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Synthesis of titania photocatalysts dispersed with nickel nanosized particles
Nanastrudurcd Mattrials.Vol. 10.No. 6. pp. 1033-1042.1998 Elsevia Scimcc.Ltd (D 1998Acb Mctalh@ca Inc. RintEdintheusA. Allrights-cd 09~9773198$19.00+ .OO
Pergaunon
PII s0965-9773(98)00124-x
SYNTHESIS OF TITANIA PHOTOCATALYSTS DISPERSED WITH NICKEL NANOSIZED PARTICLES A. Towata, Y. Uwamino, M. Sando, K. Iseda and H. Taoda National Industrial Research Institute of Nagoya l- 1, Hirate-cho, Kita-ku, Nagoya 462-85 10, Japan (AcceptedAugust 20,1998) Abstraci’ - Titaniasuper fine particle photocatalystscontaining dispersed nickel nanosizedparticlesweresynthesized.The synthesismethodwasasfollows.First, an WI0 typeemulsion wasmade withnon-ionsurfactant.Titaniapowderwithdispersednickeloxide or nickelhydroxide wassynthesize,dusinga solutionof nitricacid, nickeland titaniumtetrabutoxide(TIB). The titania photocatalystwasformed by reduction caused by heat treatmentunder a suitable reduction condition. Nickel nano-sizedparticles were distributedin the titaniaphotocatalystsand the amount of hydrogengenerated increasedinproportion tothesurface areaof thedistributednickel. The nickel particles dispersed in titaniaphotocatalystsaccelerated the generation of rutile as compared to the photocatalystwithoutnickel. 01998 Acta MetallurgicaInc. 1. INTRODUCTION Photocatalysts consisting of nano-sized particlesarereceiving much attention due to the fact that their properties differ from those of bulk photocatalysts (1). It is known, for example, that the quantum effect determines some of these properties, making particle size an important factor to control if the properties of these photocatalysts are to beimproved(2). However, when particle size is reduced, handling becomes difficult due to grain growth and aggregation phenomena occurring during heat treatment. To prevent grain growth it was attempted to coat silica particles with nano-sized particles of a semiconductor, such as titania. However, the titania was covered with silica, which might cause a drop in activity (3). Therefore, a method is required that would allow easy handling of fime particles with high surface area, by controlling the formation of a secondary structure from primary super fine particles. The photocatalysts reaction progresses smoothly by making use of a structure that has the metal as the reduction electrode and the semiconductor as the oxidation electrode (4). As a result, a compound body in which semiconductor super fine particles coexist with metallic nano-sized particles is effective as a super fine particle photocatalysts. Also, use of nickel or another magnetic material as the metallic nano-sized particles for dispersion in the composite structure would make it possible to use magnetism to recover the particles. 1033
1034
A TOWATA,Y UWAMINO,M SANDO,K ISEDAANDH TAOM
Tetra n butoxide
Heat air Reduction
H25% N2
Figure 1. The diagram of fabrication process.
The use of semiconductor super fine particles having magnetism would facilitate the potential for recycling super fine particle photocatalysts dispersed in a liquid phase. To this end, in this study, a photocatalyst was synthesized using an emulsion to disperse nickel nano-sized particles into titaniafine particles in aliquidphase.Thecharacteristics of superfine particlestitania photocatalysts with dispersed nano-sizedparticles of nickel under different heating conditions and with different amounts of nickel were investigated. 2. EXPERIMENTAL 2.1 SynthesisMethod Figure 1 shows a diagram of the fabrication process. First, nickel nitrate hexahydrate (Ni(NO3)26H20) was mixed with titanium tetra n butoxide (Ti(OC$Ig)4) (TIJ3) disso+d in hexane. In another receptacle, polarity surfactant (Span60) in a concentration of 1.5~10~ mol.4 was dissolved in hexane and an amount of water stoichiometrically equivalent to the titanium tetra n butoxide. An emulsion was made by Muxing this solution by ultrasonic treatment. The amorphous compound was synthesized by adding the alkoxide solution to this emulsion. Then, this amorphous compound was heat-treated at 300°C for 1 hour in air to remove the hydrocarbon
SYNTHESISOFTITANIAPH~T~~ATALYSTS DISPERSED WITHNICKELNAIW-SIZEDPAW~CES
1035
Figure 2. TEM micrograph of amorphous phase before reduction. and surfactant ,and the reduction process was carriedout for one hour in nitrogen atmosphere with 5% HZat a fixed temperature. 2.2. CharacteristicEvaluationof Particle Compound ln order to examine the heat-treatingcondition before formation of the nickel and titanium particle compound, tbermogravimetricanalysis (TGA)was carried out. The shape and size of the particles thought to influence the photocatalystsreaction were observed by transmission electron microscope (TEM) and specific surface area was measured by the BET method. The crystal structure of the particles was also examined by X-ray diffraction.The ratio of nickel and titanium was measuredlby ICE analysis. The photocatalystscharacteristicswere established as follow (5). 0.03g of the sample was put in a 60 ml quartz reactor and refluxed in 50% ethanol. Next, it was put under the light of a 5OOWmercury lamp, and the rate of generation of H2 gas was estimated. 3. RESULTS AND DISCUSSION
3.1 Synthesisof Particle Compound Figure Z!shows the TEM photograph of the amorphous phase before the reduction process. Differences of contrast caused by the elements are not noticeable,and it appears as a single phase. However, energy dispersion X-ray analysis shows peaks of titanium and nickel. Figure 3 shows the DTG curve obtained by differentiationof the weight loss of the amorphous phases synthesized in N2 gas including 5% hydrogen. ln the curve, the peak at 220°C is attributed to loss of TlB generating hydrocarbon and of surfactant.Another peak is seen at 380°C.The heat analysis result
1036
A TOWATA, Y UWAMNO, M SANDO, K ISEMANDH TAODA
0
200
400 600 Temperature
800 [ “C]
1000
Figure 3. DTG curve of amorphous material in 955 ArH2 gas mixture.
200
400 600 Temperature
800 [ “C]
1000
Figure 4. DTG cmve of an oxide of the nickel particles in the 955 ArzH2gas mixture.
!&NTHESIS OF TITANIAPHOTCCATALYSTS DISPERSEDWITHNICKELNANO-SIZEDPAFIJKLES
1037
Figure: 5. TEM micrograph of the material formed by the reduction processing.
of the oxide in the nickel is shown in Figure 4 for comparison. The peak seen at 400°C shows the transformation of nickel oxide into metallic nickel by reduction. Therefore, it is thought that the peak of 380°C of the particle compound marks the generation of the nickel metal. Figure 5 shows a TEM micrograph of the material generated by the reduction process. A portion of the particles forms globular masses of secondary particles, some hollow particles of 50 nm diameter also appear. It is thought that these hollow particles were formed due to the synthesis of titania in the inter-facial neighborhood of the W/O type emulsion (6). Distributed nickel super fine particles with a particle size from 10 to 15 nm, are also observed. 3.2 Influence of Heat-treatmenton Characteristicsof Particle Compound Influence of the amount of nickel and of the heat-treating temperature on the characteristics of the particle compound, were examined by observation of the crystal structure and specific surface area. First of all, the X-ray diffraction chart obtained from pure titania particles after heat treat at different temperature are shown in Figure 6(a) for comparison. Similarly Figd(b) shows the X-ray diffraction result for titania powder dispersed with nickel particles heat treated at various temperatures. At 300°C titania is still amorphous. Anatase is generated at 350°C and it is still detected up to 450°C. Rutile is formed at 600°C and coexists with anatase. Similarly, when the heat-treating conditions were changed, nickel metal is formed at 300°C and titania does not have a definite crystal structure. Anatase and r-utile appeared at the same time at 35O”C, and coexisted up to 450°C. Anatase disappeared at 600°C and only r-utileexists. That is, the phase change of the crystalline titania was promoted by the presence of nickel metallic super fine particles and the generation rate of r-utile is accelerated compared with titania without nickel. This result is similar to that reported for Co(I1) doped titania, that is the effect of Co(I1) doping greatly reduced the
1036
A TOWATA,Y UWAMNO,M SANDO,K ISEDAANDt-l TA~DA
I
I
30
40
I
50
2 6 NW
(b)
1
I
30
40
I
50
I 60
2 0 (deg)
Figure 6. X-ray diffraction chart of the change due to heat-treatment of titania. (a) pure titania particles, (b) titania powder dispersed with nickel particles.
temperature needed to crystallize the material as compared to pure titania (7). The compound body was observed by TEM (Figure 7). At the temperatures of 35O’C and 45O’C the nickel particles size was in the range from 10 to 20 nm. At 6OO’Cthe grains have grown to 40 nm. Growth of the titania particles with increased temperature was also observed. Figure 8 shows the specific surface area calculated from the specific surface area of the particle compound and nickel particle size and weight ratio of nickel and titanium, when the temperature changed. The specific surface area of particle compound decreased as the temperature increased. The calculated specific surface of titania in the particle compound also decreased. Grain growth was observed, indicating growth of the titania particles. The photocatalytic property as measured by Hz generation rate is shown in Figure 9. At 300°C the emission of hydrogen is slow because the crystal structure of titania is not fully
SYNTHESISOF TITANIAPHOTOCATALYSTS DISPERSED WITHNICKELNA~KJ-SIZED PARTICLES
1039
Figure 7. TEM micrograph of particles heat-treated at 600°C.
@lSO % p20 lu 8 80 2 ; E
40
ki CE
0 300
400
500
600
Temperature[“C] Figure 8. The calculated specific surface area of the titania.
300
400 500 Temperature[“C]
600
Figure 9. The rate of H2 generation of the particle compound photocatalysts.
developed. Thle peak of the H2 generation rate was at 350 “C. At 450°C and 600°C titania grain growth retards the rate. It is assumed that from 350°C to 600°C the rate of H2 generation is related to the particle size of the titania.
1040
A TOWATA,Y UWAMINO,M SANDO, K
ISEDA AND
H TAODA
Figure 10. X-ray diffraction of the particles component in the case of the change of the nickel content.
3.3. Effect of Nickel Content on the Photocatalytic Property of the Particle Compound The X-ray diffraction of the particles for different nickel contents is shown in Figure 10. Titania was generated as the content of nickel increased from zero percent to 25%. And at 27% nickel, nickel titanium oxide was generated by reaction between the nickel and titania. TEM micrographs of Figure 1l(a) and (b) show the specimens prepared by heat treatment at 350°C with a nickel content of 17.6% and 27% respectively. Up to 17.6% of nickel content the size of nickel particles remains almost unchanged in the range of 10 nm to 15 run. But the particle size almost doubled at 27%. Figure 12 shows the variation of specific surface area of the particle compound with nickel content. The figure shows the calculated values for specific surface area of titania particles. The specific surface area of the particle compound does not change up to 17.6% content, and decreases for 27% of nickel content, due possibly to particle growth. The value of the titania increases a little at 17.6% content and decreases for 27% of nickel content. Figure 13 shows the generation of hydrogen gas. The volume of Hz produced increases, as did the content of nickel, reaching a peak at 24%. There is a dramatic difference between the value of H2 generated at 24% and 27% content of nickel. As the nickel particle size was the same up to
!SYYMHESIS OF TITANIAPHOTOCATALYSTS DISPERSED WITHNICKELNANO-SIZEDPARTICLES
1041
Figure 11. TEM micrograph of particles heat-treated at 350°C. (a) nickel content of 17.6%, (b) 27%.
17.64 b,the :total surface area of the nickel particles must be changing. When the nickel content vvas 271, the] ?ick:el particle growth and synthesis of nickel titanate retards the generati on rate. 4. CONCLUSION
WP
BY( :onlrolling the dispersion and hydrolysis of Ni(NO3)26H20 and TIB using an emuls;ion
typetitania
super fine particle photocatalysts with dispersed nickel could be successfi ully
1042
A TOWATA,Y UWAMINO,M SANCO,K ISEDAANDH TAODA
1
Ill-
8
o0
10
20
d
30
0
Ni Content [wt.%]
Ni Content [wt.%] Figure 12. The calculated specific surface area of the titania.
Figure 13. The rate of the generation of the hydrogen gas.
prepared. The characteristics of the synthesized compound can be summarized as follows. 1. The amount of hydrogen generated increased in proportion to the surface area of the dispersed nickel super fine particles. 2. The nickel particles dispersed in titaniaphotocatalysis accelerated the generation of t-utile. This compound presents superior photocatalytic characteristics. This suggests that this compound is well suited for use in liquid environments - for example, in seawater dispersed with oil. REFERENCES 1.
2. 3. 4. 5. 6. 7.
Steigerwald, M.L. and Brus, L.E., Accounts of Chemical Research, 1990 23,183. Weller, H., Angewandte Chemie, International Edition in English, 1993,32,4 1. Tada, H., Miyata, K. and Yoshida, H., Sikizai, 1988, 61,665. Kawai, T., Sakata, T., Hashimoto, K. and Kawai, M., Journal of Chemical Society of Japan, 1984, 277. Sakata, T. and Kawai, T., Chemical Physics Letters, 1981,80,341. Nakahara, Y. , Journal of the Society of Powder Technology, Japan, 1995,32,97. Poniatowski, E.H.,Munos, S.V.,Murllo, R.A.,Talavera, R.R. and Diamant, R., Materials Research Bulletin, 1996,3 1,329.
Published without the benefit of Authors’ fiil
corrections as they were not available at press time.
Pergaunon
PII s0965-9773(98)00124-x
SYNTHESIS OF TITANIA PHOTOCATALYSTS DISPERSED WITH NICKEL NANOSIZED PARTICLES A. Towata, Y. Uwamino, M. Sando, K. Iseda and H. Taoda National Industrial Research Institute of Nagoya l- 1, Hirate-cho, Kita-ku, Nagoya 462-85 10, Japan (AcceptedAugust 20,1998) Abstraci’ - Titaniasuper fine particle photocatalystscontaining dispersed nickel nanosizedparticlesweresynthesized.The synthesismethodwasasfollows.First, an WI0 typeemulsion wasmade withnon-ionsurfactant.Titaniapowderwithdispersednickeloxide or nickelhydroxide wassynthesize,dusinga solutionof nitricacid, nickeland titaniumtetrabutoxide(TIB). The titania photocatalystwasformed by reduction caused by heat treatmentunder a suitable reduction condition. Nickel nano-sizedparticles were distributedin the titaniaphotocatalystsand the amount of hydrogengenerated increasedinproportion tothesurface areaof thedistributednickel. The nickel particles dispersed in titaniaphotocatalystsaccelerated the generation of rutile as compared to the photocatalystwithoutnickel. 01998 Acta MetallurgicaInc. 1. INTRODUCTION Photocatalysts consisting of nano-sized particlesarereceiving much attention due to the fact that their properties differ from those of bulk photocatalysts (1). It is known, for example, that the quantum effect determines some of these properties, making particle size an important factor to control if the properties of these photocatalysts are to beimproved(2). However, when particle size is reduced, handling becomes difficult due to grain growth and aggregation phenomena occurring during heat treatment. To prevent grain growth it was attempted to coat silica particles with nano-sized particles of a semiconductor, such as titania. However, the titania was covered with silica, which might cause a drop in activity (3). Therefore, a method is required that would allow easy handling of fime particles with high surface area, by controlling the formation of a secondary structure from primary super fine particles. The photocatalysts reaction progresses smoothly by making use of a structure that has the metal as the reduction electrode and the semiconductor as the oxidation electrode (4). As a result, a compound body in which semiconductor super fine particles coexist with metallic nano-sized particles is effective as a super fine particle photocatalysts. Also, use of nickel or another magnetic material as the metallic nano-sized particles for dispersion in the composite structure would make it possible to use magnetism to recover the particles. 1033
1034
A TOWATA,Y UWAMINO,M SANDO,K ISEDAANDH TAOM
Tetra n butoxide
Heat air Reduction
H25% N2
Figure 1. The diagram of fabrication process.
The use of semiconductor super fine particles having magnetism would facilitate the potential for recycling super fine particle photocatalysts dispersed in a liquid phase. To this end, in this study, a photocatalyst was synthesized using an emulsion to disperse nickel nano-sized particles into titaniafine particles in aliquidphase.Thecharacteristics of superfine particlestitania photocatalysts with dispersed nano-sizedparticles of nickel under different heating conditions and with different amounts of nickel were investigated. 2. EXPERIMENTAL 2.1 SynthesisMethod Figure 1 shows a diagram of the fabrication process. First, nickel nitrate hexahydrate (Ni(NO3)26H20) was mixed with titanium tetra n butoxide (Ti(OC$Ig)4) (TIJ3) disso+d in hexane. In another receptacle, polarity surfactant (Span60) in a concentration of 1.5~10~ mol.4 was dissolved in hexane and an amount of water stoichiometrically equivalent to the titanium tetra n butoxide. An emulsion was made by Muxing this solution by ultrasonic treatment. The amorphous compound was synthesized by adding the alkoxide solution to this emulsion. Then, this amorphous compound was heat-treated at 300°C for 1 hour in air to remove the hydrocarbon
SYNTHESISOFTITANIAPH~T~~ATALYSTS DISPERSED WITHNICKELNAIW-SIZEDPAW~CES
1035
Figure 2. TEM micrograph of amorphous phase before reduction. and surfactant ,and the reduction process was carriedout for one hour in nitrogen atmosphere with 5% HZat a fixed temperature. 2.2. CharacteristicEvaluationof Particle Compound ln order to examine the heat-treatingcondition before formation of the nickel and titanium particle compound, tbermogravimetricanalysis (TGA)was carried out. The shape and size of the particles thought to influence the photocatalystsreaction were observed by transmission electron microscope (TEM) and specific surface area was measured by the BET method. The crystal structure of the particles was also examined by X-ray diffraction.The ratio of nickel and titanium was measuredlby ICE analysis. The photocatalystscharacteristicswere established as follow (5). 0.03g of the sample was put in a 60 ml quartz reactor and refluxed in 50% ethanol. Next, it was put under the light of a 5OOWmercury lamp, and the rate of generation of H2 gas was estimated. 3. RESULTS AND DISCUSSION
3.1 Synthesisof Particle Compound Figure Z!shows the TEM photograph of the amorphous phase before the reduction process. Differences of contrast caused by the elements are not noticeable,and it appears as a single phase. However, energy dispersion X-ray analysis shows peaks of titanium and nickel. Figure 3 shows the DTG curve obtained by differentiationof the weight loss of the amorphous phases synthesized in N2 gas including 5% hydrogen. ln the curve, the peak at 220°C is attributed to loss of TlB generating hydrocarbon and of surfactant.Another peak is seen at 380°C.The heat analysis result
1036
A TOWATA, Y UWAMNO, M SANDO, K ISEMANDH TAODA
0
200
400 600 Temperature
800 [ “C]
1000
Figure 3. DTG curve of amorphous material in 955 ArH2 gas mixture.
200
400 600 Temperature
800 [ “C]
1000
Figure 4. DTG cmve of an oxide of the nickel particles in the 955 ArzH2gas mixture.
!&NTHESIS OF TITANIAPHOTCCATALYSTS DISPERSEDWITHNICKELNANO-SIZEDPAFIJKLES
1037
Figure: 5. TEM micrograph of the material formed by the reduction processing.
of the oxide in the nickel is shown in Figure 4 for comparison. The peak seen at 400°C shows the transformation of nickel oxide into metallic nickel by reduction. Therefore, it is thought that the peak of 380°C of the particle compound marks the generation of the nickel metal. Figure 5 shows a TEM micrograph of the material generated by the reduction process. A portion of the particles forms globular masses of secondary particles, some hollow particles of 50 nm diameter also appear. It is thought that these hollow particles were formed due to the synthesis of titania in the inter-facial neighborhood of the W/O type emulsion (6). Distributed nickel super fine particles with a particle size from 10 to 15 nm, are also observed. 3.2 Influence of Heat-treatmenton Characteristicsof Particle Compound Influence of the amount of nickel and of the heat-treating temperature on the characteristics of the particle compound, were examined by observation of the crystal structure and specific surface area. First of all, the X-ray diffraction chart obtained from pure titania particles after heat treat at different temperature are shown in Figure 6(a) for comparison. Similarly Figd(b) shows the X-ray diffraction result for titania powder dispersed with nickel particles heat treated at various temperatures. At 300°C titania is still amorphous. Anatase is generated at 350°C and it is still detected up to 450°C. Rutile is formed at 600°C and coexists with anatase. Similarly, when the heat-treating conditions were changed, nickel metal is formed at 300°C and titania does not have a definite crystal structure. Anatase and r-utile appeared at the same time at 35O”C, and coexisted up to 450°C. Anatase disappeared at 600°C and only r-utileexists. That is, the phase change of the crystalline titania was promoted by the presence of nickel metallic super fine particles and the generation rate of r-utile is accelerated compared with titania without nickel. This result is similar to that reported for Co(I1) doped titania, that is the effect of Co(I1) doping greatly reduced the
1036
A TOWATA,Y UWAMNO,M SANDO,K ISEDAANDt-l TA~DA
I
I
30
40
I
50
2 6 NW
(b)
1
I
30
40
I
50
I 60
2 0 (deg)
Figure 6. X-ray diffraction chart of the change due to heat-treatment of titania. (a) pure titania particles, (b) titania powder dispersed with nickel particles.
temperature needed to crystallize the material as compared to pure titania (7). The compound body was observed by TEM (Figure 7). At the temperatures of 35O’C and 45O’C the nickel particles size was in the range from 10 to 20 nm. At 6OO’Cthe grains have grown to 40 nm. Growth of the titania particles with increased temperature was also observed. Figure 8 shows the specific surface area calculated from the specific surface area of the particle compound and nickel particle size and weight ratio of nickel and titanium, when the temperature changed. The specific surface area of particle compound decreased as the temperature increased. The calculated specific surface of titania in the particle compound also decreased. Grain growth was observed, indicating growth of the titania particles. The photocatalytic property as measured by Hz generation rate is shown in Figure 9. At 300°C the emission of hydrogen is slow because the crystal structure of titania is not fully
SYNTHESISOF TITANIAPHOTOCATALYSTS DISPERSED WITHNICKELNA~KJ-SIZED PARTICLES
1039
Figure 7. TEM micrograph of particles heat-treated at 600°C.
@lSO % p20 lu 8 80 2 ; E
40
ki CE
0 300
400
500
600
Temperature[“C] Figure 8. The calculated specific surface area of the titania.
300
400 500 Temperature[“C]
600
Figure 9. The rate of H2 generation of the particle compound photocatalysts.
developed. Thle peak of the H2 generation rate was at 350 “C. At 450°C and 600°C titania grain growth retards the rate. It is assumed that from 350°C to 600°C the rate of H2 generation is related to the particle size of the titania.
1040
A TOWATA,Y UWAMINO,M SANDO, K
ISEDA AND
H TAODA
Figure 10. X-ray diffraction of the particles component in the case of the change of the nickel content.
3.3. Effect of Nickel Content on the Photocatalytic Property of the Particle Compound The X-ray diffraction of the particles for different nickel contents is shown in Figure 10. Titania was generated as the content of nickel increased from zero percent to 25%. And at 27% nickel, nickel titanium oxide was generated by reaction between the nickel and titania. TEM micrographs of Figure 1l(a) and (b) show the specimens prepared by heat treatment at 350°C with a nickel content of 17.6% and 27% respectively. Up to 17.6% of nickel content the size of nickel particles remains almost unchanged in the range of 10 nm to 15 run. But the particle size almost doubled at 27%. Figure 12 shows the variation of specific surface area of the particle compound with nickel content. The figure shows the calculated values for specific surface area of titania particles. The specific surface area of the particle compound does not change up to 17.6% content, and decreases for 27% of nickel content, due possibly to particle growth. The value of the titania increases a little at 17.6% content and decreases for 27% of nickel content. Figure 13 shows the generation of hydrogen gas. The volume of Hz produced increases, as did the content of nickel, reaching a peak at 24%. There is a dramatic difference between the value of H2 generated at 24% and 27% content of nickel. As the nickel particle size was the same up to
!SYYMHESIS OF TITANIAPHOTOCATALYSTS DISPERSED WITHNICKELNANO-SIZEDPARTICLES
1041
Figure 11. TEM micrograph of particles heat-treated at 350°C. (a) nickel content of 17.6%, (b) 27%.
17.64 b,the :total surface area of the nickel particles must be changing. When the nickel content vvas 271, the] ?ick:el particle growth and synthesis of nickel titanate retards the generati on rate. 4. CONCLUSION
WP
BY( :onlrolling the dispersion and hydrolysis of Ni(NO3)26H20 and TIB using an emuls;ion
typetitania
super fine particle photocatalysts with dispersed nickel could be successfi ully
1042
A TOWATA,Y UWAMINO,M SANCO,K ISEDAANDH TAODA
1
Ill-
8
o0
10
20
d
30
0
Ni Content [wt.%]
Ni Content [wt.%] Figure 12. The calculated specific surface area of the titania.
Figure 13. The rate of the generation of the hydrogen gas.
prepared. The characteristics of the synthesized compound can be summarized as follows. 1. The amount of hydrogen generated increased in proportion to the surface area of the dispersed nickel super fine particles. 2. The nickel particles dispersed in titaniaphotocatalysis accelerated the generation of t-utile. This compound presents superior photocatalytic characteristics. This suggests that this compound is well suited for use in liquid environments - for example, in seawater dispersed with oil. REFERENCES 1.
2. 3. 4. 5. 6. 7.
Steigerwald, M.L. and Brus, L.E., Accounts of Chemical Research, 1990 23,183. Weller, H., Angewandte Chemie, International Edition in English, 1993,32,4 1. Tada, H., Miyata, K. and Yoshida, H., Sikizai, 1988, 61,665. Kawai, T., Sakata, T., Hashimoto, K. and Kawai, M., Journal of Chemical Society of Japan, 1984, 277. Sakata, T. and Kawai, T., Chemical Physics Letters, 1981,80,341. Nakahara, Y. , Journal of the Society of Powder Technology, Japan, 1995,32,97. Poniatowski, E.H.,Munos, S.V.,Murllo, R.A.,Talavera, R.R. and Diamant, R., Materials Research Bulletin, 1996,3 1,329.
Published without the benefit of Authors’ fiil
corrections as they were not available at press time.