Tian Yi-Qi, Mu Wen-Lei, Wu Lin-Lin, Yi Xiao-Yi, Yan Jun, Liu Chao
Hunan Provincial Key Laboratory of Chemical Power Sources, College of Chemistry and Chemical Engineering, Central South University Changsha 410083 Hunan P. R. China
Chem Sci. 2023 Sep 5;14(37):10212-10218. doi: 10.1039/d3sc02793g. eCollection 2023 Sep 27.
The accurate identification of catalytic sites in heterogeneous catalysts poses a significant challenge due to the intricate nature of controlling interfacial chemistry at the molecular level. In this study, we introduce a novel strategy to address this issue by utilizing a thiacalix[4]arene (TC4A)-protected Ti-oxo core as a template for loading Ag ions, leading to the successful synthesis of a unique Ag/Ti bimetallic nanocluster denoted as TiAg. This nanocluster exhibits multiple surface-exposed Ag sites and possesses a distinctive "core-shell" structure, consisting of a {Ti@Ag(TC4A)} core housing a {TiO@Ag(TC4A)} motif and two {Ti@Ag(TC4A)} motifs. To enable a comprehensive analysis, we also prepared a TiAg cluster with the same {TiO@Ag(TC4A)} structure found within TiAg. The structural disparities between TiAg and TiAg provide an excellent platform for a comparison of catalytic activity at different Ag sites. Remarkably, TiAg exhibits exceptional performance in the electroreduction of CO (eCORR), showcasing a CO faradaic efficiency (FE) of 92.33% at -0.9 V RHE, surpassing the FE of TiAg (69.87% at -0.9 V RHE) by a significant margin. Through density functional theory (DFT) calculations, we unveil the catalytic mechanism and further discover that Ag active sites located at {Ti@Ag(TC4A)} possess a higher value compared to those at {TiO@Ag(TC4A)}, enhancing the stabilization of the *COOH intermediate during the eCORR. This study provides valuable insights into the accurate identification of catalytic sites in bimetallic nanoclusters and opens up promising avenues for efficient CO reduction catalyst design.
由于在分子水平上控制界面化学的复杂性，准确识别多相催化剂中的催化位点是一项重大挑战。在本研究中，我们引入了一种新策略来解决这个问题，即利用硫代杯[4]芳烃（TC4A）保护的钛氧核作为负载银离子的模板，成功合成了一种独特的Ag/Ti双金属纳米簇，称为TiAg。这种纳米簇具有多个表面暴露的银位点，并具有独特的“核壳”结构，由一个包含{TiO@Ag(TC4A)}基序的{Ti@Ag(TC4A)}核和两个{Ti@Ag(TC4A)}基序组成。为了进行全面分析，我们还制备了一种具有与TiAg中相同{TiO@Ag(TC4A)}结构的TiAg簇。TiAg和TiAg之间的结构差异为比较不同银位点的催化活性提供了一个极好的平台。值得注意的是，TiAg在CO的电还原（eCORR）中表现出优异的性能，在-0.9 V RHE下的CO法拉第效率（FE）为92.33%，大大超过了TiAg在-0.9 V RHE下的FE（69.87%）。通过密度泛函理论（DFT）计算，我们揭示了催化机理，并进一步发现位于{Ti@Ag(TC4A)}的银活性位点比位于{TiO@Ag(TC4A)}的银活性位点具有更高的值，在eCORR过程中增强了*COOH中间体的稳定性。这项研究为准确识别双金属纳米簇中的催化位点提供了有价值的见解，并为高效CO还原催化剂的设计开辟了有希望的途径。
