신소재공학과

행사일 20161108 

학과 정기세미나 안내



■ 제  Overcoming tradeoff between catalytic activity and stability of perovskite oxides

                     
■ 연  :  Dr. Nikolai Tsvetkov (EEWS, KAIST) 

 

■ 초청자 : 안병태 교수


■ 일  : 11 8 () 16:00 

 

■ 장  : 응용공학동 (W1) 1층 영상강의실

 

■ 내용

Perovskite oxides (ABO3) have become a bustling area of research in recent years, with potential applications in areas ranging from fuel cell electrodes, to nonvolatile memory chips for computers, to solar thermochemical fuel production through the splitting of water and carbon dioxide. But the relative instability of the materials surface over time has been one of the major limitations to use of highly reactive perovskite oxides. In this talk Dr. Tsvetkov will present his recent investigations, conducted in MIT, on developing of a practical and physically-based way of treating the surface of perovskite oxides, to make them more durable and improve their performance. 

One key reason behind the instability of perovskite oxide surfaces is the electrostatic attraction of the negatively charged A-site dopants (for example, ) by the positively charged oxygen vacancies () enriched at the surface causing the surface reactions to slow down by more than an order of magnitude. In our work we show that reducing the surface concentration improves the oxygen surface exchange kinetics and stability significantly, albeit contrary to the well-established understanding that surface oxygen vacancies facilitate reactions with O2 molecules.

We took La0.8Sr0.2CoO3 (LSC) as a model perovskite oxide, and modify its surface with additive cations that are more and less reducible than Co on the B-site of LSC. By using ambient pressure X-ray absorption and photoelectron spectroscopy, we proved that the dominant role of the less reducible cations is to suppress the enrichment and phase separation of Sr while reducing the concentration of and making the LSC more oxidized at its surface. Consequently, we found that these less reducible cations significantly improve stability, with up to 30x acceleration of the oxygen exchange kinetics, after 54 hours in air at 550 oC achieved by Hf addition onto LSC. Finally, the results revealed a volcano relation between the oxygen exchange kinetics and the oxygen vacancy formation enthalpy of the binary oxides of the additive cations. This volcano relation highlights the existence of an optimum surface oxygen vacancy concentration that balances the gain in oxygen exchange kinetics and the chemical stability loss.

Thus, surface treatment could solve one of the major challenges that has hindered widespread deployment of fuel cell technology that, when operated reversibly, can present a promising alternative to batteries for renewable-energy storage. These new findings are being reported in June 2016 in the journal Nature Materials.

No. Subject Author Date Views
Notice 5/30 (Tue) 고창현 교수 (숙명여자대학교) ADMINI 2017.05.26 7
223 5/23 (Tue) 하돈형 교수 (중앙대학교 융합공학부) ADMINI 2017.05.19 50
222 5/16 (Tue) 조은선 교수 (카이스트 생명화학공학과) ADMINI 2017.05.10 96
221 5/2 (Tue) 이승우 교수 (성균관대학교) ADMINI 2017.04.28 106
220 4/25 (Tue) 최형섭 교수 (서울과학기술대학교) ADMINI 2017.04.20 70
219 4/11 (Tue) 최경숙 교수 (을지대학교 의과대학) ADMINI 2017.04.07 78
218 4/4 (Tue) 장은주 마스터 (삼성전자 종합기술원) ADMINI 2017.03.31 98
217 3/28 (Tue) 임원빈 교수 (전남대학교) ADMINI 2017.03.24 103
216 3/21 (Tue) 박상덕 교수 (서울대학교) ADMINI 2017.03.20 98
215 3/14 (Tue) 김화년 박사 (LG) ADMINI 2017.03.11 120
214 3/7(화) 박중근, 이정용 교수님 기념강연 ADMINI 2017.03.02 114
213 02/28 (화) 스티브 박 교수 (카이스트 신소재공학과) ADMINI 2017.02.24 190
212 02/20 (월) 특별세미나 안내, 황철성 교수 (서울대) ADMINI 2017.02.14 161
211 02/08 (수) 특별 세미나 안내, 강용호 박사, UC Santa Barbara ADMINI 2017.02.02 296
210 12/23(금) 특별세미나 안내, 김재진 박사님(Chemical Sciences and Engineering Division, Argonne National Laboratory) ADMINI 2016.12.16 269
209 12/13(화) 송재용 박사 (한국표준과학연구원) ADMINI 2016.12.12 274
208 12/6 (화) 엄광섭 교수 (GIST 신소재공학부) ADMINI 2016.12.02 288
207 11/16(수) 특별 세미나 안내, 강승균 박사 (Dept. of MSE, University of Illinois at Urbana-Champaign) ADMINI 2016.11.16 262
206 11/15 (화) 전상은 교수 (경북대학교 신소재공학과) ADMINI 2016.11.14 306
» 11/8(화) Dr. Nikolai Tsvetkov (EEWS, KAIST) ADMINI 2016.11.07 304