736
M. Ved’ et al.
where () L are the particles in the solution, () S are intermediate products and the
particles adsorbed by the electrode surface.
The given series fails to reflect the process mechanism in full because, in addition
to the solution components, intermediate metal oxides that are formed on the catalyst
electrode surface during the anode polarization can participate in it. In this case, the
reversibility of the processes that occur on the electrodes is the precondition for the
efficient operation of catalysts.
Let’s consider the individual stages of the electrode process and detect the specific
features of each stage. The first stage of the adsorption of methanol molecules on the
electrode surface that corresponds to the (CH 3 OH) L → (CH 3 OH) S transformation
can limit the electrode process only in the case of fast and completely reversible
single-stage charge transfer in the electrochemical reaction. It is known that the
oxidation of compound molecules is not of that type; therefore, we can conclude that
the adsorption process will be reversible with regard to the charge transfer stage. The
second stage (CH 3 OH) S → (HCHO) S is directly related to the charge transfer, and it
is electrochemical. The methanol oxidation that results in the formation of aldehyde
is accompanied by the hydrogen atom and carbon σ-bond rupture, and the formation
of the double bond between carbon and oxygen:
(CH 3 OH) S + 2OH
−
→ (HCHO) S + 2H 2 O + 2e,
(2)
Particularly this stage is considered to be limiting, and its rate can be controlled by
the system cycling without carbon dioxide formation and solution carbonization. The
conduction of the process in the interval of potentials that corresponds to the given
stage is an essential and sufficient condition for the control of the entire oxidation
process.
The next stage of methanol oxidation conducted to get methane acid is also electrochemical, and it is related to the substitution of hydrogen atom by oxygen one
according to the gross scheme:
(HCHO) S + 3OH
−
→ (HCOO
−
) S + 2H 2 O + 2e.
(3)
A degree of the reversibility of this stage will depend on the lability of oxygen
atoms whose donor can be the hydroxide ions that are present in the solution.
However, it is more probable that the surface oxides of electrode material that are
formed during the anode polarization will participate in this stage. For example,
according to the transfer reaction of oxygen atom from the metal oxide MO x to
carbon:
(HCHO) S + (MO x ) S → (HCOOH) S + (MO x−1 ) S ,
(4)
the reaction is transformed into the chemical one, and as a consequence, the process
probability and the rate of it, on the whole, are increased. It is evident that the catalytic
activity of the alloys of cobalt, molybdenum, and tungsten (zirconium) is explained
particularly by a high donor acceptance capacity with regard to oxygen, and the
M. Ved’ et al.
where () L are the particles in the solution, () S are intermediate products and the
particles adsorbed by the electrode surface.
The given series fails to reflect the process mechanism in full because, in addition
to the solution components, intermediate metal oxides that are formed on the catalyst
electrode surface during the anode polarization can participate in it. In this case, the
reversibility of the processes that occur on the electrodes is the precondition for the
efficient operation of catalysts.
Let’s consider the individual stages of the electrode process and detect the specific
features of each stage. The first stage of the adsorption of methanol molecules on the
electrode surface that corresponds to the (CH 3 OH) L → (CH 3 OH) S transformation
can limit the electrode process only in the case of fast and completely reversible
single-stage charge transfer in the electrochemical reaction. It is known that the
oxidation of compound molecules is not of that type; therefore, we can conclude that
the adsorption process will be reversible with regard to the charge transfer stage. The
second stage (CH 3 OH) S → (HCHO) S is directly related to the charge transfer, and it
is electrochemical. The methanol oxidation that results in the formation of aldehyde
is accompanied by the hydrogen atom and carbon σ-bond rupture, and the formation
of the double bond between carbon and oxygen:
(CH 3 OH) S + 2OH
−
→ (HCHO) S + 2H 2 O + 2e,
(2)
Particularly this stage is considered to be limiting, and its rate can be controlled by
the system cycling without carbon dioxide formation and solution carbonization. The
conduction of the process in the interval of potentials that corresponds to the given
stage is an essential and sufficient condition for the control of the entire oxidation
process.
The next stage of methanol oxidation conducted to get methane acid is also electrochemical, and it is related to the substitution of hydrogen atom by oxygen one
according to the gross scheme:
(HCHO) S + 3OH
−
→ (HCOO
−
) S + 2H 2 O + 2e.
(3)
A degree of the reversibility of this stage will depend on the lability of oxygen
atoms whose donor can be the hydroxide ions that are present in the solution.
However, it is more probable that the surface oxides of electrode material that are
formed during the anode polarization will participate in this stage. For example,
according to the transfer reaction of oxygen atom from the metal oxide MO x to
carbon:
(HCHO) S + (MO x ) S → (HCOOH) S + (MO x−1 ) S ,
(4)
the reaction is transformed into the chemical one, and as a consequence, the process
probability and the rate of it, on the whole, are increased. It is evident that the catalytic
activity of the alloys of cobalt, molybdenum, and tungsten (zirconium) is explained
particularly by a high donor acceptance capacity with regard to oxygen, and the