CN102476053B - Preparation method of Pd-Ag/C catalyst - Google Patents
Preparation method of Pd-Ag/C catalyst Download PDFInfo
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- CN102476053B CN102476053B CN2010105672238A CN201010567223A CN102476053B CN 102476053 B CN102476053 B CN 102476053B CN 2010105672238 A CN2010105672238 A CN 2010105672238A CN 201010567223 A CN201010567223 A CN 201010567223A CN 102476053 B CN102476053 B CN 102476053B
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Abstract
The invention relates to a preparation method of a Pd-Ag/C catalyst, wherein, Pd accounts for 1-30% by mass, and the mass of Ag is not greater than 25% of Pd content. The catalyst is prepared by an impregnation-reduction method, which comprises: (1) dispersion of a carbon carrier, (2) preparation of an impregnation solution and (3) preparation of a Pd-Ag/C catalyst. In the preparation process of the catalyst, a protective agent is not needed to be added to control catalyst particle size and alloy degree. In an alkaline medium, the catalyst has high catalytic activity on oxidation of small molecular alcohol and good stability, and the preparation process has no toxicity and pollution, so that the catalyst can be produced in large scale. And the catalyst of the invention can be used as an electrochemical oxidation catalyst of medium and small molecular alcohol in an alkaline medium, and is especially suitable to be used as a small molecular alcohol fuel oxidation catalyst of alkaline direct alcohol fuel cells.
Description
Technical field
The present invention relates to small molecular alcohol oxidation catalyst under a kind of alkali condition, relate to a kind of preparation method of the small molecular alcohol fuel oxidizing catalyst agent for alkaline fuel cell specifically.
Background technology
Along with the research and development of anion-exchange membrane, the problem of alkaline fuel cell carbonating has obtained solution to a certain degree.In alkaline solution, because the dynamic process of the electrochemical oxidation of little molecule fuel such as methyl alcohol, ethanol and hydrogen reduction is very fast, can improve the catalytic efficiency of fuel cell greatly on the one hand; Because it can adopt non-Pt eelctro-catalyst, can reduce the cost of fuel cell on the other hand.Therefore, alkaline fuel cell has caused scientific research personnel's extensive concern again.
Document (Electrochemistry Communications 2007; 9:2760-2763) point out: the catalytic activity that carbon carries the oxidation of Pd eelctro-catalyst catalyzing alcohols in alkaline medium is higher than the Pt eelctro-catalyst, and compare with Pt, Pd has that price is low, reserves are abundant and have identical characteristics such as outer electronic structure with Pt, can be used as the catalyst based alternative metals of Pt.At present, the catalyst based research of Pd mainly concentrate on carbon carrier change, catalyst microscopic appearance change and add several aspects such as other metals or metal oxide.But still the catalyst that the catalytic activity of relatively not generally acknowledged is higher, stability is better, with low cost.
According to the d-band principle, the Ag that lattice paprmeter is bigger (a=0.409nm) is doped to and can causes among the less Pd of lattice paprmeter (a=0.389nm) that Pd atom d-band energy raises, and with the binding ability increase of reactant, and then improves its catalytic activity, reduce the Pd consumption, reduce cost.
Document (Applied Catalysis B:Environmental 2009; 91:507-515) adopt the coreduction method to prepare the Pd-Ag/C catalyst.Similar to conventional method, in order to reduce to have added protective agent in its preparation process of catalyst particle size, therefore cause adopting catalytic activity and the stability of catalyst of this method preparation still unsatisfactory, still need do further improvement on the prior art basis.
Summary of the invention
The present invention is directed to the deficiencies in the prior art; purpose is to provide a kind of small molecular alcohol oxidized eelctro-catalyst that is applied to alkaline fuel cell and preparation method thereof; this catalyst is active high for the electro-oxidizing-catalyzing of small molecular alcohol fuel; good stability; abundant and cost is lower with the catalyst based raw material sources of comparing of Pt commonly used; preparation process is simple, is conducive to the large-scale production of product.
For achieving the above object, the present invention adopts following concrete scheme to realize:
A kind of Pd-Ag/C Preparation of catalysts method may further comprise the steps,
1) dispersion of carbon carrier: get carbon carrier and mix with absolute ethyl alcohol, stir and make carbon carrier evenly dispersion in ethanol, form slurries; Carbon carrier forms uniform slurries because himself close and distant water characteristic makes it disperse than being easier in ethanol, if use instead water do dispersant stir stop after, carbon carrier is coagulation again easily.
2) preparation of maceration extract:
With Pd (NO
3)
2, or Pd (NO
3)
2With AgNO
3Mixed dissolution forms solution in deionized water, this solution is dropwise dripped or is poured in the step (1) fill in the container of carbon carrier slurries; Pd (NO
3)
2And AgNO
3Solution soluble in water is conducive on the carbon carrier surface evenly dipping;
Or with Pd (NO
3)
2With AgNO
3Be dissolved in respectively and form solution in the deionized water, by first Pd (NO
3)
2AgNO behind the solution
3Solution or first AgNO
3Pd (NO behind the solution
3)
2The order of solution successively dropwise drips or is poured in the step (1) and fills in the container of carbon carrier slurries; Metal precursor Pd (NO
3)
2, or Pd (NO
3)
2With AgNO
3Mixed solution dropping order is different, can form the diverse microcosmic structure on the carbon carrier surface; If reaction is by external diffusion control usually, eggshell type is advisable; Reaction is during by dynamics Controlling: evenly be distributed as suitable; Toxic then be advisable by albumen, yolk type in the medium.Can regulate and control the metallic atom structure of final catalyst by the difference dropping order of precursor, and then regulate and control the catalyst activity;
In the dipping system volume of deionized water be the ethanol volume 0.5-1.5 doubly; Dip time 〉=3h;
3) Pd-Ag/C Preparation of catalysts:
A. with the maceration extract evaporate to dryness that obtains in the above-mentioned steps (2); Prevent that metal precursor becomes bulky grain at the carbon carrier surface aggregation in dry run, influence the catalyst activity;
B. in 50-85 ℃ of evaporate to dryness thing drying 〉=5h that obtains in above-mentioned steps (3) a, obtain black powder; Temperature is too low can not be fully dry, and temperature is grown up very much easy gathering of high catalyst particle, influences catalytic activity;
C. the black powder that above-mentioned steps is obtained places tube furnace temperature programming under inert gas atmosphere to handle, black powder from normal temperature with the speed temperature programming of 1-10 ℃/min to 105-130 ℃, and under this temperature heat treatment 20-60min, afterwards with the speed temperature programming of 1-10 ℃/min to 150-700 ℃;
D. keep the final temperature in the above-mentioned steps, feeding volume fraction in tube furnace is the H of 1-15%
2Mist with inert gas, behind the heat treatment 1-3h, to black powder wash, drying, obtain target product Pd-Ag/C catalyst, active constituent is Pd or Pd and Ag in the catalyst, the total mass content of active constituent in catalyst is 1-30%, and the quality of Ag is not more than 25% of Pd content.
The ratio of described carbon carrier and absolute ethyl alcohol is that the volume of every 20mg carbon carrier adding absolute ethyl alcohol is 5-40mL.
Above-mentioned steps 2) Pd (NO in the dipping system of preparing in the process for preparation of maceration extract
3)
2Mass concentration is 0.02mg/mL to 7.8mg/mL, AgNO
3Mass concentration is 0.005mg/mL to 1.95mg/mL.
With the black powder that obtains among above-mentioned steps (3) b grind, weighing is placed in quartz or the pottery; Send in the tube furnace then.
Above-mentioned steps (3) a is in 30-70 ℃ of maceration extract rotation evaporate to dryness that obtains in above-mentioned steps (2).
Described dipping process carries out dipping 〉=3h under 0-50 ℃ of magnetic agitation condition.
Described carbon carrier is one or more the mixture in XC-72R, BP2000, acetylene black, CNT, the graphite oxide.
Described inert atmosphere is one or more the mixture in nitrogen, argon gas, the helium.
Described Pd-Ag/C catalyst can be used as small molecular alcohol oxidized eelctro-catalyst in the alkaline medium; Described small molecular alcohol fuel is the alcohols of C1-C6, as methyl alcohol, ethanol, propyl alcohol, ethylene glycol, glycerine, n-butanol, glucose etc.
Compared with prior art, Pd-Ag/C Preparation of catalysts method of the present invention has the following advantages:
1. adopt the Pd-Ag/C catalyst of the method for the invention preparation, can be by control H
2Flow, recovery time and reduction temperature regulate and control to synthesize catalyst microscopic appearances such as the particle diameter, crystal structure, alloy degree of this catalyst, can realize catalyst is carried out the design of nano-scale.
2. adopt the method for the invention to prepare the Pd-Ag/C catalyst, do not introduce the growth that protective agent is controlled particle diameter in the preparation process, the phenomenon that protective agent is difficult to remove and suppress catalytic activity can not occur, therefore the activity than conventional catalyst is high.
3. adopt the Pd-Ag/C catalyst of the method for the invention preparation, can regulate and control the metallic atom structure of final catalyst by the difference dropping of precursor in proper order, and then improve the catalyst activity;
4. adopt the method for the invention to prepare the Pd-Ag/C catalyst, preparation process does not have noxious material and participates in, and safety non-pollution, is conducive to environmental protection;
5. adopt the method for the invention to prepare the Pd-Ag/C catalyst, preparation process is simple, is conducive to the amplification production of this catalyst, accelerates its process of industrialization;
6. the Pd-Ag/C catalyst that adopts the method for the invention to prepare can pass through to select suitable baking temperature, the size of control catalyst particle when guaranteeing the abundant drying of catalyst, and then improve catalytic activity;
7. adopt the method for the invention to prepare the Pd-Ag/C catalyst, the selection of alcohol dispersant is conducive to carbon carrier and is uniformly dispersed therein; Pd (NO
3)
2And AgNO
3As the selection of precursor, be conducive to the two and evenly flood on the carbon carrier surface;
8. adopt the Pd-Ag/C catalyst of the method for the invention preparation, in alkaline medium, active high to the electro-oxidizing-catalyzing of small molecular alcohol fuel, stability better concerning oxidation of ethanol, obviously is better than commodity Pt/C catalyst;
Description of drawings:
Fig. 1 is the XRD spectra of the sample for preparing according to comparative example 1,3,4,5.
Fig. 2 is for according to comparative example 5,6 and the XRD spectra of the sample for preparing of embodiment 1,2,3,4,9.
Fig. 3 is the XRD spectra of the sample for preparing according to embodiment 5-9.
Fig. 4 for the sample for preparing according to comparative example 1-5 at N
2CV figure in the saturated 1.0MNaOH electrolyte.
Fig. 5 for the sample for preparing according to comparative example 1-5 at N
2Saturated 1.0M NaOH+1.0MCH
3CH
2CV figure in the OH electrolyte.
Fig. 6 for according to comparative example 5,7 and the sample for preparing of embodiment 1,2,3,4,9 at N
2CV figure in the saturated 1.0M NaOH electrolyte.
Fig. 7 for according to comparative example 5,7 and the sample for preparing of embodiment 1,2,3,4,9 at N
2Saturated 1.0M NaOH+1.0M CH
3CH
2CV figure in the OH electrolyte.
Fig. 8 for the sample for preparing according to embodiment 5-9 at N
2Saturated 1.0M NaOH+1.0MCH
3CH
2CV figure in the OH electrolyte.
The specific embodiment
Be explained in detail below in conjunction with the present invention of embodiment.Certainly the present invention is not limited in these specific embodiments.
Embodiment 1:20% Pd
4Ag
1/ C-500 (20% refers to that the mass content of active component Pd and Ag is 20%, and wherein the mol ratio of Pd and Ag is 4: 1, and-500 expression reduction temperatures are 500 ℃)
Be in the absolute ethyl alcohol with the ultrasonic 30mL of being scattered in of 80mg Vulcan XC-72 carbon black at first, adding the 30mL mass fraction then is the Pd (NO of 7.8mg/mL
3)
2Aqueous solution 2.04mL and 6.4mgAgNO
3Mixed aqueous solution.Above-mentioned solution is flooded stirring 6h under room temperature, 65 ℃ of Rotary Evaporators are removed solvent then, and 65 ℃ of dryings obtain black powder.Above-mentioned black powder is ground, weighs, and place quartz boat, be transferred to tube furnace then, at N
2Under the atmosphere with 5 ℃ of min
-1Speed temperature programming to 120 ℃, and under this temperature, handle 0.5h, then with 5 ℃ of min
-1Speed temperature programming to 500 ℃, entire body integration number is 5% H
2And N
2Gaseous mixture, constant temperature heat treatment 2h, namely obtaining target product is 20%Pd
4Ag
1/ C-500 eelctro-catalyst.
Embodiment 2:20%Pd
3Ag
1/ C-500 (14.95%Pd-5.05%Ag/C-500) (20% refers to that the mass content of active component Pd and Ag is 20%, and wherein the mol ratio of Pd and Ag is 3: 1, and-500 expression reduction temperatures are 500 ℃)
At first be scattered in the 30mL absolute ethyl alcohol 80mg Vulcan XC-72 carbon black is ultrasonic, adding the 30mL mass fraction then is the Pd (NO of 7.8mg/mL
3)
2Aqueous solution 1.92mL and 8.0mgAgNO
3Mixed aqueous solution.Above-mentioned solution is flooded stirring 6h under room temperature, 65 ℃ of Rotary Evaporators are removed solvent then, and 65 ℃ of dryings obtain black powder.Above-mentioned black powder is ground, weighs, and place quartz boat, be transferred to tube furnace then, at N
2Under the atmosphere with 5 ℃ of min
-1Speed temperature programming to 120 ℃, and under this temperature, handle 0.5h, then with 5 ℃ of min
-1Speed temperature programming to 500 ℃, entire body integration number is 5% H
2And N
2Gaseous mixture, constant temperature heat treatment 2h, namely obtaining target product is 20%Pd
3Ag
1/ C-500 eelctro-catalyst.
Embodiment 3:20%Pd
1Ag
1/ C-500 (20% refers to that the mass content of active component Pd and Ag is 20%, and wherein the mol ratio of Pd and Ag is 1: 1, and-500 expression reduction temperatures are 500 ℃)
At first be scattered in the 30mL absolute ethyl alcohol 80mg Vulcan XC-72 carbon black is ultrasonic, adding the 30mL mass fraction then is the Pd (NO of 8.7mg/mL
3)
2Aqueous solution 1.27mL and 15.9mgAgNO
3Mixed aqueous solution.Above-mentioned solution is flooded stirring 6h under room temperature, 65 ℃ are used Rotary Evaporators that solvent is removed down then, and 65 ℃ of dryings obtain black powder.Above-mentioned black powder is ground, weighs, and place quartz boat, be transferred to tube furnace then, at N
2Under the atmosphere with 5 ℃ of min
-1Speed temperature programming to 120 ℃, and under this temperature, handle 0.5h, then with 5 ℃ of min
-1Speed temperature programming to 500 ℃, entire body integration number is 5% H
2And N
2Gaseous mixture, constant temperature heat treatment 2h, namely obtaining target product is 20%Pd
1Ag
1/ C-500 eelctro-catalyst.
Embodiment 4:20%Pd
1Ag
2/ C-500 (20% refers to that the mass content of active component Pd and Ag is 20%, and wherein the mol ratio of Pd and Ag is 1: 2, and-500 expression reduction temperatures are 500 ℃)
At first be scattered in the 30mL absolute ethyl alcohol 80mg Vulcan XC-72 carbon black is ultrasonic, adding the 30mL mass fraction then is the Pd (NO of 7.8mg/mL
3)
2Aqueous solution 0.85mL and 21.1mgAgNO
3Mixed aqueous solution.Above-mentioned solution is flooded stirring 6h under room temperature, 65 ℃ are used Rotary Evaporators that solvent is removed down then, and 65 ℃ of dryings obtain black powder.Above-mentioned black powder is ground, weighs, and place quartz boat, be transferred to tube furnace then, at N
2Under the atmosphere with 5 ℃ of min
-1Speed temperature programming to 120 ℃, and under this temperature, handle 0.5h, then with 5 ℃ of min
-1Speed temperature programming to 500 ℃, entire body integration number is 5% H
2And N
2Gaseous mixture, constant temperature heat treatment 2h, namely obtaining target product is 20%Pd
1Ag
2/ C-500 eelctro-catalyst.
Embodiment 5:20%Pd
2Ag
1/ C-150 (20% refers to that the mass content of active component Pd and Ag is 20%, and wherein the mol ratio of Pd and Ag is 2: 1, and-150 expression reduction temperatures are 150 ℃)
At first be scattered in the 30mL absolute ethyl alcohol 80mg Vulcan XC-72 carbon black is ultrasonic, adding the 30mL mass fraction then is the Pd (NO of 7.8mg/mL
3)
2Aqueous solution 1.70mL and 10.7mgAgNO
3Mixed aqueous solution.Above-mentioned solution is flooded stirring 6h under room temperature, 65 ℃ are used Rotary Evaporators that solvent is removed down then, and 65 ℃ of dryings obtain black powder.Above-mentioned black powder is ground, weighs, and place quartz boat, be transferred to tube furnace then, at N
2Under the atmosphere with 5 ℃ of min
-1Speed temperature programming to 120 ℃, and under this temperature, handle 0.5h, then with 5 ℃ of min
-1Speed temperature programming to 150 ℃, entire body integration number is 5% H
2And N
2Gaseous mixture, constant temperature heat treatment 2h, namely obtaining target product is 20%Pd
2Ag
1/ C-150 eelctro-catalyst.
Embodiment 6:20%Pd
2Ag
1/ C-200 (20% refers to that the mass content of active component Pd and Ag is 20%, and wherein the mol ratio of Pd and Ag is 2: 1, and-200 expression reduction temperatures are 200 ℃)
At first be scattered in the 30mL absolute ethyl alcohol 80mg Vulcan XC-72 carbon black is ultrasonic, adding the 30mL mass fraction then is the Pd (NO of 7.8mg/mL
3)
2Aqueous solution 1.70mL and 10.7mgAgNO
3Mixed aqueous solution.Above-mentioned solution is flooded stirring 6h under room temperature, 65 ℃ are used Rotary Evaporators that solvent is removed down then, and 65 ℃ of dryings obtain black powder.Above-mentioned black powder is ground, weighs, and place quartz boat, be transferred to tube furnace then, at N
2Under the atmosphere with 5 ℃ of min
-1Speed temperature programming to 120 ℃, and under this temperature, handle 0.5h, then with 5 ℃ of min
-1Speed temperature programming to 150 ℃, entire body integration number is 5% H
2And N
2Gaseous mixture, constant temperature heat treatment 2h, namely obtaining target product is 20%Pd
2Ag
1/ C-200 eelctro-catalyst.
Embodiment 7:20%Pd
2Ag
1/ C-300 (20% refers to that the mass content of active component Pd and Ag is 20%, and wherein the mol ratio of Pd and Ag is 2: 1, and-300 expression reduction temperatures are 300 ℃)
At first be scattered in the 30mL absolute ethyl alcohol 80mg Vulcan XC-72 carbon black is ultrasonic, adding the 30mL mass fraction then is the Pd (NO of 7.8mg/mL
3)
2Aqueous solution 1.70mL and 10.7mgAgNO
3Mixed aqueous solution.Above-mentioned solution is flooded stirring 6h under room temperature, 65 ℃ are used Rotary Evaporators that solvent is removed down then, and 65 ℃ of dryings obtain black powder.Above-mentioned black powder is ground, weighs, and place quartz boat, be transferred to tube furnace then, at N
2Under the atmosphere with 5 ℃ of min
-1Speed temperature programming to 120 ℃, and under this temperature, handle 0.5h, then with 5 ℃ of min
-1Speed temperature programming to 150 ℃, entire body integration number is 5% H
2And N
2Gaseous mixture, constant temperature heat treatment 2h, namely obtaining target product is 20%Pd
2Ag
1/ C-300 eelctro-catalyst.
Embodiment 8:20%Pd
2Ag
1/ C-400 (20% refers to that the mass content of active component Pd and Ag is 20%, and wherein the mol ratio of Pd and Ag is 2: 1, and-400 expression reduction temperatures are 400 ℃)
At first be scattered in the 30mL absolute ethyl alcohol 80mg Vulcan XC-72 carbon black is ultrasonic, adding the 30mL mass fraction then is the Pd (NO of 7.8mg/mL
3)
2Aqueous solution 1.70mL and 10.7mgAgNO
3Mixed aqueous solution.Above-mentioned solution is flooded stirring 6h under room temperature, 65 ℃ are used Rotary Evaporators that solvent is removed down then, and 65 ℃ of dryings obtain black powder.Above-mentioned black powder is ground, weighs, and place quartz boat, be transferred to tube furnace then, at N
2Under the atmosphere with 5 ℃ of min
-1Speed temperature programming to 120 ℃, and under this temperature, handle 0.5h, then with 5 ℃ of min
-1Speed temperature programming to 150 ℃, entire body integration number is 5% H
2And N
2Gaseous mixture, constant temperature heat treatment 2h, namely obtaining target product is 20%Pd
2Ag
1/ C-400 eelctro-catalyst.
Embodiment 9:20%Pd
2Ag
1/ C-500 (20% refers to that the mass content of active component Pd and Ag is 20%, and wherein the mol ratio of Pd and Ag is 2: 1, and-500 expression reduction temperatures are 500 ℃)
At first be scattered in the 30mL absolute ethyl alcohol 80mg Vulcan XC-72 carbon black is ultrasonic, adding the 30mL mass fraction then is the Pd (NO of 7.8mg/mL
3)
2Aqueous solution 1.70mL and 10.7mgAgNO
3Mixed aqueous solution.Above-mentioned solution is flooded stirring 6h under room temperature, 65 ℃ are used Rotary Evaporators that solvent is removed down then, and 65 ℃ of dryings obtain black powder.Above-mentioned black powder is ground, weighs, and place quartz boat, be transferred to tube furnace then, at N
2Under the atmosphere with 5 ℃ of min
-1Speed temperature programming to 120 ℃, and under this temperature, handle 0.5h, then with 5 ℃ of min
-1Speed temperature programming to 150 ℃, entire body integration number is 5% H
2And N
2Gaseous mixture, constant temperature heat treatment 2h, namely obtaining target product is 20%Pd
2Ag
1/ C-500 eelctro-catalyst.
Comparative example 1:20%Pd/C-150 (20% refers to that the mass content of active component Pd is 20%, and-150 expression reduction temperatures are 150 ℃)
At first be scattered in the 30mL absolute ethyl alcohol 80mg Vulcan XC-72 carbon black is ultrasonic, add the Pd (NO that 30mL contains 2.56mL mass fraction 7.8mg/mL then
3)
2The aqueous solution.Above-mentioned solution is flooded stirring 6h under room temperature, 65 ℃ are used Rotary Evaporators that solvent is removed down then, and 65 ℃ of dryings obtain black powder.Above-mentioned black powder is ground, weighs, and place quartz boat, be transferred to tube furnace then, at N
2Under the atmosphere with 5 ℃ of min
-1Speed temperature programming to 120 ℃, and under this temperature, handle 0.5h, then with 5 ℃ of min
-1Speed temperature programming to 150 ℃, entire body integration number is 5% H
2And N
2Gaseous mixture, constant temperature heat treatment 2h namely obtains target product 20%Pd/C-150 eelctro-catalyst.
Comparative example 2:20%Pd/C-200 (20% refers to that the mass content of active component Pd is 20%, and-200 expression reduction temperatures are 200 ℃)
At first be scattered in the 30mL absolute ethyl alcohol 80mg Vulcan XC-72 carbon black is ultrasonic, add the Pd (NO that 30mL contains 2.56mL mass fraction 7.8mg/mL then
3)
2The aqueous solution.Above-mentioned solution is flooded stirring 6h under room temperature, 65 ℃ are used Rotary Evaporators that solvent is removed down then, and 65 ℃ of dryings obtain black powder.Above-mentioned black powder is ground, weighs, and place quartz boat, be transferred to tube furnace then, at N
2Under the atmosphere with 5 ℃ of min
-1Speed temperature programming to 120 ℃, and under this temperature, handle 0.5h, then with 5 ℃ of min
-1Speed temperature programming to 200 ℃, entire body integration number is 5% H
2And N
2Gaseous mixture, constant temperature heat treatment 2h namely obtains target product 20%Pd/C-200 eelctro-catalyst.
Comparative example 3:20%Pd/C-300 (20% refers to that the mass content of active component Pd is 20%, and-300 expression reduction temperatures are 300 ℃)
At first be scattered in the 30mL absolute ethyl alcohol 80mg Vulcan XC-72 carbon black is ultrasonic, add the Pd (NO that 30mL contains 2.56mL mass fraction 7.8mg/mL then
3)
2The aqueous solution.Above-mentioned solution is flooded stirring 6h under room temperature, 65 ℃ are used Rotary Evaporators that solvent is removed down then, and 65 ℃ of dryings obtain black powder.Above-mentioned black powder is ground, weighs, and place quartz boat, be transferred to tube furnace then, at N
2Under the atmosphere with 5 ℃ of min
-1Speed temperature programming to 120 ℃, and under this temperature, handle 0.5h, then with 5 ℃ of min
-1Speed temperature programming to 300 ℃, entire body integration number is 5% H
2And N
2Gaseous mixture, constant temperature heat treatment 2h namely obtains target product 20%Pd/C-300 eelctro-catalyst.
Comparative example 4:20%Pd/C-400 (20% refers to that the mass content of active component Pd is 20%, and-400 expression reduction temperatures are 400 ℃)
At first be scattered in the 30mL absolute ethyl alcohol 80mg Vulcan XC-72 carbon black is ultrasonic, add the Pd (NO that 30mL contains 2.56mL mass fraction 7.8mg/mL then
3)
2The aqueous solution.Above-mentioned solution is flooded stirring 6h under room temperature, 65 ℃ are used Rotary Evaporators that solvent is removed down then, and 65 ℃ of dryings obtain black powder.Above-mentioned black powder is ground, weighs, and place quartz boat, be transferred to tube furnace then, at N
2Under the atmosphere with 5 ℃ of min
-1Speed temperature programming to 120 ℃, and under this temperature, handle 0.5h, then with 5 ℃ of min
-1Speed temperature programming to 400 ℃, entire body integration number is 5% H
2And N
2Gaseous mixture, constant temperature heat treatment 2h namely obtains target product 20%Pd/C-400 eelctro-catalyst.
Comparative example 5:20%Pd/C-500 (20% refers to that the mass content of active component Pd is 20%, and-500 expression reduction temperatures are 500 ℃)
At first be scattered in the 30mL absolute ethyl alcohol 80mg Vulcan XC-72 carbon black is ultrasonic, add the Pd (NO that 30mL contains 2.56mL mass fraction 7.8mg/mL then
3)
2The aqueous solution.Above-mentioned solution is flooded stirring 6h under room temperature, 65 ℃ are used Rotary Evaporators that solvent is removed down then, and 65 ℃ of dryings obtain black powder Pd (NO
3)
2/ C.Above-mentioned black powder is ground, weighs, and place quartz boat, be transferred to tube furnace then, at N
2Under the atmosphere with 5 ℃ of min
-1Speed temperature programming to 120 ℃, and under this temperature, handle 0.5h, then with 5 ℃ of min
-1Speed temperature programming to 500 ℃, entire body integration number is 5% H
2And N
2Gaseous mixture, constant temperature heat treatment 2h namely obtains target product 20%Pd/C-500 eelctro-catalyst.
Comparative example 6:20%Ag/C-150 (20% refers to that the mass content of active component A g is 20%, and-150 expression reduction temperatures are 150 ℃)
At first be scattered in the 30mL absolute ethyl alcohol 80mg Vulcan XC-72 carbon black is ultrasonic, add 30mL then and contain 31.5mgAgNO
3The aqueous solution.Above-mentioned solution is flooded stirring 6h under room temperature, 65 ℃ are used Rotary Evaporators that solvent is removed down then, and 65 ℃ of dryings obtain black powder AgNO
3/ C.Above-mentioned black powder is ground, weighs, and place quartz boat, be transferred to tube furnace then, at N
2Under the atmosphere with 5 ℃ of min
-1Speed temperature programming to 120 ℃, and under this temperature, handle 0.5h, then with 5 ℃ of min
-1Speed temperature programming to 150 ℃, entire body integration number is 5% H
2And N
2Gaseous mixture, constant temperature heat treatment 2h namely obtains target product 20%Ag/C-150 eelctro-catalyst.
Comparative example 7:20%Ag/C-500 (20% refers to that the mass content of active component A g is 20%, and-500 expression reduction temperatures are 500 ℃)
At first be scattered in the 30mL absolute ethyl alcohol 80mg Vulcan XC-72 carbon black is ultrasonic, add 30mL then and contain 31.5mgAgNO
3The aqueous solution.Above-mentioned solution is flooded stirring 6h under room temperature, use Rotary Evaporators that solvent is removed then, obtain black powder AgNO
3/ C.Above-mentioned black powder is ground, weighs, and place quartz boat, be transferred to tube furnace then, at N
2Under the atmosphere with 5 ℃ of min
-1Speed temperature programming to 120 ℃, and under this temperature, handle 0.5h, then with 5 ℃ of min
-1Speed temperature programming to 500 ℃, entire body integration number is 5% H
2And N
2Gaseous mixture, constant temperature heat treatment 2h namely obtains target product 20%Ag/C-500 eelctro-catalyst.
Fig. 1 is the XRD spectra of the sample for preparing according to comparative example 1,3,4,5.The PCPDF standard card of contrast Fig. 1 below all has the characteristic peak of Pd, 39,46,68 and 82 ° of (111) that can belong to Pd respectively, (200), the diffraction maximum of (220) and (311) crystal face as can be seen in embodiment 1,3,4, the 5 prepared samples.The particle diameter that is calculated Pd among the embodiment 1,3,4,5 by the Scherrer formula is respectively 7.2,8.7, and 10.1 and 11.6nn.
Fig. 2 is for according to comparative example 5,6 and the XRD spectra of the sample for preparing of embodiment 1,2,3,4,9.Contrast the PCPDF standard card of Fig. 2 below as can be seen, comparative example 5,6 prepared samples all have the characteristic peak of Pd and Ag, 39,46,68 and 82 ° of (111) that can belong to Pd respectively, (200), (220), (311) diffraction maximum of crystal face, and 38,44,64 and 77 ° of (111) that then belong to for Ag, (200), the diffraction maximum of (220) and (311) crystal face.Among the embodiment 1,2, reduce each peak position pests occurrence rule with the atomic ratio of PdAg metal and move, illustrate to have formed the PdAg alloy.Among the embodiment 3,4,9, with the increase of Ag content, occur the characteristic peak of Pd and Ag respectively, illustrated that Ag separates out from the PdAg alloy.By the Scherrer formula calculate comparative example 5,6 and embodiment 1,2,3,4,9 in the PdAg particle diameter be respectively 9.5,27.8 and 6.8,6.3,5.2,5.2,5.1nm.
Fig. 3 is the XRD spectra of the sample for preparing according to embodiment 5-9.Contrast the PCPDF standard card of Fig. 3 below as can be seen, each peak position of embodiment 5-9 illustrates that each embodiment has formed the PdAg alloy between the characteristic peak of Pd and Ag.The particle diameter that is calculated alloy among the embodiment 5-9 by the Scherrer formula is respectively 3.4,3.8, and 3.9,4.1 and 5.2nm.
Fig. 4 for the sample for preparing according to comparative example 1-5 at N
2CV figure in the saturated 1.0M NaOH electrolyte.The electrochemistry specific area that obtains comparative example 1-5 according to the reduction calculated by peak area of PdO in the negative inswept journey is respectively 4.39,4.16, and 2.82,2.61 and 2.10cm
-2, illustrate that the rising electrochemistry specific area with reduction temperature reduces gradually.
Fig. 5 for the sample for preparing according to comparative example 1-5 at N
2Saturated 1.0M NaOH+1.0MCH
3CH
2CV figure in the OH electrolyte.The take-off potential of each comparative example is identical as seen from the figure, raises with heat treatment temperature, and the EOR current density of comparative example 1-5 increases gradually.
Fig. 6 for according to comparative example 5,7 and the sample for preparing of embodiment 1,2,3,4,9 at N
2CV figure in the saturated 1.0M NaOH electrolyte.In the comparative example 5 ,-0.8 to 0.5V corresponding peak is hydrogen adsorption desorption peak, and-0.4 to 0V corresponding peak is PdO in the negative inswept journey
xReduction peak.In the comparative example 7,0.1 to 0.3V corresponding peak is AgO
x Reduction peak.In embodiment 1,2,3,4,9, the adsorption desorption peak of hydrogen is all by in various degree inhibition, and do not have AgO
xReduction peak occur, in conjunction with XRD result as can be known among the embodiment PdAg formed alloy.
Fig. 7 for according to comparative example 5,7 and the sample for preparing of embodiment 1,2,3,4,9 at N
2Saturated 1.0M NaOH+1.0M CH
3CH
2CV figure in the OH electrolyte.As seen from the figure, comparative example 7 does not have catalytic activity to oxidation of ethanol in alkaline medium, comes to the same thing with bibliographical information.The catalytic activity of embodiment 1,2,3,4,9 catalysis ethanol oxidations all is higher than comparative example 5, and wherein embodiment 2 and 9 catalytic activitys are higher.
Fig. 8 for the sample for preparing according to embodiment 5-9 at N
2Saturated 1.0M NaOH+1.0MCH
3CH
2CV figure in the OH electrolyte.As seen from the figure, when the PdAg atomic ratio was identical, heat treatment temperature raise, and the activity of catalysis ethanol oxidation increases.In conjunction with XRD result as can be known, embodiment 5-9 lattice paprmeter is identical, and particle diameter increases gradually, illustrates that Ethanol Oxidation in the alkaline medium needs the appropriate catalyst particle diameter to satisfy the adsorption desorption requirement of ethanol and intermediate product in the course of reaction.
Claims (7)
1. a Pd-Ag/C Preparation of catalysts method may further comprise the steps, and it is characterized in that:
1) dispersion of carbon carrier: get carbon carrier and mix with absolute ethyl alcohol, stir and make carbon carrier evenly dispersion in ethanol, form slurries;
2) preparation of maceration extract:
With Pd (NO
3)
2With AgNO
3Mixed dissolution forms solution in deionized water, this solution is dropwise dripped or is poured in the step (1) fill in the container of carbon carrier slurries;
Or with Pd (NO
3)
2With AgNO
3Be dissolved in respectively and form solution in the deionized water, by first Pd (NO
3)
2AgNO behind the solution
3Solution or first AgNO
3Pd (NO behind the solution
3)
2The order of solution successively dropwise drips or is poured in the step (1) and fills in the container of carbon carrier slurries;
In the dipping system volume of deionized water be the ethanol volume 0.5-1.5 doubly; Dip time 〉=3h;
3) Pd-Ag/C Preparation of catalysts:
A. with the maceration extract evaporate to dryness that obtains in the above-mentioned steps (2);
B. in 50-85 ℃ of evaporate to dryness thing drying 〉=5h that obtains in above-mentioned steps (3) a, obtain black powder;
C. the black powder that above-mentioned steps is obtained places tube furnace temperature programming under inert gas atmosphere to handle, black powder from normal temperature with the speed temperature programming of 1-10 ℃/min to 105-130 ℃, and under this temperature heat treatment 20-60min, afterwards with the speed temperature programming of 1-10 ℃/min to 150-700 ℃;
D. keep the final temperature in the above-mentioned steps, feeding volume fraction in tube furnace is the H of 1-15%
2Mist with inert gas, behind the heat treatment 1-3h, to black powder wash, drying, obtain target product Pd-Ag/C catalyst, active constituent is Pd and Ag in the catalyst, the total mass content of active constituent in catalyst is 1-30%, and the quality of Ag is not more than 25% of Pd content.
2. Pd-Ag/C Preparation of catalysts method according to claim 1 is characterized in that: the ratio of described carbon carrier and absolute ethyl alcohol is that the volume that every 20mg carbon carrier adds absolute ethyl alcohol is 5-40mL.
3. Pd-Ag/C Preparation of catalysts method according to claim 1 is characterized in that: above-mentioned steps 2) Pd (NO in the dipping system of preparing in the process for preparation of maceration extract
3)
2Mass concentration is 0.02mg/mL to 7.8mg/mL, AgNO
3Mass concentration is 0.005mg/mL to 1.95mg/mL.
4. Pd-Ag/C Preparation of catalysts method according to claim 1 is characterized in that:
With the black powder that obtains among above-mentioned steps (3) b grind, weighing is placed in quartz or the pottery; Send in the tube furnace then.
5. Pd-Ag/C Preparation of catalysts method according to claim 1 is characterized in that:
Above-mentioned steps (3) a is in 30-70 ℃ of maceration extract rotation evaporate to dryness that obtains in above-mentioned steps (2).
6. Pd-Ag/C Preparation of catalysts method according to claim 1 is characterized in that:
Described carbon carrier is: the mixture of one or more in XC-72R, BP2000, acetylene black, CNT, the graphite oxide;
Described inert atmosphere is one or more the mixture in nitrogen, argon gas, the helium.
7. Pd-Ag/C Preparation of catalysts method according to claim 1 is characterized in that:
Described dipping process carries out dipping 〉=3h under 0-50 ℃ of magnetic agitation condition.
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|---|
| Enhancement effect of Ag for Pd/C towards the ethanol electro-oxidation in alkaline media;Son Truong Nguyen et al;《Applied Catalysis B: Environmental》;20090625;第91卷;第507-515页 * |
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| Nanostructured palladium-silver coated nickel foam cathode for magnesium-hydrogen peroxide fuel cells;Weiqian Yang;《Electrochimica Acta》;20060425;第52卷;第9-14页 * |
| Son Truong Nguyen et al.Enhancement effect of Ag for Pd/C towards the ethanol electro-oxidation in alkaline media.《Applied Catalysis B: Environmental》.2009,第91卷第507-515页. |
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