An effective chemical way to optimize the oxygen electrocatalyst and Li‐O2 electrode functionalities of metal oxide can be developed by the control of chemical bond nature with the surface anchoring of highly oxidized selenate (SeO42−) clusters. The bond competition between (Se6+−O) and (Mn−O) bonds is quite effective in stabilizing Jahn–Teller‐active Mn3+ state and in increasing oxygen electron density of α‐MnO2 nanowire (NW). The selenate‐anchored α‐MnO2 NW shows excellent oxygen electrocatalytic activity and electrode performance for Li‐O2 batteries, which is due to the improved charge transfer kinetics and reversible formation/decomposition of Li2O2. The present study underscores that the surface anchoring of highly oxidized cluster can provide a facile, effective way of improving the oxygen electrocatalyst and electrochemical performances of nanostructured metal oxide in Li‐O2 cells.

No abstract

Mesoporous hybrid network of reduced graphene oxide (rG-O) and layered MnO(2) nanosheets could act as an efficient immobilization matrix for improving the electrochemical activity of layered double hydroxide (LDH). The control of MnO(2) /rG-O ratio is crucial in optimizing the porous structure and electrical conductivity of the resulting hybrid structure. The immobilization of Co-Al-LDH on hybrid MnO(2) /rG-O network is more effective in enhancing its electrode activity compared with that of on pure rG-O network. The Co-Al-LDH-rG-O-MnO(2) nanohybrid deliveres a greater specific capacitance than does MnO(2) -free Co-Al-LDH-rG-O nanohybrid. The beneficial effect of MnO(2) incorporation on the electrode performance of nanohybrid is more prominent for higher current density and faster scan rate, underscoring the significant enhancement of the electron transport of Co-Al-LDH-rG-O. This is supported by electrochemical impedance spectroscopy. The present study clearly demonstrates the usefulness of the porously assembled hybrid network of graphene and metal oxide nanosheets as an effective platform for exploring efficient LDH-based functional materials.

An effective lattice engineering method to simultaneously control the defect structure and the porosity of layered double hydroxides (LDHs) was developed by adjusting the elastic deformation and chemical interactions of the nanosheets during the restacking process. The enlargement of the intercalant size and the lowering of the charge density were effective in increasing the content of oxygen vacancies and enhancing the porosity of the stacked nanosheets via layer thinning. The defect-rich Co−Al-LDH−NO 3 − nanohybrid with a small stacking number exhibited excellent performance as an oxygen evolution electrocatalyst and supercapacitor electrode with a large specific capacitance of ∼2230 F g −1 at 1 A g −1 , which is the largest capacitance of carbon-free LDH-based electrodes reported to date. Combined with the results of density functional theory calculations, the observed excellent correlations between the overpotential/capacitance and the defect content/stacking number highlight the importance of defect/stacking structures in optimizing the energy functionalities. This was attributed to enhanced orbital interactions with water/hydroxide at an increased number of defect sites. The present cost-effective lattice engineering process can therefore provide an economically feasible methodology to explore high-performance electrocatalyst/electrode materials.

Figure 8. a) Schematic illustration of the formation of heterolayered superlattice structure. b) XRD patterns of GO/LDH superlattice (black) and rGO/ LDH superlattice (red) and c) cross-sectional HR-TEM images of sandwiched LDH and graphene nanosheets. b, c) Reproduced with permission. [118] Copyright 2014, Wiley-VCH. d) Atomic force microscopy images and height profile for PDDA modified graphene nanosheet, e) XRD patterns and f) cross-sectional HR-TEM image of MoS 2 /PDDA-rGO superlattice. d-f) Reproduced with permission. [122]