Li Haolin, Wang Kuan-Wen, Hu Alice, Chou Jyh-Pin, Chen Tsan-Yao
Department of Mechanical Engineering, City University of Hong Kong, Hong Kong, China.
Phys Chem Chem Phys. 2021 Sep 7;23(33):18012-18025. doi: 10.1039/d1cp01989a. Epub 2021 Aug 13.
The crux of the hot topic concerning the widespread replacement of fuel cells (FCs) with traditional petrochemical energy is to balance improving the oxygen reduction reaction (ORR) and reducing the cost. The present study employs density functional theory (DFT) to investigate the effect of Pt ensemble size regulation from a single atom to full coverage on the physio-chemical properties, oxygen adsorption energies and overall ORR efficiency of bimetallic nanocatalysts (NCs) with a Co-Pd structure. Our results reveal that the electronegativity difference and lattice strain between neighboring heteroatoms are enhanced to trigger a synergetic effect in local domains, with the Pt cluster size reduced from nanometers to subnanometers. They induce a directed and tunable charge relocation mechanism from deep Co to topmost Pt to optimize the adsorption energies of O/O* and achieve excellent ORR kinetics performance with minimum Pt usage but maximum Pt atom utilization (i.e., Pt to Pt) compared with benchmark Pt(111). Such a dependency between the cluster size and corresponding ORR performance for the established Co@Pd-Pt system can be applied to accurately guide the experimental synthesis of ordered heterogeneous catalysts (e.g., other core@shell-clusters structures) toward low Pt, high efficiency and green economy.
燃料电池广泛替代传统石化能源这一热门话题的关键在于平衡改善氧还原反应（ORR）和降低成本。本研究采用密度泛函理论（DFT）来研究从单原子到全覆盖的铂系综尺寸调控对具有Co-Pd结构的双金属纳米催化剂（NCs）的物理化学性质、氧吸附能和整体ORR效率的影响。我们的结果表明，随着铂团簇尺寸从纳米级减小到亚纳米级，相邻杂原子之间的电负性差异和晶格应变增强，从而在局部区域引发协同效应。它们诱导了一种从深层钴到最顶层铂的定向且可调的电荷迁移机制，以优化O/O*的吸附能，并在使用最少铂但最大程度利用铂原子（即铂对铂）的情况下实现优异的ORR动力学性能，与基准Pt(111)相比。对于已建立的Co@Pd-Pt体系，这种团簇尺寸与相应ORR性能之间的依赖关系可用于准确指导有序多相催化剂（如其他核@壳团簇结构）的实验合成，以实现低铂、高效率和绿色经济。
