Synthesis of Platinum Nanostructures and Their Effects on Catalysis
|摘要:||本論文利用簡易之電鍍法於ITO導電玻璃或碳電極上成長奈米鉑金屬，當電鍍環境僅有鉑氯酸溶液時，在2 V的電壓下，可得到大小約100 nm的刺狀鉑顆粒，當添加5 mM硝酸於電鍍液時，沈積產物轉變成寬100 nm、厚20 nm的片狀結構；此兩種特殊形貌之鉑電極在電催化甲醇實驗中，展現優於塊材鉑金屬之電催化活性。另外，利用錫金屬與鉑離子間的賈凡尼置換反應，也可於碳電極上修飾奈米樹狀、球狀之鉑金屬，但實驗中發現，低濃度的鉑氯酸離子將催化錫金屬與質子間的氧化還原反應，在界面活性劑CTAC的輔助下，可生成摻雜鉑離子的奈米圈狀二價氧化錫，線徑約50∼100 nm ，整體大小達1 µm，經大氣下高溫燒結，可轉變成摻雜鉑離子的四價氧化錫，期望其特殊的形貌可在氣體偵測展現良好的應用價值。|
We demonstrate the syntheses of Pt thornlike and sheet nanostructures on indium tin oxide substrates via electroplating. Thornlike nanoparticles, with a size in the range of 100 nm were electrodeposited (potentiostatic deposition at 2 V) on ITO substrates using a H2PtCl6 solution. Furthermore, a large amount of Pt nanosheets were electrodeposited from an aqueous solution of H2PtCl6 and HNO3. The width and thickness of the nanosheets were 100 nm and 20 nm, respectively. These novel Pt nanostructures on ITO electrodes were applied on methanol oxidation catalysis. They revealed higher current and lower voltage than bulk Pt electrode did. These novel modefied Pt electrodes will be expected for other electrochemical applications. In addition to the method mentioned above, we also employed the spontaneous Sn-Pt4+ redox process to synthesize Pt nanostructure in a solution containing cationic surfactant (cetyltrimethylammonium chloride, CTAC), and produced Pt dendritelike and particle nanostructures on carbon electrode. In the past, platinum and its complexes have been widely used as catalysts in various chemical reaction, especially in proton reduction to generate hydrogen. We found it could act as a catalytic agent for Sn-H+ redox process when reacting at low concentration of [PtCl6]2-. As a result, large amount of SnO:Pt2+ nanorings with diameter of 50~100 nm and width up to 1 µm were grown when CTAC was used as the growth control agent. Following an annealing step in atmosphere, the product turned to SnO2:Pt2+. These novel SnO2:Pt2+ nanorings will be expected for many applications such as gas sensors.