Shape Control of Monodispersed Sub‐5 nm Pd Tetrahedrons and Laciniate Pd Nanourchins by Maneuvering the Dispersed State of Additives for Boosting ORR Performance
Huaifang Zhang, Xiaoyu Qiu, Yifan Chen, Shangzhi Wang, Sara E. Skrabalak, Yawen Tang
Abstract
Abstract It is a great challenge to simultaneously control the size, morphology, and facets of monodispersed Pd nanocrystals under a sub‐5 nm regime. Meanwhile, quantitative understanding of the thermodynamic and kinetic parameters to maneuver the shape evolution of nanocrystals in a one‐pot system still deserves investigation. Herein, a systematic study of the density functional theory (DFT)‐calculated adsorption energy, thermodynamic factors, and reduction kinetics on Pd growth patterns is reported by combining theory and experiments, with a focus on the dispersed state of additives. As pure models, monodispersed Pd tetrahedrons enclosed by (111) facets with a narrow size distribution of 4.9 ± 1 nm and a high purity approaching 98% can be obtained when using 1,1′‐binaphthalene (C 20 H 14 ) +2NH 3 as additives. Specifically, laciniate Pd nanourchins (Pd LUs) can evolve via anisotropic growth when replacing additive with dose‐consistent 1,1′‐binaphthyl‐2,2′‐diamine (C 20 H 16 N 2 , two NH 2 binding in C 20 H 14 ). Catalytic investigations show that the sub‐5 nm Pd tetrahedrons exhibit higher activity in both the oxygen reduction ( E onset = 1.025 V, E 1/2 = 0.864 V) and formic acid oxidation reaction with respect to the Pd LUs and Pd black, which represents a great step for the development of well‐defined Pd nanocrystals with size in the sub‐5 nm regime as non‐Pt electrocatalysts.