Pd Atomic Ratio Research Articles

Iron–palladium nanoparticle biocomposites with increased metal loading

Biocomposites containing magnetic nanoparticles have the potential to combine the unique, tunable properties of nanoparticles with the strong mechanical and environmentally sustainable properties of natural fibers like cotton. Recently, a method to synthesize Fe–Pd nanoparticles on cellulose has been developed. This study presents a detailed investigation on how the structural and magnetic properties of these nanoparticle biocomposite materials are affected by increasing metal loading with respect to the cellulose while maintaining a fixed 1:1 Fe:Pd atomic ratio. Infrared spectroscopy and electron microscopy (SEM and TEM) indicate that spherical Fe–Pd nanoparticles (approximately 3–8 nm in diameter) are distributed heterogeneously throughout the fiber matrix along with amorphous iron oxide, while XRD suggests the dominant crystalline phase within the nanoparticles is likely FePd3 under significant strain. The magnetic response of the biocomposites in static and dynamic magnetic fields (as a function of frequency and temperature) reveals a polydisperse ensemble of Fe–Pd nanoparticles with up to four distributions of blocking temperatures. The lower temperature distributions are prevalent at low metal loading. As the metal loading increases, the higher temperature distributions emerge, while the lower temperature distributions are suppressed. This result points towards enhanced nanoparticle heterogeneity and agglomeration as the metal loading increases.

Facile electrooxidation of ethanol on reduced graphene oxide supported Pt–Pd bimetallic nanocomposite surfaces in acidic media

Development of electrocatalysts with extended homogeneity and improved metal–support interactions is of urgent scientific need in the context of electrochemical energy applications. Herein, bimetallic Pt–Pd nanoparticles with good homogeneity are fabricated using a convenient solution phase chemical reduction method onto a reduced graphene oxide (rGO) support. X-ray diffraction studies revealed that Pt–Pd/rGO possesses the crystallite size of 3.1 nm. The efficacies of Pt–Pd/rGO catalyst (20 wt% Pt + 10 wt% Pd on rGO support, Pt:Pd atomic ratio = 1:1) towards ethanol electrooxidation reaction (EOR) are evaluated in acidic conditions by cyclic voltammetry using catalyst-coated glassy carbon electrode as a working electrode. With the better dispersion on rGO support the Pt–Pd/rGO nancomposite catalyst exhibit highest mass specific activity (0.358 mA/µg-Pt) which is observed to be 1.9 times of similarly synthesized 20 wt% Pt/rGO (0.189 mA/µg-Pt) and 2.5 times of commercial 20 wt% Pt/C (0.142 mA/µg-Pt), respectively. Apart from the observed improved EOR activity, the Pt–Pd/rGO catalyst exhibited better stability than Pt/rGO and Pt/C catalysts. Strong synergy offered by Pt, Pd and rGO support could contribute to the observed higher EOR activity of Pt–Pd/rGO.

Insight towards kinetics and stability of carbon supported Pd–Y2O3 as cathode catalyst for polymer electrolyte fuel cells

Pd–Y 2 O 3 on carbon (Pd–Y 2 O 3 /C) in different mass ratios of Pd to Y 2 O 3 (1:1, 2:1, 3:1) were prepared and subjected as cathode electrocatalyst for polymer electrolyte fuel cells (PEFC). X-ray diffraction (XRD) and transmission electron microscopy (TEM) were used to determine the structure, crystalline size and dispersion of Pd–Y 2 O 3 /C respectively. The electrochemical characterizations of the electrocatalysts were evaluated from Cyclic Voltammetry (CV) and Linear Sweep Voltammetry (LSV). These electrocatalysts were evaluated for their catalytic activity towards oxygen reduction reaction (ORR) in fuel cell. Pd 2 –Y 2 O 3 /C catalyst shows higher power density of 325 mW cm −2 than Pd 1 –Y 2 O 3 /C, Pd 3 –Y 2 O 3 /C and Pd/C. • Various atomic ratios of Pd–Y 2 O 3 /C prepared and evaluated as ORR catalyst for PEFC. • Pd 2 –Y 2 O 3 /C as a cathode catalyst shows high peak power density of 325 mW cm −2 . • Pd 2 –Y 2 O 3 /C exhibits higher ORR activity due to SMSI effect.

High Efficiency for Methanol Electrooxidation of Self-Supporting 3D Nanoporous PdAg Alloy Foams

The self-supporting three-dimensional (3D) nanoporous PdAg alloy (NP–PdAg) foams have been prepared by a simple one-step dealloying melt-spun Al–Pd–Ag ribbons in a 20[Formula: see text]wt.% NaOH aqueous solution at 90∘C for 1.5[Formula: see text]h. The structure is advantageous to the diffusion and removal of the intermediate products and the transmission of the methanol molecules. The NP–PdAg foams exhibit better electrocatalytic performance than the NP-Pd foam toward the methanol oxidation in potassium hydroxide (KOH) solution. The optimal atomic ratio of Pd to Ag in the NP–PdAg foams is 1:1, and its electrocatalytic activity is about 2.6 times that of the NP–Pd foam. The significant improvement in the electrocatalytic performance is attributed to the addition of a moderate amount of Ag. In the whole electrocatalytic process, Ag can provide OHads to oxidize the intermediate products on the surface of active Pd sites into carbon dioxide or other cleaning products. Also, the Ag can increase electrochemical active surface area and the adsorption energy of Pd to methanol molecules and OHads. These significantly prevent the accumulation of poisoning intermediates on the surface of Pd and quickly release more active Pd sites.

Intermetallic PdAg nanoparticles supported on Bi2MoO6 nanoplates and their enhanced photocatalytic activities

Intermetallic PdAg nanoparticles with different atomic ratios of Pd and Ag were supported on Bi2MoO6 nanoplates by photoreduction method. The as-prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), photoluminescence (PL) spectroscopy and X-ray photoelectron spectroscopy (XPS). The intermetallic PdAg nanoparticles with size of 10–12 nm were supported on the orthorhombic Bi2MoO6 nanoplates. The photocatalytic activities of the as-prepared samples were evaluated through the degradation of rhodamine B (RhB) illuminated with visible radiation. The heterostructure 5% Pd0.8Ag0.2/Bi2MoO6 nanocomposites have the highest decolorization efficiency in degrading of RhB molecules. The enhanced photocatalytic activity is attributed to the acceleration in the rate of charge separation and charge diffusion efficiency. Main active radicals for the photodegradation and stability of the photocatalyst were also investigated.

Factors affecting the catalytic activity of Pd-based electrocatalysts in the electrooxidation of glycerol: element doping and functional groups on the support

In this paper, the loaded Pd-based (Pd–Ni, Pd-Co, Pd–Ag, Pd-Pb and Pd-Pr) electrocatalyst was prepared by the method of impregnation-freeze-drying-H2/Ar2 reduction. The crystal structure, spatial distribution and surface chemical state of Pd-based electrocatalysts were characterized by X-ray diffraction, transmission electron microscope, and X-ray photoelectron spectroscopy. The effects of doping elements and functional groups of the support on the electrocatalytic activity of Pd-based electrocatalysts were studied using cyclic voltammetry and chronoamperometry. The results show that when the atomic ratio of Pd to Pr is 1.25, the PdPr/rGO nanocatalyst has the best catalytic activity for the electrooxidation of glycerol, which is 2.76 times that of pure Pd. In comparison to MWCNTs with -COOH, -NH2 and -OH functional groups, nitrogen-doped MWCNTs are more beneficial to increase the reaction rate of glycerol electrooxidation. The reason may be that Pr can produce praseodymium hydroxide in alkaline solution. In the electrooxidation reaction of glycerol, praseodymium hydroxide can act as an electrocatalyst. In addition, the doping of Pr increases the content of Pd0, and there is a synergistic effect between Pd and Pr. These are beneficial for increasing the electrooxidation rate of glycerol on the Pd6Pr4/N-MWCNT catalyst. The functional groups on the support may be affect the adsorption capacity and the degree of reduction for metal ions, and then affect the electrocatalytic activity. The influence of doping in the electrocatalyst is greater than that of the functional groups on the support.

Strong metal–support interaction between palladium and gallium oxide within monodisperse nanoparticles: self-supported catalysts for propyne semi-hydrogenation

The strong metal–support interaction (SMSI) between metals and reducible supports (e.g., CeO2, TiO2, and SnO2), which has been widely investigated, plays a very important role in heterogeneous catalysis. We report the first example of SMSI between palladium (Pd) and gallium oxide (Ga2O3) within a PdGa nanoparticle (denoted as PdxGay NP, where x:y is the atomic ratio of Pd and Ga). The typical features of classic SMSI, such as electron transfer between Ga2O3 and Pd and suppression of H2 and CO adsorption, are successfully observed on PdxGay NPs. Detailed characterizations and control experiments demonstrate that the coexistence of PdGa alloy and Ga2O3 in PdxGay NPs plays a vital role in the formation of SMSI. To systematically study the effects of SMSI on catalytic performance, PdxGay NPs were used as “self-supported catalysts” for propyne semi-hydrogenation (PSH), a critical process for removing trace propyne from propylene in industry. It is shown that optimized Pd0.34Ga1 NPs give a propylene selectivity of 98.2% at a propyne conversion of 96.6% at 30 °C and atmospheric pressure, which is much higher than that of pure Pd NPs and Pd/Ga2O3 catalysts prepared by a conventional wet-impregnation method. The reaction paths of PSH on PdxGay NPs have been further revealed by density functional theory (DFT) calculations. This work may not only deepen the basic understanding of SMSI, but also promote the design and application of heterogeneous catalysts.

Preformed Pd-Based Nanoparticles for the Liquid Phase Decomposition of Formic Acid: Effect of Stabiliser, Support and Au–Pd Ratio

Hydrogen is one of the most promising energy carriers for the production of electricity based on fuel cell hydrogen technology. Recently, hydrogen storage chemicals, such as formic acid, have been proposed to be part of the long-term solution towards hydrogen economy for the future of our planet. Herein we report the synthesis of preformed Pd nanoparticles using colloidal methodology varying a range of specific experimental parameters, such as the amount of the stabiliser and reducing agent, nature of support and Pd loading of the support. The aforementioned parameters have shown to affect mean Pd particle size, Pd oxidation, atomic content of Pd on the surface as well as on the catalytic performance towards formic acid decomposition. Reusability studies were carried out using the most active monometallic Pd material with a small loss of activity after five uses. The catalytic performance based on the Au–Pd atomic ratio was evaluated and the optimum catalytic performance was found to be with the Au/Pd atomic ratio of 1/3, indicating that the presence of a small amount of Pd is essential to promote significantly Au activity for the liquid phase decomposition of formic acid. Thorough characterisation has been carried out by means of XPS, SEM-EDX, TEM and BET. The observed catalytic performance is discussed in terms of the structure/morphology and composition of the supported Pd and Au–Pd nanoparticles.

Novel carbon nanotube supported Co@Ag@Pd formic acid electrooxidation catalysts prepared via sodium borohydride sequential reduction method

At present, monometallic Pd/CNT, bimetallic Pd50Ag50/CNT, Pd50Co50/CNT, Ag50Pd50/CNT catalysts are prepared by NaBH4 co-reduction method. Ag@Pd/CNT catalysts at varying Ag:Pd ratios and Co@Ag@Pd/CNT catalysts at varying Co:Ag:Pd atomic ratios are prepared via NaBH4 sequential reduction method. These catalysts are characterized with X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). The characterization results show that all catalysts are successfully synthesized at desired molar composition. Furthermore, Ag and Co addition change electronic state of catalyst. Formic acid electrooxidation measurements of these catalysts are performed by cyclic voltammetry (CV), chronoamperometry (CA), and electrochemical impedance spectroscopy (EIS) to investigate the effect of Ag and Co addition through the formic acid electrooxidation activity. Considering the bimetallic catalysts, Ag20@Pd80/CNT exhibits better catalytic activity than the one of other bimetallic catalysts. It is clear that the addition of Ag to Pd improves electrocatalytic activity due to synergetic effects. Furthermore, Co0.072@Ag19.98@Pd79.98/CNT has the best activity, lowest charge transfer resistance (Rct), and a long term stability. EIS and CA results are in a good agreement with CV results. Co0.072@Ag19.98@Pd79.98/CNT is a promising catalyst for Direct formic acid fuel cells.

PtPdNi Catalysts Supported on Porous Carbon for Ethanol Electro‐oxidation

AbstractIn this work, we prepared four electrocatalysts based on trimetallic PtPdNi nanoparticles on different carbon supports, i. e., i) two activated carbons produced from biomass, ii) micro‐mesoporous carbon synthesized by the nanocasting method, and iii) commercial carbon black. The electrocatalytic activity of the prepared materials was tested in the electro‐oxidation of ethanol in alkaline medium. Well‐distributed nanoparticles with sizes in the range of 3.5–5.2 nm were obtained through galvanic replacement. The bulk Pt, Pd and Ni contents were about 65, 25 and 15 at. %, measured by EDX and ICP‐AES. By XPS the surface Pt : Pd atomic ratios were in the range of 1.82–2.2. Electrochemical experiments showed that the trimetallic nanoparticles deposited over micro‐mesoporous carbon material exhibit the highest electrochemical activity towards ethanol electro‐oxidation in alkaline medium. Results showed that both synthetic carbon and biomass‐derived carbon are suitable materials to support electrocatalysts in low‐temperature fuel cells.

Preparation and investigation of Pd doped Cu catalysts for selective hydrogenation of acetylene

A series of PdCu bimetallic catalysts with low Cu and Pd loadings and different Cu: Pd atomic ratios were prepared by conventionally sequential impregnation (CSI) and modified sequential impregnation (MSI) of Cu and Pd for selective hydrogenation of acetylene. Characterization indicates that the supported copper (II) nitrate in the PdCu bimetallic catalysts prepared by MSI can be directly reduced to Cu metal particles due to the hydrogen spillover from Pd to Cu(NO3)2 crystals. In addition, for the catalysts prepared by MSI, Pd atoms can form PdCu alloy on the surface of metal particles, however, for the catalysts prepared by CSI, Pd tends to migrate and exist below the surface layer of Cu. Reaction results indicate that compared with CSI, the MSI method enables samples to possess preferable stability as well as comparable reaction activity. This should be due to the MSI method in favor of the formation of PdCu alloy on the surface of metal particles. Moreover, even Pd loading is super low, < 0.045 wt-% in this study, by through adjusting Cu loading to an appropriate value, attractive reactivity and selectivity still can be achieved.

Fabrication of BixPdy bimetallic materials characterized by catalytic activity at low temperature: Nitro reduction and Suzuki−Miyaura coupling reactions under green conditions

A simple method for synthesizing the BixPdy bimetallic particles is described. The structure, composition distribution and size of synthesized BixPdy bimetallic particles were characterized using a number of analytical techniques. The Bi:Pd atomic ratio (x:y) of the nanoparticles was determined to be approximately 1:3 (Bi24Pd76), 1:1 (Bi54Pd46) and 3:1 (Bi74Pd26). The (111) diffraction peaks within the X-ray diffraction patterns of the bimetallic nanoparticles shifted from 39.9° to 38.5° as the Bi content increased from 0% to 75%. The d-spacings calculated from the 2θ data of (111) planes were 2.33, 2.34, 2.32 and 2.26 nm for nanoparticles with a Bi:Pd atomic ratio of 3:1, 1:1, 1:3 and 0:1 respectively. The crystalline properties of the surface of the BixPdy bimetallic nanoparticles were observed in high-resolution transmission electron microscopy analysis. The d-spacings between the adjacent lattice planes were measured on the surface of BixPdy bimetallic nanoparticles by averaging 10 lattice fringes distance. A regular face-centered cubic lattice was observed throughout the prepared BixPdy bimetallic nanoparticles. The lattice d-spacing of the Bi3Pd1, Bi1Pd1 and Bi1Pd3, bimetallic nanoparticles was approximately 2.34, 2.33 and 2.32 Å, respectively, which can be indexed to the (111) planes. These measurements correspond to the values calculated using the Bragg equation (d = nλ/2sinθ). The catalytic activity of BixPdy bimetallic nanoparticles was determined for the nitro compound reduction and Suzuki-Miyaura coupling reactions under green conditions (in an aqueous solution). Bi1Pd3 nanoparticles were shown to provide the best catalytic performance during both reactions, resulting in a yield of 98% in both cases.

Effect of Stoichiometry on Shape Memory Properties and Functional Stability of Ti⁻Ni⁻Pd Alloys.

Ti–Ni–Pd shape memory alloys are promising candidates for high-temperature actuators operating at above 373 K. One of the key issues in developing high-temperature shape memory alloys is the degradation of shape memory properties and dimensional stabilities because plastic deformation becomes more pronounced at higher working temperature ranges. In this study, the effect of the Ti:(Ni + Pd) atomic ratio in TixNi70−xPd30 alloys with Ti content in the range from 49 at.% to 52 at.% on the martensitic transformation temperatures, microstructures and shape memory properties during thermal cycling under constant stresses were investigated. The martensitic transformation temperatures decreased with increasing or decreasing Ti content from the stoichiometric composition. In both Ti-rich and Ti-lean alloys, the transformation temperatures decreased during thermal cycling and the degree of decrease in the transformation temperatures became more pronounced as the composition of the alloy departed from the stoichiometric composition. Ti2Pd and P phases were formed during thermal cycling in Ti-rich and Ti-lean alloys, respectively. Both Ti-rich and Ti-lean alloys exhibited superior dimensional stabilities and excellent shape memory properties with higher recovery ratio and larger work output during thermal cycling under constant stresses when compared with the alloys with near-stoichiometric composition.

Characterization of mechanical strength and hydrogen permeability of a PdCu alloy film prepared by one-step electroplating for hydrogen separation and membrane reactors

A single phase, dense PdCu alloy film was prepared by one-step electroplating. The electroplated film was easily delaminated from the SUS electrode by cutting around the edge, and the single alloy film was thus collectable. The phase structure, surface morphologies, and alloy compositions were determined by X-ray diffraction (XRD), scanning electron microscopy (SEM), and electron probe microanalysis (EPMA). The plated film before and after hydrogen permeation tests consisted of a single face-centered cubic α phase and an ordered body-centered cubic β phase, respectively. The atomic ratios of Pd and Cu were 49 and 51 at%, respectively; the Pd and Cu contents were slightly higher and lower than Pd47Cu53, which shows the highest hydrogen permeability among Pd-Cu systems. The as-plated film exhibited high mechanical strength, and its load force at break point and displacement were 3 and 1.7 times those of the as-rolled Pd47Cu53 films. The hydrogen permeability of the plated film with the β phase was almost the same as that of the rolled film and the values reported in literature.

One-pot synthesis of unprotected PtPd nanoclusters with enhanced catalytic activity, durability, and methanol-tolerance for oxygen reduction reaction

Bimetallic PtPd alloys are regarded as promising high performance oxygen reduction reaction (ORR) catalysts. However, the application of a subnanometer scale PtPd bimetallic nanoclusters (NCs) is rarely studied. In this work, ordered mesoporous carbon (OMC) supported PtPd NCs with the constant metal loading of 10 wt% and various Pt:Pd atomic ratios were synthesized by a modified polyol reduction route. The PtPd NCs show a maximum activity at Pt:Pd molar ratio close to 3:1 with a mean size of ∼2.35 nm. The specific activity (SA) and mass activity (MA) of Pt3Pd1 NCs/OMC (PtPd loading: 10 wt%) is 2.5 and 4.1 times higher than those of the commercial Pt/C (Pt loading: 20 wt%) in 0.1 M HClO4. Meanwhile, the Pt3Pd1 NCs/OMC exhibits improved methanol tolerance and durability for ORR. Therefore, the Pt3Pd1 NCs/OMC is excellent candidate that may become a practical cathode catalyst for fuel cells.

Investigation on Electron Distribution and Synergetic to Enhance Catalytic Activity in Bimetallic Ni(II)/Pd(II) Molecular Monolayer

AbstractNovel graphene oxide (GO)‐supported ordered diimine Ni/Pd bimetallic monolayers with ratio of Ni to Pd atomic ratios (2136 : 1, 333 : 1 and 97 : 1) (denoted as GO‐Diimine‐Ni/Pd1, GO‐Diimine‐Ni/Pd2, GO‐Diimine‐Ni/Pd3) were fabricated and their catalytic performances and synergetic mechanism were systematic investigated. For the as‐prepared GO‐Diimine‐Ni/Pd1, that trace palladium complex was responded for changing the electronic environment, tuning catalytic actives and modifying the electronic states which could enhance the highlighted catalytic activity. The more dramatic aspect of the GO‐Diimine‐Ni/Pd1 with high efficient catalytic activity could be achieved even with atom ratio of Ni/Pd even in 2136 : 1 (TOFNi=21277 h−1; TOFPd=4.545×107 h−1), in which the noble Pd could almost be replaced by non‐noble Ni according to requirement for economic chemistry. Interestingly, the synergetic mechanism between nickel and palladium was that the electron of Pd may transfer to Ni, which is different from the conventional Pd/Ni for catalyzing coupling reaction. Especially, the formation of Ni0 around Pd (II) as active centers was proposed and its size could be controlled with adjusting the palladium content on the surface. The results exhibited that the synergic effect between Ni and Pd made it easy for Ni2+ reduced into Ni0. It was crucial for adjusting the catalytic activity by designing the fine structure of ligand, the supports selection and modulating the Pd content at the molecular level.

Enhanced Electrocatalytic Activity over Structurally Ordered Intermetallic PdCu3 Nanoparticles

Structurally ordered phase of PdCu3 nanoparticles (NPs)/carbon black (CB), in which PdCu3 has a Cu3Au-type structure, was prepared by co-reduction of Pd and Cu precursor using ethylene glycol as reducing agent and annealing procedure. The obtained catalysts were characterized by using X-ray diffraction technique (XRD), transmission electron microscopy (TEM), scanning transmission electron microscopy (STEM) and X-ray photoelectron spectroscopy (XPS). The XRD and STEM measurements allowed us to confirm the crystal structures of both atomically disordered Pd-Cu NPs/CB and ordered intermetallic PdCu3 NPs/CB. From the TEM and EDS measurements, it was found that PdCu3 NPs are uniformly dispersed on the CB surface and the atomic ratio of Pd and Cu is 25.3 : 74.7. The DFT calculations suggested that the as-prepared PdCu3 NPs have a uniformly ordered structure of Pd and Cu atoms without segregation of Pd and/or Cu, while the Cu-free surface structured PdCu3 NPs, which are formed by a so-called electrochemical dealloying, i.e., the surface and sub-surface Cu dissolution from the PdCu3 ordered structure, possess a superior electrocatalytic activity for the ORR compared with Pd NPs/CB. This catalytic activity can be explained reasonably based on the measured d – band center value and the theoretical calculation of catalyst – oxygen binding energies. In addition, a possibility of PdCu3 NPs/CB as a cathode catalyst in direct methanol fuel cells is discussed briefly.

Oxygen reduction reaction on Pt-Pd catalysts supported on carbon xerogels: Effect of the synthesis method

In this work, Pt-Pd nanoparticles supported on carbon xerogels (Pt-Pd/CX) were synthesised employing unusual routes, in order to evaluate its activity toward the oxygen reduction reaction (ORR). The synthesis methods produced materials with the planned composition (metal content close to 40 wt % and Pt:Pd atomic ratios around 1:2), with Pt, Pd and alloyed Pt-Pd nanoparticles well dispersed on the carbon support. The content of Pt in the nanoparticles was optimised through these procedures, placing this metal at the surface. As a consequence, the Pt-Pd/CX catalysts displayed high activity toward the ORR and remarkable resistance to corrosion, overcoming the electrocatalytic properties of a commercial Pt/C catalyst. Moreover, these catalysts involve four electrons in the ORR. Therefore, the study here presented indicated that the as-synthesised Pt-Pd/CX catalysts are suitable candidates to be employed as cathodes in proton exchange membrane fuel cells.

Catalytic activity of carbon supported-Pt-Pd nanoparticles toward the oxygen reduction reaction

In this work, Pt-Pd catalysts (≈ 35 wt.%, Pt:Pd atomic ratio ≈ 1:2) supported on carbon black, carbon nanofibers and carbon xerogels have been synthesized in order to assess their activity toward the oxygen reduction reaction (ORR). X-ray diffraction (XRD) and transmission electron microscopy (TEM) analysis showed low particle and crystallite sizes with good dispersion on carbon supports. Regarding the ORR, the Pt-Pd nanoparticles supported on carbon black displayed the best performance in terms of high diffusional current densities, high specific and mass activities, number of electrons involved in the ORR and enhanced corrosion resistance. The improved performance of this catalyst has been explained from the modification of the Pt-Pt interatomic distance by Pd and the holding/re-reducing of the hydrogen peroxide formed during the ORR, promoting the water formation. In general, the synthesized materials displayed an upgraded corrosion resistance compared with that of the commercial Pt catalyst, suggesting them as suitable candidates to be employed as cathodes in PEMFCs since their Pt content is lower than that of the commercial Pt/C.

Improved Performance of Fiber Bragg Hydrogen Sensors Assisted by Controllable Optical Heating System

A novel fiber Bragg grating (FBG) hydrogen sensor based on the Pd/Ni composite film and controllable laser heating system is proposed and demonstrated with enhanced sensitivity. The Pd/Ni composite film was sputtered around the greatly etched FBG, and the atomic ratio of Pd and Ni was controlled at 91:9 during the sputtering process. A 980-nm pump laser and proportion integration differentiation controller are employed to induce heating in the Pd/Ni composite film. Experimental results show that the stability of the hydrogen sensor is significantly improved with ±1 pm fluctuation at 1% hydrogen concentration. In addition, the proposed sensor exhibits higher sensitivity and quicker response rate during hydrogen exposure.