Deposition and characterization of RF-sputtered-Ta2O5 thin films for O2 reduction reaction in polymer electrolyte membrane fuel cells (PEMFC)

Ta2O5 thin films, proposed as the replacement of the precious Pt-based electro-catalyst in fuel cells, were sputtered on laser textured silicon substrate at 200 °C and then air annealed at 350 °C, 400 °C and 450 °C with the aim to improve crystallinity and uniformity. Characterization such as FESEM, XRD, Hall effect and Cyclic Voltammetry were employed to investigate the morphological, structural, electrical and electrochemical properties of the as-sputtered as well as annealed samples. Initial results showed that the films obtained by increasing the substrate temperature during sputtering are smoother and have better adhesion to the etched silicon substrates. It has also been observed that the rate of deposition increases resulting in thicker films for longer deposition time at higher temperature. Upon annealing, Ta2O5 films achieved better crystallinity consisting of orthorhombic phases. The average thicknesses of the films are in the range of 400 nm-700 nm. The proposed catalyst also shows better enhancement for oxygen reduction reaction (ORR) in prolonged time of continuous potentiostatic electrolysis as to be used in fuel cells.