Acidic dissolution of transition metals from Pt based alloy catalysts for oxygen reduction reaction (ORR) is an unavoidable process during fuel cell operation. In this work we studied the effect of acid treatment of graphene-supported Pt 1 Ni x (x ) 0, 0.25, 0.5, 1, and 2) alloys on the kinetics of the ORR in both alkaline and acidic solutions together with the generation of OH radicals in alkaline solutions. The alloy nanoparticles were synthesized through coimpregnation and chemical reduction. The electronic and structural features of the alloy were characterized by X-ray photoelectron spectroscopy, X-ray diffraction, transmission electron microscopy, and high-resolution transmission electron microscopy. The ORR performances were studied using cyclic voltammetry and rotating ring disk electrode techniques in 0.05 M H 2 SO 4 and 0.1 M NaOH, respectively. The alloy catalysts were more active than pure Pt toward ORR, and after acid treatment the ORR activity of Pt-Ni alloy was enhanced in both acidic and alkaline media. The maximum activity of the Pt-based catalysts was found with ca. 50 atom % Ni content in the alloys (Pt 1 Ni 1 @graphene). OH radicals were generated through dissociation of hydroperoxide at the catalysts' surface and detected by fluorescence technique using terephthalic acid as capture reagent, which readily reacts with OH radical to produce highly fluorescent product, 2-hydroxyterephthalic acid. More OH radicals were found to be generated at Pt 1 Ni 1 @graphene catalyst. This work may be valuable in the design of electrocatalysts with higher ORR activity but lower efficiency of OH radical generation.

The construction of an efficient oxygen reduction reaction and oxygen evolution reaction (ORR/OER) bifunctional electrocatalyst is of great significance but still remains a giant challenge for high-performance metal−air batteries. In this study, uniform FeS/Fe 3 C nanoparticles embedded in a porous N,S-dual doped carbon honeycomb-like composite (abbr. FeS/Fe 3 C@NS-C-900) have been conveniently fabricated by pyrolysis of a single-crystal Fe-MOF, which has a low potential gap ΔE of ca. 0.72 V, a competitive power density of 90.9 mW/cm 2 , a specific capacity as high as 750 mAh/g Zn , and excellent cycling stabilities over 865 h (1730 cycles) at 2 mA/cm 2 when applied as a cathode material for rechargeable zinc−air batteries. In addition, the two series-linked Zn−air batteries successfully powered a 2.4 V LED light as a real power source. The efficient ORR/OER bifunctional electrocatalytic activity and longterm durability of the obtained composite might be attributed to the characteristic honeycomb-like porous structure with sufficient accessible active sites, the synergistic effect of FeS and Fe 3 C, and the N,S codoped porous carbon, which provides a promising application potential for portable electronic Zn−air battery related devices.