电化学和sol-gel法结合制备Cu-SiO_2薄膜——不同pH值CuSO_4硅溶胶中Cu的电化学行为

Preparation of Copper-Silicon Dioxide Gel Film by Combining Electrochemical Method with Sol-Gel Method——Electrochemical Behavior of Cupric Ion in Copper Sulfate Silica Sol with Different pH Values

研究金属或半导体在溶胶中的电化学行为对电化学和溶胶-凝胶(sol-gel)法结合制备掺杂金属和半导体的复合凝胶薄膜有极大指导意义。用循环伏安(CV)和计时安培(CA)法研究了电化学和sol-gel法结合制备Cu-SiO2凝胶薄膜时不同pH值CuSO4硅溶胶中Cu在玻碳电极上的电沉积和电结晶行为。结果表明:在pH=1.0~3.0的CuSO4硅溶胶中,Cu2+的扩散系数在pH=2.0时最小,pH=1.0时较pH=3.0时大,这也是造成硅溶胶中pH=2.0时还原最难,pH=3.0时次之,pH=1.0时最易的原因;Cu在硅溶胶中的电沉积为Langmuir型吸附-三维瞬时成核机理;硅溶液中Cu2+的传递系数均大于0.9,存在吸附层;Cu2+在吸附过程的总放电量Qads随pH值增大而增大;Cu的成核数密度都随电位增大而增大,随pH值增大而减小,故pH值在1.0~3.0内越大越不利于制备Cu-SiO2薄膜。

Electrochemical method was combined with sol-gel method to prepare Cu-SiO_2 gel film.The electrodeposition behavior and electrocrystallization behavior of Cu^(2+) in CuSO_4 silica sol with different pH values were investigated by utilizing cyclic voltammetry and chronoamperometry.Results indicated that,in CuSO_4 silica sol with a pH value of 1.0 ~3.0,the minimum diffusion coefficient of Cu^(2+) was obtained at pH = 2.0,and the diffusion coefficient of Cu^(2+) at pH = 1.0 was larger than the one at pH = 3.0.As a result,the liability for Cu'* to be reduced at various pH values of CuSO_4 silica sol was ranked as pH = 1.0 >pH = 3.0 > pH = 2.0.The electrodeposition of Cu^(2+) in the CuSO_4 silica sol could be well described by a model that involved a Langmuir-type adsorption process and a three-dimensional instantaneous nucleation mechanism.The transfer coefficient of Cu^(2+) in the CuSO_4 silica sol was always larger than 0.9,and there existed an adsorbed layer on the electrode surface.Moreover,the total charge for the adsorption process increased with increasing pH value of the electrolyte;and the nucleation number density of copper increased with increasing potential while it declined with increasing pH value.Therefore,in CuSO_4 silica sol with a pH value range of 1.0 ~ 3.0,elevating pH value was unbeneficial to the preparation of Cu-SiO_2 film.