Tracking the Role of Defect Types in Co₃O₄ Structural Evolution and Active Motifs during Oxygen Evolution Reaction

Abstract

Dynamic reconstruction of catalyst active sites is particularly important for metal oxide-catalyzed oxygen evolution reaction (OER). However, the mechanism of how vacancy-induced reconstruction aids OER remains ambiguous. Here, we use Co3O4 with Co or O vacancies to uncover the effects of different defects in the reconstruction process and the active motifs relevant to alkaline OER. Combining in situ characterization and theoretical calculations, we found that cobalt oxides are converted to an amorphous [Co(OH)6] intermediate state, and then the mismatched rates of *OH adsorption and deprotonation lead to irreversible catalyst reconstruction. The stronger *OH adsorption but weaker deprotonation induced by O defects provides the driving force for reconstruction, while Co defects favor dehydrogenation and reduce the reconstruction rate. Importantly, both O and Co defects trigger highly OER-active bridge Co sites in reconstructed catalysts, of which Co defects induce a short Co–Co distance (3.38 Å) under compressive lattice stress and show the best OER activity (η10 of 262 mV), superior to reconstructed oxygen-defected Co3O4-VO (η10 of 300 mV) and defect-free Co3O4 (η10 of 320 mV). This work highlights that engineering defect-dependent reconstruction may provide a rational route for electrocatalyst design in energy-related applications.

Selenite-Decorated Polycrystalline NiO Nanosheets Generated from Cathodic Reconstruction for Electrocatalytic Hydrogen Production

“…The only prominent peak at the binding energy of 58.5 eV belongs to the characteristic peak of SeO 3 2– groups, consistent with those reported analogues. , The O 1s spectrum of NiSeO 3 ·2H 2 O/NF can be deconvoluted into two peaks at 531.5 and 533.3 eV, respectively, which are ascribed to the Se–O bond and surface-absorbed water (Figure h) . After reconstruction, the lattice oxygen-related peak at 529.9 eV appears prominently due to the existence of NiO nanocrystals in SeO 3 2– -NiO/NF . And the other two peaks at about 530.8 and 532.1 eV are usually associated with incidental oxygen in terminated hydroxide and absorbed water, respectively .…”

Facet Dependence and Vacancy-Controlled Reversibility of the Spinel-to-Rocksalt Phase Transformation at Co3O4 Surfaces

“…A typical example is the Co 3 O 4 spinel oxide, which represents one of the most active electrocatalysts for the OER. Using in situ X-ray diffraction/adsorption techniques, it was found that the Co 3 O 4 spinel surface transformed to an amorphous CoO x (OH) y phase (a hydroxylated, defective rocksalt structure) under the OER condition, − which was considered to be the true catalytically active phase. This CoO x (OH) y phase can reversibly transform back to the spinel phase at the rest condition, favoring an elegant balance between the electrocatalytic activity and durability. , …”

Ultrasensitive Dopamine Detection at Co3O4-Anchored N-Doped Hollow Mesoporous Carbon Nanospheres

“…As shown in Figure A, the observed strong and weak diffraction peaks are located at 18.8°, 31.2°, 36.8°, 38.5°, 44.8°, 50.1°, 55.6°, 59.3°, 65.2°, 69.7°, 77.3°, and 78.4°, which are indexed to the (111), (220), (311), (222), (400), (331), (422), (511), (440), (442), (533), and (622) planes, respectively . All the obtained peaks are well matched with standard Co 3 O 4 patterns (PDF #98-001-0547), which are attributed to the cubic crystalline Fd3m spinel-like Co 3 O 4 structure (Figure B) . It can be seen that for Co 3 O 4 /NDHCS-0.1, -0.2, and -0.3 samples, the peak intensities are greatly improved with increasing the loading quantity of the Co precursor.…”