設計及合成新的ORR鉑基奈米結構觸媒，是本實驗的主題。先前，本實驗室曾提出無載體二氧化鈦核鉑殼之核殼結構作為模型催化劑，可以有效的產生ORR催化作用，然而以此光沉積方式的TiO2@Pt觸媒，其鉑殼結構不連續，ORR催化性能有相當的改善空間。在本研究工作中，以滴定方式改善了光沉積方法來合成TiO2@Pt觸媒，控制白金粒子生長。由HRTEM之影像和TEM mapping中顯示此二氧化鈦核上已形成一完整鉑殼，其鉑殼厚度約為2~3奈米。從XRD的角度顯示此鉑殼為許多超小鉑顆粒堆積而成。由XAS可知此二氧化鈦核鉑殼觸媒系統具有強觸媒-載體交互作用(Strong Metal-Support Interaction, SMSI)。而電化學測試方面表示，此TiO2@Pt比商業化鉑奈米顆粒具有超過5倍的單位面積活性和8倍的質量活性，且由於此TiO2@Pt結構設計配置使在提高穩定性方面有重大的進展，在5000次循環後ECSA和質量活性均未降低。 預期在將來透過殼結構調整可以開發出更有效的ORR催化劑。

Design and synthesis of new nano-structured Pt-based ORR catalysts is highly needed. In previous work, for the first time, we proposed that unsupported core-shell TiO2@Pt (TiO2cPts) particles as a model catalyst could generate efficient ORR catalysis. However, TiO2@Pt particles derived from the photo-deposition method did not have a completely covered Pt shell structure, and thus it did not achieve expected ORR catalytic activity. In this work, the photo-deposition method was improved by droplet controlled growth of Pt nanoparticles to synthesize TiO2@Pt. High-resolution transmission electron microscopy (TEM) and elemental mapping images showed that the complete Pt shell on TiO2 core was formed, and the thickness of Pt shell was 2-3 nm. X-ray diffraction (XRD) reveals that Pt shell is composed of numerous ultra-small Pt clusters. X-ray absorption spectroscopy (XAS) shows that TiO2@Pt indicate the presence of Strong Metal-Support Interaction (SMSI). Electrochemical tests demonstrate that TiO2@Pt exhibits over 5-fold specific activity and 8-fold mass activity than commercial Pt nanoparticles. This uniquely designed configuration with TiO2-core and Pt thin shell has made a significant progress in improving the stability. The durability test shows no degradation in both ECSA and mass activity after 5000 cycles. More efficient ORR catalysts can be expected by further fine tuning of the shell structure in TiO2@Pt.

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