Kinetics of hydrogen peroxide accumulation in electrosynthesis from oxygen in gas-diffusion electrode in acidic and alkaline solutions

Article abstract of DOI:10.1023/A:1026398025991

Accumulation of H₂O₂ in aqueous solutions with various pH values in electroreduction of oxygen in carbon-black gas-diffusion hydrophobized electrodes was studied. The effect of various parameters of the process on its electrochemical

Full text of DOI:10.1023/A:1026398025991

Russian Journal of Applied Chemistry, Vol. 76, No. 7, 2003, pp. 1070 1075. Translated from Zhurnal Prikladnoi Khimii, Vol. 76, No. 7,
003, pp. 1103 1108.
Original Russian Text Copyright
2
2003 by Kolyagin, Kornienko.
APPLIED ELECTROCHEMISTRY
AND CORROSION PROTECTION OF METALS
Kinetics of Hydrogen Peroxide Accumulation
in Electrosynthesis from Oxygen in Gas-Diffusion Electrode
in Acidic and Alkaline Solutions
G. A. Kolyagin and V. L. Kornienko
Institute of Chemistry and Chemical Technology, Siberian Division, Russian Academy of Sciences,
Krasnoyarsk, Russia
Received February 13, 2003
Abstract Accumulation of H O in aqueous solutions with various pH values in electroreduction of oxygen
2
2
in carbon-black gas-diffusion hydrophobized electrodes was studied. The effect of various parameters of
the process on its electrochemical component and decomposition rate of the H O formed was analyzed.
2
2
In the last 20 years, much interest has been shown
in indirect oxidation of organic and inorganic sub-
stances with hydrogen peroxide generated electro-
chemically from oxygen [1 3]. This interest stems
from the wide use by modern chemical industries of
principles of conjugated processes [4] involving
environmentally safe reagents, such as electric current
of H O , which makes the cost of hydrogen peroxide
2 2
much lower [7, 8].
It is known that the rate of H O accumulation
2
2
in the electrolyte in electroreduction of oxygen is
described by the equation [9]
Va = dc/d = Vs
Vd = A I/v
V ,
(1)
1
d
and chemically bound forms of oxygen (O , H O ,
3
2
2
1
where V is the rate of H O accumulation (mol l h );
a
2 2
ROOH, etc.).
V , rate of H O electrosynthesis; V , rate of H O
s
2
2
d
2
2
2
2
Hydrogen peroxide as oxidizing agent has a number
of unique properties. It is well soluble in water and is
nontoxic. Use of hydrogen peroxide does not yield
dangerous wastes, only water and oxygen being prod-
ucts of its decomposition. Hydrogen peroxide shows
a pronounced oxidizing power and allows oxidation of
various organic and inorganic compounds both in
alkaline and in acidic media. The range of its ap-
decomposition; A, electrochemical equivalent of H O
(mol A 1 h ); I, electrolysis current (A); v, catholyte
1
volume (l); , fraction of current consumed for O2
reduction to H O ; c, H O concentration in the
2
2
2 2
catholyte (M); and , electrolysis time (h).
Decomposition of hydrogen peroxide is a complex
process which depends on numerous factors, including
the degree of dissociation in aqueous solutions. In
plicability is exceedingly wide: aqueous H O solu-
acidic solutions, H O molecules are little dissociated
2
2
2 2
tions are used in pulp-and-paper industry, in manufac-
ture of detergents, in hydrometallurgy, in wastewater
purification, and in many other industries requiring an
environmentally safe oxidizing agent [5, 6].
and the decomposition process follows the equation
[5, 6]
2
H O = 2H O + O .
(2)
2
2
2
2
In alkaline solutions, H O is largely dissociated
It is known that hydrogen peroxide can be com-
paratively easily obtained by cathodic reduction of ox-
ygen on graphitic carbon electrodes in alkaline solu-
tions. Since the solubility of oxygen in aqueous elec-
trolyte solutions is low, hydrophobized gas-diffusion
electrodes are presently used for intensifying its reduc-
tion process. This method is waste-free and enables
production of H O at its consumption site in the
2 2
[
10, 11]:
H O + OH = HO2 + H O.
(3)
2
2
2
When perhydroxide ions appear in considerable
amounts, decomposition of H O may involve these
2
2
ions [7, 11, 12]:
HO2 = 2OH + O2,
HO2 + H O2 = H O + OH + O2.
2
2
2
(4)
(5)
form of aqueous solutions and use of these solutions
as a commercial product without preliminary isolation
2
2
1
070-4272/03/7607-1070$25.00 2003 MAIK Nauka/Interperiodica

KINETICS OF HYDROGEN PEROXIDE ACCUMULATION
1071
Table 1. Effect of electrolyte composition on coefficients of Eqs. (6), (7), and (9) and on electrolysis parameters*
1
c
,
Run
no.
Agitation
mode
V , mol l 1 h ,
H O
2
M
d
2
Electrolyte, M
k
av
at c
= 0.6 M
H O
2
2
1
2
3
4
5
6
7
8
**
**
I
II
II
I
I
I
0.25 NaOH
0.12 h 1
0.072
0.10
0.122
0.086
0.027
0.03
0.96
0.97
0.97
0.97
0.98
0.98
0.4
0.93
0.8
0.69
0.59
0.52
0.55
0.68
0.86
0.32
0.63
1
0.25 NaOH
0.25 NaOH
0.5 NaOH
1.0 NaOH
0.17 h
0.34 mol l 1 h 1
0.68
0.72
0.89
1.13
0.25
0.83
1
1
1.54 mol l
8.0 mol l
h
h
1
1
1.0 NaOH + 0.017 Na SiO 0.05 h 1
2 3
II
II
0.1 H SO
0.05 h 1
2
4
0.05 K SO + 0.15 H SO
0.085 h 1
0.051
0.75
2
4
2
4
*
c
and
are the concentration and current efficiency by H O after 7 h of electrolysis.
2 2
H O
2
2
*
* Experiments carried out with electrodes fabricated from paste heated at 340 C.
Among the factors affecting the rate of H O de-
EXPERIMENTAL
2
2
composition [3, 5, 6, 10 20], the composition and pH
value of solutions are among those most important
The experimental conditions and the electrolyzer
design were similar to those described in [4, 7, 8].
Preparative electrolysis was carried out in the galvano-
[
5, 10 12, 19, 20]. The rate of decomposition in alka-
line solutions can be formally described using various
equations:
static mode at 20 C for 7 h at a current density of
2
5
0 mA cm , as calculated per unit apparent frontal
2
surface area (5 cm ). The catholyte volume was
.023 l. Oxygen was fed into the electrode from its
Vd = kc
[9],
(6)
(7)
(8)
,
H O
2
2
0
ud
2
back surface under atmospheric pressure. To reveal
the influence exerted by the mass transfer of sub-
stances involved in the process, the catholyte was
agitated by bubbling of argon through a tube 1.5 mm
Vd = kc
cHO2 [12],
+ k0 [11],
2
H O
2
ud
2
Vd = kc
H O
1
in diameter at a rate of 10 ml min continuously
ud
2
where c
is the total concentration of H O ; c
(agitation mode I) or at a rate of 38 ml min 1 for
H O
2
2
H O
2
2
2
concentration of the undissociated H O2 species;
2
1 min before sampling a solution to determine the
content of H O every hour (agitation mode II).
c
, concentration of perhydroxide anions; and
HO
2
2 2
k and k , constants.
0
The catholyte and anolyte were separated by an
MF-4SK-100 cation-exchange membrane. The elec-
trodes were prepared from A-437E acetylene carbon
black containing 40 wt % Ftoroplast-4D (Teflon), with
In acidic solutions, the decomposition rate is com-
monly described by Eq. (6) [8], whereas in alkaline
solutions, each particular case should be considered
separately.
6
1
5 vol % porosity, and sintered in air at 360 C for
0 min [17]. The electrode paste was preliminarily
The known studies concerned with H O electro-
2
2
heated at a temperature of up to 300 C. Part of elec-
trodes were prepared from a paste heated at 340 C.
The results obtained with these electrodes are listed
in Table 1 and shown in Fig. 1, curves 3 and 4.
synthesis from O paid little attention to kinetics of
2
H O accumulation and did not consider as a whole
2
2
the wide variety of factors affecting the process simul-
taneously. Revealing the fundamental aspects of the
process of H O accumulation is an important and
The fraction of current consumed for synthesis of
H O was determined by gasometry, or, when pos-
2
2
2
2
necessary stage as regards practical application of the
electrochemical method for obtaining H O in solu-
sible, calculated from experimental data [16]. The rate
of H O decomposition was found using Eq. (1) by
2
2
2
2
tions with varied pH value.
differentiating graphically the curves of H O ac-
2
2
This study is concerned with the effect of the com-
position, concentration, and pH of the electrolyte on
cumulation. The electrode potential was measured
relative to a silver chloride reference electrode. In
acidic and alkaline solutions, oxygen is reduced to
H O in the same range of potentials 0.4 0.6 V,
the kinetics of accumulation of H O in its synthesis
2
2
from O in gas-diffusion electrodes.
2
2 2
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 76 No. 7 2003

1072
KOLYAGIN, KORNIENKO
H O stabilizer. Table 1 lists constants k for Eqs. (6),
2
2
c, M
(
7), and (9), current efficiencies by H O , and its con-
2 2
centrations after 7 h of electrolysis. Also listed for
comparison are rates of H O decomposition at a con-
2
2
centration of 0.6 M.
As seen from Fig. 1 (curves 1, 2, 5) and Table 1
run nos. 4 6), raising the concentration of alkali and
(
adding sodium silicate to the solution make higher the
H O concentration and the current efficiency by
2
2
H O , which can be accounted for by a decrease in
2
2
the rate of H O decomposition [12, 19, 20]. At
2
2
c
= 0.6 M, the action of the stabilizing agent is
H O
2
2
,
h
not manifested yet; when, however, the content of
H O is raised further, the decomposition rate de-
creases.
Fig. 1. Curves of hydrogen peroxide accumulation in alka-
line electrolytes. (c) H O concentration and ( ) time; the
same for Figs. 4 and 5. Electrolyte (M): (1) 1.0 NaOH +
.017 Na SiO , (2) 1.0 NaOH, (3, 4) 0.25 NaOH, and
2
2
2
2
0
(
2
3
The accumulation rate is strongly affected by the
5) 0.5 NaOH. Agitation mode (1 3, 5) I and (4) II. Points,
technology of electrode fabrication (Table 1, run
nos. 2 and 3). Raising the temperature to which the
electrode paste is heated leads to a change of the run
experiment; lines, calculation.
ci, M
PC, mol2 l 2
of the V = f(c
) dependence, presumably owing
H O
2 2
d
to more complete removal of surfactants and other
adsorbed substances [18] and to partial oxidation of
the carbon black [16]. These electrodes have lower
electrolyte porosity (0.5 vol %). The potential of these
electrodes in electrolysis is shifted, compared with the
other electrodes, to the cathodic region by 0.2 0.3 V.
In experiments with electrodes fabricated from a paste
heated at 340 C, the rate of H O decomposition is
2
2
described by Eq. (6). With the other electrodes, the
rate of H O decomposition in 0.5 and 1.0 M NaOH
solutions is described by Eq. (7), that in a solution
with addition of sodium silicate, by Eq. (6), and that
in a 0.25 M NaOH solution, by the equation
2
2
c, M
Fig. 2. Concentrations c of (1) OH and (2) HO ions,
3) undissociated H O , and (4) product of concentrations
i
2
(
2 2
ud
2
PC, c
c
, vs. hydrogen peroxide concentration c in
H O HO
2
2
0
.5 M NaOH solution.
2
Vd = k(c
) .
(9)
H O
2
2
despite that the zero-current potential is about 0.2 V
in alkaline solutions and is shifted to the anodic
region in acidic solutions. As in [21], the potential is
Figure 2 shows as an example the influence of
in a 0.5 M NaOH solution on the values of
c
c
H O
2
2
ud
2
, cHO , and cOH , calculated using equations
independent of c
. For example, the potential re-
H O
H O
2
2
2
2
taken from [10]. The equilibrium constant of reac-
tion (3) at 20 C is 261.4 [10]. Despite the fact that
concentrations were taken instead of activities in the
mained within 0.56 0.58 V at H O concentrations
2
2
in the range from 0.54 to 0.024 M at pH 0.9 (0.05 M
K SO + 0.15 M H SO ) and shifted in the negative
2
4
2
4
calculations, the resulting products of cHO and cOH
direction to 0.53 V with pH increasing to 2.1. The
overvoltage of O reduction to H O in acidic solu-
2
were in good agreement with the values reported
in [12].
2
2 2
tions much exceeds that in alkaline solutions. No
evolution of hydrogen occurs under the given condi-
tions because of the high overvoltage of its reduction
on carbon black.
As seen from Fig. 2, the concentration of hydrox-
ide ions decreases and the concentrations of per-
hydroxide ions and undissociated H O , and the prod-
2
2
uct of these, grow with increasing total concentration
of H O . In a 0.5 M NaOH solution, at c of up to
Figure 1 shows curves of H O accumulation in
the cathode chamber in solutions with various NaOH
concentrations and with sodium silicate added as
2
2
2
2
H O
2 2
approximately 0.5 M, when H O is mainly in the
2
2
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 76 No. 7 2003

KINETICS OF HYDROGEN PEROXIDE ACCUMULATION
1073
form of perhydroxide ions, the decomposition rate can
be described using Eq. (6) with k = 0.05 h . This
V , mol l 1 h 1
1
d
value is equal to that for a solution with sodium sili-
cate, which must be the case, since the accumulation
curves coincide up to 0.5 M of H O at equal . When
2
2
a considerable amount of undissociated H O is addi-
2
2
tionally present in the solution, the decomposition rate
is described by Eq. (7) in the whole concentration
range.
Figure 3 shows the dependence of the H O de-
2
2
composition rate in 0.5 and 1.0 M NaOH solution on
ud
PC, mol2 l 2
the product c
c
. The slope of the straight line,
H O HO
2
2
2
ud
i.e., the value of k, grows with increasing alkali con-
centration, but the product decreases, as also does the
decomposition rate.
Fig. 3. Effect of the product of concentrations, PC, cH O
2
2
c
, on the decomposition rate V of H O in (1) 1.0 M
HO
d
2 2
2
NaOH solution and (2) 0.5 M NaOH. Agitation mode I;
the same for Fig. 5.
Figure 1 (curves 2, 5) shows the accumulation
curves calculated using Eqs. (1) and (7) and values of
k and from Table 1. These curves are in good agree-
ment with experimental data.
c, M
Depending on the type of the equations Vd
=
f(c ) and = f(c ), solutions to Eq. (1) are also
H O
H O
2 2
2
2
different:
c = g[exp(2gk )
g = [A I/(kv)]1/2
2)2 and
1][1 + exp(2gk )] 1,
(10)
(11)
,
h
Fig. 4. Curves of H O accumulation in solutions with pH
at V = k(c
= const;
2 2
d
H O
2
0
0
.9. Electrolyte (M): (1) 0.1 H SO and (2) 0.05 K SO +
2 4 2 4
.15 H SO . Points, experiment; lines, calculation by
c = AI [1
exp( k )]/(kv)
2
4
Eq. (2).
at V = kc
and
= const [8];
d
H O
2
2
trode, when the appearing oxygen undergoes repeated
reduction, and with further reduction of H O . In alka-
2
2
AIb{exp[(AIa/v
k) ]
k]v
1}
c =
(12)
line solutions, H O is reduced on graphitic carbon
2 2
[
AIa/v
materials at high overvoltage, whereas in acidic solu-
tions this process is markedly facilitated. Therefore,
the insignificant decrease in in alkaline solutions is
at V = kc
and
= b
ac
H O
2
[4].
d
H O
2
2
2
Equation (12) was used to calculate curves 1, 3,
and 4 in Fig. 1.
only due to a rise in the rate of H O decomposition
2 2
in the electrode with increasing H O concentration,
2
2
whereas in acidic solutions the decrease in is mainly
due to an increase in the rate of H O reduction.
In alkaline electrolytes,
is large and virtually
independent of c and other electrolysis param-
2
2
H O
2
2
Thus, the process occurring in an electrode are
strongly affected by H O removal from the electrode
eters, even though it tends to decrease somewhat
(
linearly) with increasing H O concentration, as is
2 2
2
2
and by the activity of hydrogen ions, which depends
on the electrolyte composition and electrolysis condi-
tions [8], within the electrode. Compared to acidic
solutions, removal of H O from the pore volume of
also the case in [22]. For example, = 1 0.085c
H O
2
2
in a 0.25 M NaOH solution (Table 1, run no. 1). In
acidic solutions, depends on the solution composi-
tion, but also is a linear function of c
[8]. For
2 2
H O
2
2
the electrode is somewhat facilitated in alkaline solu-
tions, since perhydroxide ions are removed not only
by diffusion, but also via migration under the action
of the electric field. Figure 4 illustrates the influence
of the composition of an acidic solution by the exam-
example, = 1 0.39c
in a solution containing
H O
2
2
0
.05 M K SO + 0.15 M H SO .
2 4 2 4
In alkaline and acidic solutions, changes in are
associated both with H O decomposition in the elec-
2
2
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 76 No. 7 2003

1074
KOLYAGIN, KORNIENKO
Table 2. Electrolysis parameters* used to calculate curves of H O2 accumulation, shown in Fig. 6
2
Curve no.
I, A
Catholyte volume, l
b
a, l mol 1
k, h 1
, h
1
2
3
4
5
6
7
0.25
0.25
0.50
0.25
0.25
0.25
0.25
0.023
0.01
1
1
1
1
1
0
0
2.47
1.33
1.55
2.85
3.10
3.43
8.78
1.00
0.81
0.80
0.86
0.80
0.72
0.28
0.5
0.5
0.01
0.5
0.5
0.5
0.1
0.1
0.1
0.05
0.1
0.1
0.023
0.023
0.023
0.023
0.023
1
0.6
*
and
are the time of electrolysis, necessary for the H O concentration of 0.5 M to be reached, and the resulting current
2 2
efficiency, respectively.
ple of the curves of H O accumulation in solutions
with pH 0.9 (Table 1, run nos. 7 and 8).
trode of hydrogen ions involved in H O reduction
2 2
2
2
to water. For example, in a solution containing
.05 M K SO + 0.15 M H SO , decreases by a
0
2
4
2
4
The aforesaid is also confirmed by the fact that the
agitation mode affects differently the values of and
factor of nearly 2 in going from agitation mode I to
mode II, whereas already at pH 3.2 (0.495 M K SO +
2
4
c
in acidic and alkaline solutions. Raising the
H O
2
2
0.005 M H SO ) the agitation mode has virtually no
2 4
intensity of agitation in alkaline solutions leads to
a decrease in the rate of decomposition because of the
effect, since the activity of hydrogen ions decreases by
a factor of more than 100.
change in c
in the near-electrode space (Table 1,
H O
2
2
The linear dependence of the current efficiency
run nos. 1 and 2) and has virtually no effect on ,
whereas in acidic solutions, a decrease in is ob-
served because of the increasing supply to the elec-
on c
(Fig. 5) is preserved at higher H O concen-
H O
2 2
2
2
trations on raising the concentration of alkali and on
introducing a stabilizer, i.e., in the case when the
decomposition rate depends on c
linearly [23];
H O
2
2
further, the current efficiency falls dramatically
because of an increase in the rate of H O decomposi-
2
2
tion. In acidic electrolytes, in contrast to alkaline solu-
tions, the type of the equation V = f(c ) is in-
d
H O
2 2
dependent of the electrolyte composition and the
dependence = f(c ) is linear during the whole
time of electrolysis [4]. For example,
0.37c for a solution containing 0.05 M K SO +
H O
2
2
= 0.97
c, M
H O
2
4
2
2
0
.15 M H SO (Table 1, run no. 8).
Fig. 5. Current efficiency
various electrolytes. Electrolyte (M): (1) 0.5 NaOH,
2) 1.0 NaOH, and (3) 1.0 NaOH + 0.017 Na SiO .
vs. H O concentration c in
2 4
2
2
To evaluate the influence exerted by the electroly-
(
2
3
sis parameters on the run of an accumulation curve
and to predict the current efficiency, which is one of
the most important electrosynthesis parameters, it is
necessary to analyze Eq. (12), which turns into
Eq. (11) at a = 0 ( = b). Figure 6 shows curves of
H O accumulation for various values of the elec-
c, M
2
2
trolysis parameters (Table 2). Table 2 also lists for
comparison the times required for solutions with
c
= 0.5 M to be obtained and the resulting current
2
H O
2
efficiencies. For clarity, the values of the parameters
are chosen so that curves do not overlap. All the com-
parisons are made relative to curve 6 (Fig. 6). Curve 1
,
h
is calculated using the equation c
= A I /v.
H O
2
2
Fig. 6. Effect of electrolysis parameters (Table 2) on the
run of curves of H O accumulation, calculated by Eq. (2).
As seen from Fig. 6 and Eq. (12), the multiplier
2
2
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 76 No. 7 2003

KINETICS OF HYDROGEN PEROXIDE ACCUMULATION
1075
AIb/v determines the initial slope of an accumulation
curve, i.e., the rate of H O accumulation, which
2. Pletcher, D., Acta Chem. Scand., 1999, vol. 53, p. 745.
2
2
3. Brillas, E., Bastida, R. M., Llosa, E., and Casado, J.,
decreases with increasing H O concentration because
2
2
J. Electrochem. Soc., 1995, vol. 142, no. 6, pp. 1733
of a decrease in and rise in the decomposition rate.
The highest H O concentration is obtained when
1
741.
2
2
4
5
. Nagiev, T.M., Usp. Khim., 1985, vol. 54, no. 10,
pp. 1654 1673.
the accumulation rate becomes equal to the rate of
H O decomposition. When the decomposition rate is
2
2
. Schumb, W.C., Satterfield, Ch.N., and Went-
worth, R.L., Hydrogen Peroxide, New York: Chap-
man and Hall, 1955.
described by Eq. (6), the maximum concentration is
given by the expression c = A I/(kv).
H O
2
2
The rate of H O accumulation is strongly affected
2
2
6. Khimiya i tekhnologiya perekisi vodoroda (Chemistry
and Technology of Hydrogen Peroxide), Sery-
shev, G.A., Ed., Leningrad: Khimiya, 1984.
by coefficient b (Fig. 6, curve 7). The decrease in k
and a starts to affect the accumulation rate at higher
H O concentrations (curves 4 and 5). The quantity
2
2
7
. Kornienko, V.L., Kolyagin, G.A., and Saltykov, Yu.V.,
I/v is the volume current density and, consequently,
Zh. Prikl. Khim., 1999, vol. 72, no. 3, pp. 353 361.
the rate of H O accumulation may become higher
2
2
8
. Kolyagin, G.A. and Kornienko, V.L., Khim. Inter.
Ustoich. Razv., 2000, vol. 8, no. 6, pp. 803 807.
with increasing current density or decreasing catholyte
volume (Fig. 6, curves 2 and 3). This may give, dur-
ing the first hours of electrolysis, an H O concentra-
9. Vert, Zh.L. and Pavlova, V.F., Zh. Prikl. Khim., 1988,
2
2
tion exceeding the concentration that would be ob-
served at a decomposition rate close to zero and = 1
vol. 61, no. 5, pp. 1148 1150.
1
1
1
0. Balej, J. and Spalek, O., Coll. Czech. Chem. Commun.,
(
Fig. 6, curve 1).
1
979, vol. 44, no. 2, pp. 488 494.
1. Spalek, O., Balej, J., and Paseka, I., J. Chem. Soc.,
Faraday Trans. 1, 1982, vol. 78, pp. 2349 2359.
CONCLUSIONS
2. Duke, F.R. and Haas, T.W., J. Phys. Chem., 1961,
(1) The rate of subsequent electroreduction of
vol. 65, no. 2, pp. 304 306.
H O to water in an alkaline electrolyte in
2
2
13. Moiseev, I.I., Izv. Akad. Nauk, Ser. Khim., 1995,
hydrophobized carbon black electrodes is low. The
accumulation rate of hydrogen peroxide is determined
under these conditions by the rate of its chemical
decomposition in the cathode chamber.
no. 3, pp. 578 588.
1
1
4. Gyenge, E.L. and Oloman, C.W., J. Appl. Electro-
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(2) In acidic solutions, the rate of hydrogen perox-
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2
2
1
1
1
1
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2
2
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7. Kolyagin, G.A. and Kornienko, V.L., Zh. Prikl. Khim.,
(
3) The equations relating c and electrolysis
H O
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2
2
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2
2
the other parameters being the same, the initial rate of
H O accumulation is determined by the volume
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2
2
current density; with increasing electrolysis duration
and H O concentration, the rate of hydrogen perox-
2
2
2
2
2
0. Raskina, I.Kh., Sadov, F.I., and Bogdanov, G.A.,
ide decomposition in an alkaline medium and reduc-
tion to water in an acidic medium starts to exert
steadily increasing influence on the accumulation rate.
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