Cathodic action of lead malate complexes at the dropping mercury electrode

1973 ◽  
Vol 26 (5) ◽  
pp. 971 ◽  
Author(s):  
SC Khurana ◽  
CM Gupta
Keyword(s):  
Stability Constants ◽  
Mercury Electrode ◽  
Reduction Reaction ◽  
Ligand Concentration ◽  
Wave Potential ◽  
Half Wave Potential ◽  
Half Wave ◽  
Dropping Mercury Electrode ◽  
The Stability

The electrode reduction reaction of lead malate, involving deprotonated malate ion and a proton, between pK1 and pK2 values of the acid has been investigated. At pH < pK1 protonated ion participates and a proton is involved. The effect of ligand concentration on the half-wave potential of Pb2+ has been investigated and the stability constants of species so formed computed.

scholarly journals Modified Carbon Nanotubes: Surface Properties and Activity in Oxygen Reduction Reaction

Catalysts ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 1354
Author(s):  
Vera Bogdanovskaya ◽  
Inna Vernigor ◽  
Marina Radina ◽  
Vladimir Sobolev ◽  
Vladimir Andreev ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Zeta Potential ◽  
Oxygen Reduction Reaction ◽  
Oxygen Reduction ◽  
Surface Area ◽  
Surface Properties ◽  
Reduction Reaction ◽  
Wave Potential ◽  
Half Wave Potential ◽  
Half Wave

In order to develop highly efficient and stable catalysts for oxygen reduction reaction (ORR) that do not contain precious metals, it is necessary to modify carbon nanotubes (CNT) and define the effect of the modification on their activity in the ORR. In this work, the modification of CNTs included functionalization by treatment in NaOH or HNO3 (soft and hard conditions, respectively) and subsequent doping with nitrogen (melamine was used as a precursor). The main parameters that determine the efficiency of modified CNT in ORR are composition and surface area (XPS, BET), hydrophilic–hydrophobic surface properties (method of standard contact porosimetry (MSP)) and zeta potential (dynamic light scattering method). The activity of CNT in ORR was assessed following half-wave potential, current density within kinetic potential range and the electrochemically active surface area (SEAS). The obtained results show that the modification of CNT with oxygen-containing groups leads to an increase in hydrophilicity and, consequently, SEAS, as well as the total (overall) current. Subsequent doping with nitrogen ensures further increase in SEAS, higher zeta potential and specific activity in ORR, reflected in the shift of the half-wave potential by 150 mV for CNTNaOH-N and 110 mV for CNTHNO3-N relative to CNTNaOH and CNTHNO3, respectively. Moreover, the introduction of N into the structure of CNTHNO3 increases their corrosion stability.

Reduction of indium(III) at dropping mercury electrode in the presence of pyridine in aqueous and ethanol–water media

2010 ◽  
Vol 75 (6) ◽  
pp. 653-663 ◽  
Author(s):  
Vinita Sharma ◽  
Krishna D. Gupta
Keyword(s):  
Mercury Electrode ◽  
Complexation Reaction ◽  
Complex Species ◽  
Diffusion Controlled ◽  
Straight Line ◽  
Half Wave ◽  
Dropping Mercury Electrode ◽  
Water Media ◽  
Single Complex ◽  
The Stability

The reduction of indium(III) at dropping mercury electrode in aqueous as well as in 25% ethanol–water media in the presence of pyridine has been studied at a constant ionic strength (0.1 M KNO3) and at 30 and 40 °C. The reduction is diffusion-controlled but the electrode process is quasi-reversible in both media. The reversible half-wave potential values,E1/2r, have been obtained by Gelling’s method. The plot ofE1/2r versus pyridine concentration is a straight line and the number of ligands,j, was determined from the slope. This shows the formation of a single complex. The stability constant has been determined by Lingane’s method. In(III) forms one complex species with composition 1:1, [In(py)]3+. The values of thermodynamic parameters ΔG, ΔHand ΔSof the complexation reaction have also been determined at 30 °C.

scholarly journals N-Doped Graphene as an Efficient Metal-Free Electrocatalyst for Indirect Nitrate Reduction Reaction

Nanomaterials ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 2418
Author(s):  
Jujiao Zhao ◽  
Bo Shang ◽  
Jun Zhai
Keyword(s):  
Nitrate Reduction ◽  
Saturated Calomel Electrode ◽  
Reduction Reaction ◽  
Onset Potential ◽  
Metal Free ◽  
Wave Potential ◽  
Half Wave Potential ◽  
Half Wave ◽  
Doped Graphene ◽  
Pyridinic N

N-doped graphene samples with different N species contents were prepared by a two-step synthesis method and evaluated as electrocatalysts for the nitrate reduction reaction (NORR) for the first time. In an acidic solution with a saturated calomel electrode as reference, the pyridinic-N dominant sample (NGR2) had an onset of 0.932 V and a half-wave potential of 0.833 V, showing the superior activity towards the NORR compared to the pyrrolic-N dominant N-doped graphene (onset potential: 0.850 V, half-wave potential: 0.732 V) and the pure graphene (onset potential: 0.698 V, half-wave potential: 0.506 V). N doping could significantly boost the NORR performance of N-doped graphene, especially the contribution of pyridinic-N. Density functional theory calculation revealed the pyridinic-N facilitated the desorption of NO, which was kinetically involved in the process of the NORR. The findings of this work would be valuable for the development of metal-free NORR electrocatalysts.

Cobalt decorated nitrogen-doped carbon bowls as efficient electrocatalysts for the oxygen reduction reaction

2020 ◽  
Vol 56 (32) ◽  
pp. 4488-4491 ◽  
Author(s):  
Haobin Zhong ◽  
Changwei Shi ◽  
Jiantao Li ◽  
Ruohan Yu ◽  
Qiang Yu ◽  
...  
Keyword(s):  
Oxygen Reduction Reaction ◽  
Oxygen Reduction ◽  
Reduction Reaction ◽  
Nitrogen Doped ◽  
Wave Potential ◽  
Half Wave Potential ◽  
Half Wave ◽  
Nitrogen Doped Carbon

Cobalt decorated nitrogen-doped carbon bowls (Co@NCB) demonstrate better ORR performance than Pt/C in terms of half-wave potential and stability.

Bimetallic ZIF derived Co nanoparticle anchored N-doped porous carbons for an efficient oxygen reduction reaction

2020 ◽  
Vol 7 (4) ◽  
pp. 946-952 ◽  
Author(s):  
Kaili Li ◽  
Daohao Li ◽  
Liangkui Zhu ◽  
Zhuangzhuang Gao ◽  
Qianrong Fang ◽  
...  
Keyword(s):  
Oxygen Reduction Reaction ◽  
Oxygen Reduction ◽  
High Performance ◽  
Reduction Reaction ◽  
Porous Carbons ◽  
Wave Potential ◽  
Half Wave Potential ◽  
Half Wave ◽  
Reaction Performance

A high-performance electrocatalytic material was derived from a new bimetallic ZIF precursor, exhibiting excellent oxygen reduction reaction performance with a half-wave potential (E1/2) of 0.849 V, superior to that of commercial Pt/C.

Direct current polarography of the ferrous-ferric oxolate system in the presence of alternating voltages

1958 ◽  
Vol 11 (1) ◽  
pp. 9
Author(s):  
P Beckmann ◽  
GS Buchanan
Keyword(s):  
Direct Current ◽  
Active Substance ◽  
Mercury Electrode ◽  
Surface Active Substance ◽  
Active Materials ◽  
Wave Potential ◽  
Half Wave ◽  
Dropping Mercury Electrode ◽  
Surface Active ◽  
Alternating Voltage

The effect of the superposition of a small alternating voltage on the normal direct voltage applied to the dropping mercury electrode (D.M.E.) was investigated in the case of the ferrous-ferric oxalate system. The wave obtained was of the type found previously for ions which are reversibly reduced at the D.M.E. (e.g. Cd++ etc.). That is, the rectification of the A.C. produced a D.C. wave (the Z wave) which crossed the normal D.C. wave (the Y wave) at the half-wave potential (E�), When surface active materials were added (e.g. cyclohexanol) the reduction became " irreversible " and at certain concentrations of the surface active substance a maximum appeared on the Y wave of a somewhat unusual nature. The effect of a superposed alternating voltage was studied in these cases and it was found that the adsorption of the cyclohexanol was influenced by the presence of the alternating voltage.

scholarly journals An ultra-dispersive, nonprecious metal MOF–FeZn catalyst with good oxygen reduction activity and favorable stability in acid

2021 ◽  
Vol 56 (14) ◽  
pp. 8600-8612
Author(s):  
Qing Zhao ◽  
Cheng Wang ◽  
Haifeng Wang ◽  
Jianlong Wang
Keyword(s):  
Oxygen Reduction ◽  
High Performance ◽  
Reduction Reaction ◽  
Graphitic Carbon ◽  
Potential Cycling ◽  
Onset Potential ◽  
Wave Potential ◽  
Reduction Activity ◽  
Half Wave Potential ◽  
Half Wave

AbstractDevelopment of the more stable nonprecious oxygen reduction reaction (ORR) catalyst is of great significance nowadays. Herein, a high-performance iron-doped integral uniform macrocyclic organic framework (MOF–FeZn) catalyst is synthesized through a combined hydrothermal and pyrolysis process, showing favorable ORR activity and stability in acid. This as-synthesized MOF–FeZn catalyst displays high porous and graphitic structures with sufficient catalytic active dopants of pyridinic N, Fe–N, pyrrolic N, graphitic N, making it a promising ORR candidate catalyst with high electrochemical stability. The onset potential, half-wave potential and limited diffusion current density of MOF–FeZn are 0.93 V @ 0.1 mA cm−2, 0.768 V@ 2.757 mA cm−2 and 5.5 mA cm−2, respectively, which are comparable to the state-of-the-art nonprecious catalyst and commercial Pt/C. ORR catalysis on MOF–FeZn follows the nearly four-electron path. What is more, MOF–FeZn can sustain the 10,000 cycles electrochemical potential cycling process in acid with the half-wave potential changed only 21 mV, superior to the reduction of 149 mV for Pt/C. The well-developed integral uniform structures, homogeneously dispersed carbides and nitrides protected by the highly graphitic carbon layers and the better agglomeration suppression of nanoparticles by the confined graphitic carbon layers on catalyst can significantly enhance the catalytic activity and stability of MOF–FeZn.

Half-wave potential-ph diagram for the parabenzoquinone system in n,n-dimethylformamide

1969 ◽  
Vol 2 (3) ◽  
pp. 123-132 ◽  
Author(s):  
J. Badoz-lambling ◽  
G. Demange-guerin
Keyword(s):  
Wave Potential ◽  
Half Wave Potential ◽  
Half Wave

scholarly journals Effect of Pyrolysis Conditions on the Performance of Co–Doped MOF–Derived Carbon Catalysts for Oxygen Reduction Reaction

Catalysts ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 1163
Author(s):  
Ning Cui ◽  
Kexiao Bi ◽  
Wei Sun ◽  
Qianqian Wu ◽  
Yinan Li ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Oxygen Reduction Reaction ◽  
Oxygen Reduction ◽  
Heating Rate ◽  
Reduction Reaction ◽  
Half Wave ◽  
Step Heating ◽  
The Stability ◽  
Carbon Catalysts ◽  
Co Doped

MOF–derived porous carbon is a type of promising catalyst to replace expensive Pt–based catalysts for oxygen reduction reaction (ORR). The catalytic activity for ORR depends closely on pyrolysis conditions. In this work, a Co–doped ZIF–8 material was chosen as a research object. The effect of pyrolysis conditions (temperature, heating rate, two–step heating) on the ORR performance of ZIF–derived carbon catalysts was systematically studied. The Co–ZIF–8 catalyst carbonized at 900 °C exhibits better ORR catalytic activity than that carbonized at 800 °C and 1000 °C. Moreover, a low heating rate can enhance catalytic activity. Two–step pyrolysis is proven to be an effective way to improve the performance of catalysts. Reducing the heating rate in the low–temperature stage is more beneficial to the ORR performance, compared to the heating rate in the high–temperature stage. The results show that the Co–ZIF–8 catalyst exhibits the best performance when the precursor was heated to 350 °C at 2 °C/min, and then heated to 900 °C at 5 °C/min. The optimum Co–ZIF–8 catalyst shows a half–wave potential of 0.82 V and a current density of 5.2 mA·cm−2 in 0.1 M KOH solution. It also exhibits high content of defects and good graphitization. TEM mapping shows that Co and N atoms are highly dispersed in the polyhedral carbon skeleton. However, two–step pyrolysis has no significant effect on the stability of the catalyst.

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