Application of Diamond Like Carbon Films to Gas Barrier for Hydrogen Fuel Cell Technology

We propose application of diamond like carbon films to Hydrogen fuel cell technology. The Hydrogen fuel cell has been developed for a new style of clean energy. The Hydrogen storage system is one of important issues especially for the vehicles. The leakage of Hydrogen through the tank wall cannot be disregarded at such a high pressure of 40-70 MPa. The brittle fracture by Hydrogen is a serious problem for safety. For such the small molecule as hydrogen, the lighter elements such as Beryllium, Boron, Carbon, Nitrogen, etc, will perform better barrier from diffusion into the material. DLC film is a promising barrier to prevent Hydrogen diffusion into the substrate. The Hydrogen leakage through DLC films deposited on polymer sheets has been investigated for the purpose of evaluation of hydrogen barrier by the DLC film. Without the DLC film, Hydrogen can easily pass through such the sheet of polyethylene terephthalate (PET) widely used for bottling drink. With a thin DLC film deposited by an RF plasma CVD method, the leakage rate through the sheet is decreased by more than 30%. Even by a thin film of a few 10 nm, the Hydrogen diffusion was partly stopped. It is necessary to optimize fabrication condition to improve the barrier performance.