Title: Unraveling the Catalytic Effect of Hydrogen Adsorption on Pt Nanoparticle Shape-Change Show Chinese title

Title: 揭示氢吸附对铂纳米粒子形状变化的催化作用

Abstract: The activity of metal catalysts depends sensitively on dynamic structural changes that occur during operating conditions. The mechanistic understanding underlying such transformations in small Pt nanoparticles (NPs) of $\sim1-5$ nm in diameter, commonly used in hydrogenation reactions, is currently far from complete. In this study, we investigate the structural evolution of Pt NPs in the presence of hydrogen using reactive molecular dynamics (MD) simulations and X-ray spectroscopy measurements. To gain atomistic insights into adsorbate-induced structural transformation phenomena, we employ a combination of MD based on first-principles machine-learned force fields with extended X-ray absorption fine structure (EXAFS) measurements. Simulations and experiments provide complementary information, mutual validation, and interpretation. We obtain atomic-level mechanistic insights into `order-disorder' structural transformations exhibited by highly dispersed heterogeneous Pt catalysts upon exposure to hydrogen. We report the emergence of previously unknown candidate structures in the small Pt NP limit, where exposure to hydrogen leads to the appearance of a `quasi-icosahedral' intermediate symmetry, followed by the formation of `rosettes' on the NP surface. Hydrogen adsorption is found to catalyze these shape transitions by lowering their temperatures and increasing the apparent rates, revealing the dual catalytic and dynamic nature of interaction between nanoparticle and adsorbate. Our study also offers a new pathway for deciphering the reversible evolution of catalyst structure resulting from the chemisorption of reactive species, enabling the determination of active sites and improved interpretation of experimental results with atomic resolution. Show Chinese abstract

Abstract: 金属催化剂的活性对在操作条件下发生的动态结构变化非常敏感。 在直径为$\sim1-5$纳米的小铂纳米颗粒（NPs）中，此类转变背后的机制理解目前还远未完整。 在本研究中，我们使用反应性分子动力学（MD）模拟和X射线光谱测量来研究氢气存在下铂纳米颗粒的结构演变。 为了获得吸附物诱导的结构转变现象的原子级见解，我们采用基于第一性原理机器学习力场的MD与扩展X射线吸收精细结构（EXAFS）测量相结合的方法。 模拟和实验提供了互补的信息、相互验证和解释。 我们获得了高度分散的非均相铂催化剂在暴露于氢气时表现出的“有序-无序”结构转变的原子级机制见解。 我们报告了在小铂纳米颗粒极限下出现的以前未知的候选结构，在这种情况下，暴露于氢气会导致“准二十面体”中间对称性的出现，随后在纳米颗粒表面形成“玫瑰花”结构。 发现氢气吸附通过降低其温度并增加表观速率来催化这些形状转变，揭示了纳米颗粒与吸附物之间相互作用的双重催化和动态特性。 我们的研究还提供了一种新的途径，用于解析由反应物种化学吸附引起的催化剂结构可逆演变，使能够确定活性位点，并以原子分辨率改进对实验结果的解释。