Defect‐Induced Atomic Arrangement in CoFe Bimetallic Heterostructures with Boosted Oxygen Evolution Activity

Abstract

6 e g 1 ) and Jahn-Teller active Mn 3+ (t 2g 3 e g 1) species enabled the promotion of O-O bond formation and thereby leading to excellent OER activity. Zhang et. al. [17] suitably engineered the low-coordination atoms in NiO/ Co 3 O 4 heterointerfaces and achieved boosting electrocatalysts. Liu et. al. [18] induced in-plane CoO@Co 3 O 4 rocksalt@spinel heterophase, which delivered drastically improved OER activity. These achievements verify that the electrochemical ability of Three CoFe-bimetallic oxides with different compositions (termed as CoFeO x -A/N/H) are prepared by thermally treating metal-organic-framework (MOF) precursors under different atmospheres (air, N 2, and NaBH 4 /N 2 ), respectively. With the aid of vast oxygen vacancies (O v ), cobalt at tetrahedral sites (Co 2+ (Th)) in spinel Co 3 O 4 is diffused into interstitial octahedral sites (Oh) to form rocksalt CoO and ternary oxide CoFe 2 O 4 has been induced to give the unique defective CoO/CoFe 2 O 4 heterostructure. The resultant CoFeO x -H exhibits superb electrocatalytic activity toward water oxidation: overpotential at 10 mA cm −2 is 192 mV, which is 122 mV smaller than that of CoFeO x -A. The smaller Tafel slope (42.53 mV dec −1 ) and higher turnover frequency (785.5 h −1 ) suggest fast reaction kinetics. X-ray absorption spectroscopy, ex situ characterizations, and theoretical calculations reveal that defect engineering effectively tunes the electronic configuration to a more active state, resulting in the greatly decreased binding energy of oxo intermediates, and consequently much lower catalytic overpotential. Moreover, the construction of hetero-interface in CoFeO x -H can provide rich active sites and promote efficient electron transfer. This work may shed light on a comprehensive understanding of the modulation of electron configuration of bimetallic oxides and inspire the smart design of high-performance electrocatalysts.

Unlocking Catalytic Potential: Encasing CoP Nanoparticles within Mesoporous CoFeP Nanocubes for Enhanced Oxygen Evolution Reaction

“…The results indicate that the average bond length of Co–P is 2.09 Å with a mean coordination number (CN) of ∼4 in CoP. Additionally, the Co–P CN in CoP/CoFeP is less than that in CoP, indicating the existence of more defect sites, which is favorable for enhancing catalytic activity . Furthermore, a notable lobe is observed by fitting at ∼2.4 Å, which shows that Fe coordinates with Co to form the Co–Fe pair.…”

High-Valence Mo Doping and Oxygen Vacancy Engineering to Promote Morphological Evolution and Oxygen Evolution Reaction Activity

“…The XRD pattern and Raman spectrum (Figure S10) of MoCoO-3 after OER activation confirm the existence of CoOOH due to structure reconstruction, which is consistent with the literatures. 6,7,45 In this regard, atomic structure models of bare CoOOH and Mo-doped CoOOH (Figure 6a) are built to examine the doping effect. The electronic states of MoCoOOH near the Fermi level increase obviously after Mo doping (Figure 6b), exhibiting increased electrical conduction, which is beneficial for suitable adsorption of oxygen species.…”

“…However, the electrochemical performance is still far from satisfactory due to poor electrical conductivity and the limited amount of reactive sites. Considerable strategies have been exploited to improve their OER activity. − Particularly, doping another heteroatom into the lattice of metal oxides can remarkably improve the catalytic performance, , and high-valence non 3 d metal dopants can be more effective, which could modulate the electronic structure of 3d TMO catalysts and optimize the adsorption energy toward OER intermediates, resulting in good catalytic stability and enhanced activity. − For instance, Mo 6+ is a typical high-valence 4d transition metal ion with a radius of 0.62 Å, which can be doped into the lattice of cobalt oxide as a substitution of Co 3+ (0.63 Å). Yang et al designed a highly efficient OER catalyst by doping Mo 6+ into an FeCoMo-based catalyst and obtained an overpotential of 277 mV at 10 mA cm –2 .…”

Upcycling of Cathode Materials from Spent Lithium-Ion Batteries: Progress, Challenges, and Outlook

“…Multicomponent transition metal-based materials exhibit good electrochemical reactivity and are promising for effective catalysts for water splitting and zinc–air batteries with the merits of abundant availability, low-cost and excellent stability. − …”