scholarly journals A Facile and Waste-Free Strategy to Fabricate Pt-C/TiO2Microspheres: Enhanced Photocatalytic Performance for Hydrogen Evolution

2014 ◽  
Vol 2014 ◽  
pp. 1-9 ◽  
Author(s):  
Hui Li ◽  
Xiaoyan Zhang ◽  
Xiaoli Cui
Keyword(s):  
Hydrogen Evolution ◽  
Photoelectron Spectroscopy ◽  
Hydrogen Generation ◽  
Synthesis Method ◽  
Diffraction Field ◽  
Light Illumination ◽  
Thermal Synthesis ◽  
X Ray ◽  
Photocatalytic Hydrogen Generation ◽  
Transmission Electron

A facile and waste-free flame thermal synthesis method was developed for preparing Pt modified C/TiO2microspheres (Pt-C/TiO2). The photocatalysts were characterized with X-ray diffraction, field emission scanning electron microscopy, transmission electron microscope, ultraviolet-visible (UV-vis) diffuse reflectance spectra, X-ray photoelectron spectroscopy, and thermogravimetry analysis. The photocatalytic activity was evaluated by hydrogen evolution from water splitting under UV-vis light illumination. Benefitting from the electron-hole separation behavior and reduced overpotential of H+/H2, remarkably enhanced hydrogen production was demonstrated and the photocatalytic hydrogen generation from 0.4 wt% Pt-C/TiO2increased by 22 times. This study also demonstrates that the novel and facile method is highly attractive, due to its easy operation, requiring no post treatment and energy-saving features.

scholarly journals MoS2-Carbon Inter-overlapped Structures as Effective Electrocatalysts for the Hydrogen Evolution Reaction

Nanomaterials ◽  
2020 ◽  
Vol 10 (7) ◽  
pp. 1389
Author(s):  
Po-Chia Huang ◽  
Chia-Ling Wu ◽  
Sanjaya Brahma ◽  
Muhammad Omar Shaikh ◽  
Jow-Lay Huang ◽  
...  
Keyword(s):  
Hydrogen Evolution ◽  
Hydrogen Evolution Reaction ◽  
Photoelectron Spectroscopy ◽  
Active Sites ◽  
Hydrogen Generation ◽  
Interlayer Spacing ◽  
Monolayer Mos2 ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron

The ability to generate hydrogen in an economic and sustainable manner is critical to the realization of a future hydrogen economy. Electrocatalytic water splitting into molecular hydrogen using the hydrogen evolution reaction (HER) provides a viable option for hydrogen generation. Consequently, advanced non-precious metal based electrocatalysts that promote HER and reduce the overpotential are being widely researched. Here, we report on the development of MoS2-carbon inter-overlapped structures and their applicability for enhancing electrocatalytic HER. These structures were synthesized by a facile hot-injection method using ammonium tetrathiomolybdate ((NH4)2MoS4) as the precursor and oleylamine (OLA) as the solvent, followed by a carbonization step. During the synthesis protocol, OLA not only plays the role of a reacting solvent but also acts as an intercalating agent which enlarges the interlayer spacing of MoS2 to form OLA-protected monolayer MoS2. After the carbonization step, the crystallinity improves substantially, and OLA can be completely converted into carbon, thus forming an inter-overlapped superstructure, as characterized in detail using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). A Tafel slope of 118 mV/dec is obtained for the monolayer MoS2-carbon superstructure, which shows a significant improvement, as compared to the 202 mV/dec observed for OLA-protected monolayer MoS2. The enhanced HER performance is attributed to the improved conductivity along the c-axis due to the presence of carbon and the abundance of active sites due to the interlayer expansion of the monolayer MoS2 by OLA.

scholarly journals Synthesis of Ce1−xPdxO2−δ Solid Solution in Molten Nitrate

Catalysts ◽  
2020 ◽  
Vol 10 (6) ◽  
pp. 640
Author(s):  
Hideaki Sasaki ◽  
Keisuke Sakamoto ◽  
Masami Mori ◽  
Tatsuaki Sakamoto
Keyword(s):  
Electron Microscopy ◽  
Solid Solution ◽  
Solid Solutions ◽  
Photoelectron Spectroscopy ◽  
Synthesis Method ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Co Precipitation ◽  
Ionic States

CeO2-based solid solutions in which Pd partially substitutes for Ce attract considerable attention, owing to their high catalytic performances. In this study, the solid solution (Ce1−xPdxO2−δ) with a high Pd content (x ~ 0.2) was synthesized through co-precipitation under oxidative conditions using molten nitrate, and its structure and thermal decomposition were examined. The characteristics of the solid solution, such as the change in a lattice constant, inhibition of sintering, and ionic states, were examined using X-ray diffraction (XRD), scanning electron microscopy–energy-dispersive X-ray spectroscopy (SEM−EDS), transmission electron microscopy (TEM)−EDS, and X-ray photoelectron spectroscopy (XPS). The synthesis method proposed in this study appears suitable for the easy preparation of CeO2 solid solutions with a high Pd content.

scholarly journals Synthesis and Characterization of K-Ta Mixed Oxides for Hydrogen Generation in Photocatalysis

2012 ◽  
Vol 2012 ◽  
pp. 1-7 ◽  
Author(s):  
Beata Zielińska ◽  
Ewa Mijowska ◽  
Ryszard J. Kalenczuk
Keyword(s):  
Diffuse Reflectance ◽  
Hydrogen Generation ◽  
Mixed Oxides ◽  
X Ray Diffraction ◽  
X Ray ◽  
Raman Spectroscopic ◽  
Photocatalytic Hydrogen Generation ◽  
Irregular Structure ◽  
Transmission Electron

K-Ta mixed oxides photocatalysts have been prepared by impregnation followed by calcination. The influence of the reaction temperature (450°C–900°C) on the phase formation, crystal morphology, and photocatalytic activity in hydrogen generation of the produced materials was investigated. The detailed analysis has revealed that all products exhibit high crystallinity and irregular structure. Moreover, two different crystal structures of potassium tantalates such as KTaO3and K2Ta4O11were obtained. It was also found that the sample composed of KTaO3and traces of unreacted Ta2O5(annealed at 600°C) exhibits the highest activity in the reaction of photocatalytic hydrogen generation. The crystallographic phases, optical and vibronic properties were examined by X-ray diffraction (XRD) and diffuse reflectance (DR) UV-vis and resonance Raman spectroscopic methods, respectively. Morphology and chemical composition of the produced samples were studied using a high-resolution transmission electron microscope (HR-TEM) and an energy dispersive X-ray spectrometer (EDX) as its mode.

scholarly journals Amorphous Ni x Co y P-supported TiO2 nanotube arrays as an efficient hydrogen evolution reaction electrocatalyst in acidic solution

2019 ◽  
Vol 10 ◽  
pp. 62-70 ◽  
Author(s):  
Yong Li ◽  
Peng Yang ◽  
Bin Wang ◽  
Zhongqing Liu
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Hydrogen Evolution ◽  
Hydrogen Evolution Reaction ◽  
Photoelectron Spectroscopy ◽  
Electrochemical Impedance ◽  
Nanotube Arrays ◽  
Active Surface Area ◽  
X Ray ◽  
Transmission Electron

Bimetallic phosphides have been attracting increasing attention due to their synergistic effect for improving the hydrogen evolution reaction as compared to monometallic phosphides. In this work, NiCoP modified hybrid electrodes were fabricated by a one-step electrodeposition process with TiO2 nanotube arrays (TNAs) as a carrier. X-ray diffraction, transmission electron microscopy, UV–vis diffuse reflection spectroscopy, X-ray photoelectron spectroscopy and scanning transmission electron microscopy/energy-dispersive X-ray spectroscopy were used to characterize the physiochemical properties of the samples. The electrochemical performance was investigated by cyclic voltammetry, linear sweep voltammetry, and electrochemical impedance spectroscopy. We show that after incorporating Co into Ni–P, the resulting Ni x Co y P/TNAs present enhanced electrocatalytic activity due to the improved electron transfer and increased electrochemically active surface area (ECSA). In 0.5 mol L−1 H2SO4 electrolyte, the Ni x Co y P/TNAs (x = 3.84, y = 0.78) demonstrated an ECSA value of 52.1 mF cm−2, which is 3.8 times that of Ni–P/TNAs (13.7 mF cm−2). In a two-electrode system with a Pt sheet as the anode, the Ni x Co y P/TNAs presented a bath voltage of 1.92 V at 100 mA cm−2, which is an improvment of 79% over that of 1.07 V at 10 mA cm−2.

scholarly journals Promising Cr-Doped ZnO Nanorods for Photocatalytic Degradation Facing Pollution

2021 ◽  
Vol 12 (1) ◽  
pp. 34
Author(s):  
Fatemah. H. Alkallas ◽  
Amira Ben Gouider Trabelsi ◽  
Ramzi Nasser ◽  
Susana Fernandez ◽  
Ji-Ming Song ◽  
...  
Keyword(s):  
Photoelectron Spectroscopy ◽  
Zno Nanorods ◽  
Hexagonal Structure ◽  
Oh Radicals ◽  
Light Illumination ◽  
Interstitial Oxygen ◽  
X Ray Diffraction ◽  
Kinetic Rate Constant ◽  
X Ray ◽  
Transmission Electron

Chromium (Cr)-doped zinc oxide (ZnO) nanorods with wurtzite hexagonal structure were prepared through a thermal decomposition technique. The concentration effect of the Cr doping on the structural, morphological, and optical properties of the ZnO nanorods was established by correlating various measurements: transmission electron microscopy (TEM), photoluminescence (PL), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and several UV-visible studies. The obtained nanorods were investigated as photocatalysts for the photodegradation process of methyl orange (MO), under UV-vis light illumination. Different weights and time intervals were studied. A 99.8% photodegradation of MO was obtained after 100 min in the presence of 1 wt.% Cr III acetate hydroxide and zinc acetate dehydrate “ZnO-Cr1”. The kinetic rate constant of the reaction was found to be equal to 4.451 × 10−2 min−1 via a pseudo-first order rate model. Scavenger radicals demonstrated the domination of OH• radicals by those of O2•− superoxide species during the photodegradation. The interstitial oxygen site Oi is proposed to play a key role in the generation of holes in the valence band under visible irradiation. The ZnO-Cr1 photocatalyst displayed good cycling stability and reusability.

TPPH/g-C3N4 Nanohybrids Constructed with Surfactant-Assisted Co-assembly for Photocatalytic Hydrogen Generation

NANO ◽  
2021 ◽  
Author(s):  
Ye Shang ◽  
Manfei Lv ◽  
Songtian Li
Keyword(s):  
Hydrogen Production ◽  
Photoelectron Spectroscopy ◽  
Hydrogen Generation ◽  
Separation Efficiency ◽  
Electrochemical Impedance ◽  
Production Capacity ◽  
Noncovalent Interaction ◽  
Full Spectrum ◽  
X Ray ◽  
Photocatalytic Hydrogen Generation

A new type of pure organic 5,10,15,20-tetra (4-hydroxyphenyl) porphyrin (TPPH)/[Formula: see text]-C3N4 nanohybrid was prepared to expand the light absorption range of graphitic carbon nitride materials. The morphology and structure of the composites were systematically characterized by scanning electron microscope, transmission electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy. Results show that after the introduction of TPPH, the visible light area optical absorption of the composite sample increased significantly under the noncovalent interaction of TPPH and [Formula: see text]-C3N4, and the electrochemical impedance spectroscopy and [Formula: see text]–[Formula: see text] measurements confirmed the improved charge separation efficiency of the sample and showed excellent photocatalytic hydrogen production capacity. Under full spectrum irradiation, the hydrogen production of 1.67% TPPH/[Formula: see text]-C3N4 without adding co-catalyst reached 10.87[Formula: see text]mmol[Formula: see text][Formula: see text], about 2.68 times that of pure [Formula: see text]-C3N4 (4.06[Formula: see text]mmol[Formula: see text][Formula: see text]), which showed effective promotion of the electron transfer between TPPH and [Formula: see text]-C3N4.

scholarly journals Electrochemical Hydrogen Evolution over Hydrothermally Synthesized Re-Doped MoS2 Flower-Like Microspheres

Molecules ◽  
2019 ◽  
Vol 24 (24) ◽  
pp. 4631 ◽  
Author(s):  
Juan Aliaga ◽  
Pablo Vera ◽  
Juan Araya ◽  
Luis Ballesteros ◽  
Julio Urzúa ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Hydrogen Evolution ◽  
Photoelectron Spectroscopy ◽  
Charge Transfer Resistance ◽  
Chemical Analyses ◽  
X Ray Diffraction ◽  
Transfer Resistance ◽  
X Ray ◽  
Transmission Electron ◽  
Scanning Electron

In this research, we report a simple hydrothermal synthesis to prepare rhenium (Re)- doped MoS2 flower-like microspheres and the tuning of their structural, electronic, and electrocatalytic properties by modulating the insertion of Re. The obtained compounds were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). Structural, morphological, and chemical analyses confirmed the synthesis of poorly crystalline Re-doped MoS2 flower-like microspheres composed of few stacked layers. They exhibit enhanced hydrogen evolution reaction (HER) performance with low overpotential of 210 mV at current density of 10 mA/cm2, with a small Tafel slope of 78 mV/dec. The enhanced catalytic HER performance can be ascribed to activation of MoS2 basal planes and by reduction in charge transfer resistance during HER upon doping.

scholarly journals Novel Route to Obtain Carbon Self-Doped TiO2 Mesoporous Nanoparticles as Efficient Photocatalysts for Environmental Remediation Processes under Visible Light

Materials ◽  
2019 ◽  
Vol 12 (20) ◽  
pp. 3349 ◽  
Author(s):  
Pablo A. Ochoa Rodríguez ◽  
Tamara B. Benzaquén ◽  
Gina A. Pecchi ◽  
Sandra G. Casuscelli ◽  
Verónica R. Elías ◽  
...  
Keyword(s):  
Photoelectron Spectroscopy ◽  
Environmental Remediation ◽  
Synthesis Method ◽  
Mesoporous Structure ◽  
Acid Orange 7 ◽  
X Ray Diffraction ◽  
Visible Radiation ◽  
X Ray ◽  
Transmission Electron ◽  
Adsorption Desorption

Titanium dioxide materials were synthesized using two different methods. The samples were characterized by X-ray diffraction (XRD), UV–Visible diffusion reflectance spectroscopy (UV-Vis DR), Raman spectroscopy, N2 adsorption/desorption, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), transmission electron spectroscopy (TEM) and X-ray photoelectron spectroscopy (XPS). Although both kind of materials were found to have mesoporous structure and anatase crystalline phase, one of them was obtained from a synthesis method that does not involve the use of surfactants, and therefore, does not require calcination at high temperatures. This implies that the synthesized solid was self-doped with carbon species, coming only from the same source used for titanium. Then, the relationship between the presence of these species, the final calcination temperature, and the photocatalytic activity of the solids was studied in terms of the degradation and mineralization of an Acid Orange 7 aqueous solution, under visible radiation. A photosensitizing effect caused by the non-metal presence, that allows the solid to extend its absorption range, was found. Hence, a novel route to prepare C-modified photoactive mesoporous TiO2, simpler and cheaper, where neither a template nor an external carbon source is used, could be performed.

scholarly journals Comparative Study of the Photocatalytic Hydrogen Evolution over Cd1−xMnxS and CdS-β-Mn3O4-MnOOH Photocatalysts under Visible Light

Nanomaterials ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 355
Author(s):  
Ksenia O. Potapenko ◽  
Anna Yu. Kurenkova ◽  
Andrey V. Bukhtiyarov ◽  
Evgeny Yu. Gerasimov ◽  
Svetlana V. Cherepanova ◽  
...  
Keyword(s):  
Solid Solution ◽  
Visible Light ◽  
Hydrogen Evolution ◽  
Photoelectron Spectroscopy ◽  
Diffuse Reflectance Spectroscopy ◽  
Diffraction Method ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Manganese Salts

A series of solid solutions of cadmium and manganese sulfides, Cd1−xMnxS (x = 0–0.35), and composite photocatalysts, CdS-β-Mn3O4-MnOOH, were synthesized by precipitation with sodium sulfide from soluble cadmium and manganese salts with further hydrothermal treatment at 120 °C. The obtained photocatalysts were studied by the X-ray diffraction method (XRD), UV-vis diffuse reflectance spectroscopy, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and N2 low temperature adsorption. The photocatalysts were tested in hydrogen production using a Na2S/Na2SO3 aqueous solution under visible light (λ = 450 nm). It was shown for the first time that both kinds of photocatalysts possess high activity in hydrogen evolution under visible light. The solid solution Cd0.65Mn0.35S has an enhanced photocatalytic activity due to its valence and conduction band position tuning, whereas the CdS-β-Mn3O4-MnOOH (40–60 at% Mn) samples were active due to ternary heterojunction formation. Further, the composite CdS-β-Mn3O4-MnOOH photocatalyst had much higher stability in comparison to the Cd0.65Mn0.35S solid solution. The highest activity was 600 mmol g−1 h−1, and apparent quantum efficiency of 2.9% (λ = 450 nm) was possessed by the sample of CdS-β-Mn3O4-MnOOH (40 at% Mn).

Photocatalytic H2 production on trititanate nanotubes coupled with CdS and platinum nanoparticles under visible light: revisiting H2 production and material durability

2017 ◽  
Vol 198 ◽  
pp. 419-431 ◽  
Author(s):  
Hyunwoong Park ◽  
Hsin-Hung Ou ◽  
Minju Kim ◽  
Unseock Kang ◽  
Dong Suk Han ◽  
...  
Keyword(s):  
Visible Light ◽  
Photoelectron Spectroscopy ◽  
H2 Production ◽  
X Ray Diffraction ◽  
Experimental Conditions ◽  
Thermal Synthesis ◽  
X Ray ◽  
Transmission Electron ◽  
Detailed Surface ◽  
Efficient Charge

The photocatalytic production of molecular hydrogen (H2) on ternary composites of Pt, CdS, and sodium trititanate nanotubes (NaxH2−xTi3O7, TNTs) is examined in an aqueous 2-propanol (IPA) solution (typically 5 vol%) at a circum-neutral pH under visible light (λ > 420 nm). The H2 production rates are dependent on the Pt-loading level, and the optimum production rate in the Pt/CdS/TNTs is approximately six times higher than that in Pt/CdS/TiO2. A D2O solution containing 5 vol% IPA leads only to the production of D2 molecules, whereas increasing the IPA amount to 30 vol% leads to the production of DH molecules. This indicates that the Pt/CdS/TNTs composites enable H2 production via true water splitting under our typical experimental conditions. X-ray photoelectron spectroscopy (XPS) analyses of the as-synthesized Pt/CdS/TNTs and those used for 6 and 12 h show that metallic Pt on the CdS/TNTs is less susceptible to oxidation than Pt on CdS/TiO2. In addition, photocorrosion of CdS (i.e., sulfate formation) is significantly inhibited during the photocatalytic H2 production reactions in the Pt/CdS/TNTs because of the efficient charge transfer via the TNTs framework. The Pt/CdS/TNTs samples are thermally more stable than Pt/CdS/TiO2 and CdS/TNTs, effectively inhibiting the formation of CdO during the thermal synthesis. Detailed surface characterizations of the as-synthesized ternary composites are performed using X-ray diffraction, transmission electron microscopy, energy dispersive spectroscopy, and XPS.

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