TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Components: The solid nitrogen source is melamine or urea; and the inert carrier gas is nitrogen or argon. Preferred Method: The preparation of the nitrogen-doped carbon nano tube catalyst comprises: (i) mixing solid nitrogen source with ferrocene in a mass ratio of 1:2, grinding and passing into the low-temperature region of a tubular furnace, placing quartz sheet in a high-temperature region of the tubular furnace, passing inert gas into the furnace for 0.5 hour to remove air from the tubular furnace, heating the low-temperature region to 400 degrees C and heating the high-temperature region to 800 degrees C, passing the inert carrier gas into the low-temperature region for sublimating precursor to the high-temperature region; controlling the flow rate of the inert carrier gas at 50 ml/minute and reacting for 40 minutes to obtain nitrogen-doped carbon nano tubes with different sizes and shapes; and (ii) oxidizing the nitrogen-doped carbon nano tube catalyst at 200 degrees C for 6 hours to remove amorphous carbon, heating with concentrated nitric acid and stirring 5 hours and purifying the final product by filtering, washing and drying; or (i) mixing solid nitrogen source with ferrocene in a mass ratio of 1:4, grinding and passing into the low-temperature region of a tubular furnace, placing quartz sheet in a high-temperature region of the tubular furnace, passing inert gas into the furnace for 1 hour to remove air from the tubular furnace, heating the low-temperature region to 200 degrees C and heating the high-temperature region to 600 degrees C, passing the inert carrier gas into the low-temperature region for sublimating precursor to the high-temperature region; controlling the flow rate of the inert carrier gas at 100 ml/minute and reacting for 20 minutes to obtain nitrogen-doped carbon nano tubes with different sizes and shapes; and (ii) oxidizing the nitrogen-doped carbon nano tube catalyst at 300 degrees C for 3 hours to remove amorphous carbon, heating with concentrated nitric acid and stirring 10 hours and purifying the final product by filtering, washing and drying; or (i) mixing solid nitrogen source with ferrocene in a mass ratio of 1:1, grinding and passing into the low-temperature region of a tubular furnace, placing quartz sheet in a high-temperature region of the tubular furnace, passing inert gas into the furnace for 0.8 hour to remove air from the tubular furnace, heating the low-temperature region to 500 degrees C and heating the high-temperature region to 900 degrees C, passing the inert carrier gas into the low-temperature region for sublimating precursor to the high-temperature region; controlling the flow rate of the inert carrier gas at 150 ml/minute and reacting for 80 minutes to obtain nitrogen-doped carbon nano tubes with different sizes and shapes; and (ii) oxidizing the nitrogen-doped carbon nano tube catalyst at 400 degrees C for 10 hours to remove amorphous carbon, heating with concentrated nitric acid and stirring 5 hours and purifying the final product by filtering, washing and drying; or (i) mixing solid nitrogen source with ferrocene in a mass ratio of 1:6, grinding and passing into the low-temperature region of a tubular furnace, placing quartz sheet in a high-temperature region of the tubular furnace, passing inert gas into the furnace for 0.6 hour to remove air from the tubular furnace, heating the low-temperature region to 300 degrees C and heating the high-temperature region to 700 degrees C, passing the inert carrier gas into the low-temperature region for sublimating precursor to the high-temperature region; controlling the flow rate of the inert carrier gas at 200 ml/minute and reacting for 60 minutes to obtain nitrogen-doped carbon nano tubes with different sizes and shapes; and (ii) oxidizing the nitrogen-doped carbon nano tube catalyst at 100 degrees C for 6 hours to remove amorphous carbon, heating with concentrated nitric acid and stirring 3 hours and purifying the final product by filtering, washing and drying.