Limits...
Catalytic properties of Co3O4 nanoparticles for rechargeable Li/air batteries.

Kim KS, Park YJ - Nanoscale Res Lett (2012)

Bottom Line: The electrochemical property of the air electrodes containing Co3O4 nanoparticles is significantly associated with the shape and size of the nanoparticles.It appears that the capacity of electrodes containing villiform-type Co3O4 nanoparticles is superior to that of electrodes containing cube- and flower-type Co3O4 nanoparticles.This is probably due to the sufficient pore spaces of the villiform-type Co3O4 nanoparticles.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Advanced Materials Engineering, Kyonggi University, San 94-6, Yiui-dong, Yeongtong-gu, Suwon, Gyeonggi-do, 443-760, Republic of Korea. yjpark2006@kyonggi.ac.kr.

ABSTRACT
Three types of Co3O4 nanoparticles are synthesized and characterized as a catalyst for the air electrode of a Li/air battery. The shape and size of the nanoparticles are observed using scanning electron microscopy and transmission electron microscopy analyses. The formation of the Co3O4 phase is confirmed by X-ray diffraction. The electrochemical property of the air electrodes containing Co3O4 nanoparticles is significantly associated with the shape and size of the nanoparticles. It appears that the capacity of electrodes containing villiform-type Co3O4 nanoparticles is superior to that of electrodes containing cube- and flower-type Co3O4 nanoparticles. This is probably due to the sufficient pore spaces of the villiform-type Co3O4 nanoparticles.

No MeSH data available.


Related in: MedlinePlus

SEM images of the air electrodes. Air electrodes composed of Co3O4 nanoparticles, carbon (Ketjen black), and binder before the test and after discharge at 2.3 V. (a) Cube type, (b) villiform type, and (c) flower type.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC3275460&req=5

Figure 4: SEM images of the air electrodes. Air electrodes composed of Co3O4 nanoparticles, carbon (Ketjen black), and binder before the test and after discharge at 2.3 V. (a) Cube type, (b) villiform type, and (c) flower type.

Mentions: After 10 cycles, the electrode was discharged to 2.3 V, and the surface was observed by SEM to investigate the morphology change during cycling. In the SEM images of the air electrodes before testing, the Co3O4 nanoparticles and carbon (Ketjen black) could be clearly identified (Figure 4). It was noticeable that the villiform-type Co3O4 nanoparticles maintained their shape during the electrode-fabrication process. However, the flower-type Co3O4 nanoparticles were almost separated to become the nanorod type. When they discharged to 2.3 V, it was observed that the surface of the electrode was homogenously covered with precipitates, which appeared to be reaction products such as lithium oxides, and lithium carbonates formed due to electrolyte decomposition [15,16]. These reaction precipitates could block the catalyst/carbon contact area, thereby preventing O2 intake and Li+ delivery to the active reaction site and terminating the discharge process. According to previous reports [13,14], there was a strong correlation between average pore diameter and discharge capacity. Reaction precipitates are likely to be formed near active sites so that the micropore of a porous electrode would be easily sealed with precipitates of lithium oxides during discharge. Thus, securing enough space between catalytic active sites might increase the discharge capacity of the air electrode. The cube- and flower- (nanorod- in the electrode) type Co3O4 nanoparticles may be well covered with small carbon particles (Ketjen black) in the air electrode so that a sufficiently small pore space could be obtained. On the other hand, the villiform-type Co3O4 nanoparticles were composed of a nucleus covered with many nanorods of approximately 100 nm in size, which could offer enough space between active catalytic sites. Thus, a greater amount of lithium oxide precipitation may be needed to block the pore orifices and terminate the discharge process; this could be an explanation for the higher discharge capacity of the air electrode containing villiform-type Co3O4 nanoparticles in comparison with the air electrode containing other types Co3O4 nanoparticles.


Catalytic properties of Co3O4 nanoparticles for rechargeable Li/air batteries.

Kim KS, Park YJ - Nanoscale Res Lett (2012)

SEM images of the air electrodes. Air electrodes composed of Co3O4 nanoparticles, carbon (Ketjen black), and binder before the test and after discharge at 2.3 V. (a) Cube type, (b) villiform type, and (c) flower type.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3275460&req=5

Figure 4: SEM images of the air electrodes. Air electrodes composed of Co3O4 nanoparticles, carbon (Ketjen black), and binder before the test and after discharge at 2.3 V. (a) Cube type, (b) villiform type, and (c) flower type.
Mentions: After 10 cycles, the electrode was discharged to 2.3 V, and the surface was observed by SEM to investigate the morphology change during cycling. In the SEM images of the air electrodes before testing, the Co3O4 nanoparticles and carbon (Ketjen black) could be clearly identified (Figure 4). It was noticeable that the villiform-type Co3O4 nanoparticles maintained their shape during the electrode-fabrication process. However, the flower-type Co3O4 nanoparticles were almost separated to become the nanorod type. When they discharged to 2.3 V, it was observed that the surface of the electrode was homogenously covered with precipitates, which appeared to be reaction products such as lithium oxides, and lithium carbonates formed due to electrolyte decomposition [15,16]. These reaction precipitates could block the catalyst/carbon contact area, thereby preventing O2 intake and Li+ delivery to the active reaction site and terminating the discharge process. According to previous reports [13,14], there was a strong correlation between average pore diameter and discharge capacity. Reaction precipitates are likely to be formed near active sites so that the micropore of a porous electrode would be easily sealed with precipitates of lithium oxides during discharge. Thus, securing enough space between catalytic active sites might increase the discharge capacity of the air electrode. The cube- and flower- (nanorod- in the electrode) type Co3O4 nanoparticles may be well covered with small carbon particles (Ketjen black) in the air electrode so that a sufficiently small pore space could be obtained. On the other hand, the villiform-type Co3O4 nanoparticles were composed of a nucleus covered with many nanorods of approximately 100 nm in size, which could offer enough space between active catalytic sites. Thus, a greater amount of lithium oxide precipitation may be needed to block the pore orifices and terminate the discharge process; this could be an explanation for the higher discharge capacity of the air electrode containing villiform-type Co3O4 nanoparticles in comparison with the air electrode containing other types Co3O4 nanoparticles.

Bottom Line: The electrochemical property of the air electrodes containing Co3O4 nanoparticles is significantly associated with the shape and size of the nanoparticles.It appears that the capacity of electrodes containing villiform-type Co3O4 nanoparticles is superior to that of electrodes containing cube- and flower-type Co3O4 nanoparticles.This is probably due to the sufficient pore spaces of the villiform-type Co3O4 nanoparticles.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Advanced Materials Engineering, Kyonggi University, San 94-6, Yiui-dong, Yeongtong-gu, Suwon, Gyeonggi-do, 443-760, Republic of Korea. yjpark2006@kyonggi.ac.kr.

ABSTRACT
Three types of Co3O4 nanoparticles are synthesized and characterized as a catalyst for the air electrode of a Li/air battery. The shape and size of the nanoparticles are observed using scanning electron microscopy and transmission electron microscopy analyses. The formation of the Co3O4 phase is confirmed by X-ray diffraction. The electrochemical property of the air electrodes containing Co3O4 nanoparticles is significantly associated with the shape and size of the nanoparticles. It appears that the capacity of electrodes containing villiform-type Co3O4 nanoparticles is superior to that of electrodes containing cube- and flower-type Co3O4 nanoparticles. This is probably due to the sufficient pore spaces of the villiform-type Co3O4 nanoparticles.

No MeSH data available.


Related in: MedlinePlus