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• Defective MnCo-LDH nanoflowers is obtained by simple hydrothermal method. • The MnCo-LDH shows well 3D nanostructure and bimetallic defective vacancy. • The activity of MnCo-LDH is excellent as HER and OER bifunctional catalysts. • The MnCo-LDH show high catalytic activity and stability in potential application. Manganese-cobalt layered double hydroxide (MnCo-LDH) is a kind of layered bimetallic hydroxide with good catalytic performance and stability for water decomposition. In this paper, a series of defective MnCo-LDH materials with different Mn/Co molar ratio was prepared by hydrothermal method. The results show that the MnCo-nanoflowers containing Mn and Co elements are successfully prepared, and all of them contain N, O, Mn and Co elements. The hydrogen evolution reaction (HER) catalytic performance of Co vacancy (V Co)-MnCo-LDH is better than that of commercial electrode Pt/C, and oxygen evolution reaction (OER) catalytic performance of Mn vacancy (V Mn)-MnCo-LDH is better than that of commercial electrode RuO 2. Two-electrode overall water splitting (OWS) test showed that the overpotential required by V Mn -MnCo-LDH/NF||V Co -MnCo-LDH/NF and Pt/C/NF||RuO 2 /NF were 1.56 V and 1.72 V respectively at the current density of 10 mA cm−2, and the catalytic activity of the prepared defective MnCo-LDH is excellent bifunctional electrocatalysts for both HER and OER. [ABSTRACT FROM AUTHOR]

Ternary nickel cobalt iron layered double hydroxide nanosheet arrays are synthesized on nickel foam (NiCoFe-LDH/NF) and applied as an oxygen evolution reaction electrocatalyst. The oxidative etching and cation exchange caused by Fe-incorporating induce the change of morphology and the formation of Ni3+, thus increase the specific surface area and expose more active sites, finally greatly enhance the electrocatalytic OER performance. As a result, the Ni 2 CoFe 0.5 -LDH/NF electrode exhibits significantly enhanced oxygen evolution reaction performance with a small overpotential of 240 mV at the current density of 10 mA cm−2, a small Tafel slope of 65 mV dec−1 as well as an excellent durability in alkaline conditions for 72 h. Especially, the overpotential of Ni 2 CoFe 0.5 -LDH/NF is only 269 mV and 291 mV at 50 and 100 mA cm−2, respectively. This work provides a good paradigm for the design and fabrication of ternary NiCoFe-based functional electrocatalysts, and demonstrates the great practical potential of the Ni 2 CoFe 0.5 -LDH/NF electrocatalyst in oxygen evolution reaction. Image 1 [ABSTRACT FROM AUTHOR]

Layered double hydroxides are one of the most effective electrocatalysts owing to their compositional and structural flexibility. However, their self-stacking leads to limited active sites and low conductivity. In this work, a three-dimensional (3D) core–shell architecture with spatially separated active sites has been fabricated based on layered ternary nickel cobalt iron hydroxide (NiCoFe-LTH) nanosheets and cobalt iron Prussian blue analog (CoFe-PBA) on nickel foam (NF) (i.e., CoFe-PBA@NiCoFe-LTH/NF) with CoFe-PBA as self-sacrificial templates that are partially in situ transformed into NiCoFe-LTH nanosheets. The CoFe-PBA@NiCoFe-LTH/NF has a well-defined core–shell 3D flower-like nanostructure in which NiCoFe-LTH nanosheets create the larger shell while CoFe-PBA nanocubes form the small core. This hybrid structure is evaluated as an electrocatalyst for oxygen evolution reaction (OER) and found to exhibit a low overpotential of 228 mV at 10 mA cm−2, a low Tafel slope of 36 mV dec−1, and good catalytic stability for 72 h in 1.0 M alkaline solution. The strong performance is attributed to the unique 3D core–shell flower-like nanosheet architecture that avoids the stacking of the 2D LTH, provides abundant spatially separated active sites, and enhances electron transport and stability. Furthermore, the OER mechanism and growth process of the electrocatalysts were systematically studied. These results suggest that such electrocatalysts with unique architecture are promising for efficient and durable OER. [ABSTRACT FROM AUTHOR]