Coordination of Atomic Co–Pt Coupling Species at Carbon Defects as Active Sites for Oxygen Reduction Reaction

Abstract

Platinum (Pt) is the state-of-the-art catalyst for oxygen reduction reaction (ORR), but its high cost and scarcity limit its large-scale use. However, if the usage of Pt reduces to a sufficiently low level, this critical barrier may be overcome. Atomically dispersed metal catalysts with high activity and high atom efficiency have the possibility to achieve this goal. Herein, we report a locally distributed atomic Pt-Co nitrogen-carbon-based catalyst (denoted as A-CoPt-NC) with high activity and robust durability for ORR (267 times higher than commercial Pt/C in mass activity). The A-CoPt-NC shows a high selectivity for the 4e pathway in ORR, differing from the reported 2e pathway characteristic of atomic Pt catalysts. Density functional theory calculations suggest that this high activity originates from the synergistic effect of atomic Pt-Co located on a defected C/N graphene surface. The mechanism is thought to arise from asymmetry in the electron distribution around the Pt/Co metal centers, as well as the metal atoms' coordination with local environments on the carbon surface. This coordination results from N8V4 vacancies (where N8 represents the number of nitrogen atoms and V4 indicates the number of vacant carbon atoms) within the carbon shell, which enhances the oxygen reduction reaction via the so-called synergistic effect.

Charge Transfer Modulated Activity of Carbon‐Based Electrocatalysts

“…By DFT and X‐ray absorption spectroscopies (XAS) analysis, the density of state (DOS) near the Fermi level of Ni atoms at defect sites is increased, which results in a stronger interaction with the adsorbates (e.g., H + for HER, OH − for OER) and substrate, thus leading to a high HER and OER performance (Figure e,f). As shown in Figure g,i, they also coordinated the atomic Co–Pt coupling species in defects of carbon materials (A‐CoPt‐NC) and employed as the highly efficient ORR electrocatalyst . The d orbital shift and charge redistribution caused by the synergetic Co and Pt atoms in the unique coordination structure resulted in high ORR activity.…”

“…The cyan spots and bright yellow spots are carbon atoms and metal atoms, respectively. Reproduced with permission . Copyright 2018, American Chemical Society.…”

Multidimensional Ordered Bifunctional Air Electrode Enables Flash Reactants Shuttling for High‐Energy Flexible Zn‐Air Batteries

“…STEMEELS (Figure 2i) of the Co nanoparticles reveal the high likelihood of Co atoms in the CNT being adjacent to N atoms, suggesting possible chemical bonding of CoN x in the carbon lattices. [39] Additionally, the first deriva tive XANES spectra in Figure 3e shows the Co white line peak of MPZCC@CNT exhibits a small shift to the higher energy compared to that of pure Co, likely due to the strong coupling between Co and CNT through the CoN x coordination. The Co 2p spectrum demonstrates the presence of both zerovalence state and ionic state Co species, which are derived from metallic Co and CoN x coordination, respectively ( Figure 3c).…”

Engineering Local Coordination Environments of Atomically Dispersed and Heteroatom‐Coordinated Single Metal Site Electrocatalysts for Clean Energy‐Conversion

“…d) The charge density distributions of the dual Co–Pt sites (top left) and the Pt–Pt control (top right) and the HAADF image of Co–Pt sites (bottom). Reproduced with permission . Copyright 2018, American Chemical Society.…”

“…By controlling the electrodeposition time or potential cycle times during electrodeposition, atomic‐level deposition of Pt on the counter electrodes can be achieved . Dual‐metal Co–Pt site on N‐doped hollow graphitic spheres have been obtained by cyclic voltammetry, from 0.1 to 1.1 V versus RHE, using CoN x catalyst and Pt wire as the working and counter electrodes, respectively …”