CN103165911A - Fuel cell cathode nonmetal catalyst with nano sandwich structure and preparation method thereof - Google Patents

Abstract

The invention provides a fuel cell cathode nonmetal catalyst with a nano sandwich structure and a preparation method thereof. The components of the catalyst are formed by a carbon element and a nitrogen element. The three-dimensional nano sandwich structure is formed by a graphene sheet layer and nano conductive carbon granules in an intermediate phase. The size of the interlamellar spacing depends on the particle sizes of the nano conductive carbon granules. Nitrogen is mainly mixed in structures of graphene and the nano conductive carbon granules. The preparation process includes the steps of dispersing the oxidized graphene and the nano conductive carbon granules into deionized water, carrying out evaporation and freeze drying to obtain fluffy taupe lamellar solid, grinding the obtained lamellar solid into powder, and carrying out heat treatment in an atmosphere where the nitrogen exists to obtain the nonmetal catalyst. The fuel cell cathode nonmetal catalyst can be used as the cathode catalyst of proton-exchange membrane fuel cells or alkaline fuel cells. The fuel cell cathode nonmetal catalyst with the nano sandwich structure and the preparation method thereof have the advantages that the preparation method is simple and cost is low; the catalyst is provided with the three-dimensional nano sandwich structure and improves the specific surface area and transmission of substances; and the catalyst is a nonmetal material and has excellent oxygen reduction activity and stability.

Description

Fuel battery negative pole non-metallic catalyst and preparation with nanometer sandwich structure

Technical field

The present invention relates to fuel battery negative pole non-metallic catalyst of a kind of nanometer sandwich structure and preparation method thereof, belong to the technical field of catalyst preparation.

Technical background

Fuel cell becomes the study hotspot of international new energy field with characteristics such as its zero pollution, high efficiency, startup are fast.Yet the performance of fuel battery negative pole oxygen reduction catalyst and cost are the principal elements that the restriction fuel cell moves towards large-scale application all the time.At present as the catalyst of fuel battery negative pole still take the alloy catalyst of Pt and Pt as main, yet, even on the Pt surface of cleaning, the Reduction of oxygen overpotential is still more than 300 millivolts, its catalytic activity to hydrogen reduction is to be not enough to obtain higher energy efficiency.In addition, Pt is as a kind of expensive noble metal, and cost is high, resource-constrained.To this, many trials, as improving the dispersion of Pt particle, Pt particle and transition metal alloy are to reduce the use amount of Pt.Therefore, study novel non-precious metal catalyst, solve the problem of Pt scarcity of resources, fundamentally solve the commercialization problem of fuel cell, be significant.

Compare with anode, cathod catalyst has that consumption is large, generating efficiency is low and the characteristics such as poor durability.The whole reduction process of oxygen molecule is complicated quadrielectron reaction, usually occurs intermediate product in course of reaction, and hydrogen peroxide is arranged, and intermediate state contains oxygen absorption or metal oxide etc.From thermodynamics, hydrogen peroxide is unsettled intermediateness, and its concentration is by dynamics but not thermodynamics determines, therefore causes the reaction mechanism mechanism of reaction complicated, and this also makes non noble metal catalyst for cathode become the emphasis of research.In recent years, domestic and international research to the fuel battery negative pole non-precious metal catalyst has obtained larger progress.

In the middle of the research of numerous novel non-precious metal catalysts, use the nitrogen-doped carbon material, be subject to extensive concern such as nitrogen-doped carbon nanometer pipe, the order mesoporous graphitic carbon of nitrogen doping, nitrogen-doped carbon nano-fiber and nitrogen-doped graphene as oxygen reduction catalyst.The Liming Dai teach problem group of U.S. Dayton university is successively reporting on Science and ACS nano that they find in the research aspect the catalysis of nitrogen-doped nanometer material with carbon element: is using 0.1M KOH as the electrolyte condition under, the aligned carbon nanotube that adulterates through N and the catalytic activity of nitrogen-doped graphene and electrochemistry acceleration cycle life are all apparently higher than the Pt/C catalyst.This is found to be the nitrogen-doped nanometer material with carbon element and provides bright prospect as the application of alkaline fuel cell (AFC) cathod catalyst.Although opinions vary to the active sites of hydrogen reduction in this type of nitrogen-doped nanometer material with carbon element fuel battery cathod catalyst system, undoubtedly, the form of carbon carrier and microscopic appearance are key factors of performance of decision catalyst.

As a kind of novel nano material with carbon element, Graphene (GNS, Graphene nanosheets) be two dimension (2D) the honeycomb lattice material that plane monolayer carbon atom is closely linked and forms, has good physics, chemical characteristic, and because its carbon atom is by sp2 hydridization, thereby stable six-membered ring structure formed, conductivity has great raising with respect to conventional carbon black, thereby is conducive to improve the activity of catalyst.Yet, owing to existing strong Van der Waals force to make its single layer structure unstable between graphene sheet layer, easily again be overlapped into graphite-structure, thus reduction that can be serious its specific area, reduce battery performance.

In order to stop the accumulation again of graphene sheet layer, the inventor introduces the conductive nano carbon granule between graphene sheet layer, thereby forms unique three-dimensional manometer sandwich structure, thereby has effectively improved the active area of catalyst; Simultaneously, also be conducive to keep the high-speed transfer of reactive material and product.

At present, there is not yet the relevant report of the fuel cell non-metallic catalyst preparation with this kind three-dimensional manometer sandwich structure.

Summary of the invention

The object of the invention aims to provide a kind of fuel battery negative pole non-metallic catalyst with nanometer sandwich structure and preparation method thereof.

Technical scheme of the present invention: a kind of fuel cell non-metallic catalyst, this catalyst has the three-dimensional manometer sandwich structure, jointly is comprised of carbon and two kinds of elements of nitrogen on composition.

In technical scheme of the present invention, described three-dimensional manometer sandwich structure is comprised of the conductive nano carbon granule of graphene sheet layer with middle phase, and its interlamellar spacing depends on the particle diameter of conductive nano carbon.

The source of described carbon is Graphene, and conductive nano carbon, conductive nano carbon comprise nanometer conductive carbon black (as Vulcan XC-72 of Cabot company etc.), nano-graphite ball, carbon nano-tube, carbon nano-fiber; Nanometer conductive carbon black, nano-graphite spherolite footpath is 5 ~ 80nm, and the caliber of carbon nano-tube, carbon nano-fiber is 2 ~ 80nm.

Described nitrogen mainly is doped in the structure of Graphene and conductive nano carbon.

Preparation method's process of fuel cell non-metallic catalyst of the present invention is followed successively by:

Step 1: with graphene oxide, conductive nano carbon is uniformly dispersed in deionized water for ultrasonic, removes most of moisture through Rotary Evaporators, and all moisture are removed in then freeze drying, obtains fluffy taupe layered solid;

Step 2: step 1 gained layered solid is pulverized, in the atmosphere that nitrogenous source exists, 600-1000 ℃ of heat treatment 20-60min obtains the black catalyst fines, be non-metallic catalyst, described nitrogenous source is urea, polyaniline, polypyrrole, melamine, ammonia or ammoniacal liquor.

Fuel cell non-metallic catalyst of the present invention is applied to Proton Exchange Membrane Fuel Cells or alkaline fuel cell cathod catalyst.

Compare with background technology, the present invention has the following advantages:

1) preparation method of this catalyst is simple, and synthetic cost is low;

2) catalyst has unique three-dimensional manometer sandwich structure, thereby effectively raises the transmission of specific area and material;

3) catalyst uses is nonmetallic materials;

4) it is active and stable that this nanometer sandwich structure catalyst has excellent hydrogen reduction.

Description of drawings:

Fig. 1 is the SEM figure of catalyst of the present invention

Fig. 2 is the TEM figure of catalyst of the present invention

It is on the rotating disk electrode (r.d.e) of 1600rpm that Fig. 3 has compared in rotary speed, in 0.1M HClO4 solution, and the polarization curve of the reduction kinetics of oxygen on this catalyst and 20wt%Pt/C catalyst.

It is on the rotating disk electrode (r.d.e) of 1600rpm that Fig. 4 has compared in rotary speed, in 0.1M KOH solution, and the polarization curve of the reduction kinetics of oxygen on this catalyst and 20wt%Pt/C catalyst.

Embodiment

Below by embodiment in detail the present invention is described in detail.

Embodiment 1

1) take 75mg graphene oxide (GO), 25mg Vulcan XC-72 in there-necked flask, add the 100ml deionized water, be warming up to 60 ℃ and continuation stirring 2h, then through the Rotary Evaporators dehydration, obtain the dark brown colloidal mixture;

2) said mixture is poured in culture dish, added the liquid nitrogen snap frozen to become solid, then put into the freeze dryer freeze drying, obtain the dark brown nonwoven fabric from filaments after 24 hours; Then in tube furnace, NH ₃Under atmosphere, in the time of 250 ℃ the insulation 1 hour, then be warming up to 1000 ℃ the insulation 30min, heating rate be 5 ℃ per minute, obtain at last the black catalyst fines.Fig. 1 is the SEM figure of this catalyst, and Fig. 2 is the TEM figure of this catalyst.

Catalyst half-cell performance test method be with catalyst-coated in rotating disk electrode (r.d.e) supporting glass-carbon electrode surface as work electrode, it is the Pt sheet of 1 * 1cm to electrode, reference electrode is saturated calomel (Hg/HgCl) electrode, and electrolyte is the HClO of 0.5mol/L ₄Perhaps KOH solution.According to the experiment needs, before test, need to pass into enough oxygen in electrolyte, make that in electrolyte, oxygen reaches capacity, in the process of test, oxygen continues to pass into, and the rotating speed of rotating disk electrode (r.d.e) is adjusted to 1600 rev/mins, with 50mVS ^-1Sweep speed and test, the scope of scanning is 0.4-1.2V.Generally before test, work electrode is used electrochemical cyclic voltammetry scanning for several times, catalyst is carried out activation processing, to obtain stable hydrogen reduction (ORR) curve.Using the Koutecky-Levich equation calculates

$\frac{1}{i}=\frac{1}{i_k}+\frac{1}{i_d}$

Wherein i represents the experiment electric current of surveying, i _dThe expression dissufion current, i _kExpression dynamics electric current.Can calculate the mass activity of reaction.Fig. 3 and Fig. 4 have compared respectively this catalyst (N-GCG) activity with respect to business Pt/C catalyst in acid and alkaline electrolyte.With respect to standard hydrogen electrode, in acidic electrolyte bath, its mass activity 7.2Ag under the 0.8V electromotive force ^-1In alkaline electrolyte, under the 0.9V electromotive force, its mass activity is 16.3A g ^-1

Embodiment 2

1) take 75mg graphene oxide (GO), 25mg nano-graphite ball in there-necked flask, add the 100ml deionized water, be warming up to 60 ℃ and continuation stirring 2h, then through the Rotary Evaporators dehydration, obtain the dark brown colloidal mixture;

2) said mixture is poured in culture dish, added the fast brush of liquid nitrogen to be frozen into solid, then put into the freeze dryer freeze drying, obtain the dark brown nonwoven fabric from filaments after 24 hours; Then in tube furnace, melamine is as nitrogenous source, and under nitrogen atmosphere, in the time of 250 ℃, insulation is 1 hour, then is warming up to 600-700 ℃ of insulation 30min, heating rate be 5 ℃ per minute, obtain at last the black catalyst fines.

In the present embodiment, catalyst half-cell performance test and above-described embodiment 1 are identical.Different is that the catalyst that adopts is the prepared catalyst of the present embodiment.With respect to standard hydrogen electrode, in acidic electrolyte bath, its mass activity 6.9A g under the 0.8V electromotive force ^-1In alkaline electrolyte, under the 0.9V electromotive force, its mass activity is 14.7A g ^-1

Embodiment 3

1) take 50mg graphene oxide (GO), 50mg carbon nano-tube in there-necked flask, add the 100ml deionized water, be warming up to 60 ℃ and continuation stirring 2h, then through the Rotary Evaporators dehydration, obtain the dark brown colloidal mixture;

2) said mixture is poured in culture dish, added the fast brush of liquid nitrogen to be frozen into solid, then put into the freeze dryer freeze drying, obtain the dark brown nonwoven fabric from filaments after 24 hours; Then in tube furnace, urea is as nitrogenous source, and under argon gas atmosphere, in the time of 250 ℃, insulation is 1 hour, then is warming up to 800-900 ℃ of insulation 30min, heating rate be 5 ℃ per minute, obtain at last the black catalyst fines.

In the present embodiment, catalyst half-cell performance test and above-described embodiment 1 are identical.Different is that the catalyst that adopts is the prepared catalyst of the present embodiment.With respect to standard hydrogen electrode, in acidic electrolyte bath, its mass activity 6.4A g under the 0.8V electromotive force ^-1In alkaline electrolyte, under the 0.9V electromotive force, its mass activity is 14.5A g ^-1

Embodiment 4

1) take 25mg graphene oxide (GO), 75mg carbon nano-fiber in there-necked flask, add the 100ml deionized water, be warming up to 60 ℃ and continuation stirring 2h, then through the Rotary Evaporators dehydration, obtain the dark brown colloidal mixture;

2) said mixture is poured in culture dish, added the fast brush of liquid nitrogen to be frozen into solid, then put into the freeze dryer freeze drying, obtain the dark brown nonwoven fabric from filaments after 24 hours; Then in tube furnace, polyaniline is as nitrogenous source, and under argon gas atmosphere, in the time of 250 ℃, insulation is 1 hour, then is warming up to 900 ℃ of insulation 30min, heating rate be 5 ℃ per minute, obtain at last the black catalyst fines.

In the present embodiment, catalyst half-cell performance test and above-described embodiment 1 are identical.Different is that the catalyst that adopts is the prepared catalyst of the present embodiment.With respect to standard hydrogen electrode, in acidic electrolyte bath, its mass activity 6.1A g under the 0.8V electromotive force ^-1In alkaline electrolyte, under the 0.9V electromotive force, its mass activity is 12.7A g ^-1

Embodiment 5

1) take 50mg graphene oxide (GO), 50mg Vulcan XC-72 in there-necked flask, add the 100ml deionized water, be warming up to 60 ℃ and continuation stirring 2h, then through the Rotary Evaporators dehydration, obtain the dark brown colloidal mixture;

2) said mixture is poured in culture dish, added the fast brush of liquid nitrogen to be frozen into solid, then put into the freeze dryer freeze drying, obtain the dark brown nonwoven fabric from filaments after 24 hours; Then in tube furnace, polypyrrole is as nitrogenous source, and under nitrogen atmosphere, in the time of 250 ℃, insulation is 1 hour, then is warming up to 1000 ℃ of insulation 30min, heating rate be 5 ℃ per minute, obtain at last the black catalyst fines.

In the present embodiment, catalyst half-cell performance test and above-described embodiment 1 are identical.Different is that the catalyst that adopts is the prepared catalyst of the present embodiment.With respect to standard hydrogen electrode, in acidic electrolyte bath, its mass activity 5.8A g under the 0.8V electromotive force ^-1In alkaline electrolyte, under the 0.9V electromotive force, its mass activity is 13.6A g ^-1

Claims (6)

1. fuel cell non-metallic catalyst, it is characterized in that: this catalyst has the three-dimensional manometer sandwich structure, jointly is comprised of carbon and two kinds of elements of nitrogen on composition.

2. fuel cell non-metallic catalyst according to claim 1, it is characterized in that: described three-dimensional manometer sandwich structure is comprised of the conductive nano carbon granule of graphene sheet layer with middle phase, and its interlamellar spacing depends on the particle diameter of conductive nano carbon.

3. fuel cell non-metallic catalyst according to claim 1, it is characterized in that: the source of described carbon is Graphene, conductive nano carbon, conductive nano carbon comprise nanometer conductive carbon black, nano-graphite ball, carbon nano-tube, carbon nano-fiber; Nanometer conductive carbon black, nano-graphite spherolite footpath is 5 ~ 80nm, and the caliber of carbon nano-tube, carbon nano-fiber is 2 ~ 80nm.

4. fuel cell non-metallic catalyst according to claim 1, it is characterized in that: described nitrogen mainly is doped in the structure of Graphene and conductive nano carbon.

5. the preparation method of fuel cell non-metallic catalyst claimed in claim 1 is characterized in that preparation process is followed successively by:

Step 1: with graphene oxide, conductive nano carbon is uniformly dispersed in deionized water for ultrasonic, removes most of moisture through Rotary Evaporators, and all moisture are removed in then freeze drying, obtains fluffy taupe layered solid;

Step 2: step 1 gained layered solid is pulverized, in the atmosphere that nitrogenous source exists, 600-1000 ℃ of heat treatment 20-60min obtains the black catalyst fines, be non-metallic catalyst, described nitrogenous source is urea, polyaniline, polypyrrole, melamine, ammonia or ammoniacal liquor.

6. the application of fuel cell non-metallic catalyst claimed in claim 1 is characterized in that being applied to Proton Exchange Membrane Fuel Cells or alkaline fuel cell cathod catalyst.

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