Nucleation and growth controlled reduced graphene oxide–supported palladium electrocatalysts for methanol oxidation reaction

Abstract

In spite of advantages of direct methanol fuel cells, low methanol oxidation reaction and fuel crossover from anode to cathode, there remains a challenge that inhibits it from being commercialized. Active electrocatalysts are in high demand to promote the methanol oxidation reaction. The methanol reached at the anode can be immediately reacted, and thus, less methanol to cross to the cathode. The performance of electrocatalysts can be significantly influenced by varying the concentration of precursor solution. Theoretically, concentrated precursor solution facilitates rapid nucleation and growth; diluted precursor solution causes slow nucleation and growth. Rapid nucleation and slow growth have positive effect on the size of electrocatalysts which plays a significant role in the catalytic performance. Upon the addition of appropriate concentration of graphene oxide, the graphene oxide was reported to have stabilizing effect towards the catalyst nanoparticles. This work synthesized reduced graphene oxide-supported palladium electrocatalysts at different concentrations (0.5, 1.0, 2.0, 3.0 and 4.0 mg mL À1) with fixed volume and mass ratio of reduced graphene oxide to palladium by microwave-assisted reduction method. Results showed that reduced graphene oxide-supported palladium synthesized at a concentration of 1.0 mg mL À1 gave the best methanol oxidation reactivity (405.37 mA mg À1) and largest electrochemical active surface area (83.57 m 2 g À1).

Microwave-Assisted Chemical Co-reduction of Pd Nanoparticles Anchored on Reduced Graphene Oxide with Different Loading Amounts

“…Due to the minimal quantity of metal loading on the support material, the crystal plane of Pd (200), (220), and (311) is missing. The diffractogram shows that increasing the amount of metal loading on the support material enhances the intensity of crystallinity while decreasing the crystallite size (CS), as reported by Ng et al [20]. The Scherrer equation is used to obtain these values, which are based on the Scherrer constant (K = 0.9) and the height (H) of the carbon nanostructure.…”

“…Furthermore, the peaks near 40° could be attributed to the (111) lattice planes of Pd's face-centered cubic crystalline structure (JCPDS No. 46-1043) [20]. Due to the minimal quantity of metal loading on the support material, the crystal plane of Pd (200), (220), and (311) is missing.…”

“…Kumar et al synthesized Pd/RGO by microwave-assisted heating reduction but using GO precursor produced from the modified Staudenmaier method [19]. Ng et al investigated the Pd/RGO using GO precursor synthesized by Tour technique, but through ultrasonic wave-assisted reduction heating type [20]. Furthermore, Li et al made Pd/RGO under microwave irradiation but used ethylene glycol as a reducing agent [21].…”

Strain gauge properties of Pd+-ion-implanted polymer

“…1,[7][8][9][13][14][15][16][17] In addition, it should be noted that metalcarbon-polymer nanocomposite films may exhibit interesting pressure-sensitive, catalytic, and gas sensing properties and are promising candidates for the realization of efficient flex, catalytic, and gas sensor devices. [18][19][20][21] In previous studies, we reported on low energy (60 keV) implantation of Cu þ and Ni þ ions in polycarbonate at fluence of 5 Â 10 16 cm À2 and 1 Â 10 17 cm À2 . 14,22 The electrical resistance was reduced considerably and a dependence on the deformation, that is, mechanical-induced strain, was observed proving the potential application of these nanocomposite surface films for the fabrication of strain gauge devices.…”

“…1,7 –9,13 –17 In addition, it should be noted that metal–carbon–polymer nanocomposite films may exhibit interesting pressure-sensitive, catalytic, and gas sensing properties and are promising candidates for the realization of efficient flex, catalytic, and gas sensor devices. 18 –21…”