.39 and 0.36 nm, respectively. To evaluate their electrochemical properties, the TTh-CMPs were examined using cyclic voltammetry (CV) and galvanostatic charge/discharge (GCD). The resulting CV curves exhibited rectangular shapes, indicative of the characteristic behavior of electric double-layer capacitors, across a range of potential and scan rates. These TPET-TTh and PyT-TTh CMPs delivered nominal specific capacitances of 74 and 76 F g−1 at 0.5 A g−1, respectively. In addition, they exhibited outstanding capacity retentions of 95.2 and 97.30 % even after 2000 cycles [analyzed at 10 A g−1]. The TTh-CMPs also exhibited excellent light-capture capabilities. The PyT-TTh CMP has faster charge separation and lower charge recombination rates than TPET-TTh CMP. This results in a higher hydrogen evolution rate from the water decomposition reaction. The H2 production rate of PyT-TTh CMP could be as high as 18,533 μmol g−1 h−1, which is approximately 4-fold that of TPET-TTh CMP. This study offers a strategy for the design of TTh-containing CMPs that exhibit exceptional energy storage application and photocatalytic efficiency for H2 evolution.

Facile synthesis of novel CoWO4/FeWO4 hetrocomposite with efficient visible light photocatalytic degradation and hydrogen evolution aspects

ABSTRACT Tungstate-based nanomaterials exhibit efficient photocatalytic performance and offer several advantages owing to their electrical and superior optical features, charge transport potentials, and superb corrosion resistance. The objective of the present study is to fabricate cobalt tungstate (CoWO4), Ferric tungstate (FeWO4) and CoWO4/FeWO4 heterojunction composite photocatalysts using a hydrothermal route with various molar concentrations (2:1, 1:1, 1:2, 1:5). The model pollutant Methyl Orange (MO) and Congo Red (CR) azo dyes were degraded 98.26% and 99.61% in 150 min by the as-synthesized CoWO4/FeWO4 at a molar concentration ratio of 1:2. A feasible photodegradation mechanism is purposed and the optimum values for different parameters are also evaluated by considering two different dyes as model organic pollutants. Hydrogen production efficiency reaches up to 36 μmolg−1 h−1 under visible light over 1:2 CoWO4/FeWO4. This work may open new possibilities for the use of CoWO4/FeWO4 composite for potential applications such as the hydrothermal synthesis of composites and their photocatalytic wastewater remedy and as hydrogen evolution applications.

Enhanced visible light photocatalytic hydrogen evolution by Ni cations precise institute S anion in CdS and P ions targeted linking with Ni

Ni directional doping in the lattice of CdSV with the Ni cations targeted linked to P (CdSV-Ni-P) was successfully synthesized via a step wise assembly method, which exhibited an excellent photocatalytic hydrogen production performance. The photoelectric performance characterization proved that the Ni directional doping and Ni cations targeted linked with P in CdSV-Ni-P not only accelerating the photo-generated electrons transfer but also decreasing efficiency of the charge recombination. The density functional theory (DFT) calculations proved that CdSV-Ni-P can also induce more charge-carriers participate in photocatalytic reaction and decrease electron binding restriction capacity. Moreover, the results of UV–vis DR spectra and VB-XPS spectra confirmed that the construction of this CdSV-Ni-P could effectively narrow the bandgap. Meanwhile, the result of Gibbs free energy demonstrated the S-H adsorption bond in CdSV-Ni-P was get weaken, which is benefit for hydrogen desorption from S sites, thus achieving a high hydrogen evolution reaction (HER) result. Based on the synergistic effects, CdSV-Ni6.7-P9.6 presented a relatively high hydrogen evolution rate of 167.5 mmol h-1g−1 under the visible light irradiation (λ ≥ 420 nm), which is almost 60 times of CdSV.

A CMP-based [FeFe]-hydrogenase dual-functional biomimetic system for photocatalytic hydrogen evolution coupled with degradation of tetracycline

A novel bio-inspired conjugated microporous polymer (CMP) had been designed, synthesized and characterized. The mimics of [FeFe]-hydrogenase active sites were covalently attached to the CMP skeleton, which facilitates charge transfer between the light-harvesting moiety and active sites, and exhibited high performance in visible-light photocatalytic hydrogen evolution (2120 μmol·h−1·g−1) in an aqueous solution. The flower-like morphology, covalently linked framework and the “single active-site” effect derived from the porous skeleton were deemed to go a long way toward boosting the properties above. Interestingly, when the electron sacrifice agent (triethanolamine) was replaced by tetracycline, the CMP-based photocatalyst maintained the capability of photocatalytic hydrogen production (370 μmol·h−1·g−1) and realized efficient photodegradation of tetracycline simultaneously. This work provides a heuristic green dual-function strategy for constructing a sustainable and efficient photocatalytic system for hydrogen evolution with concurrent antibiotic residue degradation.

Constructing the covalent organic framework and In2O3 composites via covalent bonds towards excellent visible-light photocatalytic hydrogen evolution

Covalent organic frameworks (COFs) are particularly superior platforms for photocatalysis due to their unique pore-like structures and strong covalent forces between the frameworks. However, challenges still exist in improving photocatalytic performance. Rationally combining the advantages of inorganic and organic semiconductors to produce heterojunctions has obvious applications for improving the photocatalytic activity of materials. In this work, three COFs (BDA-HTA-COF, BDA-DHTA-COF and BDA-THTA-COF) and In2O3 are covalently bonded together for the first time to construct a heterojunction. The obtained BDA-THTA-30 shows the highest photocatalytic hydrogen production activity of 9691.84 μmol g−1h−1, which is 10.1 and 128.3 times higher than those of BDA-THTA-COF and In2O3, respectively. Further studies confirm that covalent bonding between In2O3 and the components of BDA-THTA-COF could significantly improve the separation and transfer rate of light-generated charges in the composites, leading to efficient hydrogen evolution activity. This bond development and covalent hybridization approach facilitates the development of photocatalysts for COFs.

Visible Light Photocatalytic Hydrogen Evolution Paired with Excellent Intramolecular Coupling of Dithiols into Sulfurous Heterocyclic Compounds over CdS/P25/Ni2P

Visible Light Photocatalytic Hydrogen Evolution Paired with Excellent Intramolecular Coupling of Dithiols into Sulfurous Heterocyclic Compounds over CdS/P25/Ni₂P

A MOF-derived Bimetallic Co-catalyst for Promoting Visible-light Photocatalytic Hydrogen Evolution on NH2 -MIL-125.

In order to construct noble metal-free co-catalysts to facilitate the transport and separation of photocatalyst carriers, herein, a MOF-based derived bimetallic NiCu0.2 co-catalyst was loaded on NH2 -MIL-125(Ti). The obtained NiCu0.2 /NH2 -MIL-125 exhibited a photocatalytic activity of 161.4 μmol g-1 h-1 for hydrogen evolution, 12.6 times higher than that of the Ni/NH2 -MIL-125 and even slightly better than Pt/NH2 -MIL-125. The work expands the development pathway of cost-effective and highly active bimetallic co-catalysts for photocatalytic H2 evolution.

Enhancement of visible light photocatalytic pharmaceutical degradation and hydrogen evolution of Bi5O7Br by in situ disorder engineering

In order to simultaneously solve the problems of the poor light absorption capacity and high recombination rate of photogenerated carriers, Bi5O7Br photocatalyst with abundant ordered/disordered structures (O/D-Bi5O7Br) was prepared through a simple in situ disorder engineering. The prepared samples were characterized by XRD, TEM, HRTEM, SAED, XPS, UV-Vis diffuse reflectance spectra (DRS), and the activity was evaluated by photocatalytic degradation of tetracycline hydrochloride (TC) and hydrogen evolution under visible light irradiation. Results revealed that the ordered/disordered structure not only enhances the light absorption ability, uplifts conduction band position, facilitates the transfer and separation of photogenerated carriers, but also offers abundant unsaturated atoms as active sites for the photocatalytic process. Therefore, O/D-Bi5O7Br exhibits a high hydrogen evolution rate of 38.12 μmol/(g·h) and superior TC degradation rate of 86% within 135 min.

Enhanced visible-light photocatalytic hydrogen evolution using two-dimensional carbon nitride sheets with the removal of amine groups

Two-dimensional (2D) carbon nitride sheets (CNs) with atomically thin structures are regarded as one of the most promising materials for solar energy conversion. However, due to their substantially enlarged bandgap caused by the strong quantum size effect and their incomplete polymerisation with a large number of non-condensed surface amino groups, the practical applicability of CNs in photocatalysis is limited. In this study, CNs with broad visible-light absorption were synthesised using a 5-min fast thermal annealing. The removal of uncondensed amine groups reduces the bandgap of CNs from 3.06 eV to 2.60 eV, increasing their absorption of visible light. Interestingly, the CNs were distorted after annealing, which can differentiate the spatial positions of electrons and holes, enhancing the visible-light absorption efficiency. As a result, when exposed to visible light, the photocatalytic hydrogen production activity of atomically thin 2D CNs rose by 8.38 times. This research presents a dependable and speedy method for creating highly effective visible-light photocatalysts with narrowed bandgaps and improved visible-light absorption.

Enhanced visible light photocatalytic hydrogen evolution of Ta2O5 nanohoneycomb induced by plasmonic Au nanoparticle array

Polystyrene nanospheres in the sizes of 400, 200, and 100 nm were employed as a template to form hexagonal close-packed Ta2O5 nanohoneycombs (nHCs) by means of solution-based nanosphere lithography. Moreover, Au nanoparticle arrays with various diameters were further deposited on the Ta2O5nHCs to achieve surface plasmon resonance (SPR) and enhance visible-light photocatalytic hydrogen evolution. Finite difference time domain (FDTD) simulation was performed and the result showed that the 100-nm Ta2O5nHCs coupled with smaller Au nanoparticles exhibited more effective localized SPR effect to enclose the Ta2O5 photocatalyst. The photocatalytic hydrogen evolution results were consistent with those of FDTD simulation and photoelectrochemical tests. A concept of effective yield ratio is proposed to explain how the Au nanoparticle size and spacing affect the hydrogen evolution efficiency.

Oxygenated Triazine-Heptazine Heterostructure Creates an Enormous Ascension to the Visible Light Photocatalytic Hydrogen Evolution Performance of Porous C3 N4 Nanosheets.

A highly efficient g-C3 N4 photocatalyst is developed by a novel one-pot thermal polymerization method under a salt fog environment generated by heating the aqueous solution of urea and mixed metal salts of NaCl/KCl, namely SF-CN. Thanks to the synergistic effect of the oxygenation and chemical etching of the salt fog, the obtained SF-CN is an oxygenated ultrathin porous carbon nitride with an intermolecular triazine-heptazine heterostructure, meanwhile, shows enlarged specific surface area, greatly enhanced absorption of visible light, narrowed band gap with a lower conduction band, and an increased photocurrent response due to the effective separation of photogenerated holes and electrons, comparing to those of pristine g-C3 N4 . The theoretical simulations further reveal that the triazine-heptazine heterostructure possesses better photocatalytic hydrogen evolution (PHE) capability than pure triazine and heptazine carbon nitrides. In turn, SF-CN demonstrates an excellent visible light PHE rate of 18.13mmolh-1 g-1 , up to 259.00 times of that of pristine g-C3 N4 .

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.