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Electrochemical reduction of chalcogenide esters in non-aqueous medium, 2-ethoxy ethanol
ELECTROCHEMICAL REDUCTION OF CHALCOGEhIDE ESTERS IN NON-AQUEOUS MEDIUM, 2-ETHOXY ETHANOL RAFIK 0. LOUTEY Xerox Research Centre of Canada, 2660 Speakman Drive, Mississauga,Ontario L5K 2L1, Canada and S. S. Xerox Corporation,
Webster
(Received
Research
BADESHA
Centre, 800 Phillips Road, Webster, NY 14580, U.S.A.
17 November
1983; in revised form 21 June 1984)
Abstract-Electrochemical reduction of bis(arsenic triglycollate) (CH*0)2A~O(CHt)20A~(OCH2)2 dimethyl sulfite (CHJO)3S0, diethylselenite,(CtHSO)$eO, and ethylene tellurite, (OCH3CH20)sTe was studied in non-aqueous, Z-ethoxy ethanol (cellosolve) using single-sweep voltammetry and cyclic voltammetry. It is shown that arsenic, sulfur, selenium and tellurium deposit at the cathode at bias potentials of - 0.70, -0.64, - 0.51 and - 0.22 V us Ag/AgCI, aq. KC1 respectively.
INTRODUCTION Electrochemical deposition offers a novel route to the production of photoconducting and semiconducting materials[l+]. Cathodic deposition of different elements with formation of alloys and compounds from aqueous electrolytes has been known for a long time[5]. The electrochemicai behaviour of chalcogen dioxides has been extensively studied in aqueous acidic solutions[4-81. The electrode process in which the chalcogen dioxide, XO1 with X = S, Se or Te, is reduced to its corresponding element is obviously complex since it involves at least four electrons. A reoent study of the reaction of selenious acid (H&eOJ) in H2S0, solution[S] has shown that the initial cathodic reaction involves an overall transfer of six electrons and the formation of H,Se which may react with HZSe03 to yield elemental selenium. Ward, Ishler and Damjanovic[4] on the other hand, have shown that cathodic codeposition of Se and Te from acidified solution of SeO, and TeOz is possible. The electrochemistry of chalcogenide esters in nonaqueous solvents has been less thoroughly studied. Alekperov and Babaeva[9] has shown that red amorphous Se and black crystalline Te were deposited on the cathode (Pt or graphite) from alcoholic solution of SeC14 and TeCl.,. It was noted that,after dissolving the S&I, and TeCl, in alcohol the pH fell below 1, which implies that a chemical reaction between Xa and the alcohol (ROH) took place liberating HCl and (RO).J (X = Se or Tel. Most of the electrodenosited Se &solved imme&ately while Te remained-practically insoluble. Recently a novel chemical approach to the preparation of pure non-metals such as Se and Te has been described[lO]. The technique involves chemically reducing, selenite and tellurite esters in cellosolve with hydrazine. Signi6cant progress has been made in the
preparation of a broad spectrum of pure and homogeneous alloys using chemical reduction and coreduction methods[ll]. The purpose of this report is to present the results of an investigation concerning the electrochemical reduction characteristiss of chalcogenide esters in nonaqueous solvent. The aim is to develop a simple technique for the preparation of pure metals as well as binary and ternary alloys of S, Se, Te and As. This approach complements in many ways the chemical reduction process.
EXPERIMENTAL Materials Dimethyl suffite and cellosolve were obtained from Aldrich Chemicals. The diethylselenite was prepared by dissolving selenium dioxide in ethyl alcohol and using benzene to remove water isotropically[12]. Similarly ethylene tellurite and bis(arsenic triglycollate) were prepared from the reaction of ethylene glycol with tellurium dioxide and arsenic oxide, in presence of p-toluene sulphonic acid[lO, 131 respectively. Tetiabutylammonium perchlorate (TBAP) was obtained from Aldrich Chemicals and dried in uacuu at 60°C. Electrochemical
measurements
Electrochemistry was performed using EG&G Princeton Applied Research Model 174A polarographic analyser equipped with Model 175 universal programmer and Model 303 static mercury drop electrode. Cyclic voltammograms were recorded on a Houston Series 2COO x-y recorder. The working electrode was a hanging mercury drop electrode (HMDE), a platinum wire was used as auxiliary 101
102
RAFIK 0. ILWTFYAND
S. S. BADESHA
electrode and Ag/AgCl, aq. KC1 as reference electrode. All electrochemical measurements were carried out at 20°C in argon purged cellosolve solution employing 0.5 mM chalcogenide ester and 0.05 M TBAP as sup porting electrolyte. RESULTS
AND
DISCUSSION
The single-sweep cyclic voltammograms of the chalcogenide esters listed in Table 1 were recorded with a stationary mercury eIectrode in 2-ethoxy ethanol (cellosolve) solution at 20°C. The cyclic vdtammograms of the dimethyl sulfite is illustrated in Fig. I measured at 200 mV s- I scan rate: It is characterised by a cathodic wave showing well-defined current maximum but no anodic wave on the reverse scan even at sweep rate up to 1 V s-l. These results are consistent with a slow electron transfer reduction and possibly followed by a chemical reaction. The presence of a follow up chemical reaction is indicated by the appearance of an anodic wave at +O.2 V when the potential is swept positively from a point on the reduction wave. This anodic wave corresponds to the oxidation of a chemical product such as sulfur amalgam. An adsorption peak anodic of the first reduction wave was also observed. The cyclic voltammogram of diethyl selenite is shown in Fig. 2 which is characterised by the same basic pattern. At electrode potentials =z - 0.5 V red amorphous Se deposited onto the electrode. The electrodeposited Se did not dissolve away and as a result a new mercury drop was required for each cycle. Ethylene tellurite exhibited two irreverand -0.73 V sible reduction waves at -0.22 (10 mVs- ’ sweep rate). The first reduction wave corresponds to Te deposition and the second wave leads to polytelluride ions Te;‘. The cyclic voltammogram of the ethylene tellurite is illustrated in Fig. 3. In a manner similar to the sulfite an anodic wave at + 0.48 V appears only after cathodic sweep to potentials corresponding to tellurium deposition. This wave most likely corresponds to oxidation of Te amalgam. In the second cyclic scan a new cathodic wave appears anodic of Te deposition wave which corresponds to reduction of the partially oxidized Te, perhaps Te’ +. Bis(arsenic triglycollate) exhibits a single unreversible reduction wave at 0.70 V as shown in Fig. 4. The details of the sweep dependence of the cathodic waves are shown in Fig. 5 for ethylene tellurite as a representative chalcogenide ester. Both the peak potential, Ep,and peakcurrent, ip,are strongly dependent on sweep rate, u, and temperature. A closer inspection
Table 1. Cyclic voltammetric Compound Bis(arsenic triglycollatc) (CHIO),AsO(CH,),As(CH,O), Dimethyl sulfite (CH,0)2S0 Dlcthyl selenelte (CIH,O),SeO Ethylene tellurite (OCH2CH20)Te
Fig. 1. Cyclicvoltammogramofdimethyl sultlte in cellosolve containing 0.05M TBAP. Dotted line is the second scan. Note
VOLTS
Fig. 2. Cyclic voltammogram
vs
Aq
AgC?
of diethyl selenite in cellosolve.
Fig. 3. Cyclic voltammogrsmof ethylene tellurite in cellosolve. Dotted line corresponds to the second scan.
of the cyclic voltammograms reveals that the current in the foot of the cathodic waves is singualrly independent of the sweep rate. Such a behaviour, originally noted by Reinmuth[l4], strongly suggests
data for organ0 chalcogenide*
EP, V+ - 0.70
(Ep-Ep,,)
- 0.64 -0.51 - 0.22
* Measured at HMDE at10 mV s-’ in 2-ethoxyethanolcontaining etectrolyte at 20°C. + Potentials vs Ag/AgCI, aqueous KCI.
as supporting
the disappearanceof an adsorptionpeak.
0.10
0.05 0.09 0.065
ctn
k,(W
ems-’
0.96
1.8 x IO@ 6.0 x 10-S
0.53 0.74
4.4 X lo- 3 4.5 X 10-S
0.48
0.05 M tetrabutyiammonium
pcrchlorate
103
Electrochemicalreductionof chalcogenideesters
Fig. 4. Cyclic voltammogramof bis(arsenictriglycollate)in cellosolve.
-I Fig. 5. The sweep dependence ethylene
of the cathodic tellurite.
waves
of
and are listed in TabIe I. These rates are typical of many alkyl metals compounds. In contrast to the complex electrochemical behaviour of chalcogens in aqueous acidic media, the process in non-aqueous solvents appears straightforward. The electroreduction of the chalcogenide esters to their corresponding elements occurs at a well defined potentia1 and the deposit appears to be stable. Hence, electrochemical reduction of chalcogenide esters can be used as a method for the p&cation of selenium, tellurium and arsenic. In Table 2, the emission spectral analysis of tellurium obtained by electrochemical reduction of pure ethylene tellurite is compared with that of a commercial tellurium sample indicating the potential of the technique. The black crystalline tellurium was electrochemically deposited onto a ruthanised titanium cathode. Similar results were obtained with electrochemically deposited selenium. The electrochemical behaviour of a mixture of diethyl selenite and ethylene tellurite is shown in Fig. 6. As expected, both materials are reduced at their standard potential. The reduction waves of dimethyl sulfite and diethyl selenite merge together into one reduction wave when a mixture of the two materials was examined. Electrochemically codepositing As, S, Se and Te onto a substrate from a solution of their ions, in such a way that the relative deposited amounts of S, Se and Te are controlled by their relative concentration in the electrolyte and by the choice of electrochemical conditions, ie current density or electrode potential, provides a method for preparation of a wide range of useful binary and ternary alloys of As, S, Se and Te.
that electron transfer to these chalcogenide esters is electrochemically unidirectional, ie totally irreversible. The cathodic peak potential shifts cathodically with an increase in scan rate. However, the ratio of i,/vi’2 is constant. These behavioursare characteristic of an irreversible charge transfer process. Under these conditions, the heterogeneous rateconstant for electron transfer at the peak potential Ep has been shown to be given by[ 151 k(Ep)
= 2.18
RanFv”’ RT
,
where n is the number of electrons transferred in the rate determining step, 8 is the scan rate, D is the diffusion coefficient D and a is the transfer coefficient. For an irreversible charge transfer process the peak potential Ep shifts by 30 mV/an per decade of’ sweep rate. Values greater than 30 mV were observed for every chalcogenide ester studied. In a totally irreversible system the width of the wa+e has been shown by Nicholson and Shain[16] to depend on the transfer coefficient according to (Ep - Ep,,)
= O.o48/an.
(4)
From Equation (4) the product of n and a can be estimated and are listed in Table 1 for the chalcogen esters studied. Using these data and taking D z 2 x lo-’ cm2 s- ’ the heterogeneous rate constants for electron transfer at the peak potential Ep for chalcogenide deposition were determined using Equation (3)
*0.5
0.0 VOLTS
-0.5 “6
-1.0
AgInga
Fig. 6. EkctrochemicaI reduction ofethylene teilurite (a) and a mixture of diethylselenite and ethylene tellurire (b).
SUMMARY
AND
CONCLUSIONS
The cyclic voltarnmograms of chalcogenide esters were shown to be due to an irreversible electron transfer process resulting in the deposition of the chalcogen at the electrode. The electrochemical reduction occured at a well defined potential and the deposit appeared stable. All As, S and Se codeposit at a similar potential, while Te electrodeposited at a slightly lower potential. The facile reduction of chalcogenide esters by both electrochemical and chemical means represents an
IUFIK
Table 2. Emissionspectral
;-= :; (& (< 1)
cu Fe Hg Na Mg
opportunity
Cd (< (< (<
1) ‘) 5) 101
-
-
-
-
-
10 -
-
2
5 -
-
2 -
-
10 Bal
(< 1)
?
Not Detected;
to prepare
3
10
Sn Si Te Ti Tl Zn Se
-
c I’?
< 1’:;
1 -
0.5 20 -
(< 1) (-= 5) (4 1)
Bal. Balance; Numbers
new alloys of As, S, Se
7.
9.
1. F. A. Kroger, J. elecrrochem.
2. 3. 4. 5. 6.
Sw. 125,202s (19783 (other references are therein). D. Hanmann and D. J. Miller, Solar Energy Mareriols 4, 223 (1981); D. E. Hale and W. D. K. Clark, U.S. Patent, 4.253.9 19. k. S: Kazacos and B. Miller, J. electrochem. Sue. 127, 2378 (1980). A. T. Ward, J. M. Ishler and A. Damianovic, U.S. Patent 4,121,981 (1978). A. Brenner, Electrodeposition of Alloys, Vols 1 and 2. Academic Press, New York (1963). E. Pacauskas and J. Janicnik, &et. TRS Moksiu Akd. Barb., Ser B 1, 75, 85 (1972) CA.
10. 11.
12. 13. 14. 15. 16.
1 -
5 BaI 1 -
Bal
-
-
are in ppm; ?, analysis
8.
REFERENCES
Tellurium obtained from electrochemical reduction Example Example No. 1 No. 2
-
( < 0.01) (-= 0.5) (< 5)
Mn MO Ni Pb Sb
reduction
-
0.1 2
< ;‘:i
Bi ca Cd co Cr
excellent and Te.
Commercial tellurium from alfa
( < 0.05)
Ag Al AS B Ba
-,
analysis of tellurium obtained by electrochemical of tetraalkoxyttllurane
Detection limit (ppm)
Elements
S. S. BADESHA
0. LOUTFYAND
-
not complete.
A. K. Graham, H. L. Pinkerton and H. J. Boyd, J. electrochem. Sot. 106, 651 (1959). M. S. Kazacos and B. Miller, 1. eiectrockem. Sot. 127,869 (1980). A. J. Alekperovand M. A. Babaeva, CA69-10067h (1965); Zh. Khim. 7680 (1964). S. Badesha, P. Monczka and S. D. Smith, Can. 1. Chem. 61,X99 (1983); S. Badesha, U.S. Patent 4389,389 and 4411, 698 (1983). S. Bade&a and T. Smith, Prac. 4th Int. Conf Organic Chemistry of Selenium and Teliurium, Univ. of Austin, Juty (1983); J. Am. them. Sot. (submitted for publication) (1983). R. C. Mehrota and S. N. Mathur, 3. Indian them. Sot. 42, 748 (1965). 2. L. Khiaamova and G. Kamai, Bull. Inst. Polyterh. IASI “N-S” 4, 153 (1958). W. H. Reinmuth, Anolyt. Chem. 32, 1891 (1960). R. J. Klingler and J. K. Kochi, J. Am. them. Sot. 102,479O (1980). R. S. Nicholson and 1. Shain, Andyr. Ckem. 36, 7C16 (1964).
Webster
(Received
Research
BADESHA
Centre, 800 Phillips Road, Webster, NY 14580, U.S.A.
17 November
1983; in revised form 21 June 1984)
Abstract-Electrochemical reduction of bis(arsenic triglycollate) (CH*0)2A~O(CHt)20A~(OCH2)2 dimethyl sulfite (CHJO)3S0, diethylselenite,(CtHSO)$eO, and ethylene tellurite, (OCH3CH20)sTe was studied in non-aqueous, Z-ethoxy ethanol (cellosolve) using single-sweep voltammetry and cyclic voltammetry. It is shown that arsenic, sulfur, selenium and tellurium deposit at the cathode at bias potentials of - 0.70, -0.64, - 0.51 and - 0.22 V us Ag/AgCI, aq. KC1 respectively.
INTRODUCTION Electrochemical deposition offers a novel route to the production of photoconducting and semiconducting materials[l+]. Cathodic deposition of different elements with formation of alloys and compounds from aqueous electrolytes has been known for a long time[5]. The electrochemicai behaviour of chalcogen dioxides has been extensively studied in aqueous acidic solutions[4-81. The electrode process in which the chalcogen dioxide, XO1 with X = S, Se or Te, is reduced to its corresponding element is obviously complex since it involves at least four electrons. A reoent study of the reaction of selenious acid (H&eOJ) in H2S0, solution[S] has shown that the initial cathodic reaction involves an overall transfer of six electrons and the formation of H,Se which may react with HZSe03 to yield elemental selenium. Ward, Ishler and Damjanovic[4] on the other hand, have shown that cathodic codeposition of Se and Te from acidified solution of SeO, and TeOz is possible. The electrochemistry of chalcogenide esters in nonaqueous solvents has been less thoroughly studied. Alekperov and Babaeva[9] has shown that red amorphous Se and black crystalline Te were deposited on the cathode (Pt or graphite) from alcoholic solution of SeC14 and TeCl.,. It was noted that,after dissolving the S&I, and TeCl, in alcohol the pH fell below 1, which implies that a chemical reaction between Xa and the alcohol (ROH) took place liberating HCl and (RO).J (X = Se or Tel. Most of the electrodenosited Se &solved imme&ately while Te remained-practically insoluble. Recently a novel chemical approach to the preparation of pure non-metals such as Se and Te has been described[lO]. The technique involves chemically reducing, selenite and tellurite esters in cellosolve with hydrazine. Signi6cant progress has been made in the
preparation of a broad spectrum of pure and homogeneous alloys using chemical reduction and coreduction methods[ll]. The purpose of this report is to present the results of an investigation concerning the electrochemical reduction characteristiss of chalcogenide esters in nonaqueous solvent. The aim is to develop a simple technique for the preparation of pure metals as well as binary and ternary alloys of S, Se, Te and As. This approach complements in many ways the chemical reduction process.
EXPERIMENTAL Materials Dimethyl suffite and cellosolve were obtained from Aldrich Chemicals. The diethylselenite was prepared by dissolving selenium dioxide in ethyl alcohol and using benzene to remove water isotropically[12]. Similarly ethylene tellurite and bis(arsenic triglycollate) were prepared from the reaction of ethylene glycol with tellurium dioxide and arsenic oxide, in presence of p-toluene sulphonic acid[lO, 131 respectively. Tetiabutylammonium perchlorate (TBAP) was obtained from Aldrich Chemicals and dried in uacuu at 60°C. Electrochemical
measurements
Electrochemistry was performed using EG&G Princeton Applied Research Model 174A polarographic analyser equipped with Model 175 universal programmer and Model 303 static mercury drop electrode. Cyclic voltammograms were recorded on a Houston Series 2COO x-y recorder. The working electrode was a hanging mercury drop electrode (HMDE), a platinum wire was used as auxiliary 101
102
RAFIK 0. ILWTFYAND
S. S. BADESHA
electrode and Ag/AgCl, aq. KC1 as reference electrode. All electrochemical measurements were carried out at 20°C in argon purged cellosolve solution employing 0.5 mM chalcogenide ester and 0.05 M TBAP as sup porting electrolyte. RESULTS
AND
DISCUSSION
The single-sweep cyclic voltammograms of the chalcogenide esters listed in Table 1 were recorded with a stationary mercury eIectrode in 2-ethoxy ethanol (cellosolve) solution at 20°C. The cyclic vdtammograms of the dimethyl sulfite is illustrated in Fig. I measured at 200 mV s- I scan rate: It is characterised by a cathodic wave showing well-defined current maximum but no anodic wave on the reverse scan even at sweep rate up to 1 V s-l. These results are consistent with a slow electron transfer reduction and possibly followed by a chemical reaction. The presence of a follow up chemical reaction is indicated by the appearance of an anodic wave at +O.2 V when the potential is swept positively from a point on the reduction wave. This anodic wave corresponds to the oxidation of a chemical product such as sulfur amalgam. An adsorption peak anodic of the first reduction wave was also observed. The cyclic voltammogram of diethyl selenite is shown in Fig. 2 which is characterised by the same basic pattern. At electrode potentials =z - 0.5 V red amorphous Se deposited onto the electrode. The electrodeposited Se did not dissolve away and as a result a new mercury drop was required for each cycle. Ethylene tellurite exhibited two irreverand -0.73 V sible reduction waves at -0.22 (10 mVs- ’ sweep rate). The first reduction wave corresponds to Te deposition and the second wave leads to polytelluride ions Te;‘. The cyclic voltammogram of the ethylene tellurite is illustrated in Fig. 3. In a manner similar to the sulfite an anodic wave at + 0.48 V appears only after cathodic sweep to potentials corresponding to tellurium deposition. This wave most likely corresponds to oxidation of Te amalgam. In the second cyclic scan a new cathodic wave appears anodic of Te deposition wave which corresponds to reduction of the partially oxidized Te, perhaps Te’ +. Bis(arsenic triglycollate) exhibits a single unreversible reduction wave at 0.70 V as shown in Fig. 4. The details of the sweep dependence of the cathodic waves are shown in Fig. 5 for ethylene tellurite as a representative chalcogenide ester. Both the peak potential, Ep,and peakcurrent, ip,are strongly dependent on sweep rate, u, and temperature. A closer inspection
Table 1. Cyclic voltammetric Compound Bis(arsenic triglycollatc) (CHIO),AsO(CH,),As(CH,O), Dimethyl sulfite (CH,0)2S0 Dlcthyl selenelte (CIH,O),SeO Ethylene tellurite (OCH2CH20)Te
Fig. 1. Cyclicvoltammogramofdimethyl sultlte in cellosolve containing 0.05M TBAP. Dotted line is the second scan. Note
VOLTS
Fig. 2. Cyclic voltammogram
vs
Aq
AgC?
of diethyl selenite in cellosolve.
Fig. 3. Cyclic voltammogrsmof ethylene tellurite in cellosolve. Dotted line corresponds to the second scan.
of the cyclic voltammograms reveals that the current in the foot of the cathodic waves is singualrly independent of the sweep rate. Such a behaviour, originally noted by Reinmuth[l4], strongly suggests
data for organ0 chalcogenide*
EP, V+ - 0.70
(Ep-Ep,,)
- 0.64 -0.51 - 0.22
* Measured at HMDE at10 mV s-’ in 2-ethoxyethanolcontaining etectrolyte at 20°C. + Potentials vs Ag/AgCI, aqueous KCI.
as supporting
the disappearanceof an adsorptionpeak.
0.10
0.05 0.09 0.065
ctn
k,(W
ems-’
0.96
1.8 x IO@ 6.0 x 10-S
0.53 0.74
4.4 X lo- 3 4.5 X 10-S
0.48
0.05 M tetrabutyiammonium
pcrchlorate
103
Electrochemicalreductionof chalcogenideesters
Fig. 4. Cyclic voltammogramof bis(arsenictriglycollate)in cellosolve.
-I Fig. 5. The sweep dependence ethylene
of the cathodic tellurite.
waves
of
and are listed in TabIe I. These rates are typical of many alkyl metals compounds. In contrast to the complex electrochemical behaviour of chalcogens in aqueous acidic media, the process in non-aqueous solvents appears straightforward. The electroreduction of the chalcogenide esters to their corresponding elements occurs at a well defined potentia1 and the deposit appears to be stable. Hence, electrochemical reduction of chalcogenide esters can be used as a method for the p&cation of selenium, tellurium and arsenic. In Table 2, the emission spectral analysis of tellurium obtained by electrochemical reduction of pure ethylene tellurite is compared with that of a commercial tellurium sample indicating the potential of the technique. The black crystalline tellurium was electrochemically deposited onto a ruthanised titanium cathode. Similar results were obtained with electrochemically deposited selenium. The electrochemical behaviour of a mixture of diethyl selenite and ethylene tellurite is shown in Fig. 6. As expected, both materials are reduced at their standard potential. The reduction waves of dimethyl sulfite and diethyl selenite merge together into one reduction wave when a mixture of the two materials was examined. Electrochemically codepositing As, S, Se and Te onto a substrate from a solution of their ions, in such a way that the relative deposited amounts of S, Se and Te are controlled by their relative concentration in the electrolyte and by the choice of electrochemical conditions, ie current density or electrode potential, provides a method for preparation of a wide range of useful binary and ternary alloys of As, S, Se and Te.
that electron transfer to these chalcogenide esters is electrochemically unidirectional, ie totally irreversible. The cathodic peak potential shifts cathodically with an increase in scan rate. However, the ratio of i,/vi’2 is constant. These behavioursare characteristic of an irreversible charge transfer process. Under these conditions, the heterogeneous rateconstant for electron transfer at the peak potential Ep has been shown to be given by[ 151 k(Ep)
= 2.18
RanFv”’ RT
,
where n is the number of electrons transferred in the rate determining step, 8 is the scan rate, D is the diffusion coefficient D and a is the transfer coefficient. For an irreversible charge transfer process the peak potential Ep shifts by 30 mV/an per decade of’ sweep rate. Values greater than 30 mV were observed for every chalcogenide ester studied. In a totally irreversible system the width of the wa+e has been shown by Nicholson and Shain[16] to depend on the transfer coefficient according to (Ep - Ep,,)
= O.o48/an.
(4)
From Equation (4) the product of n and a can be estimated and are listed in Table 1 for the chalcogen esters studied. Using these data and taking D z 2 x lo-’ cm2 s- ’ the heterogeneous rate constants for electron transfer at the peak potential Ep for chalcogenide deposition were determined using Equation (3)
*0.5
0.0 VOLTS
-0.5 “6
-1.0
AgInga
Fig. 6. EkctrochemicaI reduction ofethylene teilurite (a) and a mixture of diethylselenite and ethylene tellurire (b).
SUMMARY
AND
CONCLUSIONS
The cyclic voltarnmograms of chalcogenide esters were shown to be due to an irreversible electron transfer process resulting in the deposition of the chalcogen at the electrode. The electrochemical reduction occured at a well defined potential and the deposit appeared stable. All As, S and Se codeposit at a similar potential, while Te electrodeposited at a slightly lower potential. The facile reduction of chalcogenide esters by both electrochemical and chemical means represents an
IUFIK
Table 2. Emissionspectral
;-= :; (& (< 1)
cu Fe Hg Na Mg
opportunity
Cd (< (< (<
1) ‘) 5) 101
-
-
-
-
-
10 -
-
2
5 -
-
2 -
-
10 Bal
(< 1)
?
Not Detected;
to prepare
3
10
Sn Si Te Ti Tl Zn Se
-
c I’?
< 1’:;
1 -
0.5 20 -
(< 1) (-= 5) (4 1)
Bal. Balance; Numbers
new alloys of As, S, Se
7.
9.
1. F. A. Kroger, J. elecrrochem.
2. 3. 4. 5. 6.
Sw. 125,202s (19783 (other references are therein). D. Hanmann and D. J. Miller, Solar Energy Mareriols 4, 223 (1981); D. E. Hale and W. D. K. Clark, U.S. Patent, 4.253.9 19. k. S: Kazacos and B. Miller, J. electrochem. Sue. 127, 2378 (1980). A. T. Ward, J. M. Ishler and A. Damianovic, U.S. Patent 4,121,981 (1978). A. Brenner, Electrodeposition of Alloys, Vols 1 and 2. Academic Press, New York (1963). E. Pacauskas and J. Janicnik, &et. TRS Moksiu Akd. Barb., Ser B 1, 75, 85 (1972) CA.
10. 11.
12. 13. 14. 15. 16.
1 -
5 BaI 1 -
Bal
-
-
are in ppm; ?, analysis
8.
REFERENCES
Tellurium obtained from electrochemical reduction Example Example No. 1 No. 2
-
( < 0.01) (-= 0.5) (< 5)
Mn MO Ni Pb Sb
reduction
-
0.1 2
< ;‘:i
Bi ca Cd co Cr
excellent and Te.
Commercial tellurium from alfa
( < 0.05)
Ag Al AS B Ba
-,
analysis of tellurium obtained by electrochemical of tetraalkoxyttllurane
Detection limit (ppm)
Elements
S. S. BADESHA
0. LOUTFYAND
-
not complete.
A. K. Graham, H. L. Pinkerton and H. J. Boyd, J. electrochem. Sot. 106, 651 (1959). M. S. Kazacos and B. Miller, 1. eiectrockem. Sot. 127,869 (1980). A. J. Alekperovand M. A. Babaeva, CA69-10067h (1965); Zh. Khim. 7680 (1964). S. Badesha, P. Monczka and S. D. Smith, Can. 1. Chem. 61,X99 (1983); S. Badesha, U.S. Patent 4389,389 and 4411, 698 (1983). S. Bade&a and T. Smith, Prac. 4th Int. Conf Organic Chemistry of Selenium and Teliurium, Univ. of Austin, Juty (1983); J. Am. them. Sot. (submitted for publication) (1983). R. C. Mehrota and S. N. Mathur, 3. Indian them. Sot. 42, 748 (1965). 2. L. Khiaamova and G. Kamai, Bull. Inst. Polyterh. IASI “N-S” 4, 153 (1958). W. H. Reinmuth, Anolyt. Chem. 32, 1891 (1960). R. J. Klingler and J. K. Kochi, J. Am. them. Sot. 102,479O (1980). R. S. Nicholson and 1. Shain, Andyr. Ckem. 36, 7C16 (1964).