Electrocatalysis of the HER in acid and alkaline media

Trends in the HER are studied on selected metals (M= Cu, Ag, Au, Pt, Ru, Ir, Ti) in acid and alkaline environments. We found that with the exception of Pt, Ir and Au, due to high coverage by spectator species on non-noble metal catalysts, experimentally established positions of Cu , Ag, Ru and Ti in the observed volcano relations are still uncertain. We also found that while in acidic solutions the M-Hupd binding energy most likely is controlling the activity trends, the trends in activity in alkaline solutions are controlled by a delicate balance between two descriptors: the M-Had interaction as well as the energetics required to dissociate water molecules. The importance of the second descriptor is confirmed by introducing bifunctional catalysts such as M modified by Ni(OH); e.g. while the latter serves to enhance catalytic decomposition of water, the metal sites are required for collecting and recombining the produced hydrogen intermediates.

Download Full-text

Neutralization of Industrial Water by Electrodialysis

Membranes ◽

10.3390/membranes11020101 ◽

2021 ◽

Vol 11 (2) ◽

pp. 101

Author(s):

Oleksandr Petrov ◽

Natalia Iwaszczuk ◽

Tina Kharebava ◽

Irina Bejanidze ◽

Volodymyr Pohrebennyk ◽

...

Keyword(s):

Current Density ◽

Ph Value ◽

Alkaline Solutions ◽

Water Molecules ◽

Bipolar Membrane ◽

Acidic Solutions ◽

Current Densities ◽

Density Process ◽

Process Productivity ◽

Limiting Value

The process of non-reagent adjustment of the pH of a NaCl solution (0.5 g/L) of different acidity was investigated by the method of bipolar electrodialysis on a device operating according to the K-system (concentration). The experiments were carried out in the range pH = 2.0–12.0 with monopolar cation-exchange MK-40 (for alkaline solutions) or anion-exchange MA-40 (for acidic solutions) and bipolar MB-2 membranes. The regularities of the change in the pH of the solution on the current density, process productivity and energy consumption for the neutralization process have been investigated. Revealed: with different productivity of the apparatus (Q = 0.5–1.5 m3/h), in the range of pH 3.0–11.0, with an increase in the current density, a neutral pH value is achieved. It has been shown that at pH above 11.0 and below 3.0, even at high current densities (i > 20 A/m2), its value cannot be changed. This is due to the neutralization of the H+ or OH− ions generated by the bipolar membrane by water ions, which are formed as a result of the dissociation of water molecules at the border of the monopolar membrane and the solution under conditions when the value of current exceeds the limiting value.

Download Full-text

Synthesis and physicochemical characterization of chemically modified chitosan by succinic anhydride

Brazilian Archives of Biology and Technology ◽

10.1590/s1516-89132006000500017 ◽

2006 ◽

Vol 49 (4) ◽

pp. 665-668 ◽

Cited By ~ 14

Author(s):

Karine Gargioni Pereira Correa de Mello ◽

Leandra de Cássia Bernusso ◽

Ronaldo Nogueira de Moraes Pitombo ◽

Bronislaw Polakiewicz

Keyword(s):

Succinic Anhydride ◽

Physicochemical Characterization ◽

Alkaline Media ◽

Alkaline Solutions ◽

Water Molecules ◽

Alkyl Chains ◽

Modified Chitosan ◽

Chemically Modified ◽

New Applications

The N-succinil-chitosan is a chemically modified derivative of the biopolymer chitosan. The succinic anhydride attached to the free amino groups presented along the chitosan's polymer chain imparts to the molecule different physicochemical properties not exhibited before the modification. These chemical modifications enhance chitosan's solubility in slightly acid, neutral and alkaline media. These properties are related to the long alkyl chains attached to hydrophilic parts. In this case the hydrophilic part of D-glucosamine promotes stronger interactions with the water molecules, and consequently, enhances the solubility of the chitosan polymer. Non-modified free chitosan is soluble only in acidic medium (pH < 5.5). These modifications made possible new applications of chitosan in biotechnological area since the solubility in neutral or slightly alkaline solutions is very important in a biological field.

Download Full-text

Isotope Effects in Exchange, Desorption, and Decomposition of Water Molecules on Ru(0001) at Cryogenic Temperatures

The Journal of Physical Chemistry C ◽

10.1021/acs.jpcc.0c09145 ◽

2020 ◽

Vol 124 (51) ◽

pp. 28139-28144

Author(s):

Ryutaro Souda ◽

Takashi Aizawa ◽

Masaki Takeguchi

Keyword(s):

Isotope Effects ◽

Water Molecules ◽

Cryogenic Temperatures ◽

Decomposition Of Water

Download Full-text

Solvent-mediated crystalline phases of NixSy anchored on rGO sheets as electrocatalysts for hydrogen evolution application

Functional Materials Letters ◽

10.1142/s1793604718500893 ◽

2019 ◽

Vol 12 (01) ◽

pp. 1850089

Author(s):

Hou Lin Yu ◽

Wenliang Shi ◽

Shuaishuai Li ◽

Junma Zhang ◽

Xiaobo Zhang ◽

...

Keyword(s):

Ethylene Glycol ◽

Hydrogen Evolution ◽

Hydrothermal Process ◽

Volume Ratio ◽

Decisive Role ◽

Catalytic Performance ◽

Deionized Water ◽

Alkaline Media ◽

One Pot ◽

Alkaline Environments

A facile, one-pot solvent-mediated hydrothermal process was adopted to prepare nickel sulfide nanoparticles decorated on reduced graphene oxide (NixSy/rGO) as electrocatalysts for hydrogen evolution reaction (HER). The designed solvent (ethylene glycol and deionized water) played a decisive role in controlling both crystalline phase and morphology of NixSy/rGO composites, leading to pure [Formula: see text]-NiS nanoparticles uniformly distributed on rGO sheets under suitable volume ratio of ethylene glycol and deionized water (2:1). The optimized [Formula: see text]-NiS/rGO showed prominent HER catalytic performance with a rather small Tafel slope of 93[Formula: see text]mV/decade and prominent current density of 10[Formula: see text]mA/cm2 at the overpotential of 177[Formula: see text]mV in alkaline environments when compared to pristine [Formula: see text]-NiS and NiS2/rGO catalysts. The excellent catalytic performance and long-term durability even after 8000 cycles confirmed the potential of [Formula: see text]-NiS/rGO composites as efficient electrocatalysts for HER in the alkaline media.

Download Full-text

SOLVATION OF THE [Cr(NCS)4(IMIDAZOLE)2] ION IN ETHANOL-WATER MIXTURES

Southern Brazilian Journal of Chemistry - Southern Brazilian Journal of Chemistry, Volume 28, No. 28, 2020 ◽

10.48141/sbjchem.v10.n11.2002.65_2002.pdf ◽

2002 ◽

Vol 10 (11) ◽

pp. 63-72

Author(s):

lon Ganescu ◽

George Bratulescu ◽

Ion Papa ◽

Anca Ganescu ◽

Alin Barbu ◽

...

Keyword(s):

Kinetic Parameters ◽

Order Reaction ◽

Water Molecules ◽

Hydrogen Ions ◽

Second Order Reaction ◽

Acidic Solutions ◽

The Third ◽

Competitive Reactions ◽

Different Temperatures ◽

Kinetics Of

Salvation kinetics of [Cr(NCS)4(imidazole)2]- has been studied in ethanol-water mixtures at different temperatures. The first stage of the solvation consists of two competitive reactions: two NCS- ions are exchanged, presumably, by water molecules and simultaneously an imidazole molecule by ethanol, the latter in a second-order reaction, accelerated by hydrogen ions. The exchange of the amine is followed by the substitution of the first two NCS- ions. The third and fourth NCS- ions are substituted only in neutral and slightly acidic solutions. Kinetic parameters have been determined for reactions (1), (2), and (4). The influence of the solvent composition and acidity is discussed

Download Full-text

The Use of a Nanoscale Copper Catalyst in the Catalytic Decomposition of Water Polluted with Organic Dyes

Journal of Nanomaterials ◽

10.1155/2013/562830 ◽

2013 ◽

Vol 2013 ◽

pp. 1-4 ◽

Cited By ~ 1

Author(s):

Samia A. Kosa

Keyword(s):

Organic Dyes ◽

Copper Catalyst ◽

Catalytic Decomposition ◽

Catalytic Process ◽

Optimal Conditions ◽

Edx Analysis ◽

Complete Decomposition ◽

Supported Copper Catalyst ◽

Decomposition Of Water ◽

Concentration Ratios

A supported copper catalyst was used as a catalyst for the decomposition of organic dyes using a commercial chlorinating agent. The catalytic process achieved complete decomposition in only 2 min. Different catalyst to dye concentration ratios is studied to determine the optimal conditions. The catalyst is fully characterized using XRD, SEM, and EDX analysis.

Download Full-text

Experimental and theoretical investigation on MoS2/MXene heterostructure as an efficient electrocatalyst for hydrogen evolution in both acidic and alkaline media

New Journal of Chemistry ◽

10.1039/d0nj00956c ◽

2020 ◽

Vol 44 (19) ◽

pp. 7902-7911

Author(s):

Le Hu ◽

Yuyun Sun ◽

Shi-Jing Gong ◽

Hui Zong ◽

Ke Yu ◽

...

Keyword(s):

Hydrogen Evolution ◽

Theoretical Investigation ◽

Alkaline Media ◽

Alkaline Solutions ◽

Acidic And Alkaline Media

A composite of MoS2/Nb2CTx with MoS2 nanoflowers grown between Nb2CTx flakes for electrolysis of water in acidic and alkaline solutions.

Download Full-text

Osmium(VIII) Catalyzed Oxidation of Acetone and Ethylmethyl Ketone by Chloramine-T

Zeitschrift für Naturforschung B ◽

10.1515/znb-1972-1010 ◽

1972 ◽

Vol 27 (10) ◽

pp. 1161-1163 ◽

Cited By ~ 17

Author(s):

S. P. Mushran ◽

R. Sanehi ◽

M. C. Agraval

Keyword(s):

Acidic Medium ◽

Present Note ◽

Alkaline Media ◽

Alkaline Solutions ◽

Slow Step ◽

First Order ◽

Chloramine T ◽

Kinetics Of ◽

Catalyzed Oxidation ◽

High Redox Potential

The Osmium (VIII) catalyzed oxidation of acetone and ethylmethyl ketone by chloramine-T, in highly alkaline solutions showed first order dependence to chloramine-T and osmium (VIII). The order of the reactions with respect to alkali and ketone were found to be fractional, being ~-0.82 and 0.3 respectively. No effects of ionic strength were evident. The mechanism has been proposed on the basis of the formation of a complex between N-chlorotoluene-p-sulfonamide and osmium (VIII) in the slow step, which in turn oxidizes the enol anion of the reducing substrate in the fast step.During the study of the mechanism of oxidations by chloramine-T, the kinetics of the oxidation of α-hydroxy acids 1 in presence of osmium (VIII) as catalyst, glycerol2 in neutral and alkaline media, p-cresol3 in an acidic medium, hexacyanoferrate (II)4 in a feebly acidic medium (pH 6-7) and aliphatic aldehydes 5 in alkaline media have been investigated.Despite the high redox potential6 of the chloramine-T/toluene sulfonamide system (1.138 V at pH 12), the oxidation of acetone does not take place in absence of catalyst and that of ethylmethyl ketone proceeds only in highly alkaline solutions7 (NaOH>0.01 M). In the present note the kinetics of the osmium (VIII) catalyzed oxidation of acetone and ethylmethyl ketone have been recorded.

Download Full-text

Nitrogen-Doped Ordered Mesoporous Carbons Supported Co3O4 Composite as a Bifunctional Oxygen Electrode Catalyst

Surfaces ◽

10.3390/surfaces2020018 ◽

2019 ◽

Vol 2 (2) ◽

pp. 229-240 ◽

Cited By ~ 1

Author(s):

Jing Wang ◽

Shuwei Zhang ◽

Haihong Zhong ◽

Nicolas Alonso-Vante ◽

Dianqing Li ◽

...

Keyword(s):

Precious Metal ◽

Solvothermal Method ◽

Oxygen Electrode ◽

Rechargeable Batteries ◽

Alkaline Media ◽

Bifunctional Catalysts ◽

Mesoporous Carbons ◽

Ordered Mesoporous Carbons ◽

Ordered Mesoporous ◽

Regenerative Cells

It is increasingly useful to develop bifunctional catalysts for oxygen reduction and oxygen evolution reaction (ORR and OER) for fuel cells, metal-air rechargeable batteries, and unitized regenerative cells. Here, based on the excellent conductivity and stability of ordered mesoporous carbons, and the best ORR and OER activity of Co3O4, the composite Co3O4/N-HNMK-3 was designed and manufactured by means of a solvothermal method, using ordered N-doped mesoporous carbon (N-HNMK-3) as substrate, and then the bifunctional electrocatalytic performance corresponding to ORR, OER in alkaline media was carefully investigated. The results showed that Co3O4/N-HNMK-3 composite, a non-precious metal centered electrocatalyst, displayed excellent ORR performance (activity, selectivity, and stability) close to that of commercial 20 wt.% Pt/C and a promising OER activity near 20 wt.% RuO2/C. The outstanding bifunctional activities of Co3O4/N-HNMK-3 was assessed with the lowest △E value of 0.86 V (EOER,10 mA cm−2-EORR,−3 mA cm−2) with respect to the two commercial precious metal-based electrocatalysts.

Download Full-text