Synthesis of three-dimensional Au-graphene quantum dots@Pt core–shell dendritic nanoparticles for enhanced methanol electro-oxidation

Abstract

Au-graphene quantum dots (GQDs)@Pt core–shell nanodendrites are synthesized through a two-step reduction approach, in which Au forms the core, GQDs form an intermediate layer and dendritic Pt forms the shell. Among the above synthesized catalysts, the GQDs can manipulate the binding of reaction intermediates on the Pt surface as well as assemble π–π* conjugate bonds, thus forming a dendritic Pt shell instead of a compact Pt shell. The obtained core–shell structure was characterized by transmission electron microscopy, energy-dispersive x-ray and x-ray photoelectron spectroscopy. The methanol electro-oxidation was investigated in alkaline media on the Au-GQDs@Pt modified electrode via cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy analysis. In particular, we discovered that Au–Pt assembled with GQDs could dramatically improve the activity and stability of the catalysts, owing to the synergistic effect raised by the GQDs, which exhibit prominent electron conductivity and great chemical/physical stability. It was also found that the Pt/Au mole ratios could control the Pt shell thickness, which significantly affected the catalytic methanol oxidation activity of the Au-GQDs@Pt nanodendrites. The Au-GQDs@Pt nanodendrites with optimum Pt/Au mole ratios of 1.0 exhibited a 2.5 times increase in electrocatalytic activity toward methanol oxidation compared with the commercial catalyst (Pt/C), and its CO tolerance was also greatly improved. The above results show that the Au-GQDs@Pt nanocatalysts have potential application prospects in direct methanol fuel cells.

Free-Standing, Interwoven Tubular Graphene Mesh-Supported Binary AuPt Nanocatalysts: An Innovative and High-Performance Anode Methanol Oxidation Catalyst

“…Figure 3 d,e show the HRTEM results acquired from the TG/Pt 0.241 and TG/Au 0.258 catalysts, respectively. Interlayer spacing values of 0.193, and 0.236 nm were observed, consistent with the lattice spacing values of Pt (200) and Au (111) [ 24 , 38 ], respectively.…”

“…XRD pattern of the TG/Au 52 Pt 48 catalyst ( Figure 2 c) shows sharp diffraction peaks at approximately 26.4° and 59.7°, which are assigned to hexagonal phase of graphite (see the PDF#41-1487). Furthermore, it also exhibits the characteristic peaks associated to the (111), (200), (220), and (311) lattice planes of face-centered cubic Au (PDF#04-0784) and the (111), (200) and (220) lattice planes of face-centered cubic Pt (PDF#04-0802), indicating the formation of Au and Pt crystal structures simultaneously [ 37 , 38 ]. The sharp peaks (200) and (220) of Pt, which were not observed in the TG/Pt 0.241 catalyst, can clearly be observed in the TG/Au 52 Pt 48 catalyst.…”

“…As indicated in Figure 6 c, the Au 4f 7/2 and 4f 5/2 binding energies of TG/Au 52 Pt 48 are 83.9 eV and 87.6 eV, respectively, same as those of TG/Au 0.258 , and lower than those of standard metallic Au 0 , indicating no change of the electron structure of Au NPs after Pt NPs growth. Furthermore, lower binding energies of the Pt 4f 7/2 (71.2 eV) and Pt 4f 5/2 (74.6 eV) (see Figure 6 d) were observed for the TG/Au 52 Pt 48 compared with those of the TG/Pt 0.241 (see Figure 6 b), suggesting that Au NPs promote the donation of electrons from Pt to TG [ 17 , 38 , 56 ].…”

Synthesis of AuPt/graphene quantum dots nanocomposites for determination of glucose by photoluminescence spectroscopy

“…Au–Pt conjugated with GQDs can significantly improve the activity and stability of the catalysts, which, because of the enhanced synergistic effect of GQDs, exhibit outstanding electronic conductivity and excellent chemical/physical stability. 34…”

Evaluación de la actividad electrocatalítica de nanoestructuras base paladio soportadas en óxido de grafeno, para la electrooxidación de ácido fórmico

“…Finalmente una vez formadas las especies OH ads reaccionan con las especies CO ads , se completa la oxidación para obtener el CO 2 que limpia la superficie del catalizador y de esta manera entrar nuevamente a un ciclo de catálisis, como se muestra en la reacción (30) 8 , [20][21][22] .…”