•Hollow PdAu NCs were synthesized successfully by a successive reduction method.•The morphology, alloy degree and composition of the PdAu NCs can be well controlled.•Hollow PdAu NCs showed an enlarged ECSA and improved performance for CH3OH oxidation.Pd-based nanocatalysts (NCs) are the potential substitutes for the Pt-based NCs used in the direct methanol fuel cells (DMFCs) because of their lower cost and comparable catalytic performance. The catalytic performance of Pd-based NCs is highly connected with the morphology, composition and surface structure of the catalysts. Here, solid bimetallic PdAu and hollow PdAu NCs were synthesized by a successive reduction and co-reduction method, respectively, using P123 both as reducing reagent and protectant. Compared with the solid PdAu NCs and commercial Pd black catalyst, the hollow PdAu NCs exhibited enlarged electrochemical surface areas (ECSA), and showed an enhanced electrocatalytic activity and stability for methanol oxidation reaction (MOR) in alkaline solution. The excellent electrocatalytic performance is contributed to the unique hollow structure and alloy effects of the PdAu NCs.

A facile hydrothermal co-reduction strategy has been demonstrated to in situ synthesize PtPd bimetallic nanocatalysts supported on graphene nanosheets (PtPd/GNs) with triblock pluronic copolymer P123 as both reducer and stabilizer. The nucleation mode and morphology of the PtPd bimetallic nanoparticles were tuned simply by changing the molar ratio of Pt and Pd precursor. Defect investigation upon graphene nanosheets predicts that the synergetic role between P123 and PtPd may have great influence on generating defects in graphene, which inducing the in situ loading of PtPd bimetallic nanocatalysts at the defect sites. Compared with the common process to assemble nanocatalysts in pre-synthesized graphene substrate, the one-pot in situ assembly is more facile, cost-effective, and ensuring the effective control of the location and distribution of PtPd nanocatalysts. Both of the PtPd/GNs showed enhanced electrocatalytic performances towards methanol oxidation reaction (MOR) in acidic media, among which Pt1Pd1/GN (Pt/Pd molar ratio 1/1) exhibited the highest specific activity, mass activity, stability and best CO tolerance for MOR. The synthetic process without any seeds, templates, or toxic organic solvent and extra reducer, turns out a promising method to construct the Pt-based nanocatalysts for direct methanol fuel cells (DMFCs).PtPd/GNs anode nanocatalysts with different composition and morphology were fabricated by the in situ synthesis strategy with triblock copolymer P123 as reducer and stabilizer. Electrochemical test demonstrating that Pt1Pd1/GN exhibits the best anti-CO poisoning property and outstanding electrocatalytic performance for MOR.Download high-res image (145KB)Download full-size image

•Carbon nanospheres supported Pt nanocatalyst was prepared by a hydrothermal process.•The reduction of Pt nanoparticles and carbonization of sucrose was happened at the same time.•The catalysts exhibit an enhanced catalytic properties than that of commercial Pt/C catalyst.One kind carbon nanosphere supported Pt nanocatalyst (Pt/CN-1) has been successfully synthesized by a facile one-pot hydrothermal synthesis using sucrose as carbon source and triblock pluronic copolymer P123 as reducer and stabilizer. The obtained Pt nanoparticles with an average diameter at 3.0 nm were uniformly distributed on the surface of the carbon nanospheres. The other kind Pt/CN-2 was prepared through the same route just in absence of P123, the carbon sphere was used as both carrier and reducer due to its reducing nature. Characterization demonstrated that the Pt/CN-2 was aggregated seriously without the protection of P123. The electrocatalytic tests indicated that the Pt/CN-1 nanocatalyst exhibited an enhanced electrocatalytic activity toward methanol oxidation in acidic media than that of Pt/CN-2 catalyst and commercial Pt/C catalyst. The promising synthetic method provides a new avenue to prepare carbon spheres supported Pt-based nanocatalysts used for direct alcohols fuel cells (DAFCs).

•Highly monodispersed PtNi nanoparticles were synthesized by galvanic displacement reaction.•The formation of Pt nanocrystals was the foremost step because of its self-catalysis effect.•The PtNi nanoparticles show a superparamagnetic behavior with a TB about 8.0 K.In this paper, we report the controlled-synthesis of PtNi nanoparticles through galvanic displacement reaction and chemical reduction. The size, composition and morphology of the products are characterized by transmission electron microscopy (TEM), powder X-ray diffraction (XRD), energy dispersed X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) analyses. The structure and composition of the PtNi nanoparticles can be controlled by adjusting the synthetic conditions. The possible formation mechanism is obtained from the academic analysis and experimental studies. The results of the magnetic measurement illustrate that the PtNi nanoparticles show a superparamagnetic behavior with a blocking temperature (TB) about 8.0 K.

•Pt nanoparticles are synthesized by a facile one-pot hydrothermal synthesis for the first time.•The size of the Pt nanoparticles can be well controlled.•The Pt nanoparticles show a better electrochemical performance than commercial Pt/C catalyst.Pt nanoparticles are synthesized by a facile one-pot hydrothermal synthesis using one kind triblock Pluronic copolymers as reducer and stabilizer for the first time. The size of the Pt nanoparticles can be controlled through simply varying the reaction conditions. The morphology and structure of the Pt nanoparticles were well characterized by different techniques. The electrocatalytic test indicated that the obtained Pt nanoparticles exhibit a better electrocatalytic performance for methanol oxidation in acidic media compared to the commercial Pt/C catalyst. The results of this paper provide a promising approach to prepare Pt-based nanocatalysts for direct alcohols fuel cells (DAFCs).

Proton exchange membrane fuel cells (PEMFCs) have found a wide variety of commercial applications to resolve the energy crisis and environmental pollution. Then the design of novel Pt-based catalysts with enhancing catalytic activity, stability and low amount of Pt used are crucial. Pt-alloy catalysts, core-shell structured Pt-based catalysts, Pt-monolayer catalysts, Pt-based catalysts with high index, nanoporous Pt-based catalysts, hollow Pt-based nanocatalysts, and non-noble catalysts are the common way to resolve the question partly. Among these catalysts, hollow Pt-based catalysts used in PEMFCs have received much attention due to the increased surface area, low density, improved utilization of the unit Pt. In this review, we present a summarization of the progress made for synthesizing hollow Pt-based nanocatalysts using different techniques. Hollow pure Pt catalysts, Pt-based alloy catalysts and other correlative hollow precious nanomaterials are covered. Galvanic replacement method is still the most used and prospective method in this field. Finding facile and appropriate sacrificial template and controllable shape will be the key in the development of this method. We also summarize other different methods and discuss the foreground of these methods in the future. The emergent challenges and future developments of hollow Pt-based nanocatalysts are also discussed in this paper.Highlights► We present a review of the progress made for synthesizing hollow Pt-based nanocatalysts applied in PEMFCs. ► Hollow pure Pt catalysts, Pt-based alloy catalysts and other correlative hollow precious nanomaterials are reviewed. ► The methods used to synthesize hollow Pt-based nanocatalysts are summarized and compared. ► Galvanic replacement method is the most used and prospective method in this field. ► The emergent challenges and future developments of hollow Pt-based nanocatalysts are discussed.

High-dispersed Pd nanospheres were synthesized successfully by a facile and green method using polyoxypropylenepolyoxyethylene copolymer as reducer and stabilizer. The size and shape of the nanospheres can be well controlled through simply varying the reaction temperature. The morphology and structure of the nanospheres were characterized by Transmission electron microscopy (TEM), high-resolution TEM (HRTEM), X-ray powder diffraction (XRD). The electrocatalytic test indicated that the obtained Pd nanospheres exhibit more negative onset oxidation potential and much higher current density for methanol oxidation in alkaline media compared to the bulk Pd electrode. The results of this paper provides a promising approach to prepare Pd-based nanocatalysts for alkaline fuel cells.Highlights► High dispersed Pd nanospheres were synthesized with a facile and green method. ► The size and shape of the Pd nanospheres can be well controlled by simply varying the reaction temperature. ► The Pd nanospheres provided high catalytic performance for CH3OH oxidation in alkaline medium. ► We provided a facile and green method to prepare Pd-based nanocatalyst for alkaline fuel cells.

We report the synthesis and characterization of hollow PtNi nanospheres by chemical successive-reduction method. The results of X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) account for the alloy formation between Pt and Ni and electronic structure change of Pt in the alloy. The prepared nanospheres show a high activity and stability for electrocatalytic oxidation of methanol as compared to the commercial Pt/C catalyst and the co-reduced PtNi nanoparticles. The reasons of the high electrocatalytic activity of the hollow PtNi nanospheres were discussed.

One-dimensional (1D) CoPt nanorods were synthesized by a galvanic displacement reaction. The morphology of the nanomaterials was characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM) and X-ray powder diffraction (XRD). Energy-dispersive X-ray spectroscopy (EDS) analysis confirmed the coexistence of Co and Pt in the 1D nanorods. Studies of cyclic voltammetry (CV) demonstrated that the 1D CoPt nanorods exhibit a better electrocatalytic property for CO oxidation than that of bulk Pt electrode does. In situ electrochemical FTIRS illustrated, for the first time, that the 1D CoPt nanorods display abnormal infrared effects (AIREs), which was previously revealed mainly on 2D film nanomaterials.It has revealed, for the first time, that the 1D CoPt nanorods present abnormal infrared effects (AIREs). The substrate materials do not affect significantly the anomalous IR features.