The present disclosure generally relates to catalyst, and particularly to PtNiN electrode catalysts for fuel cells and fuel cells with PtNiN electrode catalysts.
Fuel cells with polymer electrolyte membranes (PEMs) are used as energy sources for transportation due to their high-power density, low operation temperatures, and zero emission of harmful gases. However, electrolytes used in PEM fuel cells can include one or more components that poison anode and/or cathode catalyst materials of a PEM fuel cell and thereby reduce the power output and efficiency thereof.
The present disclosure addresses the issue of poisoning of anode and/or cathode catalyst materials of PEM fuel cells, and other issues related to PEM fuel cells.
In one form of the present disclosure, a fuel cell includes an anode, a cathode, and a polymer electrolyte membrane disposed between the anode and the cathode. Also, a cathode catalyst is disposed on the cathode and the cathode catalyst includes nitrogen doped platinum nickel (PtNiN) nanoparticles loaded on mesoporous carbon. The PtNIN nanoparticles have an average diameter between about 1.0 nm and about 10.0 nm, the mesoporous carbon has a plurality of pores, the majority of the pores have an average pore diameter less than about 8.0 nm, and at least a portion of the PtNiN nanoparticles are disposed within the majority of the pores having an average pore diameter less than about 8.0 nm.
In another form of the present disclosure, a fuel cell includes an anode, a cathode, a polymer electrolyte membrane disposed between the anode and the cathode, and an ionomer in contact with the cathode. A cathode catalyst is disposed on the cathode and the cathode catalyst includes PtNiN nanoparticles loaded on mesoporous carbon. At least a portion of the PtNiN nanoparticles are disposed within pores of the mesoporous carbon and are spaced apart from the ionomer. The PtNiN nanoparticles have an average diameter between about 1.0 nm and about 10.0 nm and at least 85% of the pores of the mesoporous carbon have an average pore diameter less than about 8.0 nm.
In still another form of the present disclosure, a fuel cell includes an anode, a cathode, and an ionomer containing polymer electrolyte membrane disposed between the anode and the cathode. A cathode catalyst is disposed on the cathode and the cathode catalyst includes PtNiN nanoparticles loaded on mesoporous carbon. At least a portion of the PtNiN nanoparticles are disposed within pores of the mesoporous carbon spaced apart from the ionomer. The PtNiN nanoparticles have an average diameter between about 1.0 nm and about 8.0 nm and at least 90% of the pores of the mesoporous carbon have an average diameter less than about 8.0 nm.
These and other features of the fuel cells will become apparent from the following detailed description when read in conjunction with the figures and examples, which are exemplary, not limiting.
The present teachings will become more fully understood from the detailed description and the accompanying drawings, wherein:
It should be noted that the figures set forth herein is intended to exemplify the general characteristics of the methods, algorithms, and devices among those of the present technology, for the purpose of the description of certain aspects. The figure may not precisely reflect the characteristics of any given aspect and are not necessarily intended to define or limit specific forms or variations within the scope of this technology.
The present disclosure provides an electrode catalyst material (also referred to herein simply as “catalyst material”) and PEM fuel cells with the catalyst material. The catalyst material includes a combination of enhanced mesoporous carbon support particles (also referred to herein simply as “enhanced mesoporous carbon particles” or “enhanced mesoporous carbon”) with pores having an average pore diameter within a predefined range and platinum (Pt) containing nanoparticles having an average particle diameter within a predefined range that is less than or equal to the average pore diameter of the enhanced mesoporous carbon particles. In addition, the Pt-containing nanoparticles are loaded (i.e., positioned) within the pores of the enhanced mesoporous carbon particles such that the Pt-containing nanoparticles are effectively shielded from ionomer poisoning, inhibited from nanoparticle agglomeration, and/or inhibited from nanoparticle growth.
As used herein, the phrase “enhanced mesoporous carbon particles” or “enhanced mesoporous carbon” refers to mesoporous carbon particles with pores and at least 80% of the pores have an average diameter less than or equal to 8.0 nm.
Referring now to
During operation of the PEM fuel cell 10, hydrogen (H2) gas is provided to and flows through an anode-side inlet 140 and oxygen (O2) gas (e.g., O2 in air) is provided to and flows through a cathode-side inlet 160. At least a portion of the H2 flows into contact with the anode 120 and migrates to the PEM 110 where H2 molecules are catalyzed into H+ ions plus electrons ‘e−’ (e.g., via an anode catalyst layer—not shown). Also, at least a portion of the O2 gas flows into contact with the cathode and migrates to the PEM 110. The electrons e″ flow through the external electrical circuit 150 to the cathode 130 and react with O2 molecules to form O2− ions (e.g., via the cathode catalyst layer 132) and the H+ ions diffuse through the PEM 110 to the cathode 130 and react with the O2− ions to form H2O (water), which is then transported out of the PEM fuel cell 10 with the flow of unreacted O2. In this manner, the Pt-containing nanoparticles 133 assist in and enhance the reaction of O2+e− to O2− and/or O2−+H+ to H2O and electricity is generated by the PEM fuel cell 10.
Referring specifically to
Referring now to
A majority of the pores 139p of the enhanced mesoporous carbon particles 139 have an average pore diameter such that the Pt-containing nanoparticles 137 are disposed within the pores 139p with a “tight fit.” As used herein, the phrase “tight fit” refers to a difference between the average pore diameter of the pores 139p and the average diameter of the Pt-containing nanoparticles 137 being less than 10 nanometers (nm). For example, in at least one variation a difference between the average pore diameter of the pores 139p and the average diameter of the Pt-containing nanoparticles 137 is less than 5 nm, and in some variations a difference between the average pore diameter of the pores 139p and the average diameter of the Pt-containing nanoparticles 137 is less than 2.5 nm.
In some variations the Pt-containing nanoparticles 137 are nitrogen-doped platinum nickel (PtNiN) nanoparticles 137 with an average particle size between about 1.0 nm and about 8.0 nm. In some variations, the Pt-containing nanoparticles 137 are generally spherical in shape, while in other variations the Pt-containing nanoparticles 137 are not generally spherical in shape. For example, the Pt-containing nanoparticles 137 are generally cuboidal in shape, generally cylindrical in shape, among others. In at least one variation, the PtNiN nanoparticles 137 are core-shell nanoparticles with a PtNiN core and a Pt shell. In other variations, the PtNiN nanoparticles 137 have a NiN core decorated with islands of Pt and/or PtN. i.e., Pt and/or PtN islands are supported on the NiN Core, and the Pt and/or PtN islands may or may not be discrete nanoparticles.
In variations where the Pt-containing nanoparticles 137 have an average particle size between about 1.0 nm and about 8.0 nm, at least than 85% of the pores 139p of the enhanced mesoporous carbon particles 139 have an average pore diameter less than about 8.0 nm. And in at least one variation, at least 90% of the pores 139p of the enhanced mesoporous carbon particles 139 have an average pore diameter less than about 8.0 nm. For example, in some variations the enhanced mesoporous carbon particles 139 have a pore size distribution of between 5-30% micropores with an average pore diameter less than 2.0 nm, between 50-95% mesoporous with an average pore diameter between 2.0 nm and 8.0 nm, and between 0-25% macropores with an average pore diameter greater than 8.0 nm.
In at least one variation, the enhanced mesoporous carbon particles 139 have a pore size distribution of 10-25% micropores with an average pore diameter less than about 2.0 nm, more than 70% mesopores with an average pore diameter between about 2.0 nm and about 8.0 nm, and less than 10% macropores with an average pore diameter greater than about 8.0 nm. And in some variations, the enhanced mesoporous carbon particles 139 have a pore size distribution of 15-20% micropores with an average pore diameter less than about 2.0 nm, more than 75% mesopores with an average pore diameter between about 2.0 nm and about 8.0 nm, and less than 7.5% macropores with an average pore diameter greater than about 8.0 nm. In addition, the enhanced mesoporous carbon particles have a BET surface area greater than 1,000 m2/g, for example, between about 1,000 m2/g and 2,000 m2/g.
Not being bound by theory, the tight fit between the average pore diameter of the pores 139p and the average diameter of the Pt-containing nanoparticles 137 results in enhanced mass activity of the composite particles 138 due to limited space for the Pt-containing nanoparticles 137 within the pores 139p to agglomerate and/or grow in size. In addition, the tight fit provides or enables a boundary layer of water ‘w’ to be present between the Pt-containing nanoparticles 137 and the ionomer 112 as illustrated in
In an effort to better describe the teachings of the present disclosure but not limit the scope in any manner, the synthesis and evaluation of different composite particles are described below.
Precursors of PtNiN catalysts were prepared by dispersing 330 mg of Pt(acac)2. 220 mg Ni(acac)2 and 500 mg of carbon support in 80 mL of acetone, followed by sonication for 2 hours. The resulting suspension was kept at room temperature with magnetic stirring for 2 hours and then the resulting mixture was dried by a rotating evaporator device to provide a dried precursor. The dried precursor was then annealed in a tube furnace under flowing NH3 to obtain samples with different particle sizes and the annealing conditions of the different PtNiN samples were: 500° C. for 2 hours to provide PtNiN nanoparticles with an average diameter equal to 2.6 nm loaded onto ketjenblack EC-300J carbon black particles (Sample 1); 500° C. for 2 hours to provide PtNiN nanoparticles with an average diameter equal to 1.7 nm loaded onto enhanced mesoporous carbon particles (Sample 2); 650° C. for 8 hours to provide PtNiN nanoparticles with an average diameter equal to 7.2 nm loaded onto enhanced mesoporous carbon particles (Sample 3); 650° ° C. for 9 hours to provide PtNiN nanoparticles with an average diameter equal to 9.3 nm loaded onto enhanced mesoporous carbon particles (Sample 4); and 500° C. for 2 hours to provide PtNiN nanoparticles with an average diameter equal to 2.4 nm loaded onto a commercially available mesoporous carbon particles (Sample 5). Table 1 below provides a summary of Samples 1-5.
The enhanced mesoporous carbon particles had a BET surface area greater than 1000 m2/g and a pore size distribution of 18.3% micropores with an average pore diameter less than about 2.0 nm, 76.7% mesopores with an average pore diameter between about 2.0 nm and about 8.0 nm, and 5.0% macropores with an average pore diameter greater than about 8.0 nm. The commercially available mesoporous carbon had a BET surface area equal to 815 m2/g and a pore size distribution of 2.7% micropores with an average pore diameter less than about 2.0 nm, 69.9% mesopores with an average pore diameter between about 2.0 nm and about 8.0 nm, and 27.4% macropores with an average pore diameter greater than about 8.0 nm. Also, the average particle size for the PtNiN nanoparticles of each sample was obtained via x-ray diffraction (XRD) with the XRD scan for Sample 1 shown in
Samples 1-5 were initially evaluated with the RDE technique by dispersing a given sample into a solution containing 4 mL of double distilled water, 2.25 mL isopropanol, and 25 μL Nafion dispersion (DE250) to produce an ink that was subjected to ultrasonication for 60 minutes in an ice bath. A 10 μL of the ink was pipetted onto a glassy carbon disk (5 mm dia., Pinc) and rotationally dried in air to form a uniform catalyst layer. The catalyst coated glassy carbon was pre-conditioned in N2-saturated 0.1M HClO4 and then scanned from 0.05 V to 1.2 V with a scan rate of 100 mV/s until the cyclic voltage did not change. Then, oxygen reduction reaction (ORR) measurements were conducted in the N2-saturated 0.1 M HClO4 and multiple independent data sets were collected with intrinsic activities corrected with N2-background and infrared (IR) compensation. The mass activity for the five samples is shown in
Samples 1-4 were evaluated with the MEA technique by mixing a given sample with ethanol, water, and ionomer to form an ink. The ionomer to carbon ratio was 0.85 and the ink was vigorously mixed and coated on a poly (tetrafluoro-ethylene) substrate (CARR) using a doctor-blade casting method to form a cathode catalyst material. Similarly, a Pt/C (30 wt. % Pt content, TEC10EA30E, TKK) catalyst layer with an ionomer to carbon ratio of 0.7 was prepared as an anode catalyst material. The coating layer was dried at 80° C. to remove the solvent and the final anode and cathode Pt loading were controlled at 0.05 mg Pt/cm2 and 0.1 mg Pt/cm2, respectively. Individual cathode and anode electrocatalyst layers (2 cm×2 cm) were punched and a 12 μm think Gore®-Select membrane was sandwiched therebetween to form a catalyst coated membrane using a decal-transfer technique. Hot-pressing of the cathode electrocatalyst layer, Gore membrane, and anode electrocatalyst layer was performed at 130° C. and 0.8 MPa for 5 minutes. Gas diffusion layers (29 BC, SGL Carbon) together with the catalyst coated membrane were assembled in a single cell with a serpentine flow field (Scribner Associates).
Samples 1-4 were evaluated with an 850e Fuel Cell test system (Scribner Associates) for MEA performance evaluation. A given MEA was first activated by sweeping between 0.9 V to 0.1 V for several hundred cycles under H2/Air (1.5 NLPM/2 NMPM) at 45° C. and 100% relative humidity (RH). Then the current-voltage (i-V) performance of the MEA was evaluated at 80° C. under 90% RH. Ultrapure H2 and Air (Airgas) were supplied to the anode and cathode, respectively, with an absolute pressure of 200 KPa. The current density was set and increased at 0.05 A/cm2 increments until 3 A/cm2 was reached and the response voltage was recorded simultaneously. The ORR activities at 0.9 V were obtained from the H2/O2 (0.5 NLPM L/2 NLPM) polarization curve at 80° C. 100% RH, and 150 KPa (abs), which was corrected with ohmic resistance and H2 crossover.
Referring to
Not being bound by theory, and even though the sample with 7.2 nm PtNiN nanoparticles loaded on enhanced mesoporous carbon particles (Sample 3) had the highest mass activity when evaluated using the RDE technique (
The preceding description is merely illustrative in nature and is in no way intended to limit the disclosure, its application, or uses. As used herein, the phrase at least one of A, B, and C should be construed to mean a logical (A or B or C), using a non-exclusive logical “or.” It should be understood that the various steps within a method may be executed in different order without altering the principles of the present disclosure. Disclosure of ranges includes disclosure of all ranges and subdivided ranges within the entire range.
The headings (such as “Background” and “Summary”) and sub-headings used herein are intended only for general organization of topics within the present disclosure and are not intended to limit the disclosure of the technology or any aspect thereof. The recitation of multiple forms or variations having stated features is not intended to exclude other forms or variations having additional features, or other forms or variations incorporating different combinations of the stated features.
As used herein the term “about” when related to numerical values herein refers to known commercial and/or experimental measurement variations or tolerances for the referenced quantity. In some variations, such known commercial and/or experimental measurement tolerances are +/−10% of the measured value, while in other variations such known commercial and/or experimental measurement tolerances are +/−5% of the measured value, while in still other variations such known commercial and/or experimental measurement tolerances are +/−2.5% of the measured value. And in at least one variation, such known commercial and/or experimental measurement tolerances are +/−1% of the measured value.
As used herein, the terms “comprise” and “include” and their variants are intended to be non-limiting, such that recitation of items in succession or a list is not to the exclusion of other like items that may also be useful in the devices and methods of this technology. Similarly, the terms “can” and “may” and their variants are intended to be non-limiting, such that recitation that a form or variation can or may comprise certain elements or features does not exclude other forms or variations of the present technology that do not contain those elements or features.
The broad teachings of the present disclosure can be implemented in a variety of forms. Therefore, while this disclosure includes particular examples, the true scope of the disclosure should not be so limited since other modifications will become apparent to the skilled practitioner upon a study of the specification and the following claims. Reference herein to one aspect, or various aspects means that a particular feature, structure, or characteristic described in connection with a form or variation is included in at least one form or variation. The appearances of the phrase “in one variation” or “in one form” (or variations thereof) are not necessarily referring to the same form or variation. It should be also understood that the various method steps discussed herein do not have to be carried out in the same order as depicted, and not each method step is required in each form or variation.
The foregoing description of the forms or variations has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular form or variation are generally not limited to that particular form or variation, but, where applicable, are interchangeable and can be used in a selected form or variation, even if not specifically shown or described. The same may also be varied in many ways. Such variations should not be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure.
While particular forms or variations have been described, alternatives, modifications, variations, improvements, and substantial equivalents that are or may be presently unforeseen may arise to applicants or others skilled in the art. Accordingly, the appended claims as filed and as they may be amended, are intended to embrace all such alternatives, modifications variations, improvements, and substantial equivalents.
The present invention was made with government support under contract number DE-SC0012704 awarded by the U.S. Department of Energy. The United States government may have certain rights in this invention.