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Proton exchange membrane fuel cells (PEMFCs) suffer extreme CO poisoning even at PPM level (

BACKGROUND: Data are limited on the economic burden of seasonal influenza in China. We estimated the cost due to influenza illness among children < 5-year-old in Suzhou, China. METHODS: This study adopted a societal perspective to estimate direct medical cost, direct non-medical cost, and indirect cost related to lost productivity. Data to calculate costs and rates of three influenza illness outcomes (non-medically attended, outpatient and hospitalization) were collected from prospective community-based cohort studies and hospital-based enhanced laboratory-confirmed influenza surveillance in Suzhou during the 2011/12 to 2016/17 influenza seasons. We used mean cost-per-episode, annual incidence rates of episodes of each outcome, and annual population size to estimate the total annual economic burden of influenza illnesses among children < 5-year-old for Suzhou. All costs were reported in 2017 U.S. dollars. RESULTS: The mean cost-per-episode (standard deviation) was $9.92 (13.26) for non-medically attended influenza, $161.05 (176.98) for influenza outpatient illnesses, and $1425.95 (603.59) for influenza hospitalizations. By applying the annual incidence rates to the population size, we estimated an annual total of 4,919 episodes of non-medically attended influenza, 21,994 influenza outpatient, and 2,633 influenza hospitalization. Total annual economic burden of influenza to society among children < 5-year-old in Suzhou was $7.37 (95% confidence interval, 6.9–7.8) million, with estimated costs for non-medically attended influenza of $49,000 (46,000–52,000), influenza outpatients $3.5 (3.3–3.8) million, and influenza hospitalizations $3.8 (3.6–3.9) million. Among outpatients, the indirect cost was 36.3% ($1.3 million) of total economic burden, accounting for 21,994 days of lost productivity annually. Among inpatients, the indirect cost was 22.1% ($829,000), accounting for 18,431 days of lost productivity annually. CONCLUSIONS: Our findings show that influenza in children < 5-year-oldcauses substantial societal economic burden in Suzhou, China. Assessing the potential economic benefit of increasing influenza vaccination coverage in this population is warranted.

Metal-nitrogen-carbon materials (M-N-C) are non-noble-metal-based alternatives to platinum-based catalysts and have attracted tremendous attention due to their low-cost, high abundance, and efficient catalytic performance towards the oxygen reduction reaction (ORR). Among them, Fe-based materials show remarkable ORR activity, but they are limited by low selectivity and low stability. To address these issues, herein, we have synthesized FeCu-based M-N-C catalysts, inspired by the bimetal center of cytochrome c oxidase (CcO). In acidic media, the selectivity was notably improved compared with Fe-based materials, with peroxide yields less than 1.2% (

Formic acid dehydrogenation (FAD) offers an ideal route for hydrogen production, where searching for efficient and selective catalysts is imperative. However, the current state-of-the-art Pd-based metallic catalysts severely suffer from low catalytic efficiency and self-poisoning, owning to the FA dehydration side reaction. In this work, we design PANI-Pd/C composite catalysts via interfacial microenvironment regulation technique. The as-prepared 0.01-PANI-Pd/C catalyst exhibits high turnover frequency (TOF, 5654 h−1) and excellent resistance to CO poisoning. The merit of polyaniline can be ascribed to: a) construction of abundant Pd–PdO interfaces; b) capturing H+ and accelerating the formation of the reactive species.

Hydrogen production from formic acid decomposition (FAD) is a promising means of hydrogen energy storage and utilization in fuel cells. Development of efficient catalysts for dehydrogenation of formic acid is a challenging topic. The surface chemical and electronic structure of the active catalysis components is important in formic acid decomposition at room-temperature. Here, the pyrdinic-nitrogen doped catalysts from hyperbranched polyamide were prepared via in situ polymerization reaction process by using activated carbon as a support. Because of the introduction of the polymer, the particles of the catalysts were stabilized, and the average particle diameter was only 1.64 nm. Under mild conditions, the catalysts activities were evaluated for FAD. The optimized Pd-N30/C catalyst exhibited high performance achieving almost full conversion, with a turnover frequency of 3481 h−1 at 30 °C.

Well-dispersed palladium nanoparticles (NPs) anchored on a porous N-doped carbon is prepared by wet chemical method, using metal organic frameworks (ZIF-8) as a precursor to derive the porous N-doped carbon support. Benefitting from the N-doping and the porous structure of the carbon materials, the final Pd NPs are in high dispersion and exhibit reduced particle sizes, with electronic structure and chemical status tuned to favor the formic acid decomposition (FAD). The prepared Pd/CZIF-8-950 catalysts show enhanced catalytic performance and selectivity for FAD, the turnover of frequency (TOF) and the mass activity up to 1166 h−1 and 11.01 mol H2 g−1 pd h−1 were obtained at 30 °C. This work provides an effective and easy way for synthesis the Pd-based catalyst, which has enormous application prospects for the next generation hydrogen energy preparation and storage.

Rational regulation on pore structure and active site density plays critical roles in enhancing the performance of Fe-N-C catalysts. As the microporous structure of the carbon substrate is generally regarded as the active site hosts, its hostility to electron/mass transfer could lead to the incomplete fulfillment of the catalytic activity. Besides, the formation of inactive metallic Fe particles during the conventional catalyst synthesis could also decrease the active site density and complicate the identification of real active site. Herein, we developed a facial hydrogen etching methodology to yield single site Fe-N-C catalysts featured with micro/mesoporous hierarchical structure. The hydrogen concentration in pyrolysis process was designated to effectively regulate the pore structure and active site density of the resulted catalysts. The optimized sample achieves excellent ORR catalytic performance with an ultralow H2O2 yield (1%) and superb stability over 10,000 cycles. Our finding provides new thoughts for the rational design of hierarchically porous carbon-based materials and highly promising non-precious metal ORR catalysts.

The anode gas diffusion layer plays an important role on mass transport. By adjusting the assembly pressure, the structure of gas diffusion layer can be controlled to investigate the two-phase behavior. The electrochemical test indicates that increasing the assembly pressure causes increase in mass transport resistance. Inhomogeneous compression of gas diffusion layer is observed by three-dimensional imaging technology. Based on the experimental data, a two-phase model is established. The simulated results show that the increment of surface roughness and the reduction of porosity, both derived from compression of gas diffusion layer, exacerbate CO2 blockage of the cell. Lowering polytetrafluoroethylene content of anode gas diffusion layer alleviates CO2 blockage by reducing the difference of surface tension between liquid-solid and gas-solid interface as well as the negative capillary pressure of gas diffusion layer. Thus, the peak power density climbs from 60.61 to 49.94 mW cm−2 to 74.79 and 70.47 mW cm−2 at the assembly pressure of 1.00 and 2.00 MPa, respectively. The optimal assembly pressure locates at where good contact between membrane electrode assembly and bipolar plate is achieved, with the least gas diffusion layer deformation possible.

The electrochemical methanol oxidation reaction (MOR) is of paramount importance for direct methanol fuel cell (DMFC) application, where efficient catalysts are required to facilitate the complicated multiple charge transfer process. The catalyst support not only determines the dispersion status of the catalysts particles, but also exerts great influence on the electronic structure of the catalysts, thereby altering its intrinsic activity. Herein, we demonstrated that nitrogen atoms, assisted by the pre-treatment of carbon matrix with oxidants, can be easily doped into carbon nanotubes at low temperature. The obtained nitrogen-doped carbon nanotubes can effectively improve the dispersion of the supported platinum nanoparticles and facilitate the MOR by modifying the electronic structure of platinum atoms, through catalyst-support interaction.

Energy management is essential for improving the fuel economy of plug-in hybrid electric vehicles (PHEVs). Some existing efforts have focused on optimizing fuel consumption and battery degradation, but without adequately considering the onboard electric motor's (EM) thermal dynamics. To address this research gap, this paper proposes a predictive energy management strategy considering EM thermal control. Specifically, we make three main contributions that distinguish our study from the existing studies. First, we design four velocity predictors based on the artificial neural network (ANN) and examine their prediction accuracy and computational efficiency. Second, we present a Pontryagin's Minimum Principle-based model predictive control (PMP-MPC) framework that includes EM thermal dynamics. The framework minimizes the operating costs while ensuring that the EM temperature is less than the limit value. Finally, we analyze and compare the effects of different reference temperature thresholds and preview horizon sizes on the fuel economy and EM temperature. The results demonstrate that the proposed PMP-MPC approach can effectively control the EM temperature rise and realize online applications with high computational efficiency.

Reducing the cost of Pt-base ORR electrocatalysts is highly desirable for fuel-cell commercialization. One of the effective strategies is increasing Pt utilization by forming structures with accessible surface. Another is increasing intrinsic activity of Pt sites by redesigning electronic structure. Here, we developed a hollow Pt sphere with a compressive Pt surface on carbonized resorcinol–formaldehyde resin. The special hollow structure with accessible channel endows the nanoparticles with high Pt atom utilization. And the compressive Pt-rich shell gives rise to the enhanced intrinsic activity via tuning Pt d-band electronic structure. As a result, the PtFe(0.9)-C catalysts with an ultralow Pt loading of 0.86% achieved a 2.3 and 2.7 times enhancement in mass activity and specific activity relative to state-of-the-art Pt/C-20% catalysts.

Pyrolyzed Fe-NX/C materials derived from Fe-doped ZIF-8 are recently emerged as promising alternatives to noble metal platinum-based catalysts towards oxygen reduction reaction (ORR) and elucidating the dependacne of Fe source on the active site structure and final ORR performance is highly desirbale for further development of these materials. Here, we designed and synthesized a series of Fe-N-C catalysts using ZIF-8 and various iron salts (Fe(acac)3, FeCl3, Fe(NO3)3) as precusors. We found that the iron precursors, mainly the molecular size, hydrolysis extent, do play a major role in determining the final morphology of Fe, namely forming the Fe-Nx coordination or Fe3C nanoparticles, as well as the site density, therefore, significantly affecting the ORR activity. Among the three iron sources, Fe(acac)3 is most advantageous to the preferential formation of single-atom Fe-Nx active sites and the derived catalyst demonstrated best ORR performance.

Direct methanol fuel cells (DMFCs) are very promising power source for stationary and portable miniature electric appliances due to its high efficiency and low emissions of pollutants. As the key material, catalysts for both cathode and anode face several problems which hinder the commercialization of DMFCs. In this review, we mainly focus on anode catalysts of DMFCs. The process and mechanism of methanol electrooxidation on Pt and Pt-based catalysts in acidic medium have been introduced. The influences of size effect and morphology on electrocatalytic activity are discussed though whether there is a size effect in MOR catalyst is under debate. Besides, the non Pt catalysts are also listed to emphasize though Pt is still deemed as the indispensable element in anode catalyst of DMFCs in acidic medium. Different catalyst systems are compared to illustrate the level of research at present. Some debates need to be verified with experimental evidences.

Metal-free electrocatalysts have eluded widespread adoption in polymer electrolyte membrane fuel cells due to their far inferior catalytic activity than most non-precious metal-N-C counterparts (M-Nx-C) for oxygen reduction reaction (ORR), despite their distinct advantages over the M-Nx-C catalysts, including lower cost and higher durability. Herein, we develop a rational bottom-up engineering strategy to improve the ORR performance of a metal-free catalyst by constructing a three-dimensional ultrathin N, P dual-doped carbon nanosheet. The resultant catalyst represents unprecedented ORR performance with an onset potential of 0.91 V, half-wave potential of 0.79 V. Impressively, a maximum power output at 579 mW cm−2 is generated in the fuel cell test, the best among reported metal-free catalysts and outperforms most of the M-Nx-C catalysts. The outstanding catalytic performance results from the highly active polarized carbon sites which are induced by selective graphitic nitrogen and phosphorous dual doping. Our findings provide new directions for the exploration of alternatives to Pt and bring a renew interests in the metal-free catalysts.

Modified micro-MEA is developed and employed to evaluate the electrocatalytic performance of Pt/C and PtRu/C. Firstly, micro-MEA displays better electrocatalytic performance including lower onset potential and higher peak current in comparison with traditional glass carbon electrode (GCE), because that micro-MEA effectively avoids interferences from specific adsorption of bisulfate ions on platinum and improve mass transfer of the fuel. Then, evaluation of the effect of Nafion content and methanol concentration on the MOR performance of Pt/C and PtRu/C is carried out. The results reveal that Pt/C shows optimized performance with 30 wt% Nafion in low concentration methanol (0.5–1 M), while PtRu/C displays best performance when Nafion content was adjusted to 10 wt% because of easier formation of complete proton pathway and triple-phase boundary (TPB) compared to Pt/C, indicating that the optimized in-situ work condition is significantly different for different electrocatalysts. Our work in this paper indicates that micro-MEA as a kind of in-situ characterization method can give more precise electrocatalytic performance of electrocatalysts close to work condition and facilitate their sieving and further application in DMFC.

It has been widely reported that natural gas dual-fuel combustion (DFC) can achieve much lower soot emissions in contrast to conventional diesel combustion (CDC). Thus, using low-pressure direct injection (LPDI) systems could be an alternative for current high-pressure common rail injection systems, which would significantly reduce the system cost. The present study aimed at exploring the feasibility of LPDI (low to 200 bar) for natural gas DFC in combination of the advanced low temperature combustion technology. The comparative study between natural gas DFC and CDC were carried out. For natural gas DFC, larger advanced injection timing was used to realize low temperature combustion and achieve long ignition delay in order to counteract the negative impact of relatively poor atomization quality caused by the low injection pressure. At DFC mode, higher CO and THC emissions were observed compared to CDC in the cases without EGR. However, DFC was much less sensitive to EGR rate and injection pressure. Natural gas DFC could break the trade-off between NOx and soot emissions, which could achieve low soot and NOx emissions (lower than Europe VI standard: 0.4 g/kW·h) simultaneously at the 42% EGR rate and the 200 bar injection pressure.

Formic acid, as the simplest carboxylic acid which can be obtained as an industrial by-product, is colorless, low toxicity, and easy to transport and storage at room temperature. Recently, Formic acid has aroused wide-spread interest as a promising material for hydrogen storage. Compared to other organic small molecules, the temperature for formic acid decomposition to produce hydrogen is lower, resulting in less CO toxicant species. Lots of catalysts on both homogeneous catalysts and heterogeneous were reported for the decomposition of formic acid to yield hydrogen and carbon dioxide at mild condition. In this paper, the recent development of mechanism and the material study for both homogeneous catalysts and heterogeneous catalysts are reviewed in detail.

Herein, a novel binuclear active site structure, Co2NxCy, is intentionally designed and successfully fabricated to efficiently catalyze the oxygen reduction reaction (ORR), which is achieved by precisely controlling the atomic scale structure of bimetal-organic frameworks before pyrolysis. Through discovering a two-atom site with Co-Co distance at 2.1–2.2 A from aberration-corrected scanning transmission electron microscopy (STEM), as well as a novel shortened Co-Co path (2.12 A) from the X-ray absorption spectroscopy, we for the first time identified the binuclear Co2NX site in the pyrolyzed catalyst. Combined with density functional theory (DFT) calculation, the structure is further confirmed as Co2N5. Excitingly, the Co2N5 site performs approximately 12 times higher activity than the conventional CoN4 site and the corresponding catalyst shows unprecedented catalytic activity in acidic electrolyte with half-wave potential of 0.79 V, approaching the commercial Pt/C catalyst and presenting the best one among the Co-N-C catalysts. Theoretical density functional theory calculations reveal that the novel binuclear site exhibits considerably reduced thermodynamic barrier towards ORR, thus contributing to the much higher intrinsic activity. Our finding opens up a new path to design efficient M-Nx/C catalysts, thus pushing the fuel cell industry field one step ahead.

Recent years have seen increased interest in dedicated exhaust gas recirculation (D-EGR) systems integrated with reciprocating engines. By dedicating one cylinder to operate at fuel rich conditions, hydrogen is generated for use in the remaining cylinders to optimize combustion and mitigate pollutant emissions. In this study, experiments were performed using a rapid compression machine (RCM) to investigate the effects of hydrogen and carbon monoxide on methane ignition and flame propagation at fuel rich and stoichiometric conditions relevant to D-EGR engines. The experiments were conducted over a range of temperatures (T = 860–1080 K) and equivalence ratios (ϕ = 1.0–1.5) and at a pressure of P = 20 atm. The results showed hydrogen addition had little effect on ignition delay time at lower temperatures (T 950 K). Carbon monoxide had little effect on ignition delay times at all conditions studied. Combustion products were acquired using a fast sampling system and analyzed using gas chromatography. The results showed at ϕ = 1.4 the hydrogen mole fraction was a maximum of 8.0% of the products of rich combustion which was consistent with predictions based on chemical equilibrium calculations and model simulation results. High speed images were taken to quantify the impact of equivalence ratio on flame speed for spark-ignited mixtures in RCM experiments using mixtures similar to those expected in the D-EGR and stoichiometric cylinders. The results indicated the H2 in the D-EGR promoted the combustion process in the stoichiometric cylinder, increasing flame speed and decreasing combustion duration. Specifically, when the equivalence ratio in the D-EGR cylinder was ϕ = 1.3, the flame speed increased by about 40% compared with ϕ = 1.0. However, higher equivalence ratios reduced the flame speed and thus adversely affected combustion in the D-EGR cylinder. The results indicate stability and effectiveness of the combustion in the D-EGR cylinder could be a major concern for D-EGR natural gas engines, and optimizing the equivalence ratio of the D-EGR cylinder is critical for D-EGR to enhance combustion performance in the engine overall.

Dedicated exhaust gas recirculation (D-EGR) is to generate H 2 via fuel-rich combustion and viewed as a potential technique to meet future emission regulations without further after-treatment. In this study, firstly, the H 2 /CO formation through fuel-rich combustion in a single-cylinder natural gas spark ignition engine was quantitatively characterized by gas chromatography. Then, the effect of H 2 /CO addition on stoichiometric natural gas combustion performance and emission characteristics at 15% and 20% EGR levels was investigated. Finally, reaction path analysis and the brute-force sensitivity of ignition delay were conducted to evaluate the effect of H 2 addition on reaction process. The yields of H 2 and CO approximately linearly increased from ∼2% to ∼10% as the equivalence ratio varied from 1.1 to 1.5. The H 2 /CO addition accelerated the flame speed of mixture and significantly shortened the combustion duration, significantly improving the indicated thermal efficiency and the total unburned hydrocarbon with the acceptable penalty of increased NOx and CO emissions. Numerical results revealed that OH + H 2 = H + H 2 O and H + O 2 = O + OH were the most sensitive reactions with the presence of H 2 . This study delivered a quantitative basis for the optimization of D-EGR fueling strategies in natural gas engines.

Summary Fuel cells are promising energy conversion devices which do not require the electrical charging process in comparison with a traditional secondary battery. Polymer electrolyte membrane fuel cells (PEMFCs), including direct methanol fuel cells (DMFCs), are the key technologies in the future due to the high energy conversion efficiency, low emission, and high energy density. DMFCs are promising to be used in mobile electronic devices (power under a few hundred watts) due to the easily and safely transport feature of methanol. Platinum is regarded as the most effective catalyst for the methanol oxidation reaction (MOR). However, the poor performance and the high cost of Pt block the DMFC large-scale applications. The essential method to overcome this shortfall is to develop effective modified-Pt, low-Pt and non-Pt catalysts. This short review paper will focus on the solution to improve the performance of anode MOR in the past 2 years. The structure of this article displays in Figure 1.

Here we report a novel Pt catalysts support material, i.e. the resorcinol-formaldehyde (RF) resin derived carbon embedded titanium dioxide (TiO2@RFC) with well-tuned pore structure and excellent electrical conductivity. The material is synthesized by in-situ polymerization of RF gel with porous texture at the presence of TiO2, followed by high temperature pyrolysis. The Pt nanoparticles (NPs) are deposited on the composites carbon material to form the methanol electrooxidation catalysts in direct methanol fuel cells (DMFCs). The optimized Pt/TiO2@RFC catalyst possesses a comparably high electrochemical active surface area of 71.6 m2 g−1 (68.3 m2 g−1 for commercial Pt/C), attributed to its smaller Pt NPs size (2.62 nm) than the commercial Pt/C (2.84 nm). The maximum current densities during methanol electrooxidation reaction (MOR) for the optimized Pt/TiO2@RFC (822.2 mA mg−1) is 1.4 times higher than commercial Pt/C (344.4 mA mg−1). Remarkably, after accelerated degradation test through 2000 cyclic voltammetry, the mass activity for Pt/TiO2@RFC was well maintained at 689.5 mA mg−1, 3.3 times that of the commercial Pt/C (206.1 mA mg−1, decline of 40.17%). The sustainable electro-catalytic stability of Pt/TiO2@RFC for MOR may be ascribed to the unique structure and composition of the supported material, which provides a strong metal-support interaction and significantly suppresses the degradation processes in the long-term cyclic measurements.

Compared to natural gas spark-ignition (SI) combustion, dual-fuel (DF) mode could achieve higher indicated thermal efficiency (ITE). The major disadvantages of natural gas DF combustion are rough combustion at high load, high CO and total hydrocarbon (THC) emissions, and low natural gas substitution rate. In the present work, a comparison of using polyoxymethylene dimethyl ethers (PODEn) and diesel as pilot fuels for natural gas DF combustion is presented. The experiments were conducted at two conditions: 1000 rpm 4 bar indicated mean effective pressure (IMEP), and 1000 rpm 12 bar IMEP. Compressed natural gas (CNG) was injected into the intake manifold and pilot fuel was injected directly into the cylinder. The experiments covered both conventional and low temperature DF combustion. Experiments were conducted with 0% exhaust gas recirculation (EGR) and 60% CNG substitution ratio at 4 bar IMEP. At 12 bar IMEP, 90% substitution ratio and 30% EGR rate were chosen. The impact of the start of pilot fuel injection (SOI) on natural gas DF combustion was studied. In comparison with the conventional combustion, low temperature combustion reduced NOx emissions and improved ITE. Compared to diesel, PODEn achieved lower THC, CO, NOx, soot emissions and higher efficiency, indicating it is a promising pilot fuel for natural gas DF combustion.

Branched alkanes represent an important class of compounds in conventional fuels and some bio-derived fuels. This study is dedicated to the investigation of the low-temperature oxidation chemistry of 2,6-dimethylheptane using a combination of experimental and computational methods. All the reactants, transition states, and products in the first oxidation stage, which are crucial to the initiation reactions in the low-temperature reaction chain, were optimized through the B3LYP/CBSB7 level of theory and a kinetic mechanism that included the new reaction pathways was assembled. Ignition delay time measurements were carried out in a rapid compression machine and the results were compared with modeling predictions. The kinetic mechanism is able to capture both the first and total ignition delay times with a root-mean-square deviation of 39.6%. In addition, sensitivity analysis is performed to quantify the impact of newly developed chemistry of 2,6-dimethylheptane on ignition delay time. Rate parameters found in this study may be applicable to other branched alkanes with similar molecular structure.

Cathode catalyst layers (CLs) with varying ionomer (Nafion) contents were prepared and the direct methanol fuel cell structure and catalytic behavior were investigated as a function of ionomer content. CL roughness and thickness increased with increasing Nafion content. Contact angle measurements determined that CL hydrophilicity also increased as a function of Nafion content. Poor bonding between the CL, microporous layer, and the proton exchange membrane was obtained when the ionomer content was too low. The electrochemical surface areas (ESAs) were found to increase with increasing Nafion content before reaching an asymptote at elevated loading levels. However, upon increasing the ionomer content above 30 wt.%, the water and oxygen mass transfer properties were difficult to control. Considering the above conditions, N30 (30 wt.% Nafion) was found to be the optimal level to effectively extend the three-phase boundaries and enhance cell performance.

Commercially available carbon black is a widely applied support material for nanocatalysts but notorious for its microporous structure, which is deleterious for catalysts utilization in the fuel cell application and causes numerable problems in other application areas. The development of mesoporous carbon as a substitute was proved successful but not scalable due to their intrinsic complex synthesis. In this work, we demonstrate a new perspective to circumvent the problem through blocking the micropores of carbon black by the in-situ formed TiO2 nano/sub-nano particles. A decompression absorption method was developed where tetrabutyl titanate was pressurized into carbon pores with diameter

As a potential fuel for proton exchange membrane fuel cell, formic acid (FA) is easily decomposed on palladium (Pd) based catalysts, which are also the most effective and commonly used FA electro-oxidation catalysts in the direct formic acid fuel cell (DFAFC). Here we try to study the interaction between these two reactions in a supporting electrolyte free electrochemical cell. Considering the operation condition in the anode of DFAFC, influence of FA decomposition on FA electro-oxidation is detected and confirmed by mechanistic study. By doping platinum (Pt) into Pd, stability of the FA electro-oxidation can be extremely improved at fuel cell operation temperature.

Molybdenum disulfide (MoS2) is reckoned as one of the most positive low-cost HER catalysts to replace platinum-based precious metals in acid media. Unfortunately, some issues preclude MoS2 from being truly applicable including limited active sites, poor conductivity and lack of intrinsic activity. Herein, we report a Cu, Pd co-doped MoS2 nanomaterial as an efficient and stable HER electrocatalysts, which partially resolve the above-mentioned problems and leads to high overall performance. Specifically, we improve the electric conductivity of the MoS2 by Cu dopant and realize the phase transition of MoS2 from pristine 2H phase to stable 1T phase by Pd dopant. More importantly, we increase active site density to facilitate fast electrocatalytic Faradaic process via synergistic effects of Cu and Pd doping, and tune electronic energy states of MoS2 to improve HER intrinsic activity. In acidic media, the performance of Cu-Pd-MoS2 catalyst in terms of a low overpotential (−93 mV) at 10 mA cm−2, a small Tafel slope of 77 mV dec−1, and an excellent stability is better than that of single-doped catalysts.

Uniform sea urchin-like Au@Pd formic acid oxidation reaction (FAOR) electrocatalysts with dendritic core-shell structure were successfully prepared via nanocatalysts self-assembly process. High electrochemical surface area with more exposed active sites as well as the suitable lattice strain were confirmed as influencing factor to enhance intrinsic activity and facilitate kinetic reaction rate, resulting improved FAOR performance. Specifically, as tuning the status of surface dendritic Pd, lattice strain presented different influence on the electrocatalytic performance. Stronger lattice strain would facilitate the surface adsorption of dissociate formic acid on the surface Pd. While, weaker lattice strain would make surface desorption of the intermediate species on surface Pd easily resulting regeneration of active sites. In this work, the optimized Au71@Pd29 DCS exhibits enhanced activity with the current density of 1405 A gPd−1, which is 8.8 times higher than that of the commercial Pd black (160 A gPd−1), as well as obvious enhanced durability.

The development of advanced catalyst supports is a promising route to obtain active and durable electrocatalysts for methanol electro-oxidation reaction. In the current work, nitrogen-doped carbon encapsulated titanium dioxide composite (TiO 2 @NC X ) is constructed and serves as support material for the Pt catalyst. The TiO 2 @NC X support is fabricated by the procedure of an in-situ polymerization and subsequent pyrolysis. The synthesized Pt/TiO 2 @NC X catalysts show enhanced electrocatalytic performance towards methanol electro-oxidation compared with the commercial Pt/C catalyst. The enhancement can be ascribed to combinatory effect of N-doped carbon and TiO 2 , in which the tolerance to CO-poisoning and the intrinsic kinetics of methanol oxidation reaction are simultaneously improved by the bifunctional mechanism and the electronic effect. As a result, the as-developed TiO 2 @NC X composite is a promising catalyst support material for the application in fuel cell.

Nanostructured ptru material is considered as the best catalyst for direct methanol fuel cells (dmfcs), but the performance decay resulting from ru loss seriously hinders the commercial application. here we demonstrated that the performance of nanostructured ptru catalyst for methanol oxidation could be significantly improved by cop material; the presence of cop could largely slow down the loss of ru and pt in ptru catalyst system, thus promising a highly active and durable performance in dmfcs. cyclic voltammetry results showed the peak current is 2.89 times higher than that of state-of-the-art commercial ptru/c-jm (231.9 ma mg(ptru)(-1)) and 3.86 times higher than that of the home-made reference (ptru/c-h) catalyst (173.6 ma mg(ptru)(-1)); kinetics study probed by electrochemical impedance spectroscopy showed a large reduced charge transfer resistance in the rate determining step. the highest maximum power density was achieved on this novel ptru-cop/c catalyst among all the evaluated catalysts at different temperatures. specifically, a maximum power density of 85.7 mw cm(-2) achieved at 30 degrees c is much higher than that of state-of-the-art commercial ptru/c catalyst at 70 degrees c (63.1 mw cm(-2)). outstanding catalytic activity and stability observed on this novel ptru-cop/c catalyst should be attributed to a synergistic effect between the nanostructured ptru and cop, in which the presence of cop increases ptru physical stability and anti-co poisoning ability. the present work is a significant step that opens an avenue in the development of highly active and durable catalysts for fuel cells technology, and makes ptru catalyst system much closer for commercial application in dmfcs. (c) 2015 elsevier ltd. all rights reserved.

The development of facile, surfactant-free strategy for the scale-up production of catalysts with superior performance for energy science is an interesting challenge. Pd/C is synthesized using an in-situ method from PdO/C for formic acid electrooxidation based on the reducibility of formic acid. The morphology, composition and electrocatalytic properties are investigated using transmission electronmicroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, linear scan voltammograms (LSV) and chronoamperometry. The in-situ synthesized Pd nanoparticles show better distribution and smaller average particle size than the normally synthesized Pd/C, which indicates that the well-known Ostwald ripening is most limited in the synthesis process. The electrochemical measurements show that the Pd/C catalyst exhibits enhanced performance towards formic acid electrooxidation. For example, the peak current of the Pd/C catalyst is approximately three times that of the homemade Pd/C catalyst and twice as high as that of the commercial Pd/C catalyst in the LSV test. The in-situ synthesized Pd/C catalyst has potential application for direct formic acid fuel cells, and the in-situ route should be an effective strategy to synthesize high performance catalysts.