Mechanistic insights into tandem amine-borane dehydrogenation and alkene hydrogenation catalyzed by [Pd(NHC)(PCy3)]

The mechanism of tandem dimethylamine-borane (NHMe₂BH₃, DMAB) dehydrogenation and alkene hydrogenation catalyzed by [Pd(NHC)(PMe₃)] are investigated by density functional theory (DFT) calculations [NHC = N,N′-bis(2,6-diisopropylphenyl) imidazole-2-ylidene]. Four possible DMAB dehydrogenation mechanisms have been carefully investigated involving concerted BH/NH activation, sequential BH/NH activation, sequential NH/BH activation, and proton transfer mechanism. DFT studies show that the NH proton transfers to ligated carbene carbon and sequential CH/BH activation is the most kinetically favorable pathway with the lowest activation barrier of 23.8 kcal/mol. For hydrogenation, it was found that a trans-dihydride Pd(II) complex, [Pd(H)₂(NHC)(PMe₃)], formed in the dehydrogenation process, serves as an effective catalyst for reduction of trans-stilbene.     

Hydrogen-iodide decomposition over PdCeO2 nanocatalyst for hydrogen production in sulfur-iodine thermochemical cycle

A highly active and stable catalyst for hydrogen-iodide decomposition reaction in sulfur-iodine (SI) cycle has been prepared in the form of PdCeO₂ nanocatalyst by sol-gel method with different calcination temperatures (300 °C, 500 °C, and 700 °C). XRD and TEM confirmed a size around 6–8 nm for PdCeO₂ particles calcined at 300 °C. Raman study revealed large number oxygen vacancies in PdCeO₂-300 when compared to PdCeO₂-500 and PdCeO₂-700. With increase in calcination temperature, the average particle size increased whereas the specific surface area and number of oxygen vacancies decreased. Hydrogen-iodide catalytic-decomposition was carried out in the temperature range of 400°C–550 °C in a quartz-tube, vertical, fixed-bed reactor with 55 wt % aqueous hydrogen-iodide feed over PdCeO₂ catalyst using nitrogen as a carrier gas. PdCeO₂-300 showed hydrogen-iodide conversion of 23.3%, which is close to the theoretical equilibrium conversion of 24%, at 550 °C. It also showed a reasonable stability with a time-on-stream of 5 h.     

Mesocrystalline Ta2O5 nanosheets supported PdPt nanoparticles for efficient photocatalytic hydrogen production

We successfully synthesized mesocrystalline Ta₂O₅ nanosheets supported bimetallic PdPt nanoparticles by the photo-reduction method. The as-prepared mesocrystalline Ta₂O₅ nanosheets in this work showed amazing visible-light absorption, mainly because of the formation of oxygen vacancy defects. And the as-prepared bimetallic PdPt/mesocrystalline Ta₂O₅ nanaosheets also showed highly enhanced UV–Vis light absorption and highly improved photocatalytic activity for hydrogen production in comparison to that of commercial Ta₂O₅, mesocrystalline Ta₂O₅ nanosheets, Pd/mesocrystalline Ta₂O₅ nanosheets and Pt/mesocrystalline Ta₂O₅ nanosheets. The highest photocatalytic hydrogen production rate of PdPt/mesocrystalline Ta₂O₅ nanaosheets was 21529.52 g^?1 h^?1, which was about 21.2 times of commercial Ta₂O₅, and the apparent quantum efficiency of PdPt/mesocrystalline Ta₂O₅ nanaosheets for hydrogen production was about 16.5% at 254 nm. The highly enhanced photocatalytic activity was mainly because of the significant roles of PdPt nanoparticles for accelerating the charge separation and transport upon illumination. The as-prepared PdPt/mesocrystalline Ta₂O₅ nanaosheets in this work could serve as an efficient photocatalyst for green energy production.     

Efficient visible-light-driven hydrogen evolution over ternary MoS2/PtTiO2 photocatalysts with low overpotential

By surface-decorating PtTiO₂ hybrid catalyst with MoS₂ nanosheets, we prepared a new MoS₂/PtTiO₂ ternary system as high-performance photocatalysts. The ternary MoS₂/PtTiO₂ outperforms both the binary MoS₂TiO₂ and PtTiO₂ systems in photocatalytic hydrogen evolution with an AQY (apparent quantum yield) value of 12.54% at 420 nm, owing to the unique ternary design that creates more efficient electron transport path and electron-hole separation mechanism. Electrochemical characterization showed that the MoS₂/PtTiO₂ ternary electrode afford an efficient pathway of photo-excited electrons from TiO₂ to surface-decorated Pt nanoparticles using MoS₂ and internal Pt nanoparticles as bridges, thus significantly promoting electron transfer, reducing the system overpotential and leading to the activation of more reactive sites. This internal electron transfer pathway (TiO₂ → Pt (internal) → MoS₂ → Pt (surface)) eliminates the need of other metal cocatalysts because the Pt nanoparticles play two roles of storing the conduction band electrons of TiO₂ and acting as co-catalyst for reduction of protons to hydrogen. This unique ternary metal-semiconductor heterojunction for efficient photocatalytic hydrogen evolution provides a meaningful reference for reasonable design of other hybrid photocatalysts.     

Preparation and performances of CuCo spinel coating on ferritic stainless steel for solid oxide fuel cell interconnect

A compact and adherent CoCu spinel coating on ferritic stainless steel was developed by electroplating a CoCu alloy layer followed by oxidation. The CoCu alloy was oxidized into a three-layer structure consisted of a thinner CuO outer layer, a middle thicker Cu_0.92Co_2.08O₄ layer and an inner Co₃O₄ layer after an oxidation treatment of 2 h at 800 °C in air. The three-layer oxide structure was transformed into a double-layer scale with a (Co,Cr,Cu,Mn,Fe)₃O₄ spinel outer layer and an inner Cr-rich oxide layer after an oxidation of 500 h at 800 °C in air. The CuCo coating enhanced the oxidation resistance of the alloy and served as a diffusion barrier against the outward migration of Cr elements. Meanwhile, the area specific resistance (ASR) of the scale for the CuCo coated alloy was significantly lower than that for the bare sample.     

Supercapacitor with superior electrochemical properties derived from symmetrical manganese oxide-carbon fiber coated with polypyrrole

A supercapacitor electrode comprising conducting polypyrrole (PPy) coated on manganese oxide-carbon fiber (CNFMnO₂) was successfully synthesized using electrospinning, followed by carbonization and in-situ polymerization. A non-uniform distribution of PPy on the surface of CNFMnO₂ was observed via FESEM analysis. The chemical bonding of CNFMnO₂/PPy and the valence state of manganese were revealed via FTIR, Raman spectroscopy, XRD and XPS measurements. CNFMnO₂/PPy composite possessed high specific capacitance and specific energy of 315.80 Fg^?1 and 13.68 Wh/kg, respectively. In addition, good electrochemical reversibility was proven upon CNFMnO₂/PPy even at higher sweep rate (5–200 mV/s). Moreover, this one-dimensional electrode achieved an excellent long-term cycling stability (82.46%) over 2000 CV cycles with low charge transfer resistance (4.61 Ω). The modification of CNFMnO₂/PPy contributes to good synergistic effects among the material which improve the electrochemical behavior of manganese oxide-based fiber composite for future supercapacitor.     

Achieving the dehydriding reversibility and elevating the equilibrium pressure of YFe2 alloy by partial Y substitution with Zr

To overcome the hydrogen-induced amorphization and phase disproportionation in the fast de-/hydrogenation of YFe₂, the alloying of partial substituting Y with Zr was carried out to obtain Y_1?xZr_xFe₂ (x = 0.1, 0.2, 0.3, 0.5) alloys. All YZrFe alloys remained single C15 Laves phase structure at states of as-annealed, hydrogenated and dehydrogenated. With the increasing of Zr content, the YZrFe alloys showed the decrease in the lattice constants and hydrogenation capacity, but the increase in the dehydrogenation capacity and dehydriding equilibrium pressure. The alloy Y_0.9Zr_0.1Fe₂ showed maximum initial hydrogenation capacity of 1.87 wt% H, while the alloy Y_0.5Zr_0.5Fe₂ showed highest desorption capacity of 1.26 wt% with obvious dehydriding plateau. Based on experiment analysis and first principle calculation of binding energy, the great improvement in the dehydriding thermodynamics for YZrFe alloys is attributed to the change in the unit cell volume, electron concentration and stability of hydrides due to the Zr substitution.     

One-pot synthesis of ultrasmall PtAg nanoparticles decorated on graphene as a high-performance catalyst toward methanol oxidation

A one-pot synthesis method is utilized for the fabrication of ultrasmall platinum-silver nanoparticles decorated on graphene (PtAg/G) catalyst. This method has several advantages such as inexpensiveness, simplicity, low temperature, surfactant free, reductant free, being environmentally friendly and greenness. In this work, graphene and silver formate were dispersed in ultrapure water in an ultrasonic bath at 25 °C followed by through a galvanic displacement reaction; to prepare PtAg/G, PtCl₂ was added to the suspension under mild stirring condition. The morphology, crystal structure and chemical compositions of the as-fabricated PtAg/G and Pt/C catalysts were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD) and Energy dispersive X-ray spectroscopy (EDS) techniques. Electrochemical techniques, including cyclic voltammetry (CV) and chronoamperometry (CA) measurements were used to analyze the electrochemical activity of the PtAg/G and Pt/C catalysts. The TEM images illustrate the uniform distribution of ultrasmall PtAg nanoparticles with the average size of 2–3 nm on the graphene nanosheets. The PtAg/G promoted the current density 2.46 times as much as Pt/C with a negative shift in onset oxidation potential and peak potential for oxidation reaction of methanol. Besides, the novel PtAg/G catalyst shows large electrochemically active surface area, lower apparent activation energy, and higher levels of durability in comparison to the Pt/C catalyst for the oxidation of methanol. The PtAg/G catalyst depicts extraordinary catalytic performance and stability to those of the Pt/C catalyst toward methanol oxidation in alkaline media.     

Effective excitons separation on graphene supported ZrO2TiO2 heterojunction for enhanced H2 production under solar light

A novel photocatalyst comprises of ZrO₂TiO₂ immobilized on reduced graphene oxide (rGO) – a ternary heterojunction (ZrO₂TiO₂/rGO) was synthesized by using facile chemical method. The nanocomposite was prepared with a strategy to achieve better utilization of excitons for catalytic reactions by channelizing from metal oxide surfaces to rGO support. TEM and XRD analysis results revealed the heterojunction formed between ZrO₂ and single crystalline anatase TiO₂. The mesoporous structure of ZrO₂TiO₂ was confirmed using BET analysis. The red shift in absorption edge position of ZrO₂TiO₂/rGO photocatalyst was characterized by using diffuse reflectance UV–Visible spectra. ZrO₂TiO₂/rGO showed greater interfacial charge transfer efficiency than ZrO₂TiO₂, which was evidenced by well suppressed PL intensity and high photocurrent of ZrO₂TiO₂/rGO. The suitable band gap of 1.0 wt% ZrO₂TiO₂/rGO facilitated the utilization of solar light in a wide range by responding to the light of energy equal to as well as greater than 2.95 eV by the additional formation of excited high-energy electrons (HEEs). ZrO₂TiO₂/rGO showed the enhanced H₂ production than TiO₂/rGO, which revealed the role of ZrO₂ for the effective charge separation at the heterojunction and the solar light response. The optimum loading of 1.0 wt% of ZrO₂ and rGO on TiO₂ showed the highest photocatalytic performance (7773 μmolh^?1$g_{cat}^{?1}$) for hydrogen (H₂) production under direct solar light irradiation.     

Ni/MgOAl2O3 catalyst derived from modified [Ni,Mg,Al]-LDH with NaOH for CO2 reforming of methane

[Ni,Mg,Al]-layered double hydroxide (LDH) was modified with NaOH solution to prepare the LDH-derived Ni/MgOAl₂O₃ catalyst and characterized by X-ray diffraction, inductively coupled plasma optical emission spectrometer, scanning electron microscope, transmission electron microscopy, temperature programmed desorption of CO₂ or NH₃, N₂ adsorption, and thermogravimetry analysis, respectively. The resultant Ni/MgOAl₂O₃ catalysts were used for CO₂ reforming of CH₄. The results showed that the concentration of NaOH solution has an obvious effect on the structure of LDH and catalytic performances of the resultant nickel-based catalysts. Aluminum species in LDH was partly dissolved with increasing NaOH solution concentration, resulting in the increase of [M²⁺/M³⁺] molar ratio and the interlayer spacing of modified LDHs. The surface area and pore volume, especially mesoporous surface area and pore volume, were improved compared with parent [Ni,Mg,Al]-LDH, and the catalytic activity of the resultant Ni/MgOAl₂O₃ catalyst in CO₂ reforming of CH₄ was enhanced. NaOH concentration has a slight influence on CO₂ conversion and stability of the resultant Ni/MgOAl₂O₃ catalyst. The Ni/MgOAl₂O₃ prepared from the modified [Ni,Mg,Al]-LDH with 0.1 mol/L NaOH exhibits the best stability and anti-coke deposit ability. CH₄ and CO₂ conversions retain at about 91% and 96%, respectively, along with a H₂/CO ratio of about 0.90 after reaction of 28 h. High CO₂/CH₄ molar ratio can improve catalytic stability, resistance to coke deposit and Ni sintering of the catalyst.     

Bimetallic Pt-M electrocatalysts supported on single-wall carbon nanotubes for hydrogen and methanol electrooxidation in fuel cells applications

A series of PtRu and PtMo bimetallic catalysts were prepared via a chemical reduction method by bubbling CO to form carbonyl compounds as metal precursors. In both cases the PtRu and PtMo bimetallic electrocatalysts achieved the maximum activity when the amount of Ru and Mo in the material was 50%wt. The physicochemical characterization of the electrocatalytic materials through X-ray diffraction (XRD) and transmission electron microscopy (TEM) has determined the presence of bimetallic structures. The electrochemical characterization using cyclic voltammetry, electrochemical impedance spectroscopy (EIS) and polarization curves in Proton Exchange Membrane Fuel Cells (PEMFC) and Direct Methanol Fuel Cell (DMFC) allowed to systematically investigate the electrocatalytic activity of the synthesized materials for the electrooxidation of hydrogen and methanol. The PtRu/SWCNT electrocatalysts showed a higher current density at least 7-fold and 3-fold compared with Pt/SWCNT and PtMo/SWCNT electrocatalysts, respectively. Besides, the Pt50%–Ru50%/SWCNT exhibited a shifting to negative values in the onset potential reaction for the electrooxidation of methanol of 200 mV in comparison with Pt100%/SWCNT and Pt50%–Mo50%/SWCNT electrocatalysts. The experimental and simulated polarization curves obtained from DMFC show that PtRu/SWCNT and PtMo/SWCNT electrocatalysts exhibited higher power and current densities values compared with the Pt/SWCNT electrocatalyst. The membrane-electrode assembly (MEA) with Nafion^® and the PtRu/SWCNT electrocatalysts showed an open-circuit voltage value of 0.730 V, significantly higher than that the values for the MEAs with Pt/SWCNT (0.663 V) and PtMo/SWCNT (0.633 V), respectively.     

Hydrogen production via propane dry reforming: Carbon deposition and reaction-deactivation study

Carbon deposition during carbon dioxide reforming reaction of C₃H₈ has been studied over alumina-supported bimetallic Mo/CoNi catalysts. To better understand the carbon-induced deactivation during the reforming reaction, changes in catalyst morphology and carbon deposition kinetics were examined. Different characterization techniques were used for both fresh and rejuvenated catalysts including liquid nitrogen adsorption/desorption, chemisorption via hydrogen, ammonia and CO₂ desorption, and thermogravimetric measurement of the coked catalysts. The time dependant reaction rate profiles indicated that MoNi catalyst has higher syngas (H₂/CO) formation rates with lower CO₂ rate of consumption compared to CoNi catalyst. However, the H₂:CO ratio values were almost the same for both catalysts suggesting similarity in the product formation pathway. Conversion-time analysis showed that MoNi catalyst was more stable and active during a 72-h run while CoNi suffered noticeable deactivation after 30 h on-stream. Reaction-deactivation models implicated a higher deactivation coefficient (k_d) with activation energy of E_d = 78.1 kJ mol^?1 for the cobalt-containing Ni catalyst, while the Ni catalyst with molybdenum had a lower deactivation coefficient with smaller activation energy of just under 70 kJ mol^?1. Post-mortem analysis (TPR-TPO dual cycle and TOC) of spent catalysts confirmed that the surface of CoNi catalyst has more carbon residue than the MoNi sample which was consistent with the higher deactivation of CoNi.     

PtPd nanoparticles supported on sulfonated nitrogen sulfur co-doped graphene for methanol electro-oxidation

In this paper, sulfonated nitrogen sulfur co-doped graphene (S-NS-GR) nanocomposite, i.e., nitrogen sulfur co-doped graphene functionalized with SO₃H group as a novel catalyst support material was prepared. PtPd nanoparticles (PtPd NPs) were deposited on the surface of S-NS-GR by a facile electrochemical approach. The morphology and structure of Pd-PtNPs/S-NS-GR were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS) and electrochemical impedance spectroscopy (EIS), respectively. In addition, the electrocatalytic performance of catalyst for methanol oxidation reaction (MOR) was systematically studied by cyclic voltammetry and chronoamperometry in alkaline media. Compared with PtPd NPs supported on nitrogen sulfur co-doped graphene (Pt-PdNPs/NS-GR), the excellent performance of Pd-PtNPs/S-NS-GR is mainly ascribed to the embedding of abundant functional groups (SO₃H) into the NS-GR layers, which not only facilitate the homogeneous distribution of metal NPs, but also strengthen the interaction between metals and support material, thus improve the stability of catalyst in MOR.     

AuCu alloys deposited on titanium dioxide nanosheets for efficient photocatalytic hydrogen evolution

This work first reports AuCu alloys deposited on the surface of TiO₂ nanosheets (TiNs) to form heterojunction. A simple deposition-precipitation method was used to construct a new type of AuCu/TiNs heterostructures through gradually depositing Au and Cu nanoparticles on TiNs. Such structures served the dual advantage of constructing a heterostructure which can improve visible light absorption, and the formation of a Schottky barrier between AuCu alloys (lower Fermi level) and TiNs (higher Fermi level) which can suppress the recombination of photo-generated charge carriers to improve the overall photocatalytic activity. The mass ratio of Au and Cu in the AuCu/TiNs heterostructures and the sequence and method of their deposition are found to be the important factors which affect the photocatalytic performance. When the mass ratio of Au to Cu was determined to be 1: 1, the AuCu/TiNs heterostructure exhibited the best photocatalytic performance for hydrogen production from water splitting (over 9 times than TiNs, 1.47 times than Au/TiNs, and 1.75 times than Cu/TiNs).     

CeO2 overlapped with nitrogen-doped carbon layer anchoring Pt nanoparticles as an efficient electrocatalyst towards oxygen reduction reaction

To engineering high-efficient, sustainable and novel Pt-based composite system, a newly “Pt-oxide” based composites electrocatalyst of “CeO₂ overlapped with nitrogen-doped carbon layer anchoring Pt nanoparticles” (PtCeO₂@CN) has been fabricated. In comparison with Pt/C, the results exhibit that PtCeO₂@CN possesses a preferable methanol tolerance ability, superior stability (30000 s degradation: 35% for PtCeO₂@CN vs. 50% for Pt/C), and more positively the onset potential (16 mV) as well as half-wave potential (29 mV) towards oxygen reduction reaction. Further, the investigation shows that PtCeO₂@CN has a certain selectivity with quasi-four electron pathway (n = 3.2–3.3 e^?). This is attributed to the establishment of “nitrogen-doped carbon layer” structure, which heightens the conductivity of CeO₂, further promotes electron transfer between Pt and CeO₂, as well as strengthens the anchoring effect for Pt nanoparticles. Overall, this study would shed bright light to develop some effective Pt-oxide based composite electrocatalysts.     

Noble metal-free FeN-CNFs as an efficient electrocatalyst for oxygen reduction reaction

Carbonaceous materials containing non-precious metal atoms and doped with nitrogen have enthralled stunning attention in the field of electrochemical energy conversion systems. Herein, we demonstrated a facile method to fabricate iron and nitrogen doped carbon nanofiber (FeN-CNFs) catalyst material from ferric chloride and interfacial synthesized polyaniline (PANI) nanofibers, by carbonization process in an inert atmosphere at 800 °C. Further, synthesized material was characterized by elemental analysis and X-ray photoelectron spectroscopy (XPS) that confirms the presence of FeN bonds. The structural and morphological features are studied using various microscopy and spectroscopy techniques. The oxygen reduction reaction (ORR) activity of synthesized catalyst materials was examined by rotating disk electrode experiments in 0.1 M KOH. Among all these synthesized materials FeN-CNFs material showed enhanced ORR activity regarding current density and onset potential. Also, FeN-CNFs catalyst exhibited tolerance to methanol and durability in comparison to commercial Pt/C catalyst. The superior performance of FeN-CNFs may be attributed due to the introduction of Fe and formation of FeN bond in catalyst material.     

Rare earth metal Gd influenced defect sites in N doped TiO2: Defect mediated improved charge transfer for enhanced photocatalytic hydrogen production

In this experimental studies, we report the synthesis of TiO₂ co-doped by both cationic and anionic sites by simple sol-gel based method. All the prepared samples exhibit the anatase crystalline morphology however, showed lattice distortion caused by the displacement of Ti⁴⁺ sites by Gd³⁺. The improved visible absorption is witnessed by the Gd and N co-doping with an assured redshift in the absorption edge. The N and Gd displacement inside TiO₂ lattice accompanied by the creation of OTiN and GdOTi bonds are characterized by the X-ray photoelectron spectra. The strong resonance signal by Gd4f electrons in the electron paramagnetic resonance spectroscopy further substantiate the displacement of lattice cites of TiO₂ by Gd³⁺ ions. The longevity of the photo produced charges observed in fluorescence spectra of Gd and N co-doped TiO₂ is because of the effective transfer of charges to the defect sites. The aforementioned catalysts are tested for their capacity for the H₂ production from water splitting. The 2 wt% gadolinium and nitrogen co-doped TiO₂ has shown 10764 μmol g^?1 H₂ production which is 26 times higher than the commercial Degussa P-25 catalyst. The enhanced activity for hydrogen production can be attributed to factors such as increased absorptivity under visible light and effective charge carrier separation.     

Self-supported Ni3S2@MoS2 core/shell nanorod arrays via decoration with CoS as a highly active and efficient electrocatalyst for hydrogen evolution and oxygen evolution reactions

A hierarchically porous MoS₂ on Ni₃S₂ nanorod array on Ni foam (MoS₂/Ni₃S₂/NF) was firstly fabricated through a simple microwave-assisted hydrothermal method, and then followed by electrochemical deposition approach in which MoS₂/Ni₃S₂/Ni foam is decorated with CoS (CoSMoS₂/Ni₃S₂/NF). In contrast to conventional hydrothermal approach, microwave irradiation accelerates the synthesis of MoS₂/Ni₃S₂/Ni foam from time of >20 h–2 h. The characterization of CoSMoS₂/Ni₃S₂/NF by scanning electron microscope (SEM) and high resolution transmission electron microscope (HRTEM) indicate that a whole scale of 1D the Ni₃S₂ nanorods were hierarchically integrated with MoS₂ and CoS nanosheets. The as-synthesized CoSMoS₂/Ni₃S₂/NF hybrid not only endows the ease transport of electrons along Ni₃S₂ nanorods to Ni foam, but also accommodates maximal exposure of active edge sites to the reactants through hierarchically porous CoS doped MoS₂ nanosheets, accomplishing the promoted kinetics and activity for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). By electrochemical measurements such as linear sweep voltammetry (LSV) and electrochemical impedance spectroscope (EIS), we find that the CoSMoS₂/Ni₃S₂/NF hybrid shows markedly enhanced electrochemical performance for both HER and OER. Specifically, the optimal CoSMoS₂/Ni₃S₂/NF8C possesses the low overpotentials (η₁₀) of 85 and 225 mV at current density (|j|) of 10 mA cm^?2 in 1.0 M KOH and the small 62.3 and 46.1 mV dec^?1 Tafel slope for HER and OER, respectively, outperforming those of most of the current noble metal-free electrocatalysts. These results highlight the fact that CoSMoS₂/Ni₃S₂/NF is a high-performance, noble-metal-free electro-catalyst, and provide a potential avenue toward achieving an enhanced electrocatalytic activity towards both in HER and OER. Yet the duration of the as prepared catalyst in OER still need to be improved.     

Highly efficient hydrogen evolution catalysis based on MoS2/CdS/TiO2 porous composites

Efficient production of hydrogen through visible-light-driven water splitting mechanism using semiconductor-based composites has been identified as a promising strategy for converting light into clean H₂ fuel. However, researchers are facing lots of challenges such as light absorption and electron-hole pair recombination and so on. Here, new sheet-shaped MoS₂ and pyramid-shaped CdS in-situ co-grown on porous TiO₂ photocatalysts (MoS₂CdSTiO₂) are successfully obtained via mild sulfuration of MoO₃ and CdO coexisted inside porous TiO₂ monolith by a hydrothermal route. The scanning electron microscopy and transmission electron microscopy results exhibit that the MoS₂CdSTiO₂ composites have average pore size about 500 nm. The 3%MoS₂10%CdSTiO₂ demonstrated excellent photocatalytic activity and high stability for a hydrogen production with a high H₂-generation rate of 4146 μmol h^?1 g^?1 under visible light irradiation even without noble-metal co-catalysts. The super photocatalytic performance of the visible-light-driven hydrogen evolution is predominantly attributed to the synergistic effect. The conduction band of MoS₂ facilitates in transporting excited electrons from visible-light on CdS to the porous TiO₂ for catalytic hydrogen production, and holes to MoS₂ for inhibiting the photocorrosion of CdS, respectively, leading to enhancing the efficient separation of electrons and holes.     

Phase stability and hydrogen desorption in a quinary equimolar mixture of light-metals borohydrides

The present study aims at investigating, for the first time, a quinary mixture of light-metals borohydrides. The goal is to design combinations of borohydrides with multiple cations in equimolar ratio, following the concept of high entropy alloys. The equimolar composition of the LiBH₄NaBH₄KBH₄Mg(BH₄)₂Ca(BH₄)₂ system was synthetized by ball milling. The obtained phases were analysed by X-ray diffraction and in-situ Synchrotron Radiation Powder X-ray Diffraction, in order to establish the amount of cations incorporated in the obtained crystalline phases and to study the thermal behaviour of the mixture. HP-DSC and DTA were also used to define the phase transformations and thermal decomposition reactions, leading to the release of hydrogen, that was detected by MS. The existence of a quinary liquid borohydride phase is reported for the first time. Effects of the presence of multi-cations compounds or a liquid phase on the hydrogen desorption reactions are described.