Which Is More Efficient in Promoting the Photocatalytic H2 Evolution Performance of g-C3N4: Monometallic Nanocrystal, Heterostructural Nanocrystal, or Bimetallic Nanocrystal?

Generally, an excellent cocatalyst could promote the photocatalytic hydrogen (H₂) evolution performance of g-C₃N₄ significantly. Herein, a superior cocatalyst of gold-platinum (AuPt) nanocrystal with an ultralow content of Pt was successfully decorated on carbon self-doping g-C₃N₄ nanosheets (AuPt/CCN) via a facile photodeposition route. The corresponding Pt/CCN, Au/CCN, Au/Pt/CCN, and Pt/Au/CCN were also prepared for comparison. It is found that AuPt/CCN exhibits much superior photocatalytic H₂ evolution performance (1135 μmol/h) when irradiated with a 300 W Xe lamp, up to 20, 12, 5, 2, and 1.5 times that of the pristine CCN, Pt/CCN, Au/CCN, Au/Pt/CCN, and Pt/Au/CCN, respectively. The quantum efficiency (QE) of AuPt/CCN at 420 nm reaches 12.5%. The experimental and density functional theory calculation results suggested that the improved AuPt performance can be mainly ascribed to the non-plasmon-related synergistic effect of Au and Pt atoms in AuPt nanocrystal: (1) the proximity and the electronegativity difference of Au and Pt atoms in AuPt accelerate the transfer and separation of charge carriers and (2) the synergistic interaction between Pt and Au atoms optimizes the Gibbs free energy (ΔG_H*) of H* (atom) adsorption on AuPt, promoting the H₂ generation kinetics of AuPt/CCN.

COx-free hydrogen production via ammonia decomposition over mesoporous Co/Al2O3 catalysts with highly dispersed Co species synthesized by a facile method

Transition metals have been considered as potential catalysts for ammonia decomposition to produce CO_x-free hydrogen for fuel cells. However, the facile synthesis of transition metal catalysts with small size active species, high porosity and good structural stability is still a challenge in catalytic NH₃ decomposition. Herein, mesoporous Co/Al₂O₃ catalysts with various cobalt contents were synthesized by a facile modified sol-gel method. The catalyst 15CoAl with 15 at% cobalt content realizes the optimal catalytic NH₃ decomposition performance. 92% NH₃ conversion at 600 °C is achieved with a gaseous hourly space velocity (GHSV) of 24 000 cm³ g_cat^-1 h^-1 and a hydrogen formation rate of 33.9 mmol g_cat^-1 min^-1 at 600 °C is maintained after a 120 h long-duration stability test. Uniform small cobalt particles with high dispersion are well embedded into the skeleton of the mesoporous Al₂O₃ matrix. The aggregation of active cobalt species during the high temperature reaction can be effectively prevented by the mesoporous Al₂O₃ matrix due to the strong interaction between them, thus ensuring a good catalytic performance for ammonia decomposition.

Silver decorated CeO2 nanoparticles for rapid photocatalytic degradation of textile rose bengal dye

High quality silver (Ag) decorated CeO2 nanoparticles were prepared by a facile one-step chemical method. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), High resolution transmission electron microscopy (HR-TEM), fourier transform infrared spectrometer (FT-IR), electron paramagnetic resonance (EPR), X-ray photoelectron spectroscopy (XPS), UV-Visible absorption (UV-Vis), photoluminescence (PL) and thermogravimetric analysis. The decoration of Ag on CeO2 surface was confirmed by XRD, EPR and HR-TEM analysis. Harmful textile pollutant Rose Bengal dye was degraded under sunlight using the novel Ag decorated CeO2 catalyst. It was found that great enhancement of the degradation efficiency for Ag/CeO2 compared to pure CeO2, it can be ascribed mainly due to decrease in its band gap and charge carrier recombination rate. The Ag/CeO2 sample exhibited an efficient photocatalytic characteristic for degrading RB under visible light irradiation with a high degradation rate of 96% after 3 h. With the help of various characterizations, a possible degradation mechanism has been proposed which shows the effect of generation of oxygen vacancies owing to the decoration of Ag on the CeO2 surface.

Highly enhanced bifunctional electrocatalytic activity of mixed copper–copper oxides on nickel foam via composition control

Fabricating Cu₂O–CuO and CuO directly on the conducting nickel foam resulted in highly enhanced OER and HER electrocatalytic activity in an alkaline medium, respectively.

Preparation of amine functionalized g-C3N4@H/SMOF NCs with visible light photocatalytic characteristic for 4-nitrophenol degradation from aqueous solution

At ambience temperature, a facile and large-scale sonochemical synthesis route was used to synthesize graphitic carbon nitride@[Ti₄C₂₄H₃₉N₃O₂₉] metal-organic framework nanocomposites (g-C₃N₄-X@^YTi-MIL125-NH₂ NCs, where X and Y stood for the weight percentages of g - C₃N₄ and the synthesis method of Ti-MIL125-NH₂, respectively) having 2-Amino-1,4-benzenedicarboxylic acid (2-ATA) ligand with amine functional free groups. The obtained NCs were characterized by FT-IR, PXRD, FE-SEM, BET, UV-DRS, PL, EIS, and zeta potential. Moreover, g-C₃N₄-X@^YTi-MIL125-NH₂ capability to eliminate 4-nitrophenol (4-NP) contaminant from water via visible light illumination was explored. Our synthesized NCs under a facile, green ultrasonic technique (i.e. g-C₃N₄-30@^STi-MIL125-NH₂) had a higher percentage of degradation than those from hydrothermal technique (i.e. g-C₃N₄-30@^HTi-MIL125-NH₂) with degradation percentages of 75% and 57%, respectively, which resulted in effective mass transfer and separation of photo - generated charge carriers. Additionally, this higher percentage of degradation could be attributed to the larger surface area and unique morphology of the ultrasonically synthesized particles with higher homogeneity and better and non-agglomerated distribution. Furthermore, excellent reusability and stability were observed for g-C₃N₄-30@^STi-MIL125-NH₂. We also explored the role of some scavengers in the degradation procedures to investigate the effect of active species. The experimental results were used to describe the suggested mechanism capability for improved photocatalysis.

Facile synthesis of ZnFe2O4 photocatalysts for decolourization of organic dyes under solar irradiation

ZnFe₂O₄ was fabricated by a simple solution-combustion method. The structural, optical and electronic properties are investigated by XRD, TEM, FESEM, UV-vis DRS, PL, FTIR and photocurrent measurements. The photocatalytic activity of the prepared material is studied with regard to the degradation of rhodamine B (Rh B) and Congo red under solar irradiation. The kinetic study showed that the material exhibits zeroth and first order reaction kinetics for the degradation of Rh B and Congo red, respectively. The photocatalytic behaviour of ZnFe₂O₄ was systematically studied as a function of the activation temperature. ZnFe₂O₄ prepared at 500 °C showed the highest activity in degrading Rh B and Congo red. The highest activity of ZnFe₂O₄-500 °C correlates well with the lowest PL intensity, highest photocurrent and lowest particle size.

The effect of sulfate pre-treatment to improve the deposition of Au-nanoparticles in a gold-modified sulfated g-C3N4 plasmonic photocatalyst towards visible light induced water reduction reaction

In continuation of our earlier work on Au-g-C₃N₄ and to improve its activity further, Au incorporated sulfated carbon nitride (g-C₃N₄) has been designed by using a simple impregnation cum borohydrate reduction method for the visible light induced water reduction reaction for hydrogen generation. The photocatalysts were characterized using various instrumental methods such as PXRD, UV-Vis DRS, SEM, HR-TEM, XPS, PL and TRPL spectral analysis. Functionalisation by the -HSO₃ group and incorporation of AuNPs in the g-C₃N₄ skeleton lead to the extension of its pi-conjugated system, modification of its semiconductor properties, such as band structure engineering with a tunable bandgap, red-shift of the optical absorption band and promotion of charge migration and separation. The sulfate pre-treated g-C₃N₄ samples are supposed to have a defected surface due to oxygen vacancies, which increases the adsorption of AuNPs onto the vacant oxygen sites. Thus the AuNPs get adsorbed on the reduced surfaces, increasing the extent and effectiveness of the electronic communication between gold and the g-C₃N₄ interface. The improved photocatalytic activity could be attributed to the surface plasmon resonance (SPR) effect of AuNPs, which synergistically facilitates the photocatalysis process. The photocatalytic activity of Au-sulfated g-C₃N₄ for photocatalytic splitting of water to produce H₂ was increased 1.5 times compared to that of Au-g-C₃N₄, 2.5 times compared to that of sulphated-g-C₃N₄ and 35 times compared to that of single-phase g-C₃N₄.

In situ synthesis of novel Cu2CO3(OH)2 decorated 2D TiO2 nanosheets with efficient photocatalytic H2 evolution activity

Semiconductor-based photocatalytic hydrogen evolution from water with earth-abundant and low cost co-catalysts has attracted much attention.

Fabrication of strong bifunctional electrocatalytically active hybrid Cu–Cu2O nanoparticles in a carbon matrix

Earth-abundant copper-based hybrid Cu–Cu₂ONPs@C in the carbon matrix exhibited enhanced OER and HER catalytic activity compared to pure Cu₂O and CuNPs@C.

Visible-light-induced water reduction reaction for efficient hydrogen production by N-doped In2Ga2ZnO7 nanoparticle decorated on RGO sheets

Efficient hydrogen production over graphene-based N-doped In₂Ga₂ZnO₇ nanocomposite under visible irradiation.

Enhanced photocatalytic activities of visible-light driven green synthesis in water and environmental remediation on Au/Bi2WO6 hybrid nanostructures

Deposition of Au NPs enhances photocatalytic activity toward selective oxidation of alcohol in water and Cr(vi) reduction over Bi₂WO₆ nanosheets.

Reduced graphene oxide/InGaZn mixed oxide nanocomposite photocatalysts for hydrogen production

A series of reduced graphene oxide and indium-gallium-zinc mixed oxide (RGO/IGZ) nanocomposites were successfully synthesised by a simple one-step hydrothermal method. The as-synthesised nanocomposites were characterised by crystallographic, microscopic, and spectroscopic methods to explore the robust photocatalytic activity of the prepared materials. XRD patterns confirmed the formation of highly pure, single-phase, hexagonal In2 Ga2 ZnO7 with no impurity-related peaks. All the photocatalysts absorbed visible light as observed from the diffuse reflectance UV/Vis spectra. The electron-hole recombination is effectively minimised by the formation of an RGO/metal oxide nanocomposite, which was successfully derived from a photoluminescence (PL) study and photoelectrochemical measurements. The decoration of IGZ nanocrystals onto reduced graphene sheets leads to significant quenching of its luminescent intensity, dramatically improved photocurrent generation (33 times more than neat IGZ) and significantly enhanced photostability. The high photocatalytic activity for H2 production is explained by the strong interaction between the IGZ nanocrystals with RGO sheets, low PL intensity, high photocurrent and large surface area.

Plasmon induced nano Au particle decorated over S,N-modified TiO(2) for exceptional photocatalytic hydrogen evolution under visible light

Nano Au deposited mesoporous S,N-TiO2 (SNT) nanocomposites have been fabricated through deposition precipitation technique by employing urea as the hydrolyzing agent. To investigate the structural, optical, and electronic properties, the photocatalysts are characterized through X-ray diffraction (XRD), UV-vis diffuse reflectance spectra, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and photoelectrochemical measurements. Here in addition to the co-catalyst nature of nano Au particles, surface plasmon resonance (SPR) effect in visible region enhances the light harvestation ability as well as transfer electrons to the conduction band of SNT. Furthermore, easy channelization of photogenerated charge carriers through sulfate facilitated redox couple makes the system more potential towards H2 evolution. TEM study exhibits well interconnective morphology in the matrix which helps easy channelization of electrons in the SNT nanocomposites. The photocatalytic activities have been evaluated for hydrogen generation under the irradiation of visible light and an enhanced activity has been observed for the Au promoted SNT due to the presence of nano Au particles, that is, 3.5 nm. The hydrogen generation activity of 3Au-SNT is nearly 9 times higher than that of neat SNT, and the energy conversion efficiency was found to be 17.6 %.

Synergistic contributions by decreasing overpotential and enhancing charge-transfer in α-Fe2O3/Mn3O4/graphene catalysts with heterostructures for photocatalytic water oxidation

Proposed mechanism of oxygen evolution from α-Fe₂O₃/Mn₃O₄-1/rGO-3 photocatalyst.