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The microscopic surface plays a crucial impact on catalytic activity. Herein, the rough-surfaced chain-like palladium nanowires with many steps and inflections are successfully synthesized by a simple one-step reduction by sodium borohydride. The mechanism of bromide ions adsorbing and the oxygen etching to control the growth of chain-like nanowires is investigated. Furthermore, the effect of the pH values of system on the microscopic surface of palladium nanowires, especially on the roughness, is discussed in depth. The nanowires prepared at pH = 11 exhibit rougher surfaces with a diameter of 10–11 nm, and the relevant catalyst has higher electrochemical active area and excellent electrocatalytic performance for oxygen reduction reaction (ORR). Its half-wave potential in 0.5 mol L−1 H2SO4 solution is 80 mV more positive than Pd nanoparticles, slightly negative than Pt/C and the half-wave potential in 0.1 mol L−1 KOH solution is 50 mV more positive than the Pd nanoparticles, and is almost the same as Pt/C. The research result reported here will have important implications for designing palladium-based catalysts to increase their electrocatalytic ability.

We report an innovative strategy to prepare the porous N-doped graphene aerogel with an open structure and abundant defects by hydrothermal self-assembly of zeolitic imidazolate framework (ZIF)-8 and graphene oxide. The in-situ hydrothermal restructuring of ZIF-8 on graphene sheets plays a key role in the synthesis of the open structure and the uniform N-doping. The dissolution and restructuring of ZIF-8 on graphene oxide obviously suppress the stacking and reunion of graphene sheets to obtain the continuous macroporous structure. Moreover, the introduction of N and Zn creates the abundant N-doped sites and microporous structure. Its unique structure and composition improve the accessible surface area, the mass transfer diffusion, the dispersion and electronic structure of Pt nanoparticles, further resulting in the high catalytic performance of Pt-based catalyst for methanol oxidation reaction (MOR). Its MOR activity is about 1.8 times of commercial Pt/C, and its long cycling durability is improved by about 18.7% compared with commercial Pt/C. This work renders a promising method by utilizing ZIF-8 derivatives to synthesize the excellent N-doped carbon materials for electrochemical applications.

Titanium nitride (TiN) as catalyst support has a very good application prospect due to its chemical stability, electrical conductivity and the metal-support interaction. But it is difficult to synthesize nano-TiN with the uniform dispersion by a simple method. This paper proposes a novel and easy strategy to address the problem. The mesoporous g-C3N4 has been synthesized and used as both nano-reactor and nitrogen source for the synthesis of nano-TiN evenly dispersed onto Vulcan XC-72. The uniform dispersion of nano-TiN is conducive to depositing and anchoring the PtRu nanoparticles, further increasing the long-time catalytic durability. Moreover, the electronic effect of TiN obviously improves the catalytic activity and the adsorbed CO tolerance ability of PtRu catalysts for methanol oxidation. Compared with the PtRu/C catalyst, the activity of PtRu/C-TiN for methanol oxidation has been increased by 47.3%. Meanwhile, its durability has been improved by 6.5% after 1000 cycles. In addition, this novel and easy method can be generalized to the synthesis of other nano-size nitrides. The applications of nano-size nitrides modified carbon black in other fields are also expected in the future.

Pd-WO3/C ternary hybrid was designed as a high-efficient catalyst towards formic acid electrooxidation. WO3/C hybrids were first prepared with two different synthesis order, and then used as the supports to synthesize two kinds of Pd-WO3/C catalysts by a quick and facile microwave-assisted ethylene glycol method. Compared with Pd/C, the catalytic performances of two Pd-WO3/C catalysts towards formic acid electrooxidation are significantly enhanced. We elected the better synthesis order and optimized the best proportion of WO3 and C in the hybrid catalyst. When the mass content of WO3 is 20% of the mass of the support, Pd nanoparticles with narrower particle size distribution are more uniformly dispersed on the surface of WO3/C support than the other counterparts, resulting in the highest performance in terms of activity and stability towards formic acid oxidation among all the samples. The reasons for the performance improvement may be: first, Pd nanoparticles in Pd-WO3/C catalysts are of small size and evenly distributed; second, there may be the catalyst-support interaction between Pd and WO3, substantially improving the catalytic capability of Pd-WO3/C catalysts; finally, the hydrogen spillover effect produced by WO3 significantly expedites the dehydrogenation of formic acid on the surface of Pd-WO3/C.

A novel hybrid composite RGO-CeO 2 NWS with the nanowire-sheet structure was synthesized by a facile hydrothermal process using ethanol/water as the solvent without any organic additives. The graphene oxide proceeds to reduce to graphene and chemical bonds form between graphene oxide and CeO 2 NWS . Pt-based catalysts with the RGO-CeO 2 NWS composite as the support were then prepared by a microwave-assisted polyol process. The resultant catalysts were characterized by X-ray diffraction, Raman spectroscopy, Scanning tunneling microscopy, X-ray photoelectron spectroscopy, High resolution transmission electron microscopy and electrochemical tests. The results show that the hybrid Pt/RGO 4 -CeO 2 NWS exhibits the best catalytic activity and the increased catalytic efficiency of Pt in the hybrid catalysts is evidence that CeO 2 NWS are anchored onto the chemical defects in the wrinkles and edges of the graphene surface. This avoids the restacking of graphene oxide, thus hindering the Pt nanoparticles embedded in folding and increasing the exposed active sites. The changed valence state from Ce 4+ to Ce 3+ in CeO 2 NWS will introduce oxygen vacancies and thus promote the tolerance of intermediate species in methanol oxidation.

Molybdenum trioxide (MoO3) has been considered an advanced auxiliary support for Pt nanoparticle anchorage due to its excellent activity and stability. Nevertheless, its non-conductivity property still impedes its applications in electrocatalytic fields. Thus, the MoO3 and carbon composite of a nanostructure is synthesized through sintering process and served as an efficient co-support for Pt-based anode catalyst in this paper. The electrochemical measurements demonstrate that Pt/MoO3-C catalyst shows higher catalytic activity and stability than the as-prepared Pt/C. Significantly, it exhibits 1.95 times higher activity and 2.36 times better durability for methanol oxidation when compared with commercial Pt/C. The remarkably enhanced performance of this novel Pt/MoO3-C catalyst for methanol electrooxidation can be ascribed to the abundant Pt nucleation active sites, uniformly dispersed Pt nanoparticles and the strong metal-support interaction between Pt and MoO3-C. These outstanding properties suggest Pt/MoO3-C a promising catalyst for practical application of fuel cell.

Carbon black (CB), multiwalled carbon nanotubes (MWNTs), reduced graphene oxide (rGO) are used as the cathode catalyst supports to investigate the effect on direct methanol fuel cell (DMFC) performance by using rotating disk electrode and fuel cell testing. The results of linear sweep voltammetry (LSV) and cyclic voltammetry (CV) show that the electrocatalytic activity sequence for oxygen reduction reaction (ORR) is Pt/rGO > Pt/MWNTs > Pt/C catalysts. The single cell tests results show that the maximum power densities of DMFC with Pt/C, Pt/MWNTs and Pt/rGO cathode catalysts are 74.0, 74.2 and 3.3 mW cm −2 , respectively. The experimental results indicate that the performance of DMFC is substantially influenced by the structures of cathode catalyst supports. The significant differences in DMFCs performance are due to the compression ratios and hydrophilic/hydrophobic properties of catalyst layers with different structures of carbon supports, which strongly affect electrochemical active sites and mass transport in cathode catalyst layers. Long-term testing of DMFCs indicates that Pt/MWNTs exhibits superior stability. Considering the factors of the power and lifetime comprehensively, MWNTs is optimal candidate among the three investigated carbon supports.

We report on a mixture of antimony doped tin oxide (ATO) and carbon nanotubes as a novel support of Pd catalyst (Pd/ATO-CNTs) with the aims to enhance electron and proton conductivity of hybrid support, and catalytic activity and stability for formic acid electrooxidation. The surface content, morphology and structure of the as-prepared Pd/ATO-CNTs catalysts with different CNTs contents have been characterized by X-ray diffraction (XRD), energy dispersive analysis of X-ray (EDAX), inductively coupled plasma-optical emission spectroscopy (ICP-OES), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM) and high angle annular dark field STEM (HAADF-STEM), respectively. The electrocatalytic properties of the samples for formic acid electrooxidation reaction are investigated by cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy. The results show that the activity and stability of Pd/ATO-CNTs catalyst is obviously higher than that of Pd/CNTs catalyst for formic acid electrooxidation due to unique physical and chemical properties of ATO and metal-support interaction between Pd nanoparticles and ATO. Moreover, the Pd/ATO-CNTs10 (CNTs content is 10 wt.% of ATO-CNTs support mass) with smaller Pd particle size and narrower size distribution on surface of the hybrid support exhibits the best performance for formic acid electrooxidation among all the samples.

In this work, Pd nanoparticles supported on TiC–C and TiO2–C as novel and efficient supports for formic acid electrooxidation are investigated. The Pd/TiC–C and Pd/TiO2–C catalysts have been synthesized by microwave-assisted polyol process. The Pd nanoparticles in the Pd/TiC–C and Pd/TiO2–C catalysts are found to disperse more uniformly and have smaller sizes on the TiC–C and TiO2–C supports than that on carbon support alone. The addition of titanium compounds (TiC and TiO2) significantly increases catalytic activity and stability of Pd for formic acid electrooxidation because of outstanding oxidation and acid corrosion resistance of titanium compounds (TiC and TiO2), and metal-support interaction between Pd nanoparticles and titanium compound (TiC or TiO2). The Pd/TiC–C catalyst displays the best performance among all the samples. The effect of TiC:C mass ratio on the catalytic activity is also investigated. It is found that the maximal catalytic activity and stability for formic acid electrooxidation is observed at the Pd/TiC–C catalyst with TiC:C mass ratio of 1:2.

Effects of different carbon sources and carbonized carbon contents during carbon riveting process (CRP) on the stability of Pt/C catalysts have been systematically studied. X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), cyclic voltammograms (CV), and accelerated potential cycling tests (APCT) have been carried out to characterize the catalysts. Experimental results show that the carbon riveted Pt/C catalysts treated by different carbon sources have different stability due to different properties of Pt and carbon after the CRP. The best carbon source for the carbon riveted Pt/C catalysts is glucose and is ascribed to the most content of Pt (0) and sp 3 -C after the CRP. APCT results indicate that the stability of Pt/C catalysts carbon-riveted by glucose exhibits the increasing trend with the increase of carbonized carbon contents because of increasing anchor effect to Pt nanoparticles. However, a larger carbon content from the carbonization of glucose can also reduce the electrochemically active specific surface areas ( ESA ) of the carbon riveted Pt/C catalyst by covering the active sites of Pt nanoparticles. Taking into account both activity and stability of the carbon riveted Pt/C catalysts, 6% carbon from the carbonization of glucose is the optimized content.

In the present study, Ir nanoparticles are deposited on the surface of IrO2 nanoparticles with microwave-assisted polyol process. Then the obtained Ir–IrO2 nanocomposite is used as a support to prepare Pt/Ir–IrO2 nanocomposite, which has been demonstrated as an excellent bifunctional oxygen catalyst for unitized regenerative fuel cell. X-ray diffraction (XRD), X-ray photoelectron spectra (XPS), and transmission electron microscopy (TEM) characterizations indicate that ultrafine Ir nanoparticles (NPs) are uniformly dispersed on the surface of IrO2, which provides a conductive network for Pt NPs. Electrocatalytic activity and stability of Pt/Ir–IrO2 are investigated using cyclic voltammetry (CV), linear sweep voltammetry (LSV), and potential cycling techniques on rotating disc electrode (RDE). Results show that the electrocatalytic activity of Pt/Ir–IrO2 towards oxygen reduction reaction (ORR) is much higher than that of Pt/IrO2, and the electrocatalytic activity of Pt/Ir–IrO2 towards oxygen evolution reaction (OER) can be comparable to that of Pt/IrO2. Life tests reveal that Pt/Ir–IrO2 exhibits excellent stability. The enhanced ORR activity of Pt/Ir–IrO2 catalyst can be attributed to the improvement in electronic conductivity, and its higher stability can be assigned to the special structure, in which the interaction between Pt NPs and Ir NPs prevents Pt from agglomerating.

In this study, we present the novel membrane electrode assembly (MEA) for direct dimethyl ether fuel cell (DDFC). The anode gas diffusion layer (AGDL) of the MEA is fabricated with mesoporous carbon to facilitate the anode mass transport and enhance the performance of DDFC. The major differences of mesoporous carbon AGDL (MAGDL) and XC-72 AGDL (XAGDL) are the BET surface, the pore volume, and the pore size distribution. The MAGDL provides many more passageways for mass transport than XAGDL. The MAGDL possesses hydrophilic small and hydrophobic middle pores, which benefit the liquid and gas transport simultaneously. The maximum power density of DDFC increases by 20% when using MAGDL instead of XAGDL at 60 °C. The electrochemical measurements indicate that the promotion of the anode two-phase mass transport is the main reason for the significant improvement of DDFC performance.

In the present paper, a proton exchange membrane fuel cell (PEMFC) using 20 wt.% Pt/C as anode and cathode catalysts, and ambient air at cathode was operated at a current density of 160 mA cm−2 for 2250 h. The measurement results showed that electrochemically active specific areas (SEAS) of both electrode catalysts calculated from CV curves after test evidently decreased. The decay rate of SEAS of anode catalyst was much lower than that of cathode one. X-ray diffraction (XRD), energy dispersive analysis of X-ray (EDAX), and X-ray photoelectron spectrometry (XPS) were employed to characterize the anode and cathode catalysts before and after the life test. The XRD results showed that their crystal structures were perfect, the particle size of new Pt/C catalyst was about 2.5 nm, however, the particle sizes of anode and cathode ones markedly increased, and were about 4.9 nm and 6.8 nm, respectively, after the life test. Furthermore, the size of cathode catalyst was much bigger than that of anode one after test. The Pt element was also found in Nafion® film as shown in EDAX result. The XPS results presented that the content of Pt oxidation states in cathode was much more than that in anode, and the corrosion of carbon support in cathode was also more severe than that in anode after the life test. The experimental results indicated that the increase of particle size of Pt/C catalyst was illustrated with the dissolution/redeposition mechanism. The degradation of cathode catalyst for oxygen electroreduction was one of the main factors affecting on the performance decay of PEMFC.