The electrocatalytic application of RuO2 in direct borohydride fuel cells

• RuO2 exhibits oxygen reduction reaction (ORR) activity in an alkaline solution.
• RuO2 provides 3.58–3.86 electron transfer number during the ORR.
• Direct borohydride fuel cell (DBFC) with RuO2 cathode displays a peak power density of 425 mW cm−2 at 60 °C.
• DBFC with RuO2 cathode exhibits a superb stability during a 200-h durability test.

A high electrocatalytic activity of RuO2 has been found for oxygen reduction reaction (ORR) in the cathode of direct borohydride fuel cells (DBFCs). The electron transfer number n during the ORR changes from 3.58 to 3.86 and the percentage of the intermediate product H2O2 decreases from 20.8% to 7.2% correspondingly when the disk potential scans negatively from −0.39 V to −0.8 V versus Hg/HgO. Peak power densities of 425 mW cm−2 has been obtained at 60 °C, when RuO2 has been used as a cathodic catalyst in DBFCs. RuO2 displays low sensitivity to the BH4− oxidation in DBFCs. Moreover, RuO2, as a cathodic catalyst, demonstrates a superb stability during a 200-h durability test. The identical X-ray diffraction (XRD) patterns of the RuO2 before and after the durability test also prove its stability.