Electronic States and Transport Phenomena of Pt Nanoparticle Catalysts Supported on Nb-Doped SnO2 for Polymer Electrolyte Fuel Cells
Electronic States and Transport Phenomena of Pt Nanoparticle Catalysts Supported on Nb-Doped SnO2 for Polymer Electrolyte Fuel Cells
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DOI：
10.1021/acsami.9b11119
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发表时间：
2019-09-25
影响因子：
9.5
通讯作者：
Uchida, Makoto
中科院分区：
文献类型：
--
作者：
Kakinuma, Katsuyoshi;Suda, Kohei;Uchida, Makoto
半导体氧化物纳米颗粒受到表面吸附分子的强烈影响，并且倾向于产生绝缘耗尽层。贵金属和半导体氧化物之间的界面构成肖特基势垒，中断电子传输。在用于聚合物电解质燃料电池的负载在具有熔融聚集体网络结构的掺杂Nb的SnO 2的半导体氧化物（Pt/Nb-SnO 2）上的Pt催化剂的情况下，电子电导率随着Pt负载量的增加而突然增加，从10（-4）S cm（-1）增加到10（-2）S cm（-1）。在低载量Pt的X射线光电子能谱（XPS）光谱表现出较高的结合能比原始的Pt金属。Pt XPS谱的峰位移大于Pt硬X射线光电子能谱（HAXPES）谱的峰位移。对于所有的光谱，随着Pt负载量的增加，峰接近原始Pt金属的结合能。Sn XPS谱峰证明了随着Pt负载量的增加，Sri金属的存在，并且峰强度大于HAXPES。这些光谱的结果，连同扫描透射电子显微镜与能量色散X射线光谱（STEM-EDX）谱，证明了PtSn合金沉积在Pt和Nb-SnO 2之间的界面作为结果的烧结程序在稀氢气氛下。两个Nb光谱都表明Nb的氧化态为+5，因此Nb阳离子充当SnO 2的n型掺杂剂。结果表明，Pt/Nb-SnO 2界面处的PtSn合金减轻了肖特基势垒的影响，增强了Pt对Nb-SnO 2的载流子贡献，改善了Pt/Nb-SnO 2的电子输运现象。
Semiconducting oxide nanoparticles are strongly influenced by surface-adsorbed molecules and tend to generate an insulating depletion layer. The interface between a noble metal and a semiconducting oxide constructs a Schottky barrier, interrupting the electron transport. In the case of a Pt catalyst supported on the semiconducting oxide Nb-doped SnO2 with a fused-aggregate network structure (Pt/Nb-SnO2) for polymer electrolyte fuel cells, the electronic conductivity increased abruptly with increasing Pt loading, going from 10(-4) to 10(-2) S cm(-1). The Pt X-ray photoemission spectroscopy (XPS) spectra at low Pt loading amount exhibited higher binding energy than that of pristine Pt metal. The peak shift for the Pt XPS spectra was larger than that of the Pt hard X-ray photoemission spectroscopy (HAXPES) spectra. For all of the spectra, the peaks approached the binding energy of pristine Pt metal with increasing Pt loading. The Sn XPS spectral peak proved the existence of Sri metal with increasing Pt loading, and the peak intensity was larger than that for HAXPES. These spectroscopic results, together with the scanning transmission electron microscopy with energy dispersive X-ray spectroscopy (STEM-EDX) spectra, proved that a PtSn alloy was deposited at the interface between Pt and Nb-SnO2 as a result of the sintering procedure under dilute hydrogen atmosphere. Both Nb spectra indicated that the oxidation state of Nb was +5 and thus that the Nb cation acts as an n-type dopant of SnO2. We conclude that the PtSn alloy at the interface between Pt and Nb-SnO2 relieved the effect of the Schottky barrier, enhanced the carrier donation from Pt to Nb-SnO2, and improved the electronic transport phenomena of Pt/Nb-SnO2.