美國威斯康星大學麥迪遜分校（UniversityofWisconsin-Madison）化學與生物工程學教授ManosMavrikakis和馬里蘭大學（UniversityofMaryland）化學與生物化學教授Bryan Eichhorn近日在《自然—材料學》網(wǎng)絡版上發(fā)表的論文中描述了一種新型催化劑,。它由被一層或兩層鉑原子包圍的釕納米顆粒組成，是一種高效的室溫催化劑,，可顯著改善關鍵的氫純化反應,，從而獲取更多的氫用于燃料電池的供能。目前,，全世界大多數(shù)氫的供應來自于化石燃料,，這個過程稱作重整?？茖W家相信,，燃料電池不久就能通過由可再生能源得到的氫來進行發(fā)電。這個過程的重要一步稱為PROX反應,，它是氫進入燃料電池前,，利用催化劑去除其中的CO。CO的存在是燃料電池實際應用的一個主要障礙,，因為它毒化了燃料電池反應中昂貴的鉑催化劑,。
質子交換膜燃料電池能夠替代應用于運輸工具中的其它電池，它通過利用多孔碳電極進行發(fā)電,，電極中含有被固體聚合物分開的鉑催化劑,。氫燃料進入電池的一極，氧進入另一極,，鉑催化劑促使氫分子中產生質子,，這些質子穿過膜與另一極的氧發(fā)生反應，結果產生電以及副產品水和熱,。傳統(tǒng)的釕,、鉑催化劑結合必須達到70℃才能發(fā)生PROX反應，但相同的元素以核殼納米顆粒結構結合后,，能夠使反應在室溫下就發(fā)生,。催化劑活化反應物以及得到產物的溫度越低，節(jié)約的能量就越多。產生這種室溫反應的原因有兩個,，首先是催化劑的核殼結構,，與單純的鉑催化劑相比，這種特別的結構核成分能夠使表面吸收較少的CO,，給氧進入并發(fā)生反應留下空間。另一個原因是新的反應機理,，利用氫原子結合氧分子并生成氫過氧基,，這樣很容易生成氧原子。氧原子與CO結合生成二氧化碳CO2,，這樣留下更多的氫分子供給燃料電池,。這項突破對于發(fā)展燃料電池技術有著重要意義，甚至對催化劑本身的發(fā)展也會產生重大影響,。（科學網(wǎng)）
生物谷推薦原始出處：
Nature Materials 7, 333 - 338 (2008)
Published online: 16 March 2008 | doi:10.1038/nmat2156
Subject Categories: Catalytic materials | Materials for energy | Nanoscale materials
Ru–Pt core–shell nanoparticles for preferential oxidation of carbon monoxide in hydrogen
Selim Alayoglu1, Anand U. Nilekar2, Manos Mavrikakis2 & Bryan Eichhorn1
Abstract
Most of the world's hydrogen supply is currently obtained by reforming hydrocarbons. 'Reformate' hydrogen contains significant quantities of CO that poison current hydrogen fuel-cell devices. Catalysts are needed to remove CO from hydrogen through selective oxidation. Here, we report first-principles-guided synthesis of a nanoparticle catalyst comprising a Ru core covered with an approximately 1–2-monolayer-thick shell of Pt atoms. The distinct catalytic properties of these well-characterized core–shell nanoparticles were demonstrated for preferential CO oxidation in hydrogen feeds and subsequent hydrogen light-off. For H2 streams containing 1,000 p.p.m. CO, H2 light-off is complete by 30 °C, which is significantly better than for traditional PtRu nano-alloys (85 °C), monometallic mixtures of nanoparticles (93 °C) and pure Pt particles (170 °C). Density functional theory studies suggest that the enhanced catalytic activity for the core–shell nanoparticle originates from a combination of an increased availability of CO-free Pt surface sites on the Ru@Pt nanoparticles and a hydrogen-mediated low-temperature CO oxidation process that is clearly distinct from the traditional bifunctional CO oxidation mechanism.
