Preparation of floatable TiO2/poly(vinyl alcohol)-alginate composite for the photodegradation of ammonia wastewater

The use of floatable photocatalyst supports is an operable strategy of increasing photocatalytic performance in terms of improving light absorption. In this work, floatable organic support based on poly(vinyl alcohol) (PVA) was used to float commercial TiO₂ P25 nanoparticles. At first, by the use of CaCl₂ and boric acid at pH 3 the cross-linking of PVA blended with sodium alginate (PVA-Alg) was improved to enhance chemical and mechanical stability, and then it was chemically modified by trimethylchlorosilane to achieve floatable organic support (modified or MPVA-Alg). The prepared support and photocatalyst were characterized by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy, energy-dispersive X-ray spectroscopy (EDX)-elemental mapping, inductively coupled plasma optical emission spectroscopy, ultraviolet-visible (UV-vis) diffuse reflectance spectroscopy, photoluminescence (PL), thermalgravimetry, Brunauer-Emmett-Teller (BET), and water contact angle (WCA) analyses and applied for the ammonia degradation under UV to visible regions. Results of WCA and FTIR confirmed that chemical modification of PVA-Alg led to lowering hydrophilicity to be floated on the ammonia wastewater. UV-vis analysis indicated that the MPVA-Alg acts as a light absorbent in UV-vis ranges and makes TiO₂/MPVA-Alg a visible light active composite. Also, the PL analysis showed that the charge recombination process was strongly suppressed in the case of the TiO₂/MPVA-Alg sample. BET theory suggested that the textural properties were not the key factor in determining photocatalytic performance. The maximum photocatalytic ammonia removal was obtained to be 63% and 57% by the TiO₂/MPVA-Alg composite under UV-vis light irradiations, respectively. The MPVA-Alg and TiO₂ exhibited the ammonia degradation of 28.5% and 15.2% under visible and 29.4% and 40.0% under UV irradiation, respectively. The TiO₂/MPVA-Alg showed favorable reuse ability after five runs due to desirable chemical and mechanical resistance. This study provides an insight into the modification of polymeric structures to be used as both floatable photocatalyst support and light sensitizer.     

Nanocomposite of graphene oxide with nitrogen-doped TiO2 exhibiting enhanced photocatalytic efficiency for hydrogen evolution

The application of hydrogen energy potentially addresses energy and environmental problems. In order to improve the photocatalytic efficiency, nanocomposite of N-doped TiO₂ with graphene oxide (NTG) is prepared and characterized with Fourier transform infrared spectra (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectra, X-ray photoelectron spectroscopy (XPS), atomic force microscope (AFM), photoluminescent spectra. The application of NTG to hydrogen evolution exhibits high photocatalytic efficiency of 716.0 or 112.0 μmol h⁻¹ g⁻¹ under high-pressure Hg or Xenon lamp, which is about 9.2 or 13.6 times higher than P25 photocatalyst. This is mainly attributed to the N-doping of TiO₂ and the incorporation of graphene oxide resulting in narrow band gap, together with the synergistic effect of fast electron-transporting of photogenerated electrons and the efficient electron-collecting of graphene oxide retarding charge recombination. These results provide a significant theoretical foundation for the potential application of N-doping photocatalysts to hydrogen evolution.     

Photocatalytic activity of TiO2 nanotube layers coated with Ag and Pt

Abstract

Abstract

Thin films of anatase TiO₂ nanotube arrays (TiO₂ NTs) were prepared in this study. Pt and Ag were coated on the TiO₂ NTs films, which intend to increase the photocatalytic activity under ultraviolet-visible (UV-vis) irradiation. The phase and structure of the films were investigated by X-ray diffraction and scanning electron microscopy. Photocatalytic activity was tested by UV-vis absorption spectroscopy and showed that UV-vis light absorption of the films was remarkably improved by coated Ag and Pt by 72% and 183% respectively. The photocatalytic activities of the films towards degraded methyl orange and HCHO were compared and were all found to follow the sequence Pt/TiO₂ NTs>Ag/TiO₂ NTs>TiO₂ NTs. It was also found that the kinetics of HCHO photocatalytic degradation by the films fits the first order reaction model better and has higher efficiency than that of the methyl orange photocatalytic degradation by the same films.     

Facile synthesis of AuPd/g-C3N4 nanocomposite: An effective strategy to enhance photocatalytic hydrogen evolution activity

AuPd bimetallic nanoparticle (NP) modified ultra-thin graphitic carbon nitride nanosheet photocatalysts were synthesized via photochemical deposition-precipitation followed by hydrogen reduction. The crystal structure, chemical properties, and charge carrier behavior of these photocatalysts were characterized by X-ray diffraction (XRD), surface photovoltage spectroscopy (SPS), transient photovoltage spectroscopy (TPV), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), high-resolution transmission electron microscopy (HRTEM), and UV-Vis diffuse-reflectance spectroscopy (DRS). Photocatalytic H₂ evolution experiments indicate that the hydrogen treated AuPd nanoparticles can effectively promote the separation efficiency of electron-hole pairs photo-excited in the g-C₃N₄ photocatalyst, which consequently promotes photocatalytic H₂ evolution. The 1.0 wt% AuPd/g-C₃N₄ (H₂) composite photocatalyst showed the best performance with a corresponding photocatalytic H₂ evolution rate of 107 μmol h^?1. The photocatalyst can maintain most of its photocatalytic activity after four photocatalytic experiment cycles. These results demonstrate that the synergistic effect of light reduction and hydrogen reduction of AuPd and g-C₃N₄ help to greatly improve the photocatalytic activity of the composite photocatalyst.     

Fabrication of CuO/MoO3 p-n heterojunction for enhanced dyes degradation and hydrogen production from water splitting

The development of excellent photocatalytic material is highly required for energy and environmental applications. In this study, visible light responsive p-n heterojunction photocatalysts based on CuO/MoO₃ with varying ratios of CuO were prepared by the facile hydrothermal method. The crystalline structure, surface morphology, chemical compositions and optical properties of the synthesized photocatalysts were studied using X-ray powder diffraction (XRD), scanning electron microscopy (SEM), Energy-dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared spectroscopy (FTIR), photoluminescence (PL) techniques and UV–Vi's absorption spectroscopy. The results showed that the 5%CuO/MoO₃ nanocomposite displayed enhanced photocatalytic performance for the production of hydrogen (98.5 μmol h^?1g^?1) and degradation of dyes rhodamine B (RhB) and alizarine yellow (AY) than all other samples. Furthermore, 5% CuO/MoO₃ composite exhibited excellent stability after five consecutive cycles for both RhB and AY dyes. Overall, the improved photocatalytic performance of 5%CuO/MoO₃ composite was due to increased adsorption of visible light, good surface morphology, enhanced charge separation/transfer which inhibited recombination of electrons and holes. This study could encourage the synthesis of novel and effective p-n heterojunction photocatalysts for practical applications.     

Photocatalytic water splitting for hydrogen production on Au/KTiNbO5

Gold nanoparticles were deposited on potassium titanoniobate, KTiNbO₅ using deposition-precipitation (DP), conventional impregnation (IMP) and photodeposition method in order to improve photocatalytic hydrogen production from water splitting. The effect of synthesis pH value of a HAuCl₄ aqueous solution used in the DP process on the morphology of gold nanoparticles, optical property and photocatalytic activity of water splitting under UV light irradiation was investigated. These catalysts were characterized by powder X-ray diffraction patterns (XRD), inductively coupled plasma mass spectrometry (ICP-MS), UV–visible spectroscopy (UV–vis), and Transmission Electron Microscopy (TEM). The Au/KTiNbO₅ catalysts prepared by the DP method consisted of a good metal–semiconductor interface which allowed for a much higher efficient electron-hole separation. The 0.63 wt% Au/KTiNbO₅ catalyst prepared by the DP method at pH = 10 showed a uniform dispersion of gold nanoparticles with an average gold particle size of 4.2 nm and exhibited an ultra-high photocatalytic water splitting activity (3522 μmol g⁻¹ h⁻¹), about 47 times higher than that exhibited by the KTiNbO₅ photocatalyst.     

Efficient hydrogen evolution with ZnO/SrTiO3 S-scheme heterojunction photocatalyst sensitized by Eosin Y

Developing efficient, stable, and cheap photocatalysts for H₂ production has aroused great interest among researchers. Herein, noble-metal-free ZnO/SrTiO₃ composite photocatalysts have been successfully prepared by hydrothermal method. X-ray diffraction, field-emission scanning electron microscopy, high-resolution transmission electron microscopy, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, ultraviolet–visible diffusion spectroscopy, and photoluminescence spectroscopy are used to characterize the obtained samples. The photocatalytic water splitting for H₂ production by ZnO/SrTiO₃ has been studied under simulated sunlight irradiation by using triethanolamine as a sacrificial agent and Eosin Y (EY) dye as a sensitizer. The orthogonal experiments are designed to optimize the photocatalytic reaction conditions for practical purposes. The influencing extents and trends of the factors have been investigated, including the catalyst composition and dosage, pH value of the solution, triethanolamine, and EY addition. Under the optimum conditions, the H₂ production rate with ZnO/SrTiO₃ is up to 16006.12 μmol g^?1 h^?1. The excellent performance of ZnO/SrTiO₃ is attributed to the formation of a step-scheme (S-scheme) heterojunction, which promotes the separation of photocarriers and reduces their recombination probability.     

Hybrid of AgInZnS and MoS2 as efficient visible-light driven photocatalyst for hydrogen production

We present a simple two-step hydrothermal method to prepare AgInZnS/MoS₂ nanocomposite. The morphology and compositional characteristics of the sample were investigated by field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The as-synthesized heterostructures exhibited superior photocatalytic activity for hydrogen evolution under visible-light irradiation and the optimum loading amount of MoS₂ is at 0.5 wt%. In an attempt to explain this phenomenon, a possible mechanism was also proposed. The enhanced photocatalytic activities toward water splitting arise from the boosted active sites for hydrogen generation and the enhanced charge transfer. This work may contribute to the design and construction of highly efficient visible-light responsive photocatalyst for sustainable energy harvesting and conversion.     

Promoted interfacial charge transfer by coral-like nickel diselenide for enhanced photocatalytic hydrogen evolution over carbon nitride nanosheet

Seeking an efficient and non-precious co-catalyst for g-C₃N₄ (CN) remains a great demanding to achieve high photocatalytic hydrogen generation performance. Herein, a composite photocatalyst with high efficiency was prepared by modifying CN with coral-like NiSe₂. The optimal hydrogen evolution rate of 643.16 μmol g^?1 h^?1 is from NiSe₂/CN-5 under visible light. Superior light absorption and interfacial charge transfer properties including suppressed photogenerated carrier recombination and efficient separation of photogenerated electron-hole pairs have been observed, which account for the enhanced photocatalytic performance of CN.     

Characterizations and photocatalytic activity comparisons of N-doped nc-TiO2 depending on synthetic conditions and structural differences of amine sources

N-doped TiO₂ nanoparticles were prepared by using 1° and 2° alkyl and alcohol amines [n-propylamine (nPRYL), ethanolamine (ETOH), propanolamine (PROH), diethylamine (DETYL), dipropylamine (DPRYL), diethanolamine (DETOH), and ammonium hydroxide (NH₄OH)] as nitrogen sources through microwave and hydrothermal growth (HT) methods. Characterization of the nanoparticles was done by X-ray diffraction, scanning electron microscopy, ultraviolet-visible absorption spectra, X-ray photoelectron spectroscopy, fourier transform infrared spectroscopy and BET analysis techniques. Nitrogen species in TiO₂ lattice were interstitial impurities. Nitrogen content of the particles depended on the preparation conditions and structural differences of nitrogen sources. Photocatalytic degradation of methylene blue was carried out under Xenon lamp irradiation. N-doped TiO₂ nanoparticles exhibited higher photocatalytic activity, compared to undoped ones. Acidity differences of amine sources and irradiation differences of synthetic conditions had an effect on photocatalytic activity. Although N doping into TiO₂ lattice was the least effective in the particle prepared by the use of nPRYL as the amine source and HT as the synthetic condition, its photocatalytic activity was slightly better compared to others.     

Cobalt oxide on mesoporous carbon nitride for improved photocatalytic hydrogen production under visible light irradiation

Cobalt oxide (Co₃O₄) nanoparticles decorated on mesoporous carbon nitride (Co₃O₄/MCN) nanocomposites for photocatalytic hydrogen evolution were investigated in this work. MCN was prepared using 3-amino-1,2,4-triazole, high nitrogen content, as a single molecular carbon and nitrogen precursor and SiO₂ nanoparticles as the hard template. Complementary characterization techniques were employed to understand the textural and chemical properties of the nanocomposites. The bare MCN showed high photocatalytic activity under visible light irradiation without using any co-catalyst. The photocatalytic activity of Co₃O₄/MCN with a Co₃O₄ mass content of 5 wt % presented two times higher than the bare MCN, which is attributed to the enhanced visible-light harvesting and more efficient charge separation. Mechanistic study shows lower electron-hole recombination rate, higher charge separation efficiency occurs after the formation of p-n type heterojunction.     

V2O5 nanoribbons/N-deficient g-C3N4 heterostructure for enhanced visible-light photocatalytic performance

Visible-light-induced heterostructure photocatalysts have been regarded as promising candidates in clean energy production and environmental treatment of organic pollutants. In this study, we have prepared nanocomposites of V₂O₅/N-deficient g-C₃N₄ (VO/Ndef-CN), which have been characterized by a variety of techniques. The as-synthesized nanocomposites show efficient bifunctional photocatalytic properties toward hydrogen generation and pollutants degradation (dye and antibiotic). The optimized 5VO/Ndef-CN photocatalyst exhibits improved photoactivity for H₂ production (5892 μmol g^?1 h^?1), with a high quantum yield of 6.5%, and fast degradation of organic pollutants, as well as high photocatalytic stability under visible light irradiation. The high photocatalytic efficiency is due to the presence of N defects and S-scheme heterojunction formation, which leads to rapid charge separation, enhanced visible-light absorption, and increased active sites. Furthermore, the possible activity-enhanced mechanism and the photodegradation pathway are proposed based on the experimental and density functional theory (DFT) investigations.     

Synthesis,characterization and photo-electrochemical properties of novel Cu(Cr1-x,Alx)2O4 spinel oxides for enhanced photodegradation of organic dyes under UV light

In the present work, physical, photo-electrochemical properties and photocatalytic activity of Cu(Cr_1-x,Al_x)₂O₄ (x = 0, 0.1, 0.5, 0.9 and 1) spinels synthesized via the nitrate route were investigated for the first time. X-ray diffraction (XRD) with Rietveld refinement confirms the purity of all samples while SEM images show the porous and spongious morphology of the oxides of 62–311 nm grain sizes. The chemical composition and the oxidation states were determined by X-ray photoelectron spectroscopy (XPS) analysis. The specific surface area is highly affected by x-ratio. The photoelectrochemical behavior of the synthesized materials was evaluated by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and Mott-Schottky in Na₂SO₄ electrolyte (0.1 M). Indeed, the electrochemical tests under the effect of light show an increase in the current intensity and a decrease in the charge transfer resistance in CV and EIS tests, respectively. These materials were applied as photocatalysts for the photodegradation of Methylene Blue (MB) under UV light with the aid of H₂O₂ serving as generator of free radicals. Our results show that Cu(Cr_0.1,Al_0.9)₂O₄ is the most performant photocatalyst of MB with a degradation efficiency of 98.8% within 80 min of irradiation. Furthermore, the photocatalytic activities of Cu(Cr_0.1,Al_0.9)₂O₄ were evaluated by the degradation of Rhodamine B (RhB) and Methyl Orange (MO) and the results reveal a good performance toward RhB degradation (85.5%), and to a lesser degree for MO decomposition (67.3%).     

Enhanced photocatalytic performance of CdO-WO3 composite for hydrogen production

Considering the renewability and cleanness of hydrogen generation system, the photocatalytic H₂ evolution through water splitting with assistance of Earth abundant co-catalysts has become a scientific hotspot. Efficient and visible light driven CdO-WO₃ composites with versatile properties have been fabricated through hydrothermal approach for H₂ evolution. X-ray diffractometer, scanning electron microscope, UV-Vis absorption spectroscopy, photoluminescence emission spectroscopy and photocatalytic activity test were employed to investigate different properties like crystallography, morphology, optical and photocatalytic properties. The effect of CdO concentration on the grain size indicated the reduction of bad gap energy of the WO₃. The concentration of CdO nanoparticles in WO₃ directly effect on the morphology of the particles that are in the form of nanorods. The atoms of CdO makes the WO₃ nanoparticles more effective and efficient up to 4% of CdO but when coupling amount increases then the CdO-WO₃ nanoparticles exhibited less photocatalytic performance to evolve H₂ energy. Results shown that 4% content in WO₃ had exceptional photocatalytic activity for water splitting when compared to other samples. The improved hydrogen production was allied with formation of active Cd species during the photocatalysis process, which has the ability to promote the interfacial charge-separation and concurrently may cause to reduce the over potential of hydrogen evolution, thus boosting the photocatalytic activity over the hybrid sample. The improved photocatalytic activity of composites could be accredited to extended absorption region of visible light, efficient separation of charge carrier's and suppress recombination of electron-hole pairs. The current work not only shows a prospect for the utilization of low cost CdO as a co-catalyst in photocatalytic hydrogen generation but also shows a substantial enhancement in H₂ evolution, first time, using CdO-WO₃ hybrid photocatalyst.     

Optimization of hydrogen production by photocatalytic steam methane reforming over lanthanum modified Titanium (IV) oxide using response surface methodology

In this study, the optimization of hydrogen production by photocatalytic steam methane reforming over Lanthanum modified TiO₂ has been investigated using response surface methodology. The La/TiO₂ photocatalysts were synthesized using wet impregnation method and characterized for physicochemical and photocatalytic properties by N₂ physisorption, X-ray powder diffraction (XRD), Scanning electron microscopy (SEM), Energy dispersive X-ray (EDX), and ultraviolet-visible (UV-vis) spectroscopy. The characterization shows that the La/TiO₂ possesses appropriate properties to be used as photocatalysts. The photocatalysts were employed in the optimization studies of hydrogen production by photocatalytic steam methane reforming. The effects of irradiation time (10–150 min), metal loading (1–3%), methane concentration (10–50%), and steam concentration (0.5–1.5%) on the rate of hydrogen production were determined employing Box-Behnken experimental design. The application of the RSM resulted in the formulation of four models out which the quadratic model was adjudged to adequately fit the experimental data. A further statistical analysis of the quadratic model established the significance of the model with p-value far less than 0.05 and coefficient of determination (R²) of 0.975. A non-significant lack of fit obtained for the model further confirm the suitability of the quadratic model in fitting the experimental data. At the desirability function of 1, optimum conditions of 146.15 min, 2.94%, 22.83% and 1.24% for irradiation time, metal loading, methane concentration, and steam concentration, respectively resulted in the production of 2.42 μmol of hydrogen/min.     

Boosting the performance of visible light‐driven WO3/g‐C3N4 anchored with BiVO4 nanoparticles for photocatalytic hydrogen evolution

In this article, a ternary WO₃/g‐C₃N₄@ BiVO₄ composites were prepared using eco‐friendly hydrothermal method to produce efficient hydrogen energy through water in the presence of sacrificial agents. The prepared samples were characterized by scanning electron microscopy (SEM), scanning transmission electron microscopy (STEM), transmission electron microscopy (TEM), X‐ray diffraction (XRD), ultraviolet‐visible (UV‐vis), Brunauer‐Emmett‐Teller (BET) surface area, and photoluminescence spectroscopy (PL) emission spectroscopy. The experimental study envisages the formation of 2‐D nanostructures and observed that such kinds of nanostructures could provide more active sites for photocatalytic reduction of water and their inherent reactive‐species mechanism. The results showed the excellent photocatalytic performance (432 μmol h^?1 g^?1) for 1.5% BiVO₄ nanoparticles in WO₃/g‐C₃N₄ composite when compared with pure WO₃ and BiVO₄. The optical properties and photocatalytic activity measurement confirmed that BiVO₄ nanoparticles in WO₃/g‐C₃N₄ photocatalyst inhibited the recombination of photogenerated electron and holes and enhanced the reduction reactions for H₂ production. The enhanced photocatalytic efficiency of the composite nanostructures may be attributed to wide absorption region of visible light, large surface area, and efficient separation of electrons/holes pairs owing to synergistic effects between BiVO₄ and WO₃/g‐C₃N₄. The prepared samples would be a precise optimal photocatalyst to increase their suppliers for worldwide applications especially in energy harvesting.     

Reduced band gap & charge recombination rate in Se doped α-Bi2O3 leads to enhanced photoelectrochemical and photocatalytic performance: Theoretical & experimental insight

For better utilization of solar spectrum and complete redox of water for water splitting applications, it is required to have a semiconductor which is photoactive in visible region. In this study, we report theoretical and experimental investigations on morphological and opto-electronic modifications induced in α-Bi₂O₃ due to Selenium (Se) doping tested for photoelectrochemical (PEC) & photocatalytic properties. Density Functional Theory (DFT) calculations revealed band gap reduction and direct to indirect transitions in Se-doped α-Bi₂O_3. This reduction in band gap is attributed to hybridization of Se p & Bi s in valence band and Se d & Bi p orbital in conduction band. To support this finding experimentally, we synthesized Se-doped α-Bi₂O₃ using simple chemical precipitation method and measured its band gap using photoluminescence and UV–Vis spectroscopy. Experimental results also confirmed the reduction in band gap energy and recombination rate of charge carriers as compared to pristine α-Bi₂O₃ sample. PEC study of Se-doped α-Bi₂O₃ showed an increased photocurrent density, charge carrier density and lowered impedance, which indicates its efficient solar spectrum utilization and better hydrogen generation efficiency. Photocatalytic measurement also revealed higher rate of dye degradation with Se doped α-Bi₂O₃.     

Enhanced photocatalytic performance and stability of multi-layer core-shell nanocomposite C@Pt/MoS2@CdS with full-spectrum response

The nanocomposite material C@Pt/MoS₂@CdS was prepared by a simple microwave-assisted hydrothermal method combined with photoreduction method. The crystal structure, microstructure, and surface physical chemistry properties of the material were analyzed by X-ray diffraction (XRD), ultraviolet–visible diffuse reflectance absorption spectroscopy (UV–vis/DRS), X-ray photoelectron energy spectroscopy (XPS), scanning electron microscopy (SEM), high resolution transmission electron microscopy (HR-TEM), nitrogen adsorption–desorption measurement, photoluminescence spectroscopy (PL), and electrochemical tests. As a result, this material has full-spectrum light absorption property and the composited CdS presents a good hexagonal phase. Moreover, the composite material presents a nanorod-like multi-layer core-shell structure, wherein the rod-like MoS₂@CdS surface is covered with Pt and C. The formation of the multi-layer core-shell structure increases the specific surface area of as-composite material and strengthens its light absorption performance. The electrochemical impedance and transient photocurrent test results show that C@Pt/MoS₂@CdS has the highest charge separation efficiency and enhanced photocurrent density compared with other systems. Photogenerated charge carriers have higher separation efficiency, and photogenerated electrons and holes exhibit longer life. During the photocatalysis experiments, the nanocomposite C@Pt/MoS₂@CdS shows enhanced photodegradation activity under multi-modal photocatalytic experiments and excellent stability under visible light irradiation. In addition, C@Pt/MoS₂@CdS has a strong photocatalytic water splitting ability. Under the same experimental conditions, its hydrogen production is 60 times that of commercially available P25. Through capture experiments, the reactive species in the photocatalytic reaction process were determined, and the possible photocatalytic reaction mechanism of this multi-layer core-shell C@Pt/MoS₂@CdS nanocomposite was inferred.     

Pd-Gardenia-TiO2 as a photocatalyst for H2 evolution from pure water

The photocatalytic activity for H₂ evolution from pure water over Pd loaded TiO₂ prepared by gardenia extract (Pd-Gardenia-TiO₂) is systematically investigated. The as-prepared photocatalysts are characterized by X-ray diffraction, high resolution transmission electron microscopy, Fourier transform infrared spectra, and X-ray photoelectron spectroscopy. Gardenia extract functions as reducing and stabilizing agents simultaneously. The mean size of the as-prepared Pd nanoparticles is in the range of 2.3 ± 0.5 nm based on TEM images. The Pd-Gardenia-TiO₂ catalyst exhibits good photocatalytic activity for H₂ evolution (93 μmol · h⁻¹ · g⁻¹), which is much higher than that of Pd photodeposited on TiO₂. Possible factors for its photocatalytic activity from pure water are also investigated.     

Enhanced photocatalytic hydrogen production of CdS embedded in cationic hydrogel

In this study, we describe the successful fabrication of CdS in ionic hydrogels by an in situ growth method and demonstrate that the as-prepared CdS in hydrogels (CdS/HGel) can be used as cost-effective and recyclable catalysts for photocatalytic hydrogen generation. The structure and morphology of CdS/HGels were characterized by various techniques including X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, UV-vis diffuse reflectance spectroscopy, and Fourier transform infrared spectroscopy. The resultant CdS in cationic hydrogel (CdS/HGel_PDAM2) showed the best performance of photocatalytic hydrogen production and the hydrogen production rate was up to 10.35 or 7.70 mmol h⁻¹ g⁻¹ when triethanolamine or Na₂S–Na₂SO₃ was used as sacrificial agent. However, CdS in anionic hydrogel (CdS/HGel_PAAM) showed poor photocatalytic hydrogen production performance under the same conditions. The solution pH and sacrificial agent type are also indispensable factors that affect the photocatalytic hydrogen production. The enhancement of hydrogen production comes from interaction between polymer chains and Cd²⁺, high dispersibility of CaS nanoparticles in hydrogels, high hydrophilic and swelling ability of hydrogel, high diffusion rate of reactant in hydrogel, and inhibited binding possibility of photogenerated electron-hole pairs. Since CdS/HGel_PDAM has excellent hydrogen production efficiency and ease recovery property, it will be a potential photocatalyst for photocatalytic reactions.