Could anyone explain what the difference is between applying current and voltage in electrodeposition of MnO2 in view of structural and morphological properties in other words what are the electrodeposition mechanisms in both cases?
Mno2 is deposited from CHLORIDE/ SULPHATE BATHS on graphite / carbon
Better to use a high C.D deposition-- oxygen evolution should ensure oxide formation
Thanks prof V.S Muralidharan for your reply. I already deposited MnO2 from KMnO4 by applying current and voltage. In each exp. i got MnO2 phase with nanoflower morphology. so now i want to interpret the findings. So i want to know what is the mechanism in both cases and what the action of the current is and voltage in seed formation.
what is an oxide? A ratio of metal to oxygen - from a monlayer adsorption , it thickens to form a thin film and then thick film - as oxygen evolution porceeds the ratio changes decided by metal ion valency - Mn has 4 in MnO2-- coming back to the question of current vs voltage
as the oxide thickens the overvoltage for oxygen evolution increases and oxygen evolution reaction rate decreases - hence i suggested to use High C.D
Thanksagian prof V.S Muralidharan for your usefull information and kind reply
Anoid oxide films by L.Young -- if you get it read
See Encylcopedia of Elements - Ed by A.J.Bard - see Mn element
I think the adhesion of the MnO2 will be good in potentiostatic method when compared with galvanostatic method.
As to our experience, D.C. is good to produce powders containing needle nanocrystallites but potentiostatic method is good to deposit thin films. By the way, oxygen evolving can be avoided in the last case and it was very important to produce films of qood quality. The best electrode material is platinum. We have used fluoride electrolytes but anode eldeposition mechanisms of Mn(II) in sulfate and fluoride electrolytes are common.
dear Georgii
are you using fused salt ?
if aqueous i feel it is better galvanostatic --medium current density - with out oxygen evolution there is MnO2
Dear V.S. Muralidharan,
we are using aqueous electrolytes. We applied high current densities to produce powders. Potentiostatic method gives better control of film quality and composition in our experiments. Depending on potential, we can choose between Mn3+- and Mn4+-containing films (It can be checked by CVA and chemical analysis). And in the last case chose conditions when MnO2 film has already formed but O2 evolving hasn't started yet.
I agree-- at high C.D s you will get powdery deposits - for large scale we use galvanostatic method -as I see from what you said the film has both 3+ and4+ ; but we want only 4+ so oxygen evolution should be there
We have used combined data of CVA, chemical analysis and EPR investigations of anode oxidation in MnSO4 electrolyte containing hydrofluoric acid and performed by our colleaques (they accumulated deposits grown at different potentials and studied it by the mentioned above methods). Unfortunately, only russian language version of their paper is available (I.S. Makeeva, N.D. Ivanova, V.V. Trachevsky, Ukr. Khim. Zhurn, 66 (2000) 88). In according to these data, we have chosen potentials where namely Mn4+-containing film can be deposited (Mn3+- defect positions are in any case present in electrolytic manganese dioxide (Brenet J., 1979 ))
a mixture of 3+ and 4+ possible - Mn partial oxidation like Mn2O3
PLEASE ADJUST THE CURRENT DENSITY
DO NOT GO TO LIMITING CD RANGE
i know the process is room temperature
regulate the CD
you should get a coating which you can remove later
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