Kim Jae Young, Youn Duck Hyun, Kim Ju Hun, Kim Hyun Gyu, Lee Jae Sung
†Division of Energy and Chemical Engineering, Ulsan National Institute of Science and Technology (UNIST), 50 UNIST-gil, Ulsan 689-798, Republic of Korea.
‡Department of Chemical Engineering, Pohang University of Science and Technology (POSTECH), 77 Cheongam-ro, Pohang 790-784, Republic of Korea.
ACS Appl Mater Interfaces. 2015 Jul 1;7(25):14123-9. doi: 10.1021/acsami.5b03409. Epub 2015 Jun 18.
High-temperature annealing above 700 °C improves the activity of photoelectrochemical water oxidation by hematite photoanodes by increasing its crystallinity. Yet, it brings severe agglomeration of nanostructured hematite thin films and deteriorates electrical conductivity of the transparent conducting oxide (TCO) substrate. We report here that the nanostructure of the hematite and the conductivity of TCO could be preserved, while the high crystallinity is attained, by hybrid microwave annealing (HMA) utilizing a graphite susceptor for efficient microwave absorption. Thus, the hematite thin-film photoanodes treated by HMA record 2 times higher water oxidation photocurrents compared to a conventional thermal-annealed photoanode. The enhanced performance can be attributed to the synergistic effect of a smaller feature size of nanostructure-preserved hematite and a good electrical conductivity of TCO. The method could be generally applied to the fabrication of efficient photoelectrodes with small feature sizes and high crystallinity, which have been mutually conflicting requirements with conventional thermal annealing processes.
700°C以上的高温退火通过提高赤铁矿光阳极的结晶度来改善其光电化学水氧化活性。然而，这会导致纳米结构的赤铁矿薄膜严重团聚，并降低透明导电氧化物（TCO）衬底的电导率。我们在此报告，通过利用石墨感受器进行高效微波吸收的混合微波退火（HMA），可以在保持赤铁矿纳米结构和TCO导电性的同时，实现高结晶度。因此，与传统热退火光阳极相比，经HMA处理的赤铁矿薄膜光阳极记录的水氧化光电流高出2倍。性能的提高可归因于纳米结构保留的赤铁矿较小特征尺寸与TCO良好导电性的协同效应。该方法可普遍应用于制造具有小特征尺寸和高结晶度的高效光电极，而这与传统热退火工艺是相互冲突的要求。
