摘要
碳毡电极材料经高温热氧化改性后,表面结构和性质发生明显变化。随热氧化温度上升,碳毡石墨结构更趋有序定向排列,石墨化程度提高。这不仅明显提高了其导电性能,同时也使表面含氧官能团的含量或O/C原子比下降。由于碳毡金属杂质含量减少以及表面担载的催化剂颗粒变大且分布更为不均匀,高温热氧化碳毡表面对析氢副反应具有较高的过电位,放氢电流大幅度降低,但提高热氧化温度使碳毡电极的电化学反应活性有所下降。为使碳毡电极上放氢电流降低的同时又保证电极具有较高的Fe^(3+)/Fe^(2+)及Cr^(3+)/Cr^(2+)反应的电化学活性,热氧化温度1700℃为宜。
The structure and property of carbon surface which have great influence on the electrode behavior can be changed with different crude materials and processing procedures and various surface treatments or modifications. In this work the heat oxidation treatment as one of the physical modification methods was used to modify the carbon felts.
Heat oxidation treatment is based on the increase of carbonizing temperature in the manufacture process of carbon felts. Data of Raman spectra analysis indicated that high temperature heat oxidation enhanced the ordered and oriented arrangement of graphite structure of carbon felts, resulting in marked decrease of electric resistivity. XPS analysis indicated that the contents of surface oxygen-containing functional groups or O/C atomic ratios were also decreased by a factor of four. Because of the reduced metallic impurities and more and less uniform catalyst particles on the carbon felt surface after high temperature oxidation, carbon felt surface exhibited higher over-potential for H+/H2 reaction. Thus, dramatic reduction of hydrogen evolution current was obtained ( more than 25 to 100 times reduction). But electrochemical activity of carbon felt electrode for Cr3+/Cr2 + and Fe3+/Fe2+ reaction was decreased due to the decreases of surface area and contents of surface oxygen-containing functional groups caused by higher ordered and oriented structure arrangement.
In order to assure not only low hydrogen evolution current but also high electrochemical reaction activity on the carbon felt electrode, a suitable heat oxidation temperature is about 1700℃
出处
《分子催化》
EI
CAS
CSCD
1991年第4期348-353,共6页
Journal of Molecular Catalysis(China)
基金
国家自然科学基金
