Li 이온을 삽입한 TiO2 nanotube의 광전기화학적 특성 연구: Lithium-inserted TiO2 nanotube array photoelectrocatalysts

by Unseock Kang (MS Candidate)

Monday Nov 12, 2012, 4:00 PM → 4:30 PM Asia/Seoul

216-1호M (제1과학관)

A quick electrochemical Li ion insertion into TiO2 nanotube arrays (TNT) markedly enhances the photoelectrochemical and photoelectrocatalytic performance. Potential pulses (1.0 ~ 1.7 VSCE for 1 ~ 11 seconds in 1 M LiClO4) to pre-annealed TNT effectively insert Li ions (pre-annealed Li-TNT) into the mouth/wall and bottom TiO2 depending on the insertion condition. Pre-annealed Li-TNT prepared under an optimal Li ion insertion condition (1.4 VSCE for 3 seconds) exhibit ~70%-enhanced photocurrent generation, ~2.5 fold-higher incident photon-to-current efficiency, and an improved photoelectrocatalytic activity for the degradation of phenolic compounds in 1 M KOH electrolyte. A change in photoluminescence (PL) emission spectra and decrease in charge transfer resistance by Li ion insertion suggest that the inserted Li ions play a role in inhibiting charge recombination by compensating for Ti3+ charges (Li+ -Ti3+ -OH). As KOH concentration is diluted, however, such enhanced Li+ effects gradually vanish primarily due to liberation of reversibly inserted Li ions. To insert Li ions irreversibly, the potential pulses were applied to non-annealed TNT followed by annealing (post-annealed Li-TNT). Comparison between pre-annealed and post-annealed Li-TNTs in circum-neutral pH (0.1 M Na2SO4 at pH ~6) indicates that the former exhibits a similar performance to bare TNT (absence of Li ion effect), whereas the latter shows a superior performance with ca. 2.5-fold higher photoelectrochemical and photoelectrocatalytic activities. Detailed surface analyses (XPS, XRD, PL,
SEM, ICP-MS, etc) and Li+ -induced reaction mechanism were discussed.

Thesis Advisor: Prof. Hyunwoong Park