Denghui Pan

Nickel core–palladium shell nanoparticles grown on nitrogen-doped graphene with enhanced electrocatalytic performance for ethanol oxidation

Herein, we report a facile two-step strategy for green synthesis of nickel core–palladium shell nanoclusters on nitrogen-doped graphene (Ni@Pd/NG) without any surfactant and additional reducing agent. During the synthesis, nitrogen-doped graphene acted as both the active substance and support by taking advantage of its moderate reducing and highly dispersing capacities. Characterization indicated that a uniform dispersion of Ni@Pd nanoparticles on nitrogen-doped reduced graphene oxide had a 2.8 nm average particle size. Unexpectedly, the as-prepared Ni@Pd/NG hybrid exhibited much greater activity and stability than that of Pd/graphene and commercial Pd/C electrocatalyst at the same Pd loadings. Possible mechanisms for the enhanced electrocatalytic performance of nitrogen-doped reduced graphene oxide after combining with Ni@Pd are proposed. The present study provides an efficient strategy to synthesize highly efficient electrocatalysts.

Ultrafine Co3O4 embedded in nitrogen-doped graphene with synergistic effect and high stability for supercapacitors

Co3O4 embedded in nitrogen-doped graphene (Co3O4/N-G-750) is prepared by a two-step synthetic method: polyol microwave heating method and vacuum tube calcination method. The diameter from 2 nm to 4 nm of the Co3O4 particles can be easily controlled on a nitrogen-doped graphene surface by adjusting the experimental parameters. The electrochemical characteristics of Co3O4/N-G-750 composite have been characterized by cyclic voltammetry (CV) and galvanostatic charge–discharge measurements (GCD) in KOH 6 M electrolyte. The specific capacitance of the electrode modified as-prepared composite exhibited a high specific capacitance of 1288.2 F g−1 at a high discharge current of 1.5 A g−1, as well as excellent cycling stability (91.5% capacitance retention after 5000 cycles). This result indicates Co3O4/N-GO-750 will be an excellent candidate for supercapacitor applications.

Formation of cobalt silicide nanoparticles on graphene with a synergistic effect and high stability for ethanol oxidation

Stable cobalt silicide (CoSi) with an average diameter of less than 4 nm is uniformly decorated with graphene by a chemical vapor deposition method. Palladium (Pd) is then supported on the CoSi–G composite (Pd/CoSi–G) using an intermittent microwave heating reduction method and this composite is used as an electrocatalyst for ethanol oxidation in alkaline media. The Pd/CoSi–G catalyst exhibits 1.8 and 4.3 times the peak current density compared with Pd loaded on graphene and Vulcan XC-72 carbon, respectively. The significant increase in catalytic activity can be contributed to CoSi benefitting the formation of smaller and highly dispersed Pd particles and the synergistic effect between CoSi and Pd. The novel multi-effects of Pd on CoSi make Pd/CoSi–G a highly active, durable and low-cost fuel cell electrocatalyst candidate.