Acidification and bubble template derived porous g-C3N4 for efficient photodegradation and hydrogen evolution

Graphitic carbon nitride (g-C₃N₄) as a metal-free candidate of photocatalyst has received worldwide attention because of its great potentials in solar light-induced degradation and hydrogen evolution, yet the industrial application is seriously hindered by the small specific surface area and rapid recombination rate of carriers. Herein, we demonstrate that porous g-C₃N₄ (HCl-CNU-X) can be prepared via the co-polymerization of acidified melamine and a green bubble template (urea). Transmission electron microscopy and nitrogen sorption characterization results show that the prepared HCl-CNU-X possesses an in-plane porous structure and large specific surface area, enabling the exposure of more accessible active sites. As a result, HCl-CNU-X exhibits both enhanced photocatalytic tetracycline hydrochloride degradation and higher hydrogen evolution than bulk g-C₃N₄. The boosted photocatalytic performance was ascribed to the formation of the porous structure, which dramatically promotes the separation of charge-carriers and facilitates the electron transfer. This work demonstrates that the acidification of nitrogen-rich precursors combined with a bubble-template can develop a new paradigm of highly porous photocatalysts for environmental remediation and water splitting.     

Activity volcanoes for the electrocatalysis of homolytic and heterolytic hydrogen evolution

This paper derives a simple kinetic model for the electrochemical current generated by a heterolytic model for hydrogen evolution, as it would apply to the reaction taking place on molecular catalysts, and compares the activity trends to the classical Volmer-Heyrovsky-Tafel models. It is demonstrated that in the heterolytic mechanism, pH plays a crucial role in optimizing the overall activity.     

Deposition features of Ni on self-assembled microtubule template from biolipid by electroless method

The self-assembly of lipid molecules is in close relationship with the structure and function of a cell membrane. A cell membrane has a variety of lipid molecules. Lipid molecules have their amphiphile na-tures, and their self-assembly can form a variety of thermodynamically stable microstructures, such as single-bilayer or multi-bilayer spherical and ellipsoidal liposome, microcylindrical and microtubular struc-tures[1]. These microstructures exhibit different bio-logical functions in living …     

The effect of composition of electrodeposited Ni-P alloys on the hydrogen evolution rate

The effect of composition and structure of electrodeposited nickel-phosphorus coatings on their catalytic properties in the hydrogen evolution reaction is studied. It is found that an increase in the content of phosphorus in the alloy from 0.1 to 12.6 wt % leads to an increase in the hydrogen evolution rate. The coatings, which were deposited under the galvanostatic conditions, exhibit higher activity than those plated under the potentiodynamic conditions. It is shown that the nature of acceleration of hydrogen evolution rate on the alloys depends on the alloy composition: only Ni-P alloys containing up to 6.5 wt % phosphorus possess true catalytic activity, whereas the coatings enriched in phosphorus promote the hydrogen evolution due to significant development of their surface area.     

模板剂及Ni掺杂对中孔TiO2材料性能的影响

1992年美国Mobil公司首次报道了以离子型表面活性剂为模板剂通过水热法合成了中孔二氧化硅及硅铝材料，由于此类材料具有较大的孔径和比表面积以及优良的吸附性能，在较大的分子或基团的反应中具有较大的优势，引起了催化、吸附分离、无机合成及材料科学等许多领域研究者的广泛关注，许多不含硅的具有半导体性能的中孔氧化物材料在光催化、气体传感、局部氧化、完全燃烧、NOx降解、加氢脱硫等方面显示出优良的性能，二氧化钛是一类应用很广的氧化物。     

Determination of hydrogen in oxygen containing zirconium hydrides by the hydrogen evolution method

Summary Hydrogen absorbed by pure zirconium can be determined quantitatively with a precision of better than ±1.4 mg or 16 ml per g of the sample, if the latter is dissolved in HP solution, the volume of hydrogen measured, and eq. 5 with R=0 is applied. For hydrogen and oxygen containing solid solutions the residue (ZrO₂) left after dissolution has to be collected, weighed, and the full eq. 5 has to be used. The precision of such determinations is about ±16 ml hydrogen per g of the alloy. Oxygen containing samples, if the hydrogen is absorbed at elevated temperatures, always leave the oxygen in the form of ZrO₂ which is insoluble in dilute HF solution. However, if hydrogen diffuses into oxygen containing Zr at low temperatures (e.g. room) then it may happen that ZrO₂ of smaller grain size (especially in the -solid solution region) will dissolve completely in the acid and if so, applying eq. 5, will result in too small an amount of absorbed hydrogen. This is a definite limitation of the method.This investigation was supported by the U.S. Atomic Energy Commission [AT (11-1)-73, Project 5].     

Studies of the hydrogen evolution reaction on smooth Co and electrodeposited Ni–Co ultramicroelectrodes

The hydrogen evolution reaction (HER) was studied on smooth Co and on electrodeposited Ni–Co ultramicroelectrodes (UMEs) in alkaline solutions at several temperatures by steady-state polarisation curves. The real electrochemical area was previously estimated by cyclic voltammetry to account for the large difference in roughness factor of the two surfaces. The values obtained for the Tafel slopes were very close to 2.303RT/βnF while the ‘apparent’ energies of activation were 59 and 41 kJ mol⁻¹ for Co and Ni–Co, respectively. A common Volmer–Heyrovsky mechanism with Heyrovsky as the rate-determining step (RDS) was initially proposed. This was confirmed when the experimental results were mathematically treated by a non-linear fitting procedure using the kinetic equations derived for that mechanism. The calculations revealed that Ni–Co is a more efficient catalyst for the HER then pure Co, with a rate constant value of 0.16×10⁻¹⁰ mol s⁻¹ cm⁻² at 25°C for the slow step. Although this value is more than one order of magnitude smaller than that already reported for deposited Ni, it is considerably larger than the one measured here (0.02×10⁻¹⁰ mol s⁻¹ cm⁻²) for pure Co at 25°C.     

In-situ doping-induced lattice strain of NiCoP/S nanocrystals for robust wide pH hydrogen evolution electrocatalysis and supercapacitor

Developing high-efficiency multifunctional nanomaterials is promising for wide p H hydrogen evolution reaction(HER) and energy storage but still challenging. Herein, a novel in-situ doping-induced lattice strain strategy of NiCoP/S nanocrystals(NCs) was proposed through using seed crystal conversion approach with NiCo₂S₄ spinel as precursor. The small amount of S atoms in NiCoP/S NCs perturbed the local electronic structure, leading to the atomic position shift of the neare...     

The effects of carbon nanotubes on the electrocatalysis of hydrogen peroxide by metallo-phthalocyanines

The pre-grafted screen-printed gold electrode modified with phenyl-amino monolayer was investigated for covalent immobilization of phenyl-amine functionalized single-walled carbon nanotubes (PA-SWCNT) and metal tetra-amino phthalocyanine (MTAPc) using Schiff-base reactions with benzene-1,4-dicarbaldehyde (BDCA) as cross-linker. The PA-SWCNT and MTAPc modified electrodes were applied as hybrids for electrochemical sensing of H₂O₂. The step-by-step fabrication of the electrode was followed using electrochemistry, impedance spectroscopy, scanning electron microscopy and Raman spectroscopy and all these techniques confirmed the fabrication and the immobilization of PA-SWCNT, MnTAPc and CoTAPc onto gold surfaces. The apparent electron transfer constant (k_app) showed that the carbon nanotubes and metallo-phthalocyanines hybrids possess good electron transfer properties compared to the bare, pre-grafted and the MTAPc modified gold electrode surfaces without PA-SWCNT. The electrochemical sensing of hydrogen peroxide was successful with PA-SWCNT-MTAPc hybrid systems showing higher electrocatalytic currents compared to the other electrodes. The analytical parameters obtained using chronoamperometry gave good linearity at H₂O₂ concentrations ranging from 1.0 to 30.0 μmol L⁻¹. The values for the limit of detection (LoD) were found to be of the orders of 10⁻⁷ M using the 3δ for all the electrodes. The PA-SWCNT-MTAPc modified SPAuEs were much more sensitive compared to PA-MTAPc modified SPAuEs.     

Effects of template sequence and secondary structure on DNA-templated reactivity

DNA-templated organic synthesis enables the translation, selection, and amplification of DNA sequences encoding synthetic small-molecule libraries. As the size of DNA-templated libraries increases, the possibility of forming intramolecularly base-paired structures within templates that impede templated reactions increases as well. To achieve uniform reactivity across many template sequences and to computationally predict and remove any problematic sequences from DNA-templated libraries, we have systematically examined the effects of template sequence and secondary structure on DNA-templated reactivity. By testing a series of template sequences computationally designed to contain different degrees of internal secondary structure, we observed that high levels of predicted secondary structure involving the reagent binding site within a DNA template interfere with reagent hybridization and impair reactivity, as expected. Unexpectedly, we also discovered that templates containing virtually no predicted internal secondary structure also exhibit poor reaction efficiencies. Further studies revealed that a modest degree of internal secondary structure is required to maximize effective molarities between reactants, possibly by compacting intervening template nucleotides that separate the hybridized reactants. Therefore, ideal sequences for DNA-templated synthesis lie between two undesirable extremes of too much or too little internal secondary structure. The relationship between effective molarity and intervening nucleic acid secondary structure described in this work may also apply to nucleic acid sequences in living systems that separate interacting biological molecules.     

Observation of bubble layer formed on hydrogen and oxygen gas-evolving electrode in a magnetic field

The evolution of hydrogen and oxygen gasses in a 0.36-M KOH electrolyte was observed in a magnetic field, and the void fraction was calculated by a hydrodynamic model. Both gasses evolving on a platinum working electrode formed a bubble layer which increased the ohmic resistance. In addition to natural convection, magnetohydrodynamic (MHD) convection in a magnetic field improved the electrolytic conductivity by supplying a fresh solution (pumping effect) and removing gas bubbles. The MHD convection reduced the void fraction of hydrogen gas more than that of oxygen, which can be explained by the poor wettability of the oxygen evolving electrode.     

An investigation of anodic film formation on electrodeposited ruthenium by potential sweep techniques

Potential sweep techniques were used to investigate the anodic behaviour of reduced ruthenium surfaces, prepared by electrodeposition on gold-plated substrates, as a function of sweep rate, temperature and pH. The most important factor appeared to be pH as this strongly influenced the oxide layer thickness and both the number and location of the peaks on the voltammogram. The formation of thin oxide films on ruthenium at intermediate pH values (3.5–9.5) is attributed to the growth of a compact amorphous film with significant metal-oxygen-metal bridging in the structure. Heavier oxide growth in strong acid is attributed to protonation of the oxide lattice resulting in the formation of a more porous anodic film. Thicker oxide growth in strong base is attributed to the growth of a higher (+6) oxide under these conditions. The effects of both sweep rate and temperature on anodic behaviour in strong acid are attributed to activation-controlled rearrangement of the oxide film.     

Morphology and internal structure of copper deposits electrodeposited by the pulsating current regime in the hydrogen co-deposition range

The effect of the regime of pulsating current (PC) on copper electrodeposition in the hydrogen co-deposition range was examined by the techniques of scanning electron and optical microscopes. The quantities of evolved hydrogen and morphologies of electrodeposited copper strongly depended on the applied parameters of square waves PC, such as the current density amplitude (or the amplitude of the cathodic current density), deposition pulse, and pause duration. The increase of the current density amplitude led to intensification of hydrogen evolution reaction, and the change of morphology of electrodeposited copper from dendrites and shallow holes to dish-like holes was observed. For the constant pause duration, the prolonging deposition pulses intensify hydrogen evolution reaction leading to the formation of the honeycomb-like structures. The set of modified equations considering the effect of hydrogen generated during metal electrodeposition processes by the pulsating current regime is also presented. The concept of “effective overpotential amplitude” was proposed to explain the change of copper surface morphology with the intensification of hydrogen evolution reaction.     

Anchoring Ni single atoms on sulfur-vacancy-enriched ZnIn2S4 nanosheets for boosting photocatalytic hydrogen evolution

Structure manipulation of photocatalysts at an atomic scale is a promising way to improve its photocatalytic performance.Herein,we realize the anchoring of sing...     

Dopamine-assisted synthesis of rGO@NiPd@NC sandwich structure for highly efficient hydrogen evolution reaction

Journal of Solid State Electrochemistry - We report a facile one-pot solvothermal synthesis of NiPd alloy homogeneously encapsulated between reduced graphene oxide sheets and N-doped carbon layers...     

A study on the direct electrochemistry and electrocatalysis of microperoxidase-11 immobilized on a porous network-like gold film: Sensing of hydrogen peroxide

We have prepared porous and network-like nanofilms of gold by galvanic replacement of a layer of copper particles acting as a template. The films were first characterized by scanning electron microscopy and X-ray diffraction, and then modified with cysteamine so to enable the covalent immobilization of the enzyme microperoxidase-11. The immobilized enzyme undergoes direct electron transfer to the underlying electrodes, and the electrode displays high electrocatalytic activity towards the reduction of oxygen and hydrogen peroxide, respectively, owing to the largely enhanced electroactive surface of the porous gold film. The detection limit of H₂O₂ is 0.4 μM (3 S/N).

The structure of hydrogen adsorbed on Ni(111) at low temperature by leed intensity analysis

Observed and calculated LEED intensity spectra for the p(2 × 2) pattern given by the adsorption of hydrogen on Ni(111) at 173 K are reported. Among the several model geometries tried that with the hydrogen atoms adsorbed in one of the two possible hollow sites seems to be the most probable.