Functional CeOx nanoglues for efficient and robust atomically dispersed catalysts-猫眼课题宝

DOI：

10.21203/rs.3.rs-604924/v1

发表时间：

2021-06

期刊：

影响因子：

通讯作者：

中科院分区：

其他

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作者：

J. Liu;Xu Li;X. Hernandez;C. Fang;Yizhen Chen;Jie Zeng;Yong Wang;B. Gates

单原子催化剂（SAC）具有独特的催化性能和稀有、昂贵金属的最大原子效率。SAC应用的一个关键障碍是在操作条件下活性金属原子的烧结。通过强金属-载体键将金属原子吸附到氧化物载体上可以减轻烧结。然而，这种方法通常是有代价的：稳定化是由于过量的氧配位使金属位点钝化--载体占据了太多的开放配位位点，而留下的催化作用位点太少。此外，当这种稳定的金属原子通过在升高的温度下还原而活化时，它们变得不连接，因此移动和烧结，导致催化功能的损失。我们报告了一种新的策略，限制原子分散的金属原子上的功能氧化物纳米团簇（表示为nanoglues），被隔离和固定在一个强大的，高表面积的支持，使金属原子不烧结条件下的催化剂活化和/或操作。高的数密度，超小的和有缺陷的CeOx纳米簇接枝到高表面积的SiO2作为纳米胶主机原子分散的Pt。Pt原子在高温下在O2和H2环境下都保留在CeOx纳米胶岛上。CeOx负载的Pt原子的活化使CO氧化的周转频率增加了150倍。在还原条件下的异常稳定性归因于Pt原子对CeOx的亲和力比对SiO2的亲和力强得多-Pt原子可以移动，但它们被限制在它们各自的纳米胶岛上，防止形成更大的Pt颗粒。使用功能性纳米胶来限制原子分散的金属原子并同时增强局部金属原子的催化性能的策略是通用的，并且使SAC作为用于广泛催化转化的稳健催化剂向实际应用更近了一大步

Single-atom catalysts (SACs) exhibit unique catalytic property and maximum atom efficiency of rare, expensive metals. A critical barrier to applications of SACs is sintering of active metal atoms under operating conditions. Anchoring metal atoms onto oxide supports via strong metal-support bonds may alleviate sintering. Such an approach, however, usually comes at a cost: stabilization results from passivation of metal sites by excessive oxygen ligation—too many open coordination sites taken up by the support, too few left for catalytic action. Furthermore, when such stabilized metal atoms are activated by reduction at elevated temperatures they become unlinked and so move and sinter, leading to loss of catalytic function. We report a new strategy, confining atomically dispersed metal atoms onto functional oxide nanoclusters (denoted as nanoglues) that are isolated and immobilized on a robust, high-surface-area support—so that metal atoms do not sinter under conditions of catalyst activation and/or operation. High-number-density, ultra-small and defective CeOx nanoclusters were grafted onto high-surface-area SiO2 as nanoglues to host atomically dispersed Pt. The Pt atoms remained on the CeOx nanoglue islands under both O2 and H2 environment at high temperatures. Activation of CeOx supported Pt atoms increased the turnover frequency for CO oxidation by 150 times. The exceptional stability under reductive conditions is attributed to the much stronger affinity of Pt atoms for CeOx than for SiO2—the Pt atoms can move but they are confined to their respective nanoglue islands, preventing formation of larger Pt particles. The strategy of using functional nanoglues to confine atomically dispersed metal atoms and simultaneously enhance catalytic performance of localized metal atoms is general and takes SACs one major step closer to practical applications as robust catalysts for a wide range of catalytic transformations

Functional CeOx nanoglues for efficient and robust atomically dispersed catalysts

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