Differential potential pulse deposition of amorphous osmium thin films and electrocatalytic activity for borohydride oxidation in alkaline media

Amorphous Os films (thickness up to 140 nm) were electrodeposited onto Pt/quartz crystal resonator-electrodes by differential potential pulse voltammetry (DPV). The morphological features of the Os films and the associated electrocatalytic activity for BH4− oxidation in 2 M NaOH were investigated by surface analysis techniques (XPS, SIMS, SEM and XRD) and electrochemical quartz crystal microbalance. The thin films, composed of both metallic Os and OsO2, morphologically are comprised of interconnected agglomerates of 100 nm diameter (or lower). The surface roughness and specific surface area of the Os film can be varied by the number of potential deposition pulses applied, which affects the electrocatalytic activity. These amorphous films demonstrated outstanding electrocatalytic activity for BH4− oxidation. The Os electrode synthesized with 15 DPV (specific surface area 3.6 m2 g−1) generated a BH4− oxidation onset potential of −0.87 V vs. SHE, mass activity of 1240 A g−1 and an electrochemical surface area (ESA) based specific activity of 347 A m−2. The mass activity of the amorphous Os thin film was over an order of magnitude higher than previously reported mass activities for carbon-supported polycrystalline Pt or Os catalysts. The high catalytic activity can be partly attributed to the enhanced adsorption of BH4− on the Os thin film electrode over a wide potential range between −0.9 V and −0.2 V.

Figure optionsDownload as PowerPoint slideHighlights
► First report of differential potential pulse deposition of amorphous Os thin films.
► Excellent electrocatalytic activity for borohydride electro-oxidation in 2 M NaOH.
► Applicable as borohydride micro-fuel cell anode.