title: Component-controlled synthesis and assembly of Cu-Pd nanocrystals on graphene for oxygen reduction reaction.
abstract: Exploring low-cost, high-activity, and long-durability hybrid electrocatalysts for cathodic oxygen reduction reaction (ORR) is vital to advance fuel cells technologies. In this paper, a series of graphene (G)-CuxPdy (Cu4Pd, Cu3Pd, CuPd, CuPd3, CuPd4) nanocomposites (G-CuxPdy NCPs) is obtained by assembly of CuxPdy alloy nanocrystals (NCs) with controlled component ratios on G nanosheets using the "dispersing-mixing-vaporizing solvent" strategy and used as electrocatalysts for ORR. Compared with pure CuxPdy NCs, greatly enhanced interfacial electron transfer dynamics are observed in G-CuxPdy NCPs, which show a strong correlation with the alloy compositions of the NCPs. The electrocatalytic experiments in alkaline solution reveal that the ORR activities of those G-CuxPdy NCPs are also strongly dependent on alloy components and exhibit a double-volcano feature with variations of alloy components. Among them, G-Cu3Pd NCPs possess the highest electrocatalytic activity, which is much better than some reported electrocatalysts and commercial Pd/C catalyst and close to Pt/C catalyst. By correlating the Pd 3d binding energies and the sizes of CuxPdy NCs with the mass-specific activities of G-CuxPdy NCPs and considering the interfacial electron transfer dynamics, the best catalytic activity of G-Cu3Pd NCPs may result from the unique electronic structure and the smallest size of Cu3Pd NCs as well as the strong synergistic effect between G and Cu3Pd NCs. Moreover, the durability of G-Cu3Pd NCPs is superior to that of Pt/C catalyst, indicating that they are promising cathodic electrocatalysts for using in alkaline fuel cells.
authors.affiliation: Jiangsu Key Laboratory of Biofunctional Materials, School of Chemistry and Materials Science, Nanjing Normal University , Nanjing 210023, People's Republic of China.
authors.forename: Yulin
authors.initials: Y
authors.lastname: Zheng
authors.forename: Shulin
authors.initials: S
authors.lastname: Zhao
authors.forename: Suli
authors.initials: S
authors.lastname: Liu
authors.forename: Huanhuan
authors.initials: H
authors.lastname: Yin
authors.forename: Yu-Yun
authors.initials: YY
authors.lastname: Chen
authors.forename: Jianchun
authors.initials: J
authors.lastname: Bao
authors.forename: Min
authors.initials: M
authors.lastname: Han
authors.forename: Zhihui
authors.initials: Z
authors.lastname: Dai
keywords: assembly; bimetallic nanocrystals; electrocatalysis; graphene; nanocomposites; oxygen reduction reaction