Tang Cheng, Chen Ling, Li Haijing, Li Laiquan, Jiao Yan, Zheng Yao, Xu Haolan, Davey Kenneth, Qiao Shi-Zhang
School of Chemical Engineering and Advanced Materials, The University of Adelaide, Adelaide, SA 5005, Australia.
University of Chinese Academy of Sciences, Beijing 100049, People's Republic of China.
J Am Chem Soc. 2021 May 26;143(20):7819-7827. doi: 10.1021/jacs.1c03135. Epub 2021 May 13.
Product selectivity in multielectron electrocatalytic reactions is crucial to energy conversion efficiency and chemical production. However, a present practical drawback is the limited understanding of actual catalytic active sites. Here, using as a prototype single-atom catalysts (SACs) in acidic oxygen reduction reaction (ORR), we report the structure-property relationship of catalysts and show for the first time that molecular-level local structure, including first and second coordination spheres (CSs), rather than individual active atoms, synergistically determines the electrocatalytic response. ORR selectivity on Co-SACs can be tailored from a four-electron to a two-electron pathway by modifying first (N or/and O coordination) and second (C-O-C groups) CSs. Using combined theoretical predictions and experiments, including X-ray absorption fine structure analyses and in situ infrared spectroscopy, we confirm that the unique selectivity change originates from the structure-dependent shift of active sites from the center Co atom to the O-adjacent C atom. We show this optimizes the electronic structure and *OOH adsorption behavior on active sites to give the present "best" activity and selectivity of >95% for acidic HO electrosynthesis.
多电子电催化反应中的产物选择性对于能量转换效率和化学生产至关重要。然而，目前一个实际的缺点是对实际催化活性位点的了解有限。在此，以酸性氧还原反应（ORR）中的单原子催化剂（SACs）作为原型，我们报告了催化剂的结构-性能关系，并首次表明分子水平的局部结构，包括第一和第二配位球（CSs），而非单个活性原子，协同决定了电催化响应。通过修饰第一（N或/和O配位）和第二（C-O-C基团）配位球，Co-SACs上的ORR选择性可以从四电子途径调整为两电子途径。利用理论预测和实验相结合的方法，包括X射线吸收精细结构分析和原位红外光谱，我们证实独特的选择性变化源于活性位点从中心Co原子向O相邻C原子的结构依赖性转移。我们表明，这优化了活性位点上的电子结构和*OOH吸附行为，从而在酸性HO电合成中实现了目前>95%的“最佳”活性和选择性。
