•A method was proposed for quantitatively assessing the anti-poisoning performance of DFFC anode catalysts.•Graphene nanosheets (GNs) were demonstrated to be superior to CNTs in enhancing the anti-poisoning performance of Pt catalysts.•The superior anti-poisoning performance of GNs was explained in terms of stronger Pt-GNs in comparison with Pt/CNTs.Pt nanoparticles were prepared and deposited on carbon nanotubes (CNTs) and graphene nano-sheets (GNs) to obtain composites of Pt/CNTs and Pt/GNs, respectively. The morphologies of Pt particles for the two catalysts were observed using transmission electron microscopy (TEM). It showed that the average Pt sizes for Pt/CNTs and Pt/GNs are similar, meaning that the differences in the electrochemical performance of the two catalysts could be ascribed to support effects. Pt/CNTs and Pt/GNs were quantitatively compared by simultaneously analyzing their cyclic voltammetry (CV) and chronoamperometry (CA) data for formate oxidation, showing that Pt/GNs is evidently superior to Pt/CNTs in terms of anti-poisoning performance. CO stripping on the two catalysts indicated that the strength of CO adsorption on GNs-supported Pt is weaker than that for CNTs-supported Pt. The X-ray photoelectron spectroscopy (XPS) spectra showed that the binding energy of Pt 4f for Pt/GNs was higher than that for Pt/CNTs, indicating a stronger interaction of Pt with GNs than with CNTs and consequently a weaker adsorption of CO on GNs-supported Pt. We believe that this study can be used as a guide for future evaluation and screening of supports and/or anode catalysts for direct liquid fuel cells.

The understanding of the intrinsic properties of Pt and Pd is important for the rational design of catalysts for methanol and ethanol oxidation in alkaline media. In this paper, Pd catalysts, Pt catalysts and bimetallic PtPd catalysts supported on nitrogen-doped graphene are investigated. The cyclic voltammograms (CVs) for the bimetallic catalysts in 1 M KOH solution demonstrate the increasing surface composition of Pt versus Pd. The linear sweep voltammetry results show that the onset potential for OH formation on Pt is lower than on Pd, indicating that Pt has a higher affinity for OH than Pd. The CVs recorded for methanol and ethanol oxidation show that ethanol oxidation occurs at lower potentials, suggesting that ethanol is a more active fuel than methanol. Ethanol and methanol oxidation occurs at lower potentials on Pt than on Pd, revealing that Pt is intrinsically more active than Pd. Chronoamperometry results show that the rate of catalysts deactivation during ethanol oxidation is more severe compared with methanol oxidation, especially for catalysts with higher Pt content. The possible reason for the deactivation behaviors is presented and recommendations are given for future catalysts development.

•Compared with Pd-on-Au catalyst, Pt-on-Au catalyst exhibits higher activity for methanol oxidation in alkaline media but lower stability.•After modifying Pd surface with low amount of Pt, the activity for methanol oxidation get improved greatly.•The Pt deposited on Pd shows improved stability in comparison with the Pt deposited on Au substrate.•The total mass activity of Pt-on-Pd/CNTs for methanol oxidation is on a similar level to that of Pt/CNTs.For optimizing both the activity and stability of Pt-based catalysts for methanol oxidation reaction (MOR), several carbon nanotubes(CNTs)-supported catalysts such as Pt-on-Au/CNTs, Pd-on-Au/CNTs, Pt-on-Pd-on-Au/CNTs, Pt-on-Pd/CNTs, and Pd-on-Pt/CNTs catalysts are synthesized mainly through electrodeposition method. The activity and stability comparisons show that Pt-on-Au/CNTs has a higher MOR activity but a lower stability than Pd-on-Au/CNTs. To utilize the merits of the Pt and Pd components, Pt-on-Pd-on-Au/CNTs and Pt-on-Pd/CNTs catalysts are synthesized. The Pt-on-Pd-on-Au/CNTs and Pt-on-Pd/CNTs catalysts shows higher MOR activity than Pd-on-Au/CNTs and Pd/CNTs catalysts and higher stability than Pt-on-Au/CNTs, suggesting a synergistic interaction between Pt and Pd in catalyzing methanol oxidation reaction. Calculation shows that the total mass activity of Pt-on-Pd/CNTs with quite low Pt amount is on a similar level as that of Pt/CNTs for MOR oxidation, indicating the Pt-on-Pd catalyst could have promising potential as a low-Pt catalyst for MOR in alkaline media.By modifying Pd surface with Pt moieties, both the methanol oxidation activity and cycling stability get evidently improved.

Several Pt-on-Au/SnO2-CNTs catalysts with different Pt loadings are synthesized through site-selective electrodeposition for catalytic methanol oxidation reaction (MOR) in alkaline media. The catalysts are tested to exhibit extremely high Pt mass activity towards MOR, and the catalytic mechanism is proposed based on the synergetic effect between Pt and Au, in which the Pt entities provide Pt-OH for oxidation of alkoxide (CH3O−) while the Au surfaces provide adsorption sites for alkoxide. It is expected that this mechanism could be extended to developing high performance non-Pt catalysts for MOR in alkaline media.

•Au particles were formed through in situ reduction by Sn(OH)2 without using any surfactant or protecting agent.•Pt-on-Au structure was realized through site-selective electro-deposition.•The activity for HCOOH oxidation was quite high on Pt-on-Au/SnO2-CNTs with ultralow Pt content.In this paper, site-selective electrodeposition method is developed to prepare Pt-on-Au composite catalysts for HCOOH electrooxidation. In the synthesis, Au nanoparticles are prepared through reduction of NaAuCl4 by Sn(OH)2 supported on carbon nanotubes and after thermal transformation of Sn(OH)2 to SnO2, composite supports (Au/SnO2-CNTs) were obtained. By adjusting the potential of Au/SnO2-CNTs coated glassy carbon electrode, Pt entities are selectively deposited on Au particles to form SnO2-CNTs supported Pt-on-Au composite catalysts. The morphology and composition of the formed composite catalysts are characterized by instrument techniques such as X-ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM). The site-selectivity of Pt electrodeposition on Au is confirmed by electrochemical measurements. The composite catalysts are tested to have high Pt mass activity toward HCOOH oxidation reaction, demonstrating that the synthesis method developed in this paper has promising potential for developing high performance composite catalysts. The Pt content effect on the catalytic activity is also tested for catalyst performance optimization.Pt-on-Au composite catalysts were prepared through site-selective deposition with ultralow Pt content and high activity for HCOOH oxidation.

To enhance the cycling stability of Pt-based catalysts, the anti-corrosion property of support and the attachment of Pt with support should both get improved. For this purpose, a novel method is presented for in situ preparing Pt/SnO2. The structure of Pt/SnO2 is characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM), confirming the homogeneous deposition of Pt on SnO2. The high resolution TEM (HRTEM) shows the large interfaces between Pt and SnO2. The TEM photos recorded after accelerated durability tests with Pt/SnO2 show that the agglomeration and size increment of Pt particles is not severe, indicating the good stability of Pt/SnO2. The electrochemical active surface area (EAS) of Pt/SnO2 keeps increasing during the 1000 cycles of cyclic voltammetric (CV) sweeping in H2SO4, while the EAS decayed by 35% when mixing Pt/SnO2 with carbon nanotubes (CNTs), indicating the superior anti-corrosion property of SnO2 in contrast to CNTs.