A Magnetron Sputtering Method for the Application of the Ni Catalyst for the Synthesis Process of Carbon Nanotube Arrays

A study on the optimization of the method of application of the Ni catalyst for the growth of carbon nanotubes (CNTs) onto the gas diffusion layers (GDLs) (predominantly carbon cloths) by magnetron sputtering is presented. The mode of magnetron sputtering of the Ni catalyst which makes it possible to obtain a uniform metal coating on the GDLs which is required for the successful synthesis of CNTs is selected for the first time. It is shown that the sputtering of Ni in the direct current mode with the supply of pulsed bias voltage to the substrate with a frequency of 100 kHz and time of supply of the negative pulse of 7 mu s makes it possible to obtain the optimum nanostructured coating of the metal with a low specific surface and a high degree of uniformity of application onto the entire area of the substrate. The applied Ni coating acts as the catalyst for the growth of CNTs. CNT arrays with the average diameters of 40 and 80 nm for the hydrophobic and hydrophilic GDLs, respectively, are grown on the GDLs with the applied Ni catalyst by pyrolytic gas-phase deposition. The CNT arrays are directly obtained on the entire surface of the carbon substrates with a high degree of uniformity. It is found that the diameter of the nanotubes is mainly determined by the structure of the GDL being used.