Kinetically-controlled growth of cubic and octahedral Rh-Pd alloy oxygen reduction electrocatalysts with high activity and durabilityElectronic supplementary information (ESI) available. See DOI: 10.1039/c4nr04942j

• Main Authors: Yan, Yucong, Zhan, Fangwei, Du, Jingshan, Jiang, Yingying, Jin, Chuanhong, Fu, Maoshen, Zhang, Hui, Yang, Deren
• Format: Article
• Language: English
• ISSN: 2040-3364; 2040-3372
• DOI: 10.1039/c4nr04942j

Rh is a promising candidate as an indispensible component in bimetallic catalysts due to its unique capability to resist against the aggressive corrosion from the reaction medium. However, Rh has a very strong oxygen binding ability and is generally not suitable for the oxygen reduction reaction (ORR). Here, we have demonstrated shape-controlled synthesis of Rh-Pd alloy nanocrystals with high activity and durability for ORR by retarding the reaction kinetics at an ultra-slow injection rate of metal salts using a syringe pump. Under precise control of sluggish reaction kinetics, Pd followed a preferential overgrowth along the direction, whereas the growth behavior of Rh was dominant along the direction. These different kinetically-controlled growth behaviors associated with Rh and Pd were essential for achieving the shape transition between the cube and the octahedron of their alloys. The Rh 8 Pd 92 alloy octahedra exhibited the highest mass activity with a value of 0.18 mA μg −1 in terms of the equivalent Pt cost, and were two-fold higher than that of commercial Pt/C. Significantly, all Rh-Pd alloy nanocrystals were highly stable with only less than 25% loss in mass activity after 30 000 CV cycles in O 2 saturated acid solution compared to ∼56% loss of the commercial Pt/C (E-TEK). Indeed, the mass activity of Rh8Pd92 was 3.3 times higher than that of commercial Pt/C after the accelerated stability test (ADT). This improvement in activity and durability may arise possibly from synergistic effects between the facet and the surface composition. Rh-Pd alloy cubes and octahedra with different compositions were readily generated by manipulating the reaction kinetics and exhibited substantially enhanced activity and durability for the oxygen reduction reaction.