Our work on "Ligand-mediated self-terminating growth of single-atom Pt on Au nanocrystals for improved formic acid oxidation activity" has been accepted for publication in Advanced Energy Materials (IF: 29.37). Congratulations to Moxuan and Zhaojun!

中文简介：本文提出了配体辅助的自终止生长策略，利用配体的选择性吸附作用显著提升了Pt-Pt键形成的能垒，从而实现了Pt原子在异质金属表面聚集态的有效调控和单原子位点的可控构筑，显著提升了甲酸电催化氧化性能。

Title: Ligand-mediated self-terminating growth of single-atom Pt on Au nanocrystals for improved formic acid oxidation activity

Authors: Moxuan Liu,† Zhaojun Liu,† Miao Xie, Zhixue Zhang, Shumeng Zhang, Tao Cheng,* and Chuanbo Gao*

Link to the Publisher: https://onlinelibrary.wiley.com/doi/full/10.1002/aenm.202103195

Materials Views China NEWS: 西安交通大学高传博课题组，苏州大学程涛课题组AEnM：配体辅助自终止生长法制备贵金属单原子催化剂 (qq.com)

Abstract:  Decreasing the ensemble size of Pt to isolated single atoms is the key to enhancing the electrocatalytic formic acid oxidation reaction (FAOR) by bypassing the indirect reaction path that involves poisoning CO intermediate. However, it is challenging to construct isolated Pt single atoms on a foreign metal substrate, especially at high Pt loadings, because Pt tends to form large ensembles due to the high Pt-Pt bond energy. Herein, we report a ligand-mediated self-terminating growth strategy for reliably controlling the ensemble size of Pt on a Au substrate. The key is to introduce a ligand of sulfite (SO32-) into the synthesis, which preferentially adsorbs at Pt sites, thus substantially increasing the kinetic barrier toward the Pt-Pt bond formation. This strategy enables reliable formation of isolated Pt single atoms even at high Pt loadings (up to 26% coverage on Au), which is difficult to achieve by regular syntheses. The resulting catalyst exhibits a high FAOR activity of 38.6 A mgPt-1 in 0.5 M H2SO4+0.25 M HCOOH, 370 times greater than that of the commercial Pt/C. We believe this strategy is general and potentially applicable to the fabrication of a wide range of noble metal catalysts with tailored ensemble sizes for energy conversion. 

解读：贵金属原子的聚集状态在电催化甲酸氧化反应（FAOR）等非均相催化反应中起着至关重要的作用。在单原子Pt位点上，甲酸通过“直接路径”脱氢生成CO₂。在Pt多原子簇上，甲酸通过“间接路径”先脱水形成CO中间体，之后该CO中间体被进一步氧化为CO₂。其中，直接路径绕过了容易导致催化剂中毒的CO中间体的形成，对甲酸氧化反应是有利的。因此，实现单原子Pt位点的可控构筑是发展高效甲酸氧化催化剂的重要途径，对直接甲酸燃料电池技术的发展具有重要意义。

然而，在异质金属基底上可控构建单原子Pt位点仍然面临挑战。这是由于Pt–Pt键具有很高的键能，因此Pt原子倾向于与已有的Pt原子成键，从而形成岛屿状多原子簇。因此，通常只有在Pt生长的早期阶段，即当Pt在异质金属基底上的载量很低时（表面覆盖率<10%），才能形成单原子Pt位点。这无疑增大了该类单原子催化剂的应用成本。

针对这一问题，我们提出了一种新颖的自终止生长机制，实现了单原子Pt位点的可控构筑。该策略的核心是在湿化学合成体系中引入SO₃^2–作为小分子配体。SO₃^2–在Pt位点具有很强的吸附能，而在Au位点则吸附能极弱。因此，当Pt原子沉积在Au基底后，Pt原子被SO₃^2–钝化，于其上继续沉积Pt原子需克服很高的能垒，这在能量上是不利的。因此，SO₃^2–的吸附作用显著改变了Pt在Au基底的生长方式，使其只能选择性生长在Au位点，成功实现了Pt的“自终止生长”。利用该策略，即使在高Pt载量（表面覆盖率：26%）条件下，Pt在Au纳米粒子表面仍能保持孤立的单原子状态，这是传统合成所难以实现的。这一单原子催化剂在甲酸电催化氧化反应中的活性达到了38.6 A mg_Pt^–1（实验条件：0.5 M H₂SO₄ + 0.25 M HCOOH），是目前报道的最高值。

本工作为贵金属原子聚集态的有效调控和单原子催化剂的可控合成提供了新的通用策略。