Anion Constructor for Atomic‐Scale Engineering of Antiperovskite Crystals for Electrochemical Reactions

Abstract

Among the Pt group metals, Pd has been considered the most efficient for application in electrocatalysts as an alternative to Pt. Despite the comparable electrochemical activities of Pd and Pd‐metal alloys, they are vulnerable to liquid acidic electrolytes, leading to degradation of catalytic activity. Pd–Ni alloys have been used to enhance catalytic activity because the electronic structure of Pd can be easily changed by adding Ni. In other studies, N atoms have been introduced for more stable M–Ni catalysts by inducing the formation of Ni4N species; however, the structural analysis and the role of nitrogen have not been fully understood yet. Herein, the Pd–Ni alloy nitride with a unique crystal structure shows a promising catalytic activity for oxygen reduction reaction (ORR). The nitride PdNi nanoparticles have a novel monolithic antiperovskite structure of chemical formula (PdxNi1−x)NNi3. The unique antiperovskite crystal (PdxNi1−x)NNi3 possesses superior ORR activity and stability, originating from the downshifted d‐band center of the monolayer Pd/antiperovskite surface and the lower formation energy of the antiperovskite core nanocrystal. Consequently, (PdxNi1−x)NNi3, as a Pt‐free Pd‐based electrocatalyst, overcomes the stability issue of Pd under acidic conditions by achieving 99‐times higher mass activity than commercial Pd/C, as shown by the durability test.

Engineering Antiperovskite Ni4N/VN Heterostructure with Improved Intrinsic Interfacial Charge Transfer as a Bifunctional Catalyst for Rechargeable Zinc–Air Batteries

“…The DOSs of antiperovskite nitrides density functional theory (DFT) calculations are continuous near the Fermi level, which illustrates their intrinsic metallic properties and remarkable superconductivity . Ni 4 N with an antiperovskite structure (NiNNi 3 ; Ni occupies sites A and B) achieves good ORR activity and stability . Although combining the benefits of high conductivity and structural flexibility, the catalytic performance of Ni 4 N is still far from satisfactory.…”

Atomic Rearrangement in Core–Shell Catalysts Induced by Electrochemical Activation for Favorable Oxygen Reduction in Acid Electrolytes

“…This reveals that the lower photon energy excited the photoelectron relatively closer to the surface than the higher photon energy. In other words, the synchrotron X-ray with a lower energy elicits more surface-sensitive characteristics . The Pt 4f binding energies and XPS spectra of Pd@Cu@Pt and Pd@Cu@Pt-EA at a photon energy range of 500–1000 eV are shown in Figures c, S4, and Table S3.…”

“…In this analysis, the electron kinetic energy ( E k ) can be adjusted, and the characteristics of the photoelectron were investigated in accordance with the depth profiles of the electrocatalysts. The inelastic mean free path (IMFP) according to the kinetic energy derived from various incident X-ray energies is shown in Figure b; it is calculated based on the following formula. where λ is the IMFP (Å), E is the electron energy (eV), E p is the free-electron plasmon energy (eV), β is the function of density (eV –1 Å –1 ), γ is the parameter related to density (eV –1 ), and C (Å –1 ) and D (eV Å –1 ) are the parameters related to the free-electron plasmon energy. , The IMFP is considered as an indicator of how far the electrons excited by the photon energy have traveled. At photon energies of 500 ( E k = 429 eV) and 1000 eV ( E k = 929 eV), the IMFP of the photoelectron excited by the former was ∼12.33 Å, while that by the latter was ∼7.36 Å.…”

“…where λ is the IMFP (Å), E is the electron energy (eV), E p is the free-electron plasmon energy (eV), β is the function of density (eV −1 Å −1 ), γ is the parameter related to density (eV −1 ), and C (Å −1 ) and D (eV Å −1 ) are the parameters related to the free-electron plasmon energy. 35,36 The IMFP is considered as an indicator of how far the electrons excited by the photon energy have traveled. At photon energies of 500 (E k = 429 eV) and 1000 eV (E k = 929 eV), the IMFP of the photoelectron excited by the former was ∼12.33 Å, while that by the latter was ∼7.36 Å.…”

“…In other words, the synchrotron X-ray with a lower energy elicits more surfacesensitive characteristics. 35 The Pt 4f binding energies and XPS spectra of Pd@Cu@Pt and Pd@Cu@Pt-EA at a photon energy range of 500−1000 eV are shown in Figures 2c, S4, and Table S3. In the case of a photon energy of 1000 eV exciting the photoelectron that is relatively farther from the surface compared to that of 500 eV, Pd@Cu@Pt exhibited a binding energy of 71.25 eV, while Pd@Cu@Pt-EA presented a binding energy of 71.55 eV.…”