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.