Boosted Oxygen Evolution Reactivity by Igniting Double Exchange Interaction in Spinel Oxides

Abstract

A double-exchange interaction (DEI) was demonstrated to boost the oxygen evolution reaction (OER) in spinel oxides. DEI was ignited by synergistic actions of constructing nanoheterojunctions and creating oxygen vacancy (V O ) in spinel NiCo 2 O 4 . DEI between octahedrally coordinated Ni and Co resulted in the generation of superior OER active centers Co (3−δ)+ and Ni 3+ . The multiple synergistic effects empower the electrocatalyst with exceptional OER activity, with an overpotential of 270 ± 3 mV at 10 mA/cm 2 and a Tafel slope of 39 mV/dec, both of which are among the best values for NiCo 2 O 4 -based nanostructures, and even better than those for IrO 2 and RuO 2 . Communication pubs.acs.org/JACS

Air‐Assisted Transient Synthesis of Metastable Nickel Oxide Boosting Alkaline Fuel Oxidation Reaction

“…The peaks located at 854.7 and 872.1 eV are indexed to Ni 2+ species and the other two at 856.4 and 873.8 eV pertain to Ni 3+ species. [ 26–28 ] For Ni@C/CC, the intense peaks for Ni 2p 3/2 are located at 853.0, 854.8, and 858.7 eV, suggesting the existence of metallic Ni, Ni 2+ , and Ni 3+ species, respectively. Remarkably, the content percentage of Ni 3+ and Ni 2+ (Ni 2p 3/2 ) were 67.8% and 32.2% for NiO@C/CC, however, 29.6% and 30.2% for Ni@C/CC, obtained by calculating the area of the corresponding peaks (regardless of shakeup satellites).…”

“…As observed in Figure 2c, three typical XPS peaks of O 1s of NiO@C/CC at ≈530.3, 531.5, and 533.3 eV (marked as O1, O2, and O3) relate to the lattice oxygen, defect sites of oxygen, and absorbed water molecule on the surface, individually. [ 17,26 ] The large area of O2 peak proves that the V O exist in the NiO@C/CC sample, which is highly beneficial for fine‐tuning the surface chemical and electronic structures to improve their reactivity. [ 30 ] Above all, the V O and the abundant high valence of Ni (Ni 3+ species) in NiO@C/CC were verified across the XPS detection.…”

Heterostructure and Oxygen Vacancies Promote NiFe2O4/Ni3S4 toward Oxygen Evolution Reaction and Zn‐Air Batteries

“…There are three peaks with binding energies at 529.75 eV, 531.25 eV and 532.71 eV, which correspond with the lattice oxygen, the defect oxygen and the oxygen from water molecules adsorbed on the surface. [33,34] The atomic percentages of different oxygen species were estimated and summarized in Table S4 Figure 2f, the peaks at 161.2 eV, 162.2 eV and 166.08 eV correspond to the S 2p 3/2 of S 2À , S 2p 1/2 of S 2À , and the bridging S 2 2À , [35] while the peaks with binding energies at 172.45 eV and 170.22 eV are attributed to sulfates due to the sulfur oxidation on the surface of Ni 3 S 4 . [32,36] The potential oxidation process of Ni 3 S 4 is as follows: 2Ni3S4þ11O2…”

“…Furthermore, the core‐level XPS spectrum of the O1s electrons for NiFe 2 O 4 /Ni 3 S 4 is illustrated in Figure 2e. There are three peaks with binding energies at 529.75 eV, 531.25 eV and 532.71 eV, which correspond with the lattice oxygen, the defect oxygen and the oxygen from water molecules adsorbed on the surface [33,34] . The atomic percentages of different oxygen species were estimated and summarized in Table S4.…”

Self‐Supported Electrocatalysts Derived from Nickel‐Cobalt Modified Polyaniline Polymer for H2‐Evolution and O2‐Evolution Reactions

“…showed that the NiCo 2 O 4 spinel phase can be obtained by a freeze drying of a solution of nickel and cobalt nitrate followed by the vacuum decomposition and thermally treatment in air at 400 °C. Recent reports utilized the calcination under different conditions, 375 °C in air, [10] 350 °C in Ar, [7a] 350 °C in N 2 , [7b] 400 °C (no indication of the type of gas that was used), [7c] 350 °C in air, [7d] and at 300 °C in air [11] . It should be emphasized that the implementation of those temperatures of 350–400 °C in the present study could probably failed because the polyaniline material has complex behavior in this temperature range [12]…”