Oxidation-Reduction Behaviours, Electrolysis Characteristics and Efficiency of Pd-50at.%Ni Electrode in Alkaline Electrolyte

Convinced on the necessity of finding effective electrodes for electrolyser- the oxidation-reduction behaviors, surface reaction kinetics, stability, electrolysis characteristics and efficiency of a Pd-50at.%Ni electrode have been investigated in 30wt.%KOH electrolyte at room temperature using cyclic voltammetry. Cyclic voltammogram of the electrode showed three couples of oxidation-reduction peaks in between the potential range - 1.0 to + 0.65 V. These peaks were found to be originated from the transformation of zero valent metal to their higher oxides in three consecutive steps and vice versa. The peak potentials, potential differences of the couples and the peak currents were found remarkably different from those of Pd and Ni electrodes. The surface reaction kinetics at Pd-Ni electrode followed the surface reaction trends similar to those of Pd and Ni electrodes. The apparent stability of the electrode was found good. The electrode showed 1.6 and 6.8 times higher oxygen evolution efficiencies than the Ni and Pd electrodes. Addition of Ni with Pd caused hydrogen evolution potentials to move to the negative direction. Tafel plot for the hydrogen evolution reactions (HER) showed two well-defined Tafel regions. Kinetic parameters, i.e., Tafel slope and exchange current density values for the low and high overpotential regions were found 127 mV/dec and 273 mV/dec, and 1.72 x 10-2 mA/cm2 and 1.52 mA/cm2, respectively. Observed slopes indicated its better efficiency over the Pd electrode. Journal of Bangladesh Academy of Sciences, Vol. 33, No. 1, 1-13, 2009 doi: 10.3329/jbas.v33i1.2945

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Investigations on the Redox Behavior and the Electrolysis Characteristics of Pd-20at.%Ni Eectrode in 30wt.%KOH Electrolyte

Bangladesh Journal of Scientific and Industrial Research ◽

10.3329/bjsir.v43i1.853 ◽

1970 ◽

Vol 43 (1) ◽

pp. 13-28 ◽

Cited By ~ 1

Author(s):

Mithun Sarker ◽

M Ashraful Islam Molla ◽

Rafiqul Islam ◽

Samina Ahmed ◽

AKM Fazle Kibria

Keyword(s):

Reaction Kinetics ◽

Hydrogen Evolution ◽

Oxygen Evolution ◽

Surface Reaction ◽

Potential Range ◽

Redox Behavior ◽

Ni Alloy ◽

Current Densities ◽

Surface Reaction Kinetics ◽

Better Than

The redox behavior, surface reaction kinetics, stability, electrolysis characteristics and efficiency of a Pd-20 at %Ni electrode have been investigated in 30wt.%KOH electrolyte at room temperature by using cyclic voltammetry. The electrode showed three couples of redox peaks in between the potential range -1.0 to + 0.65 V. The origin of the peak couples were identified by cycling Pd and Ni electrodes independently in the same potential ranges. It was realized that the peak couples were originated from the transformations of M(0) ←→ M(II) oxide, M(II) oxide ←→ M(III) oxide and M(III) oxide ←→ M(IV) oxide, respectively. The term M represents the Pd-Ni alloy. The potentials of the peaks, potential differences of the peak couples and the peak currents found remarkably different than those of Pd and Ni electrodes. The redox reaction kinetics of the electrode showed combined surface reaction trends of Pd and Ni electrodes. The apparent stability of the electrode found good. The electrode showed equal and 4.2 times higher oxygen evolution current densities than those of Ni and Pd electrodes. Hydrogen evolution current density found 2.9 times lower than that of Pd electrode but 100% better than the Ni electrode at the potential range - 1.0 to + 0.65 V. Almost 70% hydrogen evolution efficiency of Pd electrode was found at the potential range - 1.0 to - 0.05 V. On cycling the electrode at various potential ranges, it was found that the redox behavior resembled to that of Pd electrode at low potential ranges. The observed results indicated that Pd-20at.%Ni electrode is a good electrode during electrolysis for oxygen evolution reaction and its electrolysis efficiency is far better than the Ni electrode. Key words: Pd-20at. %Ni electrode, Redox behavior, Hydrogen evolution, Oxygen evolution. DOI: 10.3329.bjsir.v43i1.853 Bangladesh J. Sci. Ind. Res. 43(1), 13-28, 2008

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Effect of Ethylene Diamine Tetra Acetic Acid (EDTA) on the Surface Reaction Behavior and the Hydrogen Evolution Efficiency of Ni-30at.%Cu Electrode in Alkaline Medium

Bangladesh Journal of Scientific and Industrial Research ◽

10.3329/bjsir.v43i2.955 ◽

1970 ◽

Vol 43 (2) ◽

pp. 145-158

Author(s):

AKM Fazle Kibria

Keyword(s):

Acetic Acid ◽

Hydrogen Evolution ◽

Surface Reaction ◽

Ethylene Diamine ◽

Potential Range ◽

Cyclic Voltammogram ◽

Oxidation Reduction ◽

Hydrogen Evolution Reactions ◽

Kinetics Of ◽

Voltammetric Technique

The surface reaction characteristics, hydrogen evolution efficiency and hydrogen evolution reaction kinetics of Ni-30at.%Cu electrode have been investigated in 30wt.%KOH electrolyte in presence and absence of ethylene diamine tetra acetic acid (EDTA) at room temperature by cyclic voltammetric technique. Cyclic voltammogram of the electrode showed three couples of oxidation-reduction peaks in between the potential range - 1.1 to + 0.4 V. The peak couples were originated from the electrochemical transformations of Ni(0) ←→ Ni(OH)2, Cu(0) ←→ Cu(I) and Cu(I) ←→ Cu(OH)2. An interference of the adsorped hydrogen over Cu(0) surface on the transformation of Ni(OH) 2 → Ni(0) was found. It was realized that added EDTA forms Cu-EDTA complex over the electrode surface. With increasing the amount of EDTA, the thickness of Cu(OH) 2 layer gradually decreased. Addition of 0.04g, 0.08g and 0.12g EDTAincreased the hydrogen evolution efficiency of the electrode more than 6%, 12% and 17%. Tafel plots for both the systems showed two well-defined Tafel regions. 0.12g EDTA increased the exchange current density (i0) values 1.3 times for both the Tafel regions. The observed i0 value for the high overpotential (η) region is 1.8 and 2.9 times higher than those of Ni and Cu electrodes. The Tafel slope (b) values for both the low and high η regions are smaller than those observed for without EDTA system and also for the Ni electrode. From the achieved information, it can be concluded that addition of EDTA remarkably increased the hydrogen evolution efficiency of the Ni-30at.%Cu electrode. It seems that hydrogen evolution reactions (HER) followed like mechanisms in absence and presence of EDTA. Key words: Ni-30at.%Cu electrode, EDTA, Electrochemical transformation, Surface reactions, Hydrogen evolution, Hydrogen evolution reactions (HER)DOI: 10.3329/bjsir.v43i2.955 Bangladesh J. Sci. Ind. Res. 43(2), 145-158, 2008

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Investigations on the Redox Characteristics and Hydrogen Evolution Efficiencies of Pd and Mo Deposited Pd Electrodes in Alkaline Electrolyte

Bangladesh Journal of Scientific and Industrial Research ◽

10.3329/bjsir.v43i1.861 ◽

1970 ◽

Vol 43 (1) ◽

pp. 103-116 ◽

Cited By ~ 2

Author(s):

M Ashraful Islam Molla ◽

Mithun Sarker ◽

AKM Fazle Kibria

Keyword(s):

Hydrogen Evolution ◽

Hydrogen Adsorption ◽

Stable Condition ◽

Alkaline Electrolyte ◽

Potential Range ◽

Cyclic Voltammograms ◽

Absorption Region ◽

Potential Value ◽

Density Values ◽

Hydrogen Evolution Reactions

Redox behaviors and hydrogen evolution efficiencies of Pd and Mo deposited Pd electrodes have been investigated in 30wt.% KOH electrolyte by cyclic voltammetry. Cyclic voltammograms of Pd electrode in between the potential range - 1.05 V to + 0.75 V showed two couples of redox peaks for the transformations of Pd(0) ←→ Pd(OH)2 and Pd(OH)2 ←→ PdOOH, an anodic peak for the desorption of diffusional hydrogen (dH) and hydrogen and oxygen evolutions at the terminal potential regions. Hydrogen evolution efficiency found decreased with time and then reached to a stable condition after 35 minutes. In presence of deposited Mo, the electrode stable condition appeared after 10 minutes only. Pd found predominates over deposited Mo. Both the Pd(0) ←Pd(OH)2 and Mo(0) ← Mo(OH)2 transformations appeared at the same potential value. Mo stopped the movement of hydrogen adsorption and absorption region of Pd electrode towards negative potential direction. It increased the hydrogen evolution efficiency of Pd electrode remarkably. At the potentials - 1.1 V, - 1.2 V, - 1.25 V and - 1.3 V, currents for Pd + Mo system found 1.44, 1.25, 1.20, 1.23 times higher than those of Pd electrode. Mo also showed hydrogen migratory role to the fraction of Pd surface covered by it. Hydrogen evolution reactions (HER) over Pd and Pd + Mo surfaces seemed followed similar mechanisms. Tafel plots for the HER for both the systems showed two Tafel regions. Exchange current density values (io) for the low and high overpotential regions of Pd + Mo system showed 2.85 times and 1.29 times higher values than those of Pd electrode. Key words: Pd, Pd-Mo, Hydrogen evolution efficiency, Hydrogen evolution reactions (HER) DOI: 10.3329.bjsir.v43i1.861 Bangladesh J. Sci. Ind. Res. 43(1), 103-116, 2008

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