用两步还原法制备的PtCo/C (10 wt% Pt)纳米催化剂具有与商业催化剂Pt/C (20 wt% Pt)接近的催化反应活性，使贵金属Pt的用量减少了50%。利用上海光源BL14W1线站的质子交换膜燃料电池(Proton exchange membrane fuel cell, PEMFC)原位X射线吸收精细结构谱(X-ray absorption fine structure, XAFS)实验装置，在以该PtCo/C作为燃料电池的阴极催化剂，以Pd/C作为阳极催化剂的条件下，原位表征PtCo/C在工作状态下的结构变化，PtCo/C 的非原位 XAFS 数据没有观察到 Pt−Co 合金成分，发现存在显著的 Co−O 键和 Co−O−Co键贡献，且与Pt/C相比，Pt的氧化程度更高且具有更短的Pt−Pt金属键长，说明PtCo/C中的Co主要以氧化物种形式存在，且Co的存在影响着活性成分Pt的结构。原位XAFS数据表明随着电压的逐渐降低，PtCo/C中Pt和Co的氧化程度降低，揭示了在催化反应过程中Pt的d电子向过渡金属Co的转移过程。%AbstractBackground:The proton exchange membrane fuel cell (PEMFC) is considered as one of the most promising clean energy sources in the future, because of its high energy density and simple construction. However, the large scale commercial application of fuel cell is limited by the factors such as cost, durability and reliability. Purpose: For the purpose of reducing the cost and improving the performance of the PEMFC, transition metal elements alloy Pt nanoparticles (PtFe/C, PtCo/C, PtNi/C) catalysts have been studied in recent years.Methods:In situ X-ray absorption fine structure (XAFS) experimental testing device for PEMFC on beamline (BL14W1) of XAFS spectroscopy at the Shanghai Synchrotron Radiation Facility (SSRF) is conducted to explore the nanostructure changes of PtCo/C during the fuel cell operation. Results:In situ XAFS spectra indicts that Pt, and Co are gradually being reduced as the voltage of fuel cell decreases.Ex-situ XAFS spectra show Pt and Co did not form Pt−Co bond, but there is a strong Co−O bond and Co−O−Co bond.Conclusion: The element of Co improves the performance of PtCo/C catalysts for the oxygen reduction reaction (ORR) and decreases the cost of fuel cells by regulating the electronic structure of Pt.
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