Preparation And Modification Of Copper Oxide Nanosheet Array Films And Their (Photo)Electrochemical Properties

Copper oxide nanofilms have extensive application prospect and long-term significance in various fields such as photoelectric technology,supercapacitors,catalysis,sensors and so on,due to their unique band structure,various morphologies and nanometer size effect.This dissertation focuses on the anodization in situ synthesis of copper oxide nanosheet array films on copper foil and copper foam based on anodization method.The structures,morphologies,and elemental compositions of the as-prepared films were characterized and the photoelectrochemical properties were studied.And a facile hydrothermal deposition process was employed to fabricate Cu/Ni-based nanocomposite film on the basis of successful preparation of copper oxide nanoarray films,and their supercapacitor characteristics were measured and evaluated.Then a modified anodization process to control the phase composition of copper oxide nanofilms on Cu foam via changing the components of electrolyte was studied.Meanwhile,the pseudocapacitance and non-enzymatic sensing performance of as-prepared single-phase CuO nanofilms were further comparatively studied.Finally the in-situ transformation method was adopted for the synthesis of Cu based Metal Organic Frameworks?MOFs?materials based on the anodized CuO NSAs in order to explore a novel method for synthesizing Cu-MOFs.?1?Firstly,in situ synthesis of copper oxide nanosheet array?denoted as NSAs?films on copper foil by electrochemical anodization was studied systematically.The effects of the anodization parameters on the structures,morphologies,and elemental compositions of the as-prepared films were discussed in detail,including the electrolyte components,the current density,temperature,and the content of polyethylene glycol?PEG 20000?.The growth mechanism was discussed and the photoabsorption characteristics and photocurrent effects were further examinated.The optimized preparation parameters were obtained:the main ingredients of electrolyte are 150 g/L NaCl,40 g/L NaOH,and the anodization current density is 1.0¹.5 A/dm²,temperature is 60⁷0oC,and PEG concentration is 0.5¹.5 g/L.The regular copper nanosheet arrays are comprised of 30-nm-thick and 150-nm-long nanosheets that stand vertically on the Cu substrate and each nanosheet is composed of Cu₂O and CuO.The anodization is a 2-step oxidation process and includes Cu?Cu⁺and Cu⁺?Cu²⁺.This oxidation reaction slows sharply due to a dense layer formed between the nanosheet arrays and Cu substrate.A negative photocurrent can occur under visible light illumination due to the p-type semiconductor of the copper oxide NSAs.Optimized copper oxide NSAs can achieve the highest photocurrent?approximately 0.4 mA/cm²?with the anodization current density of 1.0 A/dm²,temperature of 70oC,and PEG concentration of0.5 g/L.?2?The?-NiOOH@CuO/Cu₂O NSAs were successfully synthesized via electrochemical anodization and hydrothermal deposition process.The XRD,XPS and TEM analyses revealed that CuO,Cu₂O and?-NiOOH were the co-existence in the nanocomposite films.The results of cyclic voltammograms?CV?and galvanostatic charge-discharge?GCD?tests showed that the samples after hydrothermal deposition had obvious redox peaks,indicating that pseudocapacitive behavior proceeded during the electrode charging and discharging process.The nanocomposite structure combined the merits of three kinds of active materials and showed a competitive and remarkable supercapacitiveperformance.ComparedwiththeCuO/Cu₂ONSAs,the NiOOH@CuO/Cu₂O NSAs after the hydrothermal deposition treatment at 0.3 mol/L Ni?NO₃?₂ solution still maintain the nanosheet characteristics of highly ordered arrangement and exhibited the highest areal capacitance of 1206 mF/cm² at 1 mA/cm²with good cycling stability,retaining 84.6%of initial capacitance after 3000charge/discharge cycles.The NiOOH@CuO/Cu₂O NSAs were expected to be a binder-free and high performance electrode material for supercapacitors.?3?A modified anodization process was presented that includes?NH₄?₆Mo₇O₂₄?AM?in the electrolyte solution,and single-phase CuO nanosheet films were successfully synthesized directly on Cu foam.The synthesis mechanism and growth process for CuO nanofilms were discussed in detail.The supercapacitive and no-enzymatic sensing performances of single-phase CuO nanofilms electrode material were studied.The results showed that the function of AM mainly included the corrosion inhibition and the synergistic effect of Cl ions?Cl^-?.AM significantly inhibited the Cu?Cu⁺oxidation reaction,and the inhibitory effect became increasingly distinct with increasing AM concentration under equivalent conditions.It was found that the supercapacitive and no enzymatic sensing performances of single-phase CuO nanofilms were superior to those of CuO/Cu₂O NSAs.The as-fabricated single-phase CuO nanosheet films exhibited a good areal capacitance greater than 600 mF/cm² at 1 mA/cm² in 2 mol/L KOH aqueous solution,and also demonstrated excellent long term cycling stability with about 94%retention of the initial areal capacitance after 10000 charge/discharge cycles.Furthermore,this single-phase CuO NSAs were employed as substrate to construct no-nenzymatic glucose sensors with excellent performance,the sensitivity was as high as 16130?A/mM/cm².?4?HKUST-1 was synthesized via in-situ transformation method based on the CuO NSAs.The influences of reaction temperature and time on morphology were preliminary obtained,and a novel method for synthesizing HKUST-1 was explored.SEM and XRD results indicated that HKUST-1 polyhedra were successfully fabricated on the surface of CuO NSAs.The HKUST-1 polyhedra showed thermochromic effect,which could be tuned between blue-violet?or dark blue?and light blue with the change of temperature.And after calcination,the HKUST-1 converted to CuO,and at the same time,the polyhedral morphology retained.Finally,CuO polyhedra with porous structure on the surface of CuO NSAs were obtained,which exhibited excellent adhesion to the substrate without stripping.