The Preparation And Electrochemical Applications Of Silica-based Nanomaterials

Direct alcohol fuel cells such as direct formic acid fuel cell and direct ethanol fuel cell have attracted increasing attention due to high energy efficiency,abundant sources,low-pollution,as well as easy storage and transportation of the fuel.However,the instability of precious metals such as Pd during the operation of fuel cell presents a challenge.In present work,silica-based materials including CaSiO3 have been employed as supporting materials for Pd,in order to improve the activity and stability of Pd-based catalysts.The effects of various factors,including preparation methods,Ca/Si ratio,the surfactant content(CTAB)and the CaSiO3/XC-72 ratio,on the structure and electrochemical properties of Pd-based catalysts have been systematically investigated.Firstly,silica materials have been prepared by the stober methord.The effect of silane coupling agent(APTMS)on the electrocatalytic performance of Pd/SiO2 in formic acid has then been studied.The results show that APTMS contributes to more uniform distribution of Pd nanoparticles on the surface of hollow silica spheres,and the improved activity and stability of Pd/SiO2 catalyst toward the electrooxidation of formic acid.In addition,CaSiO3 has been prepared by precipitation method.The effects of Ca/Si ratio and the surfactant content on the the structure and electrochemical properties of Pd-based catalysts have then been investigated.The results show that the catalyst with the Ca/Si ratio of 1:1 has the best electrochemical performance.In addition,the catalyst with the CTAB/Ca(NO3)2 ratio of 1:1 has the best electrochemical performance toward the electrooxidation of formic acid.Moreover,CaSiO3 has been prepard by thermal decomposition method.The effect of CTAB content on the structure of CaSiO3 and the electrochemical properties of Pd-based catalysts has been studied.The results show that the uniform structure of CaSiO3 can be obtained when the CTAB/CaSiO3 ratio is 1:1.Such a CaSiO3 leads to the uniform distribution of Pd nanoparticles and the best electrochemical performance toward the electrooxidation of formic acid.Finally,the effect of CaSiO3/XC-72 ratio on the electrochemical performance of Pd/C catalysts for ethanol electrooxidation has been studied.The results show that the activity of catalyst with a CaSiO3/XC-72 ratio of 1:1(referred to as Pd/50CaSiO3/C)is twice as that of Pd/C.In addition,the inclusion of CaSiO3 facilitates the adsorption of OH-on the catalyst surface,and thus significantly improves the stability and resistance to CO poisoning of Pd/C catalyst.