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WO2018179006A1 - Séléniures à base de palladium en tant que matériaux de cathode hautement stables et durables dans une pile à combustible pour la production d'énergie verte - Google Patents

Séléniures à base de palladium en tant que matériaux de cathode hautement stables et durables dans une pile à combustible pour la production d'énergie verte Download PDF

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WO2018179006A1
WO2018179006A1 PCT/IN2018/050168 IN2018050168W WO2018179006A1 WO 2018179006 A1 WO2018179006 A1 WO 2018179006A1 IN 2018050168 W IN2018050168 W IN 2018050168W WO 2018179006 A1 WO2018179006 A1 WO 2018179006A1
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catalyst
metal
acac
acetylacetonate
reaction solution
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Sebastian Chirambatte PETER
Saurav Chandra SARMA
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Jawaharlal Nehru Centre For Advanced Scientific Research
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
    • H01M4/90—Selection of catalytic material
    • H01M4/9008—Organic or organo-metallic compounds
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
    • H01M4/8605—Porous electrodes
    • H01M4/8621—Porous electrodes containing only metallic or ceramic material, e.g. made by sintering or sputtering
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
    • H01M4/88—Processes of manufacture
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
    • H01M4/90—Selection of catalytic material
    • H01M4/92—Metals of platinum group
    • H01M4/921—Alloys or mixtures with metallic elements
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
    • H01M4/90—Selection of catalytic material
    • H01M4/92—Metals of platinum group
    • H01M4/923—Compounds thereof with non-metallic elements
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/10—Fuel cells with solid electrolytes
    • H01M2008/1095—Fuel cells with polymeric electrolytes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/30—Hydrogen technology
    • Y02E60/50—Fuel cells

Definitions

  • the present invention relates to synthesis of palladium-based chalcogenides. These materials exhibit high stability and have good activity towards oxygen activation and reduction, because of which they are expected to have their application as cathode materials in fuel cell. More particularly, the present invention relates to a method to synthesize palladium based binary and ternary nanomaterials, CoPd 2 Se 2 and Pd 17 Se 15 , and its application as electrocatalyst in the fuel cell. The present invention relates to a synthesis of highly stable and durable nanomaterials with selenium rich surface. The catalyst outperforms the present state-of-the-art material Pt/C and Pd/C in terms of stability and durability. The present disclosure further relates to a unique, one-pot method to synthesize binary and ternary chalcogenides and applications of said nanomaterial as a cathodic electrode material.
  • Fuel cells are receiving growing attention as a viable energy alternative.
  • fuel cells are used to convert chemical energy stored into electrical energy with the production of environmental-friendly by-product in an efficient manner, typically via fuel oxidation and an accompanying oxygen reduction reaction (ORR).
  • ORR oxygen reduction reaction
  • Fuel cells are potential energy sources for everything ranging from small electronics to cars and homes. There are different types of fuel cells in existence today, each with varying chemistry, requirements, and uses.
  • a fuel cell comprises of a fuel electrode (anode), an oxidant electrode (cathode) and an electrolyte.
  • fuel is continuously fed to the anode where it gets oxidized, and oxygen is reduced at the cathode.
  • fuel cell and energy storage devices lack efficient and stable catalysts for such reactions for a long run.
  • designing of a stable catalyst with good activity is a must.
  • prior arts in literature demonstrated comparatively low stability towards ORR.
  • ORR oxygen reduction reaction
  • Pt-based ORR catalysts often have issues with stability during operations at a wide range of operating voltages and harsh electrolytic conditions that the catalyst is subjected to. These voltage ranges can stress both the Pt catalyst and the carbon substrate. Methods to improve the durability of the ORR catalyst and to enhance the reaction activity have been the focus of worldwide research for the past several decades.
  • the catalyst of the invention is capable of catalyzing the reduction of oxygen.
  • the reduction of oxygen may be achieved by exposing the catalyst to the oxygen.
  • the oxygen may be in any suitable form, such as pure oxygen gas or preferably as an oxygen-containing gas mixture, most preferably air (which may include dry or partially dried or treated air).
  • ORR which takes place at the cathode of a fuel cell can proceed via four or two electron process.
  • the four electron process involves the combination of oxygen with electrons and protons in a single step to produce water.
  • the two electron process consists of two steps; the first of these produces hydrogen peroxide ions as an intermediate and the second converts these to water.
  • the present invention provides a catalyst for a polymer electrolyte fuel cell comprising a metal-based chalcogenide comprising a transition metal and/or a noble metal and a chalcogen.
  • the metal-based chalcogenide is selected from the group comprising of CoPd 2 Se 2 , Pd 17 Se 15 , FePd 2 Se 2 , CoPd 2 Te 2 and compounds listed in Table 2.
  • the catalyst is supported on a support material containing carbon.
  • the support material is selected from carbon black, acetylene black, Vulcan XC-72, activated charcoal, synthetic graphite or natural graphite.
  • the catalyst is a promising cathode material in a polymer electrolyte membrane fuel cell.
  • the catalyst enhances the four- electron reduction process of oxygen.
  • the catalyst has an onset potential and half-wave potential closer to the state-of-the-art material Pd/C.
  • the catalyst is tolerant towards methanol oxidation.
  • the catalyst shows similar tafel slope as Pd/C that is 60 mVdec "1 .
  • the catalyst is used as a cathode material in a polymer electrolyte membrane fuel cell.
  • the electrolyte used in the fuel cell is oxygen-saturated KOH solution.
  • the present invention also provides a polymer electrolyte membrane fuel cell comprising the catalyst as a cathode material, and the electrolyte used in the fuel cell is oxygen- saturated KOH solution.
  • the present invention also provides a one-pot method for synthesizing metal-based chalcogenide nanoparticle comprising:
  • reaction solution (i) mixing one or more metal acetylacetonate (0.1-0.6 atomic percent) or acetate (0.1-0.6 atomic percent) based precursor with a chalcogen precursor (0.1-0.7 atomic percent) in a solvent (20-50 ml) to obtain a reaction solution;
  • step (iii) heating the reaction solution of step (ii) for 2-6 h at a temperature in the range of 220-250°C to obtain a reaction product;
  • the metal acetylacetonate or acetate based precursor is selected from a group comprising of platinum acetylacetonate (Pt(acac) 2 ), platinum acetate (Pt(OAc) 2 ), palladium acetylacetonate (Pd(acac) 2 ), palladium acetate (Pd(OAc) 2 ), cobalt acetylacetonate (Co(acac) 2 ), cobalt acetate (Co(OAc) 2 ), iron acetylacetonate (Fe(acac) 3 ), iron acetate (Fe(OAc) 3 ), nickel acetylactonate (Ni(acac) 2 ), nickel acetate (Ni(OAc) 2 ), copper acetylactonate (Cu(acac) 2 ), copper acetate (Cu(OAc) 2 ), manganese acetylacetonate (M
  • the chalcogen precursor is selected from a group comprising of selenium powder (Se), seleneous acid (H 2 Se0 3 ), sodium selenide (Na 2 Se), sodium telluride (Na 2 Te), sodium sulphide (Na 2 S), thiourea (NH 2 CSNH 2 ) and sodium selenosulphate (Na 2 0 3 SSe).
  • the solvent for the synthesis is selected from a group comprising of octyl amine, oleyl amine, ethylene diamine, ethylene glycol and tetraethylene glycol.
  • the reagent is selected from a group comprising of trioctylphosphine, sodium borohydride (NaBH 4 ) and lithium triethylborohydride (Li(C 2 H 5 ) 3 BH).
  • the metal-based chalcogenide is selected from the group comprising of CoPd 2 Se 2 , Pd 17 Se 15 , FePd 2 Se 2 , CoPd 2 Te 2 and compounds listed in Table 2.
  • the metal-based chalcogenide nanoparticle is having hexagonal or spherical morphology.
  • the metal-based chalcogenide nanoparticle has a stability of 50000 cycles towards ORR with less than 20 mV shift in half- wave potential.
  • the metal-based chalcogenide is CoPd 2 Se 2 nanoparticle and obtained by the process comprising:
  • step (iii) heating the reaction solution of step (ii) for 2-6 h at a temperature in the range of 220-250°C to obtain a reaction product;
  • the metal-based chalcogenide is PdnSeis nanoparticle and obtained by the process comprising: (i) mixing palladium acetylacetonate( Pd(acac) 2 ) (0.1-0.6 atomic percent) with a seleneous acid (H 2 Se0 3 ) (0.-0.7 atomic percent), in a tetraethylene glycol (20-50 ml) to obtain a reaction solution;
  • step (iii) heating the reaction solution of step (ii) for 2-6 h at a temperature in the range of 220-250°C to obtain a reaction product;
  • Figure 1 (a) is a X-ray diffraction pattern (XRD) of ternary chalcogenide CoPd 2 Se 2 . It shows the intensity of the diffraction peak in arbitrary unit versus the angle of diffraction. Major diffraction peaks at 34.16 °, 35.94 °, 39.90 °, 43.66 °, 50.36° and 52.26° correspond to (220), (211), (112), (231), (042) and (060) planes respectively. It corresponds to orthorhombic crystal system with Ibam space group, (b) is a PXRD pattern of binary chalcogenide PdnSe ⁇ .
  • XRD X-ray diffraction pattern
  • FIG. 2 shows (a,b) TEM images of as -synthesized CoPd 2 Se 2 nanoparticles confirming its hexagonal morphology, (c) High-Resolution Transmission Electron Microscopy (HRTEM) images indicating the exposed crystallographic facets, (d) Selected Area Electron Diffraction (SAED) pattern shows the polycrystalline nature of CoPd 2 Se 2 nanoparticles.
  • HRTEM High-Resolution Transmission Electron Microscopy
  • SAED Selected Area Electron Diffraction
  • Figure 3 shows (a,b) TEM images of as-synthesized PdnSe ⁇ nanoparticles showing the aggregated nature of the particles, (c) High-Resolution Transmission Electron Microscopy (HRTEM) images indicating the exposed crystallographic facets, (d) Selected Area Electron Diffraction (SAED) pattern shows the polycrystalline nature of PdnSe ⁇ nanoparticles.
  • Figure 4 shows (a) the FESEM images of CoPd 2 Se 2 nanoparticles. Hexagonal morphology of the nanoparticles can be clearly seen from the images, (b) EDX spectrum of CoPd 2 Se 2 nanoparticles.
  • the inset table represents the composition of individual elements present in the system.
  • Figure 5 shows (a) SEM images of the as-prepared Pd 17 Se 15 , (b) elemental mapping of Pd 17 Se 15 indicates the presence of both the elements. Elemental mapping of individual elements - (c) Se (pink) and (d) Pd (purple), (e) EDX spectrum of Pd 17 Se 15 nanoparticles.
  • the elemental composition of the sample is provided as an inset.
  • Figure 6 shows (i) core level XPS spectra of (a) Co, (b) Pd and (c) Se elements in CoPd 2 Se 2 nanocomposite and (ii) core level XPS spectra of Pd 17 Se 15 nanoparticles. High resolution XPS spectrum of (a) Pd-3 ⁇ 3 ⁇ 4 /2 , Pd-3 ⁇ 3 ⁇ 4 /2 and (b) Se-3 ⁇ i.
  • Figure 7 shows (a) LS V polarization curve at different rpm rate in 0.1 M KOH at a sweep rate of 5 mV/sec, (b) the koutecky-levich plot for CoPd 2 Se 2 /Vulcan nanocomposite at different potentials. The plots are generated from the LSV curves of all the samples tested in oxygen- saturated 0.1 M KOH solution with different rotating speeds, (c) Tafel plot (overpotential plotted vs. logarithm of current density) indicating faster reduction kinetics on hexagonal shaped nanoparticles, and (d) no. of electrons involved in ORR as a function of potential applied.
  • Figure 8 shows (a) LSV polarization curve before and after 50000 cycles in 0.1 M KOH at a sweep rate of 5 mV/sec, (b) Tafel slope comparison before and after ADT showing slight decrease in the Tafel slope value, (c) polarization curve in the presence of 1 M methanol showing almost no effect on the catalyst, and (d) Tafel slope of catalyst in absence and presence of 1 M methanol.
  • Figure 9 shows (a) Polarization curve of Pd 17 Se 15 before and after cycling, (b) CV curve as a function of cycle number showing the removal of Se from the surface due to prolonged cycling, (c) ORR polarization curve showing the negative shift due to exposed Pd sites and (d) tafel slope showing that the same mechanism is being followed before and after cycling.
  • Figure 10 shows (a) the comparison of the present invention with the state-of-the-art material Pd/C and (b) tafel slope of the present invention is similar to that of the state-of- the-art material showing that the present invention follows similar mechanism as that of the Pd/C.
  • Table 1 shows the comparison of the present invention with the state-of-the-art catalyst Pd/C 40 wt%.
  • Table 2 shows that the present invention is not limited to the referred examples but can be extended to the following list of materials.
  • the present invention addresses the issues of problem/drawbacks of the existing processes with the development of low-cost chalcogenide materials with earth abundant and less expensive elements. Moreover, catalysts of the present invention are stable for 50000 electrochemical cycles, highest reported so far for any ORR catalyst. In addition, catalysts of the present invention show activity as good as commercial Pd/C but durability is far better than Pd/C. Unlike many complicated synthesis methods, the present invention provides a facile one-pot synthesis method to synthesize the named catalysts.
  • This invention will be useful in the fabrication of highly efficient and robust fuel cell, which is a renewable and green source of energy.
  • fuel cell is being used as a green source of energy not only in portable devices but also in other stationary systems.
  • the major challenge in the development of the highly efficient fuel cell is the development of highly active and stable electrocatalysts. At the current state, the active catalysts are made of expensive and earth scarce Pt metal with very low stability.
  • Embodiments of the present invention provide a one-pot method to synthesize palladium based binary and ternary chalcogenides for oxygen reduction reaction that offers comparable activity while maintaining exceptional durability and long-term stability.
  • the activity and durability properties of the disclosed ORR catalysts may be due to the preparation methods used and crystal structure of the compound.
  • CoPd 2 Se 2 nanoparticles are synthesized by colloidal synthesis method.
  • Pd(acac) 2 , H 2 Se0 3 and Co(acac) 2 are mixed in oleyl amine in a two-necked RB.
  • Trioctylphosphine is then added to the solution.
  • the RB is then fitted with a condenser, vacuumed and purged with Ar gas. It is then heated for a few hours.
  • the product obtained is repeatedly washed with the hexane-ethanol mixture for several times and then dried in vacuum oven.
  • the amount of trioctylphosphine (stabilizing agent) used is 600-1000 ⁇ .
  • the heating is preferably done at 220 °C-250 °C for 2-6 h.
  • the drying is preferably done at 60°C for 6-12 h.
  • Pd 17 Se 15 nanoparticles are synthesized by polyol synthesis method.
  • Pd(acac) 2 (0.09-0.12 mmol) and H 2 Se0 3 (0.1 mmol) are mixed together in TEG (15 ml) in a two-necked RB (50 ml).
  • NaBH 4 40 mg
  • the RB is then fitted with a condenser, vacuumed and purged with Ar gas. It is then heated (220-250°C for 3-6 h).
  • the product obtained is repeatedly washed with hexane- ethanol mixture for several times and then dried in vacuum oven (60°C for 6-12 h).
  • Electrocatalytic evaluation of the prepared catalyst was done using a rotating disc electrode technique on samples both before and after extended use as a catalyst in ORR. Prolonged use here was accomplished by subjecting the catalyst to cyclic voltammetry, which involved cycling 50000 times repeatedly for about one week.
  • the described invention meets the present-day demand of a durable cathode catalyst with good activity for a fuel cell.
  • Methods of preparing the catalyst are also described. It consists of a transition metal and/or a noble metal, and a chalcogenide non-metal.
  • the transition metal is chosen from the group consisting of nickel, cobalt and iron. Particularly, transition metal used in one of the embodiment is cobalt.
  • the noble metal is selected from the group consisting of palladium and platinum.
  • noble metal used in one of the embodiment is palladium.
  • the chalcogen is preferably selected from a group consisting of sulphur, selenium and tellurium.
  • chalcogen used in of the embodiment is selenium.
  • non-noble metal refers to the metals of second and third triads of group VIII of the periodic table namely ruthenium, rhodium, palladium, platinum, osmium and iridium.
  • Chalcogenide refers to the elements of group 16 family in the periodic table with electronegative character.
  • the present invention discloses a cathode catalyst for a polymer electrolyte fuel cell comprising a transition metal and/or a noble metal and a chalcogen.
  • the cathode catalyst for polymer electrolyte membrane fuel cell wherein said alloy catalyst is supported on a support material containing carbon.
  • the catalyst is supported by carbon black, acetylene black, Vulcan XC-72R, activated charcoal, synthetic graphite or natural graphite.
  • present invention provides a method for making a cathode catalyst for a polymer electrolyte fuel cell comprising a transition metal and/or a noble metal and a chalcogen wherein said method comprises one-pot synthesis method.
  • the synthesis method includes heating at a temperature range of 220°C-250°C.
  • the morphology of the nanoparticles/ cathode catalyst obtained by this method can be hexagonal/spherical.
  • the cathode catalyst obtained by this method is active towards ORR.
  • the electrolyte used is oxygen- saturated KOH solution.
  • the cathode catalyst of the present invention has a stability of 50000 cycles towards ORR with less than 20 mV shift in half-wave potential.
  • the catalyst enhances the four-electron reduction process of oxygen.
  • the catalyst has an onset potential and half-wave potential closer to the state-of-the-art material Pd/C.
  • the catalyst is tolerant towards methanol oxidation.
  • the catalyst shows similar tafel slope as Pd/C i.e. 60 mVdec "1 .
  • the catalyst can be used as a cathode material in a fuel cell.
  • the ternary chalcogenide has a molar ratio of transition metal: noble metal: chalcogen as 1:2:2 and the binary chalcogenide has a compositional ratio of noble metal: chalcogenide as 17: 15.
  • the precursor of the transition and the noble metals are preferably present as a metal-organic complex.
  • Preferred ligands are acetylacetonate or acetate.
  • Selenium is preferably present as seleneous acid.
  • Decomposition of the metal organic complex precursors requires high temperature and reductive environment, which is ensured by the use of reducing solvent at high temperature.
  • the preferred solvent for the synthesis includes oleyl amine, ethylene diamine and tetraethylene glycol. Particularly, oleyl amine and tetraethylene glycol are used as the solvent in the described embodiment. At higher temperature, oleyl amine itself acts as a reducing agent and helps in the decomposition of the metal-organic framework.
  • thermally decomposable compounds When the thermally decomposable compounds are added to the solvent, a homogeneous mixture of the catalyst is ensured by conventional dispersion process. This is carried out using, for example, a magnetic bead that confirms homogeneous mixing of the precursors during the entire reaction process.
  • the support includes carbon black, acetylene black, Vulcan XC-72R, synthetic or nano-graphite.
  • suitable support materials are, for example, tin oxide, ⁇ -aluminium oxide, titanium dioxide and silicon dioxide.
  • carbon is particularly preferred as a support material.
  • An advantage of carbon as support material is that it is electrically conducting. When the catalyst is used as an electrocatalyst in a fuel cell, it is necessary for it to be electrically conducting to ensure the proper functioning of the fuel cell. CoPd 2 Se 2 has poor conductivity whereas Pd 17 Se 15 has good electronic conductivity, so the former catalyst is supported by Vulcan XC-72R.
  • CoPd 2 Se 2 may be characterized as having an orthorhombic crystal structure with Ibam space group.
  • Pd 17 Se 15 may be characterized as having a cubic crystal structure with Pm3m space group.
  • CoPchSe2 nanoparticles were synthesized by colloidal synthesis method. 0.2 mmol Pd(acac) 2 , 0.2 mmol H 2 Se0 3 and 0.1 mmol of Co(acac) 2 were mixed in 25 ml oleyl amine in a 50 ml two-necked RB. 800 ⁇ of trioctylphosphine was then added to the solution. The RB was then fitted with a condenser, vacuumed and purged with Ar gas. It was then heated at 220°C for 3 h. The product obtained was repeatedly washed with the hexane-ethanol mixture for several times and then dried in vacuum oven at 60°C for 6 h.
  • Pd 17 Se 15 nanoparticles were synthesized by polyol synthesis method.
  • Pd(acac) 2 (0.09 mmol) and H 2 Se0 3 (0.1 mmol) were mixed together in 15 ml TEG in a 50 ml two-necked RB.
  • 40 mg NaBH 4 was then added to the solution followed by stirring thoroughly.
  • the RB was then fitted with a condenser, vacuumed and purged with Ar gas. It was then heated at 220°C for 3 h.
  • the product obtained was repeatedly washed with the hexane-ethanol mixture for several times and then dried in vacuum oven at 60°C for 6 h.
  • TEM images and selected area electron diffraction patterns were collected using a JEOL JEM-2010 TEM instrument, and color mapping were done in TECHNAI.
  • the samples for these measurements were prepared by sonicating the nanocrystalline powders in ethanol and drop-casting a small volume onto a carbon-coated copper grid.
  • IPA IPA
  • Nafion solution (5 wt%, Sigma-Aldrich) is diluted with isopropyl alcohol (IPA) to 0.05 wt%.
  • IPA isopropyl alcohol
  • the GC electrode was polished with 0.05 ⁇ alumina slurry and washed several times with distilled water prior to the deposition of catalyst slurry.
  • Commercial Pt/C (10 wt%, Sigma-Aldrich) (with same Pt loading on the electrode) was used for comparison of activity with the as- synthesized catalysts.
  • Oleyl amine is a long chain primary alkyl amine. It can not only act as a solvent and a surfactant but can also serve as an electron donor at elevated temperature. Oleyl amine act as reducing agent at 220 °C and trioctylphosphine (TOP) act as stabilizing agent. TOP also prevents agglomeration of nanoparticles. Adjusting the ratio between them results in intermediate particle size. In our synthesis approach, oleyl amine act as high boiling point coordinating solvent and also as a reducing and a capping agent.
  • the PXRD pattern of CoPd 2 Se 2 and Pd 17 Se 15 nanoparticles were compared with the simulated patterns as shown in Figure 1 (a, b).
  • the prominent peaks (2 ⁇ values) for CoPd 2 Se 2 crystals were observed at 35.94°, 43.6°, 50.36° which corresponds to the (211), (231) and (042) planes of CoPd 2 Se 2 respectively.
  • PdnSei 5 has prominent peaks (20 values) observed at 27.78°, 44.2°, 48.36° corresponding to the (311), (511,333) and (440) planes of the crystal, respectively.
  • the diffraction pattern of PdnSeis could be indexed as cubic with Pm3m space group.
  • the TEM images show that the CoPd 2 Se 2 nanoparticles are less than 100 nm in size.
  • Figure 2 (a, b) clearly shows the presence of nanoparticles having hexagonal morphology.
  • the TEM images in Figure 3 show that the Pd 17 Se 15 nanoparticles are interlinked with each other and have aggregated morphology and the TEM images prove that the nanoparticles are less than 50 nm in size ( Figure 3a, b).
  • d-spacing between two lattice fringes
  • the SAED pattern shown in Figure 3d shows the polycrystalline nature of the nanoparticles.
  • the diffraction pattern contains (310), (400), (510), (810), (742) planes which confirm the formation of the Pdi 7 Sei 5 nanoparticle.
  • j is the measured current density (niAcm " )
  • j k and j d are the kinetic and diffusion limited current densities.
  • Figure 7c shows the corresponding K-L plot obtained from the inverse current densities
  • the Jd term can be termed from the Levich equation:
  • n is the number of electrons transferred
  • F is the Faraday' s constant (96485 C mol “1 )
  • A is the area of the electrode (0.0706 cm “ )
  • D is the diffusion coefficient of 0 2 in 0.1 M
  • Co2 is the concentration of molecular oxygen in 0.1 M KOH solution. (1.2 x 10 " mol L “ ).
  • Durability test was performed for both the catalyst to assess their ability to sustain activity as shown in Figure 8a. Cyclic potential sweeps were performed between 0.4 V and 0.9 V at a scan rate of 0.1 V/s and a rotation speed of 800 rpm in 0 2 saturated 0.1 M KOH. After 50000 cycles, half-wave potential of CoPd 2 Se 2 /V remains high with a slight negative shift of 11 mV in the mixed kinetic-diffusion limited region. However, Pd 17 Se 15 catalyst has a slight positive shift of 13 mV.
  • Tafel plots were plotted to understand the kinetics of the catalysts.
  • tafel slope obtained towards the ORR before cycling was 53.7 mVdec "1 at lower overpotential which decreased to 43 mVdec "1 ( Figure 8b).
  • Tafel slope has a negligible change from 65 mVdec "1 to 67.5 mVdec "1 .
  • This Tafel slope value close to 60 mVdec "1 indicates that the oxygen reduction catalyzed by the catalysts is controlled by the first charge-transfer step, similar to that of a Pt catalyst.
  • methanol tolerance test was performed to check the stability of the catalyst in the case of fuel-crossover in a fuel cell.
  • Linear sweep voltammetry was run in the presence of 1 M methanol keeping all the experimental parameters same (Figure 8c).
  • No significant change in the nature of the curve was observed after the addition of methanol.
  • Tafel slope value also remains unaffected by the addition of methanol ( Figure 8d).
  • a durability test for Pd 17 Se 15 was performed to assess their ability to sustain activity as shown in Figure 9a. Cyclic potential sweeps were performed between 0.4 V and 0.9 V at a scan rate of 0.1 V/s and a rotation speed of 800 rpm in 0 2 saturated 0.1 M KOH. After 50000 cycles, half-wave potential of Pd 17 Se 15 remains high with a slight positive shift of 13 mV in the mixed kinetic-diffusion limited region.
  • a negative shift in the polarization curve can be seen from Figure 9c. It can be due to the electrochemical leaching of selenium out of Pd 17 Se 15 leading to the formation of exposed Pd. This leads to the creation of similar active site i.e. Pd (0) state. Due to the presence of two dissimilar type of Pd i.e. Pd (0) and Pd 17 Se 15 , it leads to the formation of two types of Pd-0 reduction region. Hence, a hump in the Pd-0 reduction region can be seen.
  • Tafel plots were plotted to understand the kinetics of the catalyst as shown in Figure 9d.
  • Tafel slope obtained towards the ORR before cycling was 65 mVdec "1 at lower overpotential which increased to 67.5 mVdec "1 .
  • This Tafel slope value indicates that the oxygen reduction catalyzed by the Pd 17 Se 15 chalcogenide is controlled by the first charge- transfer step, similar to that of a Pt catalyst.
  • the density of state at Fermi level for cobalt could be changed by some electrons transfer from cobalt to selenium, and the density of state would play a significant role in the chemical adsorption process of oxygen. Therefore, the catalytic activity of the Co-Se compounds for the ORR might attribute to the electronic structure modified by selenium.
  • Palladium binds oxygen strongly to its surface. This inhibits the easy desorption of oxygen or oxygen intermediates from the surface. However, the presence of selenium weakens this oxygen binding to the surface. Selenium gains partial negative charge as seen from the XPS data. This repels the oxygen based intermediates from the surface.
  • Figure 10 a, b compares the polarisation curve of the present invention with the state-of-art- material Pd/C. Comparison between the present invention with Pd/C 40 wt% is given in Table 1 as defined below. Onset potential and half- wave potential of the present invention is comparable to that of Pd/C. Tafel plots were plotted to understand the kinetics of the catalyst. Tafel slope obtained towards the ORR was comparable to that of Pd/C showing similar mechanism being followed by the present invention.
  • the present invention can be extended to many other noble metal chalcogenides presented in Table 2 as defined below:

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Abstract

La présente invention concerne un catalyseur pour une pile à combustible à électrolyte polymère comprenant un chalcogénure à base de métal comprenant un métal de transition et/ou un métal noble et un chalcogène. La présente invention concerne également un procédé monotope pour synthétiser une nanoparticule de chalcogénure à base de métal consistant à : (i) mélanger un ou plusieurs acétylacétonate de métal ou précurseur à base d'acétate avec un précurseur de chalcogène dans un solvant pour obtenir une solution de réaction ; (ii) ajouter un réactif à la solution de réaction ; (iii) chauffer la solution de réaction de l'étape (ii) pour obtenir un produit de réaction ; et (iv) laver le produit de réaction et sécher pour obtenir une nanoparticule de chalcogénure à base de métal. La présente invention concerne une synthèse de nanomatériaux hautement stables et durables ayant une surface riche en sélénium. Le catalyseur surpasse le matériau actuel de l'état de la technique de Pt/C et Pd/C en termes de stabilité et de durabilité.
PCT/IN2018/050168 2017-03-25 2018-03-26 Séléniures à base de palladium en tant que matériaux de cathode hautement stables et durables dans une pile à combustible pour la production d'énergie verte WO2018179006A1 (fr)

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CN112626546A (zh) * 2020-12-18 2021-04-09 电子科技大学 一种rGO@Pd7Se2复合结构纳米材料及其制备方法和应用
CN112850662A (zh) * 2021-02-10 2021-05-28 中国科学技术大学 一种强耦合层状二硒化钴及其制备方法、在电催化氧还原反应制备双氧水中的应用
CN113843413A (zh) * 2021-08-24 2021-12-28 郑州大学 一种PtNi多面体纳米链及其制备方法和应用
CN114602514A (zh) * 2022-01-21 2022-06-10 扬州大学 一种硒微米球表面负载Pd17Se15合金催化剂及其制备方法和应用
CN115044932A (zh) * 2022-05-07 2022-09-13 华东理工大学 一种用于电催化制备过氧化氢的CoSe2纳米催化剂及其制备方法
CN115125563A (zh) * 2022-06-28 2022-09-30 扬州大学 非均相硒化镍载体修饰的铂催化剂、其制备方法及应用

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CN111534834A (zh) * 2020-03-19 2020-08-14 中国科学技术大学 一种抗腐蚀的光阳极复合材料及其制备方法
CN111342068B (zh) * 2020-03-26 2020-11-24 深圳氢时代新能源科技有限公司 夹层式催化剂及其制备方法和应用
CN111342068A (zh) * 2020-03-26 2020-06-26 深圳氢时代新能源科技有限公司 夹层式催化剂及其制备方法和应用
CN112626546A (zh) * 2020-12-18 2021-04-09 电子科技大学 一种rGO@Pd7Se2复合结构纳米材料及其制备方法和应用
CN112626546B (zh) * 2020-12-18 2021-09-24 电子科技大学 一种rGO@Pd7Se2复合结构纳米材料及其制备方法和应用
CN112850662B (zh) * 2021-02-10 2024-02-09 中国科学技术大学 一种强耦合层状二硒化钴及其制备方法、在电催化氧还原反应制备双氧水中的应用
CN112850662A (zh) * 2021-02-10 2021-05-28 中国科学技术大学 一种强耦合层状二硒化钴及其制备方法、在电催化氧还原反应制备双氧水中的应用
CN113843413A (zh) * 2021-08-24 2021-12-28 郑州大学 一种PtNi多面体纳米链及其制备方法和应用
CN114602514B (zh) * 2022-01-21 2023-10-27 扬州大学 一种硒微米球表面负载Pd17Se15合金催化剂及其制备方法和应用
CN114602514A (zh) * 2022-01-21 2022-06-10 扬州大学 一种硒微米球表面负载Pd17Se15合金催化剂及其制备方法和应用
CN115044932A (zh) * 2022-05-07 2022-09-13 华东理工大学 一种用于电催化制备过氧化氢的CoSe2纳米催化剂及其制备方法
CN115044932B (zh) * 2022-05-07 2024-03-22 华东理工大学 一种用于电催化制备过氧化氢的CoSe2纳米催化剂及其制备方法
CN115125563A (zh) * 2022-06-28 2022-09-30 扬州大学 非均相硒化镍载体修饰的铂催化剂、其制备方法及应用
CN115125563B (zh) * 2022-06-28 2023-11-28 扬州大学 非均相硒化镍载体修饰的铂催化剂、其制备方法及应用

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