Carbon-supported nickel-doped manganese oxides as electrocatalysts for the oxygen reduction reaction in the presence of sodium borohydride

► All (Ni)MnOx catalysts are active for the oxygen reduction reaction. ► Ni segregate phases contribute to the BOR and the heterogeneous hydrolysis of BH4−. ► (Ni)MnOx dispersed on E350G and MM225 carbons are not tolerant to BH4−. ► Low Ni-content (Ni)MnOx dispersed on M1000 carbon is tolerant to BH4−.