Small-sized and contacting Pt-WC nanostructures on graphene as highly efficient anode catalysts for direct methanol fuel cells.
Small-sized and contacting Pt-WC nanostructures on graphene as highly efficient anode catalysts for direct methanol fuel cells.
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DOI：
10.1002/chem.201103011
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发表时间：
2012-06
期刊：
影响因子：
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通讯作者：
Ruihong Wang;Ying Xie;K. Shi;Jianqiang Wang;Chungui Tian;P. Shen;H. Fu
中科院分区：
文献类型：
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作者：
Ruihong Wang;Ying Xie;K. Shi;Jianqiang Wang;Chungui Tian;P. Shen;H. Fu
铂和碳化钨之间的协同作用有利于甲醇的电氧化，使铂-碳化钨催化剂成为直接甲醇燃料电池的理想负极候选材料。本文报道了在石墨烯上设计和合成小尺寸、接触的铂-碳化钨纳米结构，以充分发挥协同作用。首先，密度泛函计算表明WC与石墨烯之间存在较强的共价相互作用，这表明WC在石墨烯上形成小尺寸、分散良好的WC颗粒具有很大的潜力。计算还表明，当铂附着在已有的WC/石墨烯杂化材料上时，铂颗粒优先生长在WC上，而不是石墨烯上。我们的实验证实了高度分散的WC纳米颗粒(约5 nm)确实可以固定在石墨烯上。尺寸为2~3 nm的铂颗粒均匀分散在WC/石墨烯杂化材料上，并优先生长在WC颗粒上，形成接触的铂-WC纳米结构。这些结果与理论发现是一致的。X射线吸收精细结构谱进一步证实了铂与碳化钨之间的紧密接触，并证明碳化钨的存在有利于铂颗粒的结晶。该新型催化剂对甲醇氧化具有较高的催化效率，其质量活性分别是工业PtRu/C和PtRu/C催化剂的1.98倍和4.52倍。
The synergistic effect between Pt and WC is beneficial for methanol electro-oxidation, and makes Pt-WC catalyst a promising anode candidate for the direct methanol fuel cell. This paper reports on the design and synthesis of small-sized and contacting Pt-WC nanostructures on graphene that bring the synergistic effect into full play. Firstly, DFT calculations show the existence of a strong covalent interaction between WC and graphene, which suggests great potential for anchoring WC on graphene with formation of small-sized, well-dispersed WC particles. The calculations also reveal that, when Pt attaches to the pre-existing WC/graphene hybrid, Pt particles preferentially grow on WC rather than graphene. Our experiments confirmed that highly disperse WC nanoparticles (ca. 5 nm) can indeed be anchored on graphene. Also, Pt particles 2-3 nm in size are well dispersed on WC/graphene hybrid and preferentially grow on WC grains, forming contacting Pt-WC nanostructures. These results are consistent with the theoretical findings. X-ray absorption fine structure spectroscopy further confirms the intimate contact between Pt and WC, and demonstrates that the presence of WC can facilitate the crystallinity of Pt particles. This new Pt-WC/graphene catalyst exhibits a high catalytic efficiency toward methanol oxidation, with a mass activity 1.98 and 4.52 times those of commercial PtRu/C and Pt/C catalysts, respectively.