Dye-sensitized Photocatalysts Research Articles

Visible light-induced degradation of phenolic contaminants utilizing nanoscale TiO2 and ZnO impregnated with SR 7B (SR) dye as advanced photocatalytic systems

ZnO and TiO2 show promise for the remediation of phenol-containing wastewater, but their wide band gaps restrict their industrial-scale application under visible light. However, harnessing visible light in dye-sensitizing systems could significantly enhance their efficacy for industrial purposes. Considering the state-of-the-art, this research represents a pioneering report to explore the development of dye-sensitized photocatalysts using Sudan Red 7B (SR) dye. For this purpose, a new surfactant-capping route was applied to synthesize spherical TiO2 and ZnO nanoparticles. The prepared materials were then impregnated with (SR) dye to produce the unprecedented visible light active dye-sensitized TiO2 (TiO2/SR) with spherical morphology, and sheet form dye-sensitized ZnO (ZnO/SR) photocatalysts. Based on the cyclic voltammetry and UV–Vis results, the LUMO and HOMO energy levels of SR dye were calculated to be −0.8 V and +3.15 V (versus NHE), respectively, providing an adequate thermodynamic driving force for the electron injection processes from dye to conduction bands of TiO2 and ZnO, thus successfully degrading pollutants via the dye-sensitized photocatalytic route. Phenol photodegradation experiments under visible light were conducted using these photocatalysts, applying a diversity of pH and catalyst loading conditions. The results showed that the visible light photocatalytic experiments using TiO2/SR and ZnO/SR had significantly higher performance in degrading phenol, with an output that was almost 5 and 3 times better, respectively, compared to their pure photocatalysts.

Metal-free carbazole-thiophene photosensitizers designed for a dye-sensitized H2-evolving photocatalyst in Z-scheme water splitting.

Dye-sensitized photocatalysts with molecular dyes and widegap semiconductors have attracted attention because of their design flexibility, for example, tunable light absorption for visible-light water splitting. Although organic dyes are promising candidates as metal-free photosensitizers in dye-sensitized photocatalysts, their efficiency in H2 production has far been unsatisfactory compared to that of metal-complex photosensitizers, such as Ru(II) tris-diimine-type complexes. Here, we demonstrate the substantial improvement of carbazole-thiophene-based dyes used for dye-sensitized photocatalysts through systematic molecular design of the number of thiophene rings, substituents in the thiophene moiety, and the anchoring group. The optimized carbazole-thiophene dye-sensitized layered niobate exhibited a quantum efficiency of 0.3% at 460nm for H2 evolution using a redox-reversible I- electron donor, which is six-times higher than that of the best coumarin-based metal-free dye reported to date. The dye-sensitized photocatalyst also facilitated overall water splitting when combined with a WO3-based O2-evolving photocatalyst and an I3-/I- redox shuttle mediator. The present metal-free dye provided a high dye-based turnover frequency for water splitting, comparable to that of the state-of-the-art Ru(II) tris-diimine-type photosensitizer, by simple adsorption onto a layered niobate. Thus, this study highlights the potential of metal-free organic dyes with appropriate molecular designs for the development of efficient water splitting.

Composite of titanium dioxide and hydrogen-bonded organic framework − A dye-sensitized photocatalyst

To improve the utilization of TiO2 with low visible light absorption behavior, a 2D hydrogen-bonded organic framework (HOF), HOF-TCPB-373, was employed and integrated with TiO2 to create a composite catalyst (TiO2@HOF). 40 %TiO2@HOF exhibits a larger BET specific surface area (26.68 m2/g) and a more negative Zeta potential (–23.78 mV) compared to HOF-TCPB-373. Compared to TiO2, 40 %TiO2@HOF is more hydrophilic with the water contact angles of 51°. A dye-sensitized catalytic system based on 40 %TiO2@HOF was established. 40 %TiO2@HOF exhibits the highest RhB removal efficiency reaching 99 %, combining photodegradation (69 %) and adsorption (30 %). The 40 %TiO2@HOF composite shows both superior adsorption and photodegradation capacities for RhB compared to pristine TiO2 and HOF-TCPB-373, attributing to the synergistic effect and heterojunction structure formed between the two components. The mechanism of dye sensitization and photocatalytic degradation was explained by energy band analysis and active species capture experiments. The degradation was driven by RhB-excited and charge transfer on 40 %TiO2@HOF.

Emerging developments in dye-sensitized metal oxide photocatalysis: exploring the design, mechanisms, and organic synthesis applications.

In the present day, the incorporation of environmentally conscious practices in the realm of photocatalysis holds a prominent position within the domain of organic synthesis. The imperative to tackle environmental issues linked to catalysts that cannot be recycled, generation of waste, byproducts, and challenges in achieving reaction selectivity during organic synthesis are more crucial than ever. One potential solution involves the integration of recyclable nanomaterials with light as a catalyst, offering the possibility of achieving sustainable and atom-efficient transformations in organic synthesis. Metal oxide nanoparticles exhibit activation capabilities under UV light, constituting a small percentage (4-8%) of sunlight. However, this method lacks sufficient environmental friendliness, and the issue of electron-hole recombination poses a significant hurdle. To tackle these challenges, multiple approaches have been proposed. This comprehensive review article focuses on the efficacy of dyes in enhancing the capabilities of heterogeneous photocatalysts, offering a promising avenue to overcome the constraints associated with metal oxides in their role as photocatalysts. The article delves into the intricate design aspects of dye-sensitized photocatalysts and sheds light on their mechanisms in facilitating organic transformations.

Visible light-driven highly-efficient hydrogen production by a naphthalene imide derivative-sensitized TiO2 photocatalyst.

Sensitizing titanium dioxide (TiO2) with dye molecules offers a cost-effective and environmentally friendly strategy for creating powerful photocatalysts for hydrogen production by reducing the band gap and enhancing sunlight absorption. Despite the challenges of identifying a stable dye with high light harvesting efficiency and effective charge recombination, we present a 1,8-naphthalimide derivative-sensitized TiO2 that achieves ultra-efficient photocatalytic hydrogen production (10.615 mmol g-1 h-1) and maintains activity after 30 hours of cycling. Our research offers valuable insights for designing optimized organic dye-sensitized photocatalysts, advancing clean and sustainable energy solutions.

Efficient water reduction by ruthenium-picolinate dye-sensitized photocatalyst under red light illumination

To utilize a wider region of the solar spectrum for solar-fuel production, we newly synthesized a heteroleptic Ru(II)-picolinate complex, [Ru(H4dpbpy)2(pic)]+ (Rupic; H4dpbpy = H4dpbpy = 2,2′-bipyridine-4,4′-diphosphonic acid, Hpic = picolinic acid) as a red light-absorbing molecular photosensitizer. Rupic exhibited metal-to-ligand charge-transfer (MLCT) absorption and emission (λabs and λem = 491 and 711 nm, respectively) over a longer wavelength region than that observed with the bipyridine derivative [Ru(H4dpbpy)2(bpy)]2+ (Rubpy, bpy = 2,2′-bipyridine). The Ru(III)/Ru(II) redox potential of Rupic (Eox = +1.07 vs NHE) was approximately 0.27 V more negative than that of Rubpy, owing to the weaker ligand field strength of pic than that of bpy. Moreover, as expected, owing to the red-light absorption ability of Rupic, the photocatalytic H2 evolution reaction activity of the Rupic-sensitized Pt-TiO2 nanoparticles (apparent quantum yield, AQY ∼ 3 %) under red light illumination (λ = 625 ± 35 nm) was significantly higher than that of its Rubpy-sensitized analog (AQY ∼ 0.5 %). These results indicate the superior photosensitizing performance of the Ru(II)-picolinate complex for H2 production under sunlight illumination.

Shedding light on small molecule coumarin dyes for efficient photocatalytic hydrogen evolution

The development of simple coumarin-based organic dyes loaded over TiO2 is found to possess great potential for efficient photocatalytic hydrogen generation. Herein, we studied a series of coumarin-based organic dyes, namely, 4-(naphthalene-1-yl)-2-oxo-2H-benzo[h]chromene-3-carbonitrile loaded over Pt–TiO2 is referred to as TC-2. The electronic as well as structural properties of the dyes were visualized experimentally and theoretically with the modification of the structural chromophoric groups over the meso-position of the coumarin dyes and revealed that the meso-substitution of the naphthalene ring over the TC-2 resulted in the decrease in electron-hole recombination dynamics. TC-2 photocatalyst depicted enhanced activity of (H2 rate-5.54 mmolg−1h−1) under neutral pH (AQY-14.5%, TON-5970), which is majorly obtained due to the increased conjugation of the naphthalene ring which thereby increases the light-sorption capacity of the materials in comparison to that of the others, synthesized materials in presence of TEOA. The extended π-π∗ conjugation in the substituent modification and the cyano groups over the simple coumarin groups leads to enhanced activity. This work paves the way towards sustainable development of dye-sensitized photocatalysts for green fuel generation.

Photocatalyst-Mediator Interface Modification by Surface-Metal Cations of a Dye-Sensitized H2 Evolution Photocatalyst.

To develop highly active H2 evolving dye-sensitized photocatalysts (DSPs) applicable for Z-scheme water splitting, we synthesized a series of Ru(II)-dye-double-layered DSPs, X'-RuCP6-Zr-RuP6@Pt-TiO2 (X'-DSP) with different surface-bound metal cations (X' = Fe2+, Y3+, Zr4+, Hf4+, and Bi3+). In 0.5 M KI aqueous solution, the photocatalytic H2 evolution activity under blue light irradiation (λ = 460 ± 15 nm) increased in the following order: nonmetal-modified DSP, H+-DSP (turn over number for 6 h irradiation = 35.2) < Fe2+-DSP (54.9) ≈ Bi3+-DSP (55.2) < Hf4+-DSP (65.5) ≈ Zr4+-DSP (68.3) ≈ Y3+-DSP (71.5), suggesting that the redox-inactive and highly charged metal cations tend to improve the electron donation from the iodide electron mediator. On the other hand, DSPs having heavy metal cations, Hf4+-DSP (18.4) and Bi3+-DSP (16.6), exhibited better activity under green light irradiation (λ = 530 ± 15 nm) than Zr4+-DSP (15.7) and H+-DSP (7.80), implying the contribution of a heavy atom effect of the surface-bound metal cation to partially allow the spin-forbidden metal-to-ligand charge-transfer excitation.

Enhancing Charge Transfer in Photocatalytic Hydrogen Production over Dye-Sensitized Pt/TiO2 by Ionic Liquid Coating

Photocatalytic hydrogen production from water is considered to be a potentially cost-efficient method to produce hydrogen fuel with little impact on the environment. Nevertheless, hydrogen production efficiencies via photocatalysis remain to be low. Here, a photocatalyst system composed of 1 wt % Pt/TiO2 and dye-sensitized Pt/TiO2 particulates encapsulated by an ionic liquid is proposed. In particular, the enhancement of photocatalytic hydrogen production over 1 wt % Pt/TiO2 particulates sensitized with N719 dye (di-tetrabutylammonium cis-bis(isothiocyanato)bis(2,2′-bipyridyl-4,4′-dicarboxylato) ruthenium(II)) and coated by a thin layer of ionic liquid [BMIM][BF4] (1-butyl-3-methylimidazolium tetrafluoroborate) has been investigated. The Pt was loaded onto the TiO2 surface by incipient wetness impregnation, while the dye and ionic liquid were loaded by solvent evaporation using ethanol and acetone, respectively. The photocatalytic tests were performed in a semibatch glass reactor under visible light irradiation provided by a solar simulator; the hydrogen production rates over Pt/TiO2, dye-sensitized Pt/TiO2, ionic liquid-coated Pt/TiO2, and ionic liquid-coated Pt/TiO2 after dye sensitization were compared. The hydrogen production rate was ∼21 μmol/h·gcat on Pt/TiO2, and it increased to ∼27 μmol/h·gcat with dye sensitization, while the [BMIM][BF4] coating alone improved hydrogen production three times (∼60 μmol/h·gcat). Coating the dye-sensitized particulates with an ionic liquid resulted in another 17% increase in hydrogen production (∼70 μmol/h·gcat). Scanning electron microscopy–energy dispersive X-ray analysis (SEM–EDAX), contrast transmission electron microscopy (CTEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, UV–vis characterization of the photocatalysts and electrochemical analysis of the respective photoelectrodes were also performed. The ionic liquid coating increased the performance of Pt/TiO2 by providing better charge transfer between the photocatalyst and the aqueous reaction medium while simultaneously preventing the recombination of photogenerated electron–hole pairs. The improved performance of the dye-sensitized photocatalyst upon the ionic liquid coating indicated that the ionic liquid stabilized the dye on the photocatalyst surface while simultaneously enhancing the charge transfer between the dye and TiO2.

Two Excited State Collaboration of Heteroleptic Ir(III)-Coumarin Complexes for H2 Evolution Dye-Sensitized Photocatalysts

Interfacial electron injection from a photoexcited surface-immobilized dye to a semiconductor substrate is a key reaction for dye-sensitized photocatalysts. We previously reported that the molecular orientation of heteroleptic Ir(III) photosensitizer on the TiO2 nanoparticle surface was important for efficient interfacial electron injection. In this work, to overcome the weak light absorption ability of heteroleptic Ir(III) photosensitizer and to improve the photoinduced charge-separation efficiency at the dye–semiconductor interface, we synthesized two heteroleptic Ir(III) complexes with different coumarin dyes, [Ir(C6)2(H4CPbpy)]Cl and [Ir(C30)2(H4CPbpy)]Cl [Ir-CX; X = 6 or 30; HC6 = 3-(2-enzothiazolyl)-7-(diethylamino)coumarin, HC30 = 3-(2-N-methylbenzimidazolyl)-7-N,N-diethylaminocoumarin, H4CPbpy = 4,4′-bis(methylphosphonic acid)-2,2′-bipyridine], as the cyclometalated ligands and immobilized them on the surface of Pt-cocatalyst-loaded TiO2 nanoparticles. Ultraviolet-visible absorption and emission spectroscopy revealed that the singlet ligand-centered (1LC) absorption and triplet 3LC emission bands of Ir-C30 occurred at shorter wavelengths than those of Ir-C6, while time-dependent density-functional-theory data suggested that the ligand-to-ligand charge transfer (LLCT) excited states of the two complexes were comparable. The photocatalytic H2 evolution activity of the Ir-C6-sensitized Pt-TiO2 nanoparticles (Ir-C6@Pt-TiO2) under visible light irradiation (λ &gt; 420 nm) was higher than that of Ir-C30@Pt-TiO2. In contrast, their activities were comparable under irradiation with monochromatic light (λ = 450 ± 10 nm), which is absorbed comparably by both Ir-CX complexes. These results suggest that the internal conversion from the higher-lying LC state to the LLCT state effectively occurs in both Ir-CX complexes to trigger electron injection to TiO2.

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

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

Enhancement of Photocatalytic Activity for Hydrogen Production by Surface Modification of Pt-TiO2 Nanoparticles with a Double Layer of Photosensitizers.

To investigate the effect of the surface structure of dye-sensitized photocatalyst nanoparticles, we prepared three types of RuII -photosensitizer (PS)-double-layered Pt-cocatalyst-loaded TiO2 nanoparticles with different surface structures, Zr-RuCP6 -Zr-RuP6 @N wt %Pt-TiO2 , RuCP6 -Zr-RuP6 @N wt %Pt-TiO2 , and RuCP2 -Zr-RuP6 @N wt %Pt-TiO2 (N=0.2, 1, and 5), and evaluated their photocatalytic H2 evolution activity in the presence of redox-reversible iodide as the electron donor. Although the driving force of the electron injection from I- to the photo-oxidized RuIII PS is comparable, the activity increased in the following order: RuCP2 -Zr-RuP6 @1 wt %Pt-TiO2 < RuCP6 -Zr-RuP6 @1 wt %Pt-TiO2 < Zr-RuCP6 -Zr-RuP6 @1 wt %Pt-TiO2 . The apparent quantum yield of Zr-RuCP6 -Zr-RuP6 @1 wt %Pt-TiO2 in the first hour reached 1 %. Zeta-potential measurements suggest that the surface Zr4+ -phosphate groups attracted I- anions to the nanoparticle-solution interface. Our results indicate that the surface modification of dye-sensitized photocatalysts is a promising approach to enhance photocatalytic activity with various redox mediators.

Enhanced dye-sensitized photocatalysis for water purification by an alveoli-like bilayer Janus membrane

Dye sensitization represents a promising route to address the limited photoabsorption in semiconductor photocatalysis. However, efficient water purification using dye-sensitized photocatalysts has remained an unmet challenge. Here we report a novel strategy to promote dye-sensitized photocatalysis by combining the advantages of interfacial Fenton reaction construction and air-liquid-solid triphase contact. An alveoli-like Janus membrane was developed with bilayer electrospun micro/nanofibers, where the outer layer is hydrophilic semiconductor catalyst sensitized by an iron (II) phthalocyanine (FePc) photosensitizer, which can also act as the trigger of H2O2 activation; the hydrophobic internal layer serves as a gas passage to deliver O2 from air to the catalytic interface, boosting the photoinduced electrons conversion and H2O2 generation. This architecture allows a superior level of photosensitizer decoration when using TiO2 as the model semiconductor catalyst, which corresponds to highly efficient activity for photodegradation of organic contaminations accompanied with a high apparent quantum yield at around 660 nm. Our work may provide new insights into the development of high-efficiency solar driven photocatalysts for widespread applications.

Pyridyl-Anchored Type BODIPY Sensitizer-TiO2 Photocatalyst for Enhanced Visible Light-Driven Photocatalytic Hydrogen Production

Dye-sensitized photocatalytic hydrogen production using a boron-dipyrromethene (BODIPY) organic material having a pyridyl group at the anchor site was investigated. Phenyl, carbazole, and phenothiazine derivatives were introduced into BODIPY dyes, and their photocatalytic activities were examined. Identification was performed by nuclear magnetic resonance (NMR), infrared (IR), mass (MS) spectra, and absorption spectra, and catalyst evaluation was performed by using visible-light irradiation and photocatalytic hydrogen production and photocurrent. These dyes have strong absorption at 600–700 nm, suggesting that they are promising as photosensitizers. When the photocatalytic activity was examined, stable catalytic performance was demonstrated, and the activity of the Pt-TiO2 photocatalyst carrying a dye having a carbazole group was 249 μmol/gcat·h. Photocurrent measurements suggest that dye-sensitized photocatalytic activity is occurring. This result suggests that BODIPY organic materials with pyridyl groups as anchor sites are useful as novel dye-sensitized photocatalysts.

Photocatalysts for H2 Generation from Starburst Triphenylamine/Carbazole Donor-Based Metal-Free Dyes and Porous Anatase TiO2 Cube.

A series of novel triphenylamine/carbazole-based D-D-π-π-A dyes DH1-4 and a mesoporous anatase cubic "microcage" TiO2 material (denoted as MC-TiO2 ) were synthesized and combined to obtain dye-sensitized photocatalysts (denoted as DHn/Pt/MC-TiO2 , n=1-4). These catalysts showed better performances in visible-light-driven H2 evolution from water than DHn/Pt/P25-TiO2 catalysts based on commercial P25-TiO2 bulk semiconductor under similar conditions. Compared with P25-TiO2 particles, the porous MC-TiO2 had a large Brunauer-Emmett-Teller surface area, porosity, and exposed {0 0 1} crystal plane, which greatly contributed to the photocatalytic activity. The optimized DH2/Pt/MC-TiO2 photocatalyst exhibited an attractive H2 production rate (16.28 mmol g-1 h-1 based on catalyst mass), and the optimized DH4/Pt/MC-TiO2 photocatalyst showed good stability [turnover number (TON) of 16 699 in 105 h based on dye number], which represents one of the best performances among all reported visible-light-driven heterogeneous catalytic systems. Compared with the other dyes in this series, the high H2 production rate of DH2 on Pt/MC-TiO2 can be attributed to its size-matching effect and thus high dye loading amount, whereas the high TON and durability of DH4/Pt/MC-TiO2 are probably related to the rapid regeneration kinetics of DH4.

Multicarbazole-Based D-π-A Dyes Sensitized Hydrogen Evolution under Visible Light Irradiation.

Donor−π bridge–acceptor (D−π–A) organic dyes, well studied in dye-sensitized solar cells (DSSCs), are found to possess great potential in light-inducing hydrogen evolution due to their distinguished light-harvesting ability and suitable electron energy level. In this work, multicarbazole-based organic dyes (2C, 3C, 4C) were used as photosensitizers of Pt/TiO2 for photocatalytic hydrogen evolution (PHE) from water under visible light irradiation. 3C-Pt/TiO2 shows the best photocatalytic activity among the three dye-sensitized photocatalysts, with a hydrogen evolution rate of 24.7 μmol h–1 and a turnover number of 247 h–1. The activity of 3C-Pt/TiO2 declines significantly after 3 h irradiation. The deactivation was caused by the partial degradation of the electron acceptor, cyanoacrylate moiety, during the photocatalytic process, which was evidenced by UV–vis, Fourier transform infrared spectra (FT-IR), NMR, and mass spectra. This work is expected to contribute toward the understanding of stability issues of organic dyes and the development of more efficient and steady dyes for hydrogen evolution from water splitting.

Photosensitization effect on visible-light-induced photocatalytic performance of $$\hbox {TiO}_{2}$$/chlorophyll and flavonoid nanostructures: kinetic and isotherm studies

Preparation and performance of natural dye-sensitized photocatalysts of \(\hbox {TiO}_{2}\) are described in this study. Such sensitized nanostructures offer visible-light-reactive systems for the photodegradation of organic pollutants. Natural pigments of chlorophyll and flavonoid extracted from parsley leaves and Curcuma longa roots are grated on \(\hbox {TiO}_{2 }\) nanoparticles as photosensitizers using an incipient wetness impregnation method. The as-prepared samples are structurally characterized by combined techniques, such as X-ray diffraction, scanning electron microscopy and Fourier transform infrared. The diffuse reflectance UV–Vis spectra are also used to investigate band-gap energies. The resultant band-gap energies confirm the ability of visible light absorption and thereby the ability of more efficient generation of photoexcited charge-carriers. The photocatalytic performance of dye-sensitized nanoparticles is tested in terms of decolourization efficiency of MB dye as a function of involved operating parameters including reaction time, amount of catalyst, initial MB concentration and pH. Both samples show the excellent photocatalytic efficiencies relevant to the red shift generated and high absorption of photons in the visible region. However, the highest efficiency is obtained for \(\hbox {TiO}_{2}\)/chlorophyll catalysts (93%) compared to \(\hbox {TiO}_{2}\)/flavonoid samples (91%), which is perfectly in agreement with their band-gap energies and visible-light absorption ability. Photodegradation process kinetics is investigated by the Langmuir–Hinshelwood model, while the adsorption equilibrium is described based on Langmuir and Freundlich isotherms.

Dye-sensitized Photocatalyst of Sepiolite for Organic Dye Degradation

The photocatalytic activity of sepiolite was examined for degradation of several dye compounds under visible light irradiation. Higher adsorption capacities and greater photocatalytic performance of cationic dyes (rhodamine B and methylene blue) were observed on sepiolite, in comparison with anionic dyes (orange II and trypan blue). Superiority in the photocatalytic activity of cationic dyes is attributed to the strong electrostatic attraction and photosensitization properties of cationic dye molecules. Sepiolite has degraded 45.3% rhodamine B within 120 min, which is the greatest photocatalytic degradation efficiency when compared with other dyes. Subsequently, the reusability of spent sepiolite after adsorption of rhodamine B was evaluated by the degradation of trypan blue under the visible light irradiation. The photocatalytic degradation performance of trypan blue by spent sepiolite after adsorption of rhodamine B increased about twice as much as with pristine sepiolite, indicating that the dye-sensitized photocatalytic process could enhance the photocatalytic degradation ability of sepiolite. Through radical scavenger tests, it was found that a superoxide radical is mainly responsible for rhodamine B degradation. The possible mechanism of rhodamine B degradation under visible light irradiation was proposed. The sepiolite could be a potential catalyst for the degradation of organic pollutants in wastewater under solar light.

Development of a Lower Energy Photosensitizer for Photocatalytic CO2 Reduction: Modification of Porphyrin Dye in Hybrid Catalyst System

A series of Zn–porphyrin dyes was prepared and anchored onto a TiO2 surface to complete a dye-sensitized photocatalyst system, Zn–porphyrin-|TiO2|-Cat, and tested as lower energy photosensitizers for photocatalytic CO2 reduction. Three major synthetic modifications were performed on the Zn–porphyrin dye to obtain a lower energy sensitization and improve the catalyst lifetime. We found that incorporating acetylene and linear hexyl groups into the Zn–porphyrin core allowed facile lower energy sensitization, and the addition of the cyanophosphonic acid as an anchoring group gave the long-term dye stability on the TiO2 surface. Under irradiation with red light of >550 nm and a light intensity of 207 mW/cm2, the hybrid ZnPCNPA catalyst showed a TONRe of ∼800 over an extended time period of 90 h. The photocatalytic activities of porphyrin hybrids differ greatly with the binding strength of the anchoring groups of dye and spectral range of the irradiated light and its intensity.

Efficient visible-light-driven photocatalytic hydrogen production from water by using Eosin Y-sensitized novel g-C3N4/Pt/GO composites

Developing an efficient dye-sensitized photocatalyst for photocatalytic H2 evolution from water is highly desired. In this study, a novel ternary g-C3N4/Pt/GO composite was synthesized via a facile liquid-phase sonochemical approach. Pt nanoparticles were firstly deposited on the surfaces and/or interlayer of g-C3N4 by chemical reduction, and then, GO was penetrated through ultrasonic treatment. This preparation method is facilitated to prohibit the agglomeration of g-C3N4 and GO because of their π–π stacking interaction and enhance electrons transport and the adsorption of dye molecules. The Eosin Y-sensitized ternary g-C3N4/Pt/GO composite shows the highest H2 production rate of 3.82 mmol·g−1·h−1 under the optimization conditions, which about 2.1 times and 7.7 times higher than the Eosin Y-sensitized binary g-C3N4/Pt and GO/Pt photocatalysts, respectively. The improved charge separation efficiency is the main reason for the enhancement in H2 evolution activity. The apparent quantum efficiency of hydrogen evolution for the Eosin Y-sensitized ternary g-C3N4/Pt/GO composite is up to 9.7% at 420 nm. Moreover, the sensitized g-C3N4/Pt/GO composite shows stable photocatalytic activity for H2 evolution under visible light irradiation. The effect of pH, g-C3N4/GO weight ratios, Pt loading amounts, dye concentrations, and different type dyes on the H2 evolution activity was also investigated in detail.