Light Photocatalytic Hydrogen Production Activity Research Articles

Synthesis and behaviors of g-C3N4 coupled with LaxCo3-xO4 nanocomposite for improved photocatalytic activeity and stability under visible light

Novel LaxCo3-xO4 doped graphitic carbon nitride photocatalysts were synthesized via a microwave-assisted hydrothermal method. The rate of H2 production varies with the ratio of the La/Co doped on g-C3N4, the highest hydrogen production activity is 63.12 μmol h−1 when the molar ratio of La/Co is 10% in the nanohybrid. The nanohybrid photocatalyst exhibited activity for hydrogen generation is higher than that of pure g-C3N4 by up to 6 times under visible light irradiation. The synergistic effect of g-C3N4 and LaxCo3-xO4 leads to efficient separation of the photogenerated charge carriers, as a result of enhances the visible light photocatalytic hydrogen production activity of the photocatalysts. The effective coupling of LaxCo3-xO4 on g-C3N4 can efficiently extend the light absorption of the g-C3N4 to visible region and enhance the charge separation efficiency of g-C3N4/LaxCo3-xO4 composites. The possible photocatalytic mechanism of the g-C3N4/LaxCo3-xO4 photocatalysts is inferred by XPS, X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM), photoluminescence spectroscopy (PL), and electrochemical workstation.

Hybridizing MoS2 and C60 via a van der Waals heterostructure toward synergistically enhanced visible light photocatalytic hydrogen production activity

Molybdenum disulfide (MoS2) as a representative transition-metal dichalcogenide (TMD) has been extensively used as a noble-metal-free cocatalyst for photocatalytic hydrogen (H2) production, but suffers from poor photocatalytic activity due to the catalytic inactivity of its basal plane. Herein, by bounding another metal-free cocatalyst, C60, with MoS2, we report the first MoS2-C60 hybrid featuring a van der Waals heterostructure prepared via a facile and eco-friendly solid-state mechanochemical route. C60 bounding onto the edge of MoS2 nanosheets leads to the decreases of both the number of layers and the size of MoS2 nanosheets, as well as a negative shift of the conduction band minimum along with a positive shift of valance band maximum relative to the bulk MoS2 and MoS2 ball-milled without C60 (MoS2-BM). Under the optimized weight ratio of MoS2:C60 (1:1) in the raw mixture subject to ball-milling, MoS2-C60 hybrid containing 2.8 wt% C60 shows an exceptional visible light photocatalytic H2 production rate of 6.89 mmol h−1 g−1 in the presence of a photosensitizer Eosin Y (EY), which is significantly enhanced relative to the bulk MoS2 and pristine C60, both of which show almost no photocatalytic H2 activity. Thus, the synergistic enhancement of photocatalytic activities of both MoS2 and C60 is revealed.

The effect of different co-catalysts (CuO, MoS2 and Pt) on hydrogen production of Er3+:YAlO3/NaTaO3 by visible-light-induced methanol splitting

In this work, a high effective up-conversion luminescence agent (from infrared and visible light to ultraviolet light), Er3+:YAlO3, was synthesized by sol–gel method. And then, the CuO, MoS2 and Pt were adopted as co-catalysts and the NaTaO3 was used as bulk catalyst, and then the three corresponding visible-light photocatalysts, Er3+:YAlO3/CuO–NaTaO3, Er3+:YAlO3/MoS2–NaTaO3 and Er3+:YAlO3/Pt–NaTaO3, were successfully prepared by hydrothermal and direct mixing methods, respectively. Er3+:YAlO3, NaTaO3, Er3+:YAlO3/CuO–NaTaO3, Er3+:YAlO3/MoS2–NaTaO3 and Er3+:YAlO3/Pt–NaTaO3 were all characterized by X-ray diffractometer (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). The visible-light photocatalytic activities of Er3+:YAlO3/CuO–NaTaO3, Er3+:YAlO3/MoS2–NaTaO3 and Er3+:YAlO3/Pt–NaTaO3 were examined through photocatalytic hydrogen evolution from methanol aqueous solution under visible-light irradiation. The influence factors such as the contents of co-catalysts (CuO, MoS2 and Pt), heat-treated temperature and initial pH value on the visible-light photocatalytic hydrogen evolution activity of Er3+:YAlO3/CuO–NaTaO3, Er3+:YAlO3/MoS2–NaTaO3 and Er3+:YAlO3/Pt–NaTaO3 were studied. The results showed that the Er3+:YAlO3/MoS2–NaTaO3 with 0.2 wt% MoS2 in solution (pH = 6.0) with 5.0 wt% methanol displayed the highest visible light photocatalytic hydrogen production activity.

Bifunctional Modification of Graphitic Carbon Nitride with MgFe2O4 for Enhanced Photocatalytic Hydrogen Generation.

To gain high photocatalytic activity for hydrogen evolution, both charge separation efficiency and surface reaction kinetics must be improved, and together would be even better. In this study, the visible light photocatalytic hydrogen production activity of graphitic carbon nitride (g-C3N4) was greatly enhanced with MgFe2O4 modification. It was demonstrated that MgFe2O4 could not only extract photoinduced holes from g-C3N4, leading to efficient charge carrier separation at the g-C3N4/MgFe2O4 interface, but also act as an oxidative catalyst accelerating the oxidation reaction kinetics at g-C3N4 surface. This dual function of MgFe2O4 thus contributed to the great improvement (up to three-fold) in photocatalytic activity for hydrogen generation over g-C3N4/MgFe2O4 as compared to pristine g-C3N4, after loading Pt by photoreduction method. It was revealed that in the Pt/g-C3N4/MgFe2O4 system, the photoinduced electrons and holes were entrapped by Pt and MgFe2O4, respectively, giving rise to the promoted charge separation; moreover, as evidenced by electrochemical analysis, the electrocatalysis effect of MgFe2O4 benefited the oxidation reaction at g-C3N4 surface.

Enhanced visible light photocatalytic hydrogen production activity of CuS/ZnS nanoflower spheres

The ZnS nanoflower architectures reach a high visible light photocatalytic hydrogen production activity with the deposition of a small portion of CuS nanoparticles.

In-situ reduction synthesis of nano-sized Cu2O particles modifying g-C3N4 for enhanced photocatalytic hydrogen production

Cu2O nanoparticles (NPs) were directly formed on g-C3N4 via a one-pot in-situ reduction method. The physical and photophysical properties of these Cu2O NPs modified g-C3N4 photocatalysts were characterized to investigate the effects of Cu2O NPs on the photocatalytic activities of g-C3N4. Close contact was formed between Cu2O and g-C3N4 and the Cu2O NPs were well dispersed on g-C3N4. The visible light photocatalytic hydrogen production activity over g-C3N4 was enhanced by more than 70% with Cu2O NPs modification. It is revealed that the efficient visible light absorption and Type II band alignment induced charge separation by Cu2O NPs modification should be the key factors for improved photocatalytic performance.

Stable hydrogen generation from vermiculite sensitized by CdS quantum dot photocatalytic splitting of water under visible-light irradiation.

CdS quantum dot/vermiculite (CdS/VMT) nanocomposites have been synthesized via a facile one-step method and characterized by X-ray diffraction, UV-vis diffuse reflection spectroscopy, X-ray photoelectron spectroscopy, and transmission electron microscopy. The photocatalytic hydrogen generation activities of these samples were evaluated using Na2S and Na2SO3 as sacrificial reagents in water under visible-light illumination (λ ≥ 420 nm). The most important aspect of this work is the use of natural products (VMT) as host photocatalysts. The effect of CdS content on the rate of visible light photocatalytic hydrogen generation was investigated for different CdS loadings. The synergistic effect of VMT and CdS quantum dots (QDs) leads to efficient separation of the photogenerated charge carriers and, consequently, enhances the visible light photocatalytic hydrogen production activity of the photocatalyst. The CdS/VMT composite with an optimal ratio of 5% exhibits the highest hydrogen evolution rate of 92 μmol h(-1) under visible light irradiation and the highest apparent quantum efficiency of 17.7% at 420 nm. A possible photocatalytic mechanism of the CdS/VMT nanocomposite is proposed and corroborated by photoelectrochemical curves.