钨源对碳化钨分散性及电催化性能的影响

Effect of tungsten source on dispersion and electrocatalytic property of tungsten carbide

  • 摘要: 碳化钨具有类铂催化性能、抗一氧化碳中毒和高导电性等特点,如能进一步改善其形貌、降低其尺寸及提高其比表面积,有望取代或部分取代贵金属催化剂.在以碳纳米管为载体,柠檬酸为络合剂的前提下,分别以偏钨酸铵、钨酸钠及仲钨酸铵为钨源,利用水热法制备了钨酸和碳纳米管复合物.采用温度控制程序,在空气气氛中于600℃对该复合物进行煅烧,得到氧化钨中间体,随之在氮气气氛中于950℃通入碳源进行碳化,得到碳化钨,发现以偏钨酸铵为钨源制备的碳化钨分散性最好,尺寸(约100 nm)最小,而以钨酸钠为钨源制备的碳化钨分散性和尺寸(约100~500 nm)次之,以仲钨酸铵为钨源制备的碳化钨分散性最差、尺寸(大于500 nm)最大.碳化钨载铂后的电催化测试结果表明,以偏钨酸铵为钨源制备的碳化钨作为载体担载铂颗粒,在硫酸体系中的峰电流密度(32.59 mA/cm2)优于钨酸钠(11.32 mA/cm2)和仲钨酸铵的(5.13 mA/cm2),在甲醇和硫酸体系中的峰电流密度(106.92 mA/cm2)优于钨酸钠(90.13 mA/cm2)和仲钨酸铵的(72.15 mA/cm2).

     

    Abstract: Tungsten carbide (WC) can be used as electrocatalyst of fuel cells for its like-Pt catalytic ability, CO anti-poisoning ability and high electric conductivity. It also can be expected to replace or partly replace noble metal catalyst because of its special morphology, reduced diameter and improved surface area. Ammonium metatungstate, sodium tungstate and ammonium paratungstate are respectively used as tungsten source, carbon nanotubes are used as carrier, citric acid is used as complexing agent, and tungsten acid and carbon nanotubes composite can be prepared after hydrothermal reaction. The tungsten source would be reduced into tungsten oxide as air pumped into reaction chamber at 600 ℃ by temperature-controlled program. And the obtained tungsten oxide can be further carbonized and changed to WC at 950℃ with nitrogen as atmosphere. The WC using ammonium metatungstate as tungsten source possesses the best dispersion and the smallest size. After the platinum nanoparticles are loaded on the surface of the obtained WC, the results demonstrated that the higher electrocatalytic activity (32.59 mA/cm2) in sulfuric acid solution of the Pt-WC prepared by using ammonium tungstate as tungsten source than those of sodium tungstate (11.32 mA/cm2) and ammonium paratungstate (5.13 mA/cm2), and higher electrocatalytic activity (106.92 mA/cm2) in methanol and sulfuric acid solution of the Pt-WC prepared by using ammonium tungstate as tungsten source than those of sodium tungstate (90.13 mA/cm2) and ammonium paratungstate (72.15 mA/cm2).

     

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