Reactive magnetron sputtering to enhance the hydrogen permeation performance of NbC/V composite membranes

Abstract

Niobium carbide (NbC) catalytic films were deposited on the surface of vanadium (V) substrates by reactive magnetron sputtering (RMS) using CH4 as the carbon source to form the NbC/V composite membranes for hydrogen separation and purification. The effects of CH4 gas flow ratio (FCH4 = CH4/(CH4+Ar)) on the phase structure, surface microstructure and catalytic properties of NbC films and the hydrogen permeation performance of the NbC/V composite membranes were investigated. The results showed that the structure of the NbC catalytic film changed from the dual-phase of NbC and Nb2C to the single-phase of cubic NbC after the addition of CH4 gas. Furthermore, with the increase of FCH4, the carbon content in the NbC catalytic films increases, but the crystallinity decreases. When FCH4 is 5%, the hydrogen permeation performance of the NbC/V composite membrane is the highest, which is attributed to the appropriate carbon content and crystallinity of the NbC phase. Typically, the hydrogen permeability is 7.0 × 10−8 mol H2 m−1 s−1 Pa−0.5 at 650 °C, which is 2.4 times that of pure Pd.