The effect of supporting carbons on the gas phase synthesis of octahedral Pt3Ni electrocatalysts with various H2:CO ratios

Abstract

The gas phase synthesis of octahedral Pt3Ni/C electrocatalysts using several carbon substrates (Ketjen black, Graphene, and Vulcan XC-72R) was investigated. Different carbon substrates altered the morphology and alloy of Pt3Ni nanoparticles, with octahedral morphology and alloy metal preferentially developing on Ketjen black and Graphene, while spherical shape and bimetallic metal preferentially developing on Vulcan. Furthermore, the shape was shown to be regulated throughout the reduction process, with the H2:CO ratio playing a crucial role in controlling octahedral morphology and carrying out the ORR activity. At a 1:3 H2:CO ratio, the Pt3Ni/Ketjen black exhibited the highest ORR activity for both mass activity (1.02 A mgPt−1) and specific activity (5.09 mA cm−2) that were 16.5 and 66.1 times larger than commercial Pt/C catalysts, respectively (0.062 A mgPt−1 and 0.077 mA cm−2). The best ORR activity of Pt3Ni onto Graphene and Vulcan XC-72R was exhibited with a 1:1 H2:CO mixture. The catalysts were tested using a 4000-voltage-cycle accelerated durability test, and the Pt3Ni/Ketjen catalyst fared the best in terms of ORR stability and durability.