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The large-scale application of oxygen evolution reaction electrocatalysts is limited by many challenges such as sluggish kinetics, low conductivity, and instability. Remarkably, Co 3+ plays a vital role in oxygen evolution catalytic process because Co 3+ ions are regarded as active sites. Developing catalysts with high Co 3+ content is highly promising to improve the efficiency of water oxidation. In this study, we report a novel design method through controlling pH value and potential guided by Pourbaix diagram to synthesize surface Co 3+ -rich catalyst. The as-prepared catalyst possesses enhanced electrode-electrolyte contact area and lower diffusion resistance. In alkaline media, this catalyst exhibits promising oxygen evolution performance, with lower onset overpotential, satisfactory overpotential, and high value of turnover frequency (TOF). [ABSTRACT FROM AUTHOR]

Currently, developing highly active and low-cost electrocatalytic materials for oxygen evolution reaction (OER) is an enormously grand challenge. Herein, we developed a novel and highly active Mn doped Co 2 Fe layer double hydroxide (LDH) electrocatalyst for OER. We discovered that these electrocatalytic materials can be directly grown on carbon papers to construct high-specific-surface-area electrode, which shows the lowest overpotential of 266 mV at 10 mA cm−2. Furthermore, after introducing Mn element, DFT + U calculation found that the ∗OOH of Fe-site on Co 2 Fe 0.67 Mn 0.33 LDH could draw more electrons than Co 2 Fe LDH due to the electronegativity differences between Fe-site on Co 2 Fe 0.67 Mn 0.33 LDH and Fe-site on Co 2 Fe LDH, which is reason that the energy level of Fe 3d (e g) was obviously downshifted by d-d repulsion of Mn 3d and Fe 3d in the neighboring sites of Co 2 Fe 0.67 Mn 0.33 LDH after doped Mn element, which leads to reduce charge-transfer energy from O 2p to Fe 3d (e g) to promote oxygen evolution processes for OER. Meanwhile, the band gap is also decreased after doped Mn element in Co 2 Fe LDH due to the downshifted e g orbital energy of Fe 3d. This study gives a general avenue to design and developing efficiently active LDH electrocatalysts for OER in the future. • Both bimetallic CoFe LDH and Mn doped CoFe LDHs directly grown on carbon paper are successfully synthesized. • The Co 2 Fe 0.67 Mn 0.33 LDH@NFs exhibits a small overpotential of 236 mV at 10 mA cm−1 for OER. • DFT + U studies reveal that the observed superb OER activity could be attributed to d-d repulsion of Mn 3d and Fe 3d. [ABSTRACT FROM AUTHOR]

[Display omitted] • CoM x O y /Co 3 O 4 nanoarrays are synthesized via an in-situ self-templating strategy. • The electrocatalysts exhibit excellent OER activities in alkaline electrolyte. • Co atoms go through a dissolution-redeposition process during long-term stability test. • Partially dissolved cobalt ions adjacent to the surface precipitate into Co(OH) 2. Developing highly active and steady electrocatalysts for oxygen evolution reaction (OER) is crucial to achieve efficient electrochemical water splitting. Herein, we report a facile in situ self-assembly strategy for the synthesis of catalysts (CoMoO 4 /Co 3 O 4 /NF, CoWO 4 /Co 3 O 4 /NF and Co 3 V 2 O 8 /Co 3 O 4 /NF) with hierarchical 1D nanostructure. This 1D well-aligned structure and phase interpenetration of mixed Co species provide a rapid channel for charge transfer and mass exchange. Meanwhile, the internal Co 3 O 4 nanowires serve as a framework to host abundant CoM x O y (M = Mo, W, V) materials and this structure is beneficial to the exposure of OER active phases. As a result, these electrocatalysts exhibit excellent OER activities with low overpotentials. Besides, after 1000 voltammetry cycles, only slight increase in the overpotential verifies the excellent stability of these catalysts during the alkaline oxygen evolution reaction process. Based on postmortem characterizations, a dissolution–redeposition process is proposed to explain the formation of Co(oxy)hydroxides on the surface of the catalysts. [ABSTRACT FROM AUTHOR]