鉑修飾氧化鎳/氧化銦異質接面奈米複合物之合成 及其室溫一氧化碳感測特性

Abstract

本研究利用化學法成功合成Pt奈米粒子修飾之NiO-In2O3複合氧化物奈米組裝結構，並發現其於室溫下之高性能CO氣體感測能力。本奈米結構之主體為一維束狀In2O3奈米階層式(hierarchical)結構，主要是由奈米短柱規則組裝而成，其表面具有許多零星散佈之零維奈米粒子。故將此奈米結構集結為薄膜供氣感應用時，束狀奈米結構可被有效分散，薄膜比表面積甚高，同時結構內外具有無數細微孔洞與通道，可以作為氣體之吸附與向內或向外擴散通道，大幅提升氣體與材料間之反應機率跟速率。而Pt奈米粒子之表面修飾則可以促進氣體分子吸附與脫附反應，大幅降低氣感材料之工作溫度。為了更進一步強化氣感效能，本研究在一維束狀In2O3奈米階層式結構之上同步合成添加不同比例之NiO奈米結構，當p型之NiO與n型之In2O3複合後，形成之p-n接面有助於提升氣感靈敏度(sensitivity)，且因NiO本身具有吸附氧氣的特性，可有效地縮短響應及回復時間。結果發現，所有Pt奈米粒子修飾之NiO-In2O3複合氧化物奈米組裝結構，在室溫下進行CO感測，都能對5 ppm之CO有響應，其中以3.8 wt% NiO-In2O3之樣品具有最佳之靈敏度和最短之響應與回復時間。

In this study, we successfully synthesized a series of Pt-nanoparticles decorated NiO-In2O3 nano-composites via a facile chemical route and found their potentials in sensing CO gas at relatively low temperatures. The base structure of such the innovative hybrid nano-composite is the one-dimensional In2O3 hierarchical nanobundles comprising numerous parallel assembled nanoparticles and short nanorods, which provide open channels for gas inward or outward diffusion, and high surface to volume ratios for gas absorption/desorption and thus enhance the chemical reactions required and thus the sensing response to the target gas. The decoration of Pt nanoparticles contributes to significantly lowering the operating temperature via two key mechanisms, namely electric effects induced by contact interfaces between metal and oxide and chemical effects of the catalytic metal nanoparticles. For further enhancing the sensing performance, NiO nanostructures with various Ni to In ratios were co-synthesized with the In2O3 nanobundles to form p-n junctions which are theoretically and experimentally proven to improve the sensitivity. In addition, the presence of NiO would significantly enhance O2 absorption, which plays a key role for reducing the response and recovery time. It was found that the fabricated Pt-nanoparticles decorated NiO-In2O3 nano-composites exhibit excellent CO sensing performance at room temperature to a very low detecting limitation of about 5 ppm CO. The specimen of 3.8 wt% NiO-In2O3 was proven as the optimized case mainly due to the appropriate ratio between NiO and In2O3 and the resulting hybrid nanostructures.