Hydrogen
may be the fuel of the future as prophesied in my blog article
entitled “PEM
Fuel Cell Technology gets Japanese Government support - Hydrogen Gas Stations
Coming in First World and Developing World Countries” but getting it to use
in motor vehicles is not an easy affair.
This
is to because electrolysis, a potentially easy way to produce Hydrogen from
water, requires the use of expensive Platinum or Iridium Electrode and very
large currents.
This
may soon be a thing of the past, as researchers at Stanford University have
figured out a cheaper material for the electrodes used in electrolysis of water
and a catalyst that reduces the power needed as reported in the article “New
device splits water into clean hydrogen and oxygen”, published June 30,
2015 By Nicolette Emmino, Digitaltrends.
The
research paper was written by Stanford graduate student Haotian Wang, who led
the Stanford University study with assistance from Professor of Materials
Science and Engineering at Stanford University, Yi Cui. Stanford graduate
student Haotian Wang work builds on earlier research done by Stanford Graduate
Student Hongjie Dai using Iron and Nickel as electrodes.
All
of this sounds a bit overblown and very strange. Don't get me wrong, it's a
very important development as published in the Stanford Newspaper article “Single-catalyst
water splitter from Stanford produces clean-burning hydrogen 24/7”,
published June 23, 2015 BY MARK SHWARTZ, Stanford
Report. But aren't these cheaper electrodes consumed when used in
electrolysis?
Stanford
graduate student Haotian Wang, who led the Stanford University study, opted to
use electrodes composed of an alloy of Iron and Nickel. Iron and Nickel are
usually consumed in the reaction, but apparently they must have treated the
electrodes so that Nickel (I) Oxide (NiO(s)) and Iron (II) Oxide (FeO(s))
salts do not form during the electrolysis process.
So
how did they do this?
Stanford University
Nickel-Iron Electrolysis Electrodes – Oxides of Iron and Nickel
Using
Rare Earth metals for Electrodes makes the process of electrolysis more
expensive.
They're
needed as any other type of metal for the electrodes for the Anode (+) Anode
Cathode (-) will react with the Oxygen (O2 (g)) gas to form oxides. Oxygen
(O2(g)) gas is formed at the Anode (+) while Hydrogen gas, which is
relatively inert, will bubble off the Cathode (-) as follows:
1.
2H+ + 2e- "H2(g)
(Reaction at the Cathode)
2.
O2- "
O2(g) + 2e- (Reaction at the Anode)
Electrolysis
of water requires charge carriers in the form of ionic salts dissolved in the
water, as pure water cannot be broken down by electrolysis. Also, to produce
large volumes of both gases required larger voltages and currents, hastening
the rate at which the electrodes were consumed as well as increasing the amount
of electricity needed to perform electrolysis.
To
overcome these problems, Stanford graduate student Haotian Wang may have opted
to use oxides or sulphides of Iron and Nickel instead of the direct metals, as Iron
and Nickel are normally consumed in electrolysis reaction.
These
oxides may have been produced by reducing the Iron and Nickel down to
nanoscopic powders that were very reactive and then introducing Oxygen (O2(g))
at very low pressure in a vacuum chamber to react with the powdered nanoparticles
of Iron and Nickel.
The
resulting oxides or sulphides meant that the metals were made inert but
non-conductive.
Oxides
formed by oxidization means that all of the available electrons have been used
in covalent bonds with Oxygen (O2 (g)) or some other Group VI such
as Sulphur (S8(s)). To get them reactive, the Stanford Researchers
then sintered the Iron and Nickel oxides together in a vacuum oven using either
intense radiation or a strong electrical heating source.
While
the powders were being heated and fused to form the electrodes, they also
introduced a strong magnetic field while being slowly cooled. This ensured that
as the metal cooled, the Nickel (I) Oxide (NiO(s)) and Iron (II)
Oxide (FeO(s)) or Nickel (I) Sulphide (NiS(s)) and Iron
(II) Sulphide (FeS(s)) formed orderly metallic crystals within their
macromolecular structure.
Stanford graduate
student Haotian Wang Black Salts – A Picture is worth a thousand Chemistry
Equations
The
result would not only be an electrode with possibly some amount of
paramagnetism, but also highly conductive, as the electrons would flow more
easily through the metallic crystal Lattice which has an orderly arrangement of
Nickel (I) Oxide (NiO(s)) and Iron (II) Oxide (FeO(s))
salts.
This
explains why the electrodes shown in the picture above with Stanford graduate
student Haotian Wang are black in colour; they're black because they're
possible oxides or sulphides of Iron and Nickel.
Because
he’s improving upon the work of Stanford Graduate Student Hongjie Dai, he may
have combined the Nickel (I) Oxide (NiO(s)) and Iron (II) Oxide (FeO(s))
or Nickel (I) Sulphide (NiS(s)) and Iron (II) Sulphide (FeS(s))
into a single electrode via sintering, based on how well those previous
experiments went to quote Stanford graduate student Haotian Wang: “Our water
splitter is unique because we only use one catalyst, nickel-iron oxide, for
both electrodes”.
Good
to note here it is Iron (II) Oxide (FeO(s)), a black salt and not
Iron (III) Oxide (Fe2O3(s)), a red salt, often called
rust, as rust has little or no catalytic properties. Same too for Nickel (I)
Oxide (NiO(s)) or Nickel (I) Sulphide (NiS(s)), both of
which are black salts.
Iron and Nickel are
Catalysts - Cheaper Electrodes All-Electric Vehicle Electrodes Special
Treatment
Aside
from this fabrication method using Nickel (I) Oxide (NiO(s)) and
Iron (II) Oxide (FeO(s)) or Nickel (I) Sulphide (NiS(s)),
Iron and Nickel both have known catalytic properties. These metals by
themselves are known Catalysts.
Like
a good catalysts, it lowers the activation energy required for a chemical
reaction to take place or in this case, breaks the bonds by supplying the
energy to overcome the covalent bonds between the Hydrogen and the Oxygen (O2(g))
molecules without being consumed in the reaction.
Iron
is used as a catalyst in the Fitz-Haber Process to make Ammonia (Lambert &
Mohammed, 1993 pp. 187) on an industrial scale and Nickel is used as a catalyst
in the production of margarine from Coconut oil in the form of Raney Nickel
(Hill & Holman, 1989, pp. 504) to produce Cyclohexane from Benzene.
The
fact that electrolysis requires a 1.5V battery source suggests that the battery
is acting as an electron charge pump, pumping extra electrons into the reaction
and thus speeding it up. Since the sintered using Nickel (I) Oxide (NiO(s))
and Iron (II) Oxide (FeO(s)) or Nickel (I) Sulphide (NiS(s))
is as very good conductor due to the fabrication process, this explains why the
reaction can take place at such a low voltage.
Stanford
graduate student Haotian Wang research has not only made the traditional
electrolysis more efficient, but his research suggests that the oxides of
transition metal catalyst can be used in lieu of Rare Earth Metals for
Batteries electrodes in All-Electric Vehicles.
All
that is required is that the process by which the metal is prepared so as to
change the properties of the metal to make it more conductive and less
reactive, while taking advantage of its catalytic properties.
References:
- Lambert, N., Mohammed, M.
(1993). Chemistry for CXC. pp.187,
Jordan Hill, Oxford: Heinemann
- Hill, G.C., Holman, J.S.
(1989). Chemistry in Context. (3rd
Ed.). pp. 504, Surrey, UK: Thomas Nelson and Sons Ltd
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