H2 and O2 photocatalytic production on TiO2 nanotube arrays: Effect of the anodization time on structural features and photoactivity
H2 and O2 photocatalytic production on TiO2 nanotube arrays: Effect of the anodization time on structural features and photoactivity
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DOI：
10.1016/j.apcatb.2013.01.054
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发表时间：
2013-06
影响因子：
22.1
通讯作者：
Marco Altomare;M. Pozzi;M. Allieta;L. Bettini;E. Selli
中科院分区：
文献类型：
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作者：
Marco Altomare;M. Pozzi;M. Allieta;L. Bettini;E. Selli
采用电化学阳极氧化法制备了不同长度的TiO 2纳米管阵列。10 cm 2面积的钛盘在NH 4F-H2O-甲酰胺溶液中进行不同时间的退火，然后在450°C下退火。在圆盘的另一面上沉积Pt后，将所获得的Ti负载的结晶阳极氧化物用作两室电池中的光活性电极，用于通过水的光分解单独产生H2和O2，并通过SEM、XRD分析和光电流测量进行表征。阳极氧化时间影响纳米管的物相组成和形貌，从而影响纳米管的光催化活性。短的阳极氧化时间（40- 60分钟）导致由锐钛矿-金红石混合相组成的排列良好的短管。较长的阳极化（>2.5h）产生较厚的NT阵列，其在顶部上被优先取向的限制其光活性的氧化层覆盖。光电流强度测量完全验证了用不同NT阵列获得的水裂解活性结果。特别是，一个正方形的快速光响应记录有序和完全顶部开放的纳米管结构。另一方面，堵塞的管不仅产生低电流密度，但也表现出延迟的光电流瞬态信号，由于优先取向的电介质层内的电荷载流子的迁移率降低。在优化条件下获得的NT阵列具有ca. 80：20 η：金红石组成，并在没有任何空穴清除剂或外部偏压的情况下确保83 mmolh − 1 m −2（即1.9NLh− 1 m −2）的氢产生速率。
TiO2nanotube (NT) arrays of different lengths were prepared by electrochemical anodization of ca. 10cm2area titanium disks in NH4F–H2O–formamide solution for different times, followed by annealing at 450°C. After Pt deposition on the opposite side of the disk, the so obtained Ti-supported crystalline anodic oxides were employed as photoactive electrodes in a two compartments cell for separate H2and O2production through water photosplitting and characterized by SEM, XRD analysis and photocurrent measurements. The anodization time affected the phase composition and morphology of the growing NTs, which strictly influenced their photocatalytic activity. Short anodization times (40–60min) resulted in well aligned short tubes composed of anatase-rutile mixed phases. Longer anodization (>2.5h) yielded thicker NT arrays covered on top by a preferentially oriented anatase layer that limited their photoactivity. Photocurrent intensity measurements perfectly paralleled the water splitting activity results obtained with the different NT arrays. In particular, a square-shaped fast photoresponse was recorded with ordered and fully top-open nanotubular structures. On the other hand, clogged tubes not only yielded low current densities, but also showed delayed photocurrent transient signals due to the reduced mobility of the charge carriers within the preferentially oriented anatase layer. NT arrays obtained under optimized conditions had a ca. 80:20 anatase:rutile composition and ensured a hydrogen production rate of 83mmolh−1m−2(i.e. 1.9NLh−1m−2) in the absence of any hole scavenger or external bias.