The Role of Lone‐Pair Electrons in Pt–N Interactions for the Oxygen Reduction Reaction in Polymer Exchange Membrane Fuel Cells

Abstract

An N‐doped carbon with various N concentrations was prepared by using a scalable ball‐milling method. The importance of the lone pair of electrons on the N species for the stability of Pt nanoparticles and their activity toward the oxygen reduction reaction was investigated. X‐ray spectroscopic analysis was used to investigate the interaction between Pt and the pyridinic N. The pyridinic N modified the Pt oxidation state and helped achieve size homogeneity and high catalytic activity by facilitating the rate‐determining step.

The Central Role of Nitrogen Atoms in a Zeolitic Imidazolate Framework‐Derived Catalyst for Cathodic Hydrogen Evolution

“…The interaction between the pyridinic N and Pt NPs is commonly described in literature reports [6b–e,7,20] . Our XPS data also support the binding of pyridinic N and Pt in the sample ZIF‐NPt (Figure 4c and d).…”

“…It has been generally considered that a strong interaction may occur between the pyridinic N on imidazole ring and the Pt nanoclusters [5a,6b–d,7,20] . The lone‐pair of electrons on pyridinic N can be readily donated to the vacant d‐orbitals of Pt atoms, [6e] whereas the lone‐pair on pyrrolic N is already included in the aromatic π system. A DFT investigation indicates that the adsorption of pyridine on Pt(111) can occur at a sufficiently high coverage in an upright position forming a bond by the lone pair electrons on the N atoms [21] …”

“…To clarify this, the interfacial properties of the ZIF‐NPt and the Pt/C electrodes were comparatively investigated by recording the cyclic voltammograms involving three potential regions: the underpotential adsorption/desorption region of H*, the double layer charging region and the Pt oxide region. The presence of these three regions is a common feature of Pt 0 ‐based materials in acidic electrolytes [6b,d,e,7b,24] …”

“…Ham et al. proposed that the electrons of Pt on N‐doped carbon might move from Pt to N owing to the formation of Pt‐N bonding, which might make a major contribution to enhancing the ORR activity by altering the activation energy of the ORR [6e] . González‐Hernández et al.…”

Enhancing Oxygen Reduction Activity of Pt‐based Electrocatalysts: From Theoretical Mechanisms to Practical Methods

“…As one example owing to this interaction, Pt/Ti 0.7 Mo 0.3 O 2 has shown an ORR activity about 7 times higher than that of commercial Pt/C catalyst . In addition, electronic interactions between Pt and defective carbon or heteroatoms such as N and S in heteroatom doped carbon supported Pt nanoparticle catalysts were also found by XPS and XANES.…”