Controllable Synthesis Of Co-based Nanocomposite Material And Research On Oxygen Evolution Electrocatalytic Performance

As the population increasing and the progress of science and technology level, the global energy shortage and environmental pollution problem become the two obstacles which block the development of the society today. The development of the new energy has become a scientific problem which must be solved urgently. Catalytic splitting of water into hydrogen and oxygen provides a potential path to produce clean H2 and O2 for human society. However,one of major hurdles of water electrolysis is anodic oxygen evolution reaction ?OER? which needs high onset potential and shows slow sluggish kinetics due to four-electron transfer process. Rutile type oxides RuO2 and IrO2 have been proven to be highly efficient OER catalysts. Unfortunately, these noble metal oxide catalysts suffer from poor chemical stability in alkaline media and high price, which limit their practical large-scale application as water splitting anodes.Consequently, extensive efforts have been undertaken to develop highly efficient catalysts with low ons??? potential and promoted reaction kinetics. Herein, we fabricated four kinds of three-dimensional ?3D? highly ordered mesoporous composite materials as excellent electrocatalysts for OER in alkaline solution with high activity and stability.?1? Highly ordered mesoporous Co₃O₄ was successfully prepared by a nanocasting method using cubic mesostructure silica KIT-6 as hard template. Owing to the high conductivity of the well-defined mesoporous Co304 with the large surface area provided by the unique mesoporous structure, the as-prepared mesoporous Co₃O₄ has exhibited a fast kinetics and excellent stability compared with Co₃O₄/C.?2? After being loaded Pt, Pd, Au nanoparticles, onset potential for OER shifts more negatively and Tafel slope becomes lower, and charge transfer resistance decreases on the mesoporous Co₃O₄. The mesoporous Co₃O₄ has an ordered Ia3d symmetric mesoporous structure with a high surface area, while the 3D mesoporous Pt-Co₃O₄?wt 1:4?,Pd-Co₃O₄?wt 1:1? and Au-Co₃O₄?wt 1:3? catalysts also have a high surface area, but have a lower value than mesoporous Co₃O₄, which can indicate that the precious metal particles have been loaded and embedded on Co₃O₄. Thus 3D highly ordered mesoporous structure with high surface area can facilitate diffusion and penetration of electrolyte and oxygen.?3? Hierarchical Co₃O₄@MnO2 core-shell arrays on Ni foam have been fabricated by a facile hydrothermal approach and further investigated as the electrode for high-performance electrocatalysts. This electrocatalysts exhibit two different morphologies, nanowires arrays and hexagonal nanosheets, and the latter would perform more excellent electrochemical performances. Owing to the high conductivity of well-defined mesoporous Co₃O₄ nanowire arrays in combination with the large surface area provided by the ultrathin MnO2 nanosheets, the unique designed Co₃O₄@MnO2 core shell arrays on Ni foam have exhibited a fast kinetics and excellent stability.?4? We report on the development of 3D hierarchical NiCo₂S₄@MnO2 core-shell nanosheet arrays on Ni foam for OER electrocatalysts with three different morphologies. After electrochemical test, the electrocatalyst performances of nanoflower morphology exhibit the best activity compared with the nanowire arrays and ball-and-stick nanomaterials because of the nanoflowers' more pores can provide efficient and rapid pathways for ion and electron transport. These merits together with the elegant synergy between NiCo₂S₄and MnO2 lead to an excellent electrochemical performance with lower onset potential and better stability.