Nice idea, Horace, but you fail to consider one important aspect of using Mg as
the anode. Oxygen that forms at the anode will react to form MgO, which is an
insulator and is insoluble. As a result, cell resistance will increase to
unacceptable values. This same kind of reaction occurs when Zr or Ti are used
as the anode as well. A very low applied current would be the only condition
permitting use of Mg. The current would have to be small enough so that the
formation rate of MgO would have to be less than its rate of dissolution from
the surface.
Regards,
Ed
Horace Heffner wrote:
> At 1:07 AM 11/27/4, Frederick Sparber wrote:
>
> >Most likely, use of a Magnesium Anode (Sacrificial Cathodic Protection) and
> >a Palladium Cathode with a LICl-D2O electrolyte will get more CF-OU bang
> >for the buck
> >than using a power supply.
>
> Lets play with this lead a bit. One problem with using Mg as the anode is
> depositing of Mg on the cathode will change its electronegativity. Mg can
> not be used as a separate (biasing) anode because then its potential,
> though possibly preserving loading when the "real" anode potential is not
> provided, does not add to the "real" anode when it is positive. To obtain
> the "bias" the Mg anode must be used as "the" anode, and thus it carries
> the full cell current and transports MG Accordingly.
>
> Perhaps this can be worked up into a viable concept. Suppose the add-on
> potential comes in the form of AC produced by capacitive coupling to the
> cell, as shown in Fig. 1 below.
>
> ------------
> | |
> IIII|IIIII | Mg bias connection
> II MMM II |
> II II |
> II II |
> | II C II | | KEY:
> | II C II | |
> | II C II | | M - Mg bias anode
> | II C II | | C - Cathode
> | II C II | | A - Current supplying anode
> | II C II | | II - Insulating dielectric
> | II C II | |
> | II C II | |
> | II C II | |
> (AC)----------| II C--------o----(-) Cathode potential
> | II C II |
> | II C II |
> | II C II |
> | II C II |----(-AC)
> | II C II |
> | II C II |
> Plate 1 | II C II | Plate 2
> | II C II |
> | II C II |
> II II
> II AAAA II
> IIIII|IIII
> |
> (+) Current Anode (Anode potential)
>
> Fig. 1 - Diagram of Biased AC Electrolysis Cell
> Top View, Cross section
>
> Perhaps elecrolysis occurs during the positive cycle for Plate 2? The
> electode "AAAA"is necessary to provide the net current which results - due
> to current flowing when Plate 1 is positive and no current flowing when
> Plate 1 is negative. Without the Current Anode the cell potential will go
> negative and stop all adsorbtion. Again deposition of Mg on the cathode
> may end the bias provided by the sacrificial Mg anode. An alternative may
> be to use a Pt current providing anode ("AAAA") which also provides the
> bias voltage (about 1.4 V) for the AC. The bias voltage provided by "MMM"
> or "AAAA" is large enough to sustain the cathode loading but small enough
> to avoid much evolved hydrogen. In this arrangement the interface
> essentially acts like a diode, an "incremental diode".
>
> It's too good to be true. Just wishful thinking? After this long day I
> can't call it one way or another. I suppose the possibility of electolysis
> improvement boils down to whether or not the current anode or bias anode is
> supplying current when Plate 1 is postitive.
>
> Regards,
>
> Horace Heffner
