CN103346331A - Palladium/titanium dioxide/graphene catalyst and preparation method thereof - Google Patents

Palladium/titanium dioxide/graphene catalyst and preparation method thereof Download PDF

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CN103346331A
CN103346331A CN201310309393XA CN201310309393A CN103346331A CN 103346331 A CN103346331 A CN 103346331A CN 201310309393X A CN201310309393X A CN 201310309393XA CN 201310309393 A CN201310309393 A CN 201310309393A CN 103346331 A CN103346331 A CN 103346331A
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杨文胜
赵莹莹
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Beijing University of Chemical Technology
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Beijing University of Chemical Technology
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Abstract

The invention relates to a palladium/titanium dioxide/graphene catalyst and a preparation method thereof, belonging to the technical field of electrocatalysts. The catalyst comprises chemical components of Pd/TiO2/G, wherein G is the graphene, the TiO2/G is a catalyst carrier, the amorphous state TiO2 is uniformly covered on the surface of G, so that the corrosion resistance of G is improved, and the electrical conductivity of the TiO2 is improved by G,; the grain size of the catalytic activity component Pd is 2-4 nanometer, the Pd are uniformly distributed on the surface of the TiO2/G carrier. The catalyst has good electro-catalysis oxygen reduction activity, methyl alcohol resistance and stability. The preparation method of the catalyst comprises the following steps of uniformly covering the amorphous state TiO2 on the G through titanium compound hydrolysis so as to prepare a TiO2/G composite carrier, and loading the Pd particles on the TiO2/G composite carrier through low carbon alcohol reducing action, so as to prepare the Pd/TiO2/G catalyst. The preparation method has the characteristics of being simple in technology, easy to operate and the like.

Description

A kind of palladium/titanium dioxide/graphen catalyst and preparation method thereof
Technical field
The invention belongs to the eelctro-catalyst technical field, particularly relate to a kind of palladium/titanium dioxide/graphen catalyst and preparation method thereof, be applicable to high activity, the direct methanol fuel cell of anti-methyl alcohol.
Background technology
Direct methanol fuel cell (DMFC) is owing to the energy density height, and fuel source is abundant, does not reform or reforming unit in the middle of not needing, and pollutant emission is low, the low (60-100 of working temperature oAnd be easy to treat liquid fuel and receive much concern C).Pt is catalyst based to be present cathodic oxygen reduction reaction (ORR) the most effective catalyst, but its resource shortage, expensive, simultaneously because there is the problem of methanol crossover in methanol fuel cell, the catalyst based easy catalytic oxidation methyl alcohol of Pt forms mixed potential, therefore the serious power output that reduces battery is sought cheap and to have a no-Pt catalyst of good anti-methyl alcohol performance significant.Pd is very similar to the character of Pt, but reserves are abundanter than Pt, and price is more cheap than Pt, and its anti-methyl alcohol performance to be far superior to Pt catalyst based, have a good application prospect.In order to improve the utilization ratio of noble metal catalyst, normally noble metal nano particles is dispersed on the carrier.
Material with carbon element is present most widely used catalyst carrier, wherein Graphene (G) is the two-dimentional graphite carbon-coating structure of piling up less than 10 layers carbon atomic layer, the electro-catalyst carrier that is regarded as having good development prospect because of its big specific area and good electrical conductivity.At document (1) J. Am. Chem. Soc., among 2011,133,3693 – 3695, people such as Chen utilize oxidizing potential and the Pd of the oxygen-containing functional group on graphene oxide surface 2+Reduction potential between difference, Pd particle reduce deposition on the surface of G, is shown good oxidation methyl alcohol and the catalytic performance of ethanol.But the corrosion of carrier carbon easily causes electro-chemical activity to reduce, and particularly the G specific area is big, and carbon corrosion is more serious.
For overcoming the carbon corrosion problem, people research and develop carbide alloy, and nitride or metal oxide are as catalyst carrier.Wherein, TiO 2And have the interaction that is beneficial to ORR between the Pd, as TiO 2Carrier can effectively increase Pd/TiO 2The bulk of highest occupied molecular orbital (HOMO), overcome HOMO and the O of Pd/C 2Lowest unoccupied molecular orbital (LUMO) cause both degrees of overlapping low because bulk differs greatly, electronics shifts the problem of difficulty, has improved Pd/TiO 2O on the electrode 2First step electronics shifts the maximum plyability of frontier orbit; The same TiO of Pd 2The strong interaction of surface O has weakened middle species in the absorption on Pd surface, is beneficial to the subsequent reactions of ORR; TiO in addition 2In acidity or alkaline medium, all have high chemical stability, so TiO 2It is the Pd catalyst carrier with good development potentiality.As at document (2) J. Power Sources, among 2009,189,982 – 987, people such as Fu etch TiO by the method for pulse anodic oxidation at titanium 2Nanotube and as carrier, Pd particle on the deposition utilizes Pd and TiO 2Between synergy obtained the hydrogen reduction catalytic performance.But because TiO 2Poorly conductive, it is unsatisfactory that institute obtains the eelctro-catalyst performance.
Summary of the invention
The object of the present invention is to provide a kind of palladium/titanium dioxide/graphen catalyst and preparation method thereof, with TiO 2Evenly covering the G(Graphene) surface forms complex carrier, can utilize the TiO of even covering 2Layer solves the etching problem of G, can utilize G to improve TiO again 2Conductivity, thereby give full play to G and TiO 2The performance advantage of two class carriers.
The chemical composition of catalyst of the present invention can be described as Pd/TiO 2/ G; TiO 2/ G is catalyst carrier, and wherein, G is Graphene; Amorphous state TiO 2Evenly cover the G surface; Catalytic activity constituent element Pd particle diameter is 2～4 nanometers, is evenly distributed on TiO 2/ G carrier surface; Catalytic activity constituent element Pd accounts for 10%～50% of catalyst gross mass, TiO 2Account for 5%～15% of catalyst gross mass, G accounts for 35%～85% of catalyst gross mass.
The preparation method of palladium/titanium dioxide of the present invention/graphen catalyst namely utilizes the titanium compound hydrolysis with amorphous TiO 2Evenly cover G and go up preparation TiO 2/ G complex carrier, recycling low-carbon alcohols reduction with the Pd particulate load at TiO 2Prepare Pd/TiO on the/G complex carrier 2/ G catalyst, its process flow diagram specifically may further comprise the steps as shown in Figure 1:
(1) preparation of graphite oxide: the preparation graphite concentration is the H of 40～50 grams per liters 2SO 4Suspension is then according to KMnO 4With the mass ratio of graphite be the ratio of 1:10～1:20 under ice bath with KMnO 4Join above-mentioned H 2SO 4In the suspension, 30～40 oStirring reaction is 1～3 hour under the C; Adding deionized water in above-mentioned suspension, is 0.6～1.2 grams per liter with the graphite concentration dilution, and temperature is risen to 90～100 oC reaction 10～20 minutes; According to H 2O 2With the mass ratio of graphite be that the ratio of 1:1000～1:800 is 0.5%～0.75% H with mass fraction 2O 2Solution adds in the above-mentioned reactant liquor with cessation reaction; With the HCl solution washing of 1～1.5 mol, supernatant is removed in centrifugation under 3000～5000 rev/mins the rotating speed, can not detect SO repeatedly for several times in supernatant 4 2-With the sample collected 40～60 oC vacuumize 10～14 hours can obtain graphite oxide.
(2) Pd/TiO 2The preparation of/G: it is the suspension of 0.5～1 grams per liter that graphite oxide is scattered in the low-carbon alcohols solvent preparation graphite oxide concentration, and ultrasonic dispersion obtained graphene oxide suspension in 1～2 hour; According to TiO 2The ratio that accounts for catalyst gross mass 5%～15% is calculated and is measured titanium compound and adds in the above-mentioned graphene suspension, obtains TiO behind hydrolysis 2/ graphene oxide carrier suspension; To TiO 2Dropping concentration is that the NaOH solution of 0.05～0.2 mol is 10～14 to regulate pH in the/graphene oxide carrier suspension; The ratio that accounts for catalyst gross mass 10%～50% according to Pd is calculated and is taken by weighing palladium compound and joins TiO 2In/graphene oxide carrier the suspension, 120～130 oBack flow reaction is 3～4 hours under the C nitrogen protection, the reduction of utilizing low-carbon alcohols with the Pd particulate load at TiO 2On/graphene oxide the carrier; Cool the temperature to 80～95 then oC also adds hydrazine hydrate, and wherein the mass ratio of the volume/graphene oxide of hydrazine hydrate is 9～11 milliliters/10 grams, reacts 20～40 minutes, in order to graphene oxide is reduced to Graphene; Temperature is down to that to add concentration after the room temperature be that the HCl solution of 0.05～0.2 mol is 2～4 to regulate pH, leaves standstill after 8～12 hours under 7000～9000 rev/mins the rotating speed centrifugation then and removes supernatant; With deionized water cyclic washing, centrifugal in supernatant, the detection less than Cl -Existence; With sample 40～60 oC vacuumize 10～14 hours can obtain catalyst P d/TiO 2/ G.Wherein, low-carbon alcohols is a kind of in methyl alcohol, ethylene glycol, the glycerol; Titanium compound is a kind of in titanium tetraisopropylate, titanium tetrachloride, the nine hydration titanium sulfates; Palladium compound is PdCl 2, K 2PdCl 4In a kind of.
Low-carbon alcohols in the step (2) is a kind of in methyl alcohol, ethylene glycol or the glycerol.
Titanium compound in the step (2) is a kind of in titanium tetraisopropylate, titanium tetrachloride or the nine hydration titanium sulfates.
Palladium compound is PdCl in the step (2) 2Or K 2PdCl 4In a kind of.
The Pd/TiO of the Pd/G sample of Comparative Examples 1 preparation of the present invention and embodiment 1-3 preparation 2The X-ray diffraction spectrogram of/G sample as shown in Figure 2, four samples all have the characteristic diffraction peak of Pd, the Pd/TiO of embodiment 1-3 preparation 2/ G sample there is no TiO 2Characteristic diffraction peak, show TiO 2It is amorphous state.
The Pd/TiO of the present invention's preparation 2The transmission electron microscope photo of/G sample as shown in Figure 3, Pd grain diameter homogeneous, size is 2～4 nanometers, is evenly distributed on carrier surface; In contrast, the transmission electron microscope photo of the Pd/G sample of Comparative Examples of the present invention preparation as shown in Figure 4, Pd particle agglomeration phenomenon is obvious.The Pd/TiO that the energy disperse spectroscopy that utilizes ESEM to dispose prepares the present invention 2/ G sample carries out face scanning, C, and O, Pd, the power spectrum face scanning analysis figure of four kinds of elements of Ti further shows amorphous TiO as shown in Figure 5 2Evenly cover the Graphene surface.
Adopt three-electrode system test the inventive method to prepare sample P d/TiO 2The electrocatalysis characteristic of/G and comparative sample Pd/G comprises electro catalytic activity, methanol tolerance performance and stability etc.The preparation method of work electrode: take by weighing 5.0 milligrams of catalyst powders, with 1 milliliter of isopropyl alcohol, 100 microlitre mass fractions are 5% Nafion alcoholic solution dispersion, ultrasonic 1 hour, get 10 microlitre suspension-turbid liquids and be coated on clean rotating circular disk glass-carbon electrode surface, dry under the air at room temperature, make the thin film work electrode; Be the Pt silk to electrode, reference electrode is Ag/AgCl, and test solution is the HClO of 0.1 mol 4Test result such as Fig. 6, Fig. 7, Fig. 8, Fig. 9, Figure 10, shown in Figure 11.Test result shows Pd/TiO 2/ G catalyst has good hydrogen reduction activity, methanol tolerance performance and stability.
Characteristics of the present invention and advantage are:
(1) catalyst P d/TiO of the present invention 2/ G is with TiO 2Compound TiO with G 2/ G had both utilized the high characteristics of G specific area as catalyst carrier, had utilized TiO again 2Improve the Pd catalytic activity and in acid solution the good characteristics of chemical stability, improved the corrosion resistance of G, the good electrical conductivity of G own has remedied semiconductor TiO simultaneously 2The problem of poorly conductive.
(2) catalyst P d/TiO of the present invention 2Among/the G, Pd and TiO 2Between synergy promoted the conduction of first step electronics to have weakened middle species again at Pd/TiO 2The absorption on surface is beneficial to the subsequent reactions of hydrogen reduction, so catalyst of the present invention has good hydrogen reduction catalytic activity, and in addition, this catalyst also has good anti-methyl alcohol performance and stability.
(3) the inventive method technology is simple, easy operating.
Description of drawings
Fig. 1 prepares the process flow diagram of palladium/titanium dioxide/graphen catalyst for the present invention.
Fig. 2 prepares the X-ray diffraction spectrogram of sample for Comparative Examples 1 of the present invention and embodiment 1-3.Abscissa is angle 2 θ, and unit is: degree ( o); Ordinate is diffracted intensity, and unit is: absolute unit (a.u).The X-ray diffraction spectrogram of curve a-Comparative Examples 1 preparation sample; The X-ray diffraction spectrogram of curve b-embodiment 1 preparation sample; The X-ray diffraction spectrogram of curve c-embodiment 2 preparation samples; The X-ray diffraction spectrogram of curve d-embodiment 3 preparation samples.
Fig. 3 is the transmission electron microscope photo of the sample of the embodiment of the invention 1 preparation.
Fig. 4 is the transmission electron microscope photo of the sample of Comparative Examples 1 preparation of the present invention.
Fig. 5 is the C of the embodiment of the invention 2 preparation samples, O, Pd, the power spectrum face scanning analysis figure of four kinds of elements of Ti.
Fig. 6 prepares sample at the HClO of 0.1 saturated mol of nitrogen for Comparative Examples 1 of the present invention and embodiment 1-3 4In cyclic voltammetry curve figure.Abscissa is current potential, and unit is: volt (V), with respect to standard hydrogen electrode; Ordinate is current density, and unit is: milliampere centimetre -2(mAcm -2).The cyclic voltammetry curve of curve a-Comparative Examples 1 preparation sample; The cyclic voltammetry curve of curve b-embodiment 1 preparation sample; The cyclic voltammetry curve of curve c-embodiment 2 preparation samples; The cyclic voltammetry curve of curve d-embodiment 3 preparation samples.
Fig. 7 prepares sample at the HClO of 0.1 saturated mol of oxygen for Comparative Examples 1 of the present invention and embodiment 1-3 4In the hydrogen reduction polarization curve.Abscissa is current potential, and unit is: volt (V), with respect to standard hydrogen electrode; Ordinate is current density, and unit is: milliampere centimetre -2(mAcm -2).The hydrogen reduction polarization curve of curve a-Comparative Examples 1 preparation sample; The hydrogen reduction polarization curve of curve b-embodiment 1 preparation sample; The hydrogen reduction polarization curve of curve c-embodiment 2 preparation samples; The hydrogen reduction polarization curve of curve d-embodiment 3 preparation samples.
Fig. 8 is that the embodiment of the invention 2 preparation samples are at the HClO of 0.1 saturated mol of oxygen 4In, the hydrogen reduction polarization curve under the different rotating speeds.Abscissa is current potential, and unit is: volt (V), with respect to standard hydrogen electrode; Ordinate is current density, and unit is: milliampere centimetre -2(mAcm -2).
Fig. 9 is that the embodiment of the invention 2 preparation samples are at the HClO of 0.1 saturated mol of oxygen 4In anti-methyl alcohol performance test data figure.Abscissa is current potential, and unit is: volt (V), with respect to standard hydrogen electrode; Ordinate is current density, and unit is: milliampere centimetre -2(mAcm -2).Curve a-specimen is the hydrogen reduction polarization curve during no methyl alcohol in solution; The hydrogen reduction polarization curve of curve b-specimen when methanol concentration is 1 mol in solution.
Figure 10 is the HClO of Comparative Examples 1 preparation sample of the present invention in 0.1 saturated mol of oxygen 4In anti-methyl alcohol performance test data figure.Abscissa is current potential, and unit is: volt (V), with respect to standard hydrogen electrode; Ordinate is current density, and unit is: milliampere centimetre -2(mAcm -2).Curve a-specimen is the hydrogen reduction polarization curve during no methyl alcohol in solution; The hydrogen reduction polarization curve of curve b-specimen when methanol concentration is 1 mol in solution.
Figure 11 is the hydrogen reduction polarization curve of embodiment 2 preparation samples after voltage range is for 50 weeks of 0.6-1.2 volt circulation and 1000.Abscissa is current potential, and unit is: volt (V), with respect to standard hydrogen electrode; Ordinate is current density, and unit is: milliampere centimetre -2(mAcm -2).The curve a-specimen hydrogen reduction polarization curve after 50 weeks that circulates; The curve b-specimen hydrogen reduction polarization curve after 1000 weeks that circulates.
Embodiment
Embodiment 1
(1) preparation of graphite oxide: taking by weighing 2 gram graphite is the H of 40 grams per liters with the preparation graphite concentration 2SO 40.05 liter of suspension takes by weighing 0.2 gram KMnO then 4Under ice bath, slowly join above-mentioned H 2SO 4In the suspension, 30 oStirring reaction is 3 hours under the C; Adding deionized water in above-mentioned suspension, is 0.6 grams per liter with the graphite concentration dilution, and temperature is risen to 90 o C reaction 20 minutes; Take by weighing 0.4 gram mass mark and be 0.5% H 2O 2Solution joins in the above-mentioned reactant liquor with cessation reaction; With the HCl solution washing of 1 mol, supernatant is removed in centrifugation under 3000 rev/mins the rotating speed, can not detect SO repeatedly for several times in supernatant 4 2-With the sample collected 60 oC vacuumize 10 hours can obtain graphite oxide.
(2) Pd/TiO 2(5%)/and the preparation of G: take by weighing 0.1 gram graphite oxide and be scattered in 0.2 liter of the suspension that preparation graphite oxide concentration in the methanol solvate is 0.5 grams per liter, ultrasonic dispersion obtained graphene oxide suspension in 1 hour; Take by weighing 14.0 milligrams of titanium tetrachlorides and add in the above-mentioned graphene oxide suspension, behind hydrolysis, obtain TiO 2/ graphene oxide carrier suspension; The NaOH solution that drips concentration in the above-mentioned suspension and be 0.05 mol is 10 to regulate pH; Take by weighing 19.6 milligrams PdCl 2Join in the above-mentioned suspension, and 120 oBack flow reaction is 4 hours under the C nitrogen protection, the reduction of utilizing methyl alcohol with the Pd particulate load at TiO 2On/graphene oxide the carrier; Cool the temperature to 80 then oC also adds 0.1 milliliter of hydrazine hydrate, reacts 30 minutes, in order to graphene oxide is reduced to Graphene; Temperature is reduced to that to add concentration after the room temperature be that the HCl solution of 0.05 mol is 2 to regulate pH, leaves standstill after 12 hours under 7000 rev/mins the rotating speed centrifugation then and removes supernatant; With deionized water cyclic washing, centrifugal in supernatant, the detection less than Cl -Existence; With sample 60 oC vacuumize 10 hours can obtain catalyst P d/TiO 2/ G.
Take by weighing 5.0 milligrams and adopt the synthetic Pd/TiO of the inventive method 2/ G catalyst powder, with 1 milliliter of isopropyl alcohol, 100 microlitre mass fractions are 5% Nafion alcoholic solution dispersion, ultrasonic 1 hour, get 10 microlitre suspension-turbid liquids and be coated on clean rotating circular disk glass-carbon electrode surface, dry under the air at room temperature, make the thin film work electrode; Be the Pt silk to electrode, reference electrode is Ag/AgCl, and test solution is the HClO of 0.1 mol 4
Fig. 2 b is the Pd/TiO of preparation 2The X-ray diffraction spectrogram of/G by finding out the characteristic diffraction peak that obvious Pd is arranged among the figure, does not have TiO 2Characteristic diffraction peak, the TiO that hydrolysis generates is described 2It is amorphous state.Fig. 3 is Pd/TiO 2The transmission electron microscope photo of/G, Pd is dispersed in carrier surface, and particle size is 2 nanometers.Electrochemical results is compared with Comparative Examples 1 shown in Fig. 6 b, Fig. 7 b, and current potential is negative moving to some extent, but the limiting diffusion current value increases to some extent.
Embodiment 2
(1) preparation of graphite oxide: taking by weighing 2.174 gram graphite is the graphite H of 43.48 grams per liters with the preparation graphite concentration 2SO 40.05 liter of suspension takes by weighing 0.145 gram KMnO then 4Under ice bath, slowly join above-mentioned H 2SO 4In the suspension, 35 oStirring reaction is 2 hours under the C; Adding deionized water in above-mentioned suspension, is 0.9 grams per liter with the graphite concentration dilution, and temperature is risen to 95 oC reaction 15 minutes; Take by weighing 0.403 gram mass mark and be 0.6% H 2O 2Solution adds in the above-mentioned reactant liquor with cessation reaction; With the HCl solution washing of 1.25 mol, supernatant is removed in centrifugation under 4000 rev/mins the rotating speed, can not detect SO repeatedly for several times in supernatant 4 2-With the sample collected 50 oC vacuumize 12 hours can obtain graphite oxide.
(2) Pd/TiO 2The preparation of/G: take by weighing 0.1 gram graphite oxide and be scattered in the ethylene glycol solvent 0.125 liter of the suspension that preparation graphite oxide concentration is 0.8 grams per liter, ultrasonic dispersion obtained graphene oxide suspension in 1.5 hours; Take by weighing 69.0 milligrams of titanium tetraisopropylates and add in the above-mentioned graphene oxide suspension, behind hydrolysis, obtain TiO 2/ graphene oxide carrier suspension; The NaOH solution that drips concentration in the above-mentioned suspension and be 0.1 mol is 12 to regulate pH; Take by weighing 49.8 milligrams of PdCl 2Join in the above-mentioned suspension, 125 oBack flow reaction is 3.5 hours under the C nitrogen protection, the reduction of utilizing ethylene glycol with the Pd particulate load at TiO 2On/graphene oxide the carrier; Cool the temperature to 95 then oC also adds 0.09 milliliter of hydrazine hydrate, reacts 40 minutes, in order to graphene oxide is reduced to Graphene; Temperature is down to that to add concentration after the room temperature be that the HCl solution of 0.1 mol is 3 to regulate pH, leaves standstill after 10 hours under 9000 rev/mins the rotating speed centrifugation then and removes supernatant; With detecting less than Cl in deionized water cyclic washing, the centrifuged supernatant -Existence; With sample 50 oC vacuumize 12 hours can obtain catalyst P d/TiO 2/ G.
Take by weighing 5.0 milligrams and adopt the synthetic Pd/TiO of the inventive method 2/ G catalyst powder, with 1 milliliter of isopropyl alcohol, 100 microlitre mass fractions are 5% Nafion alcoholic solution dispersion, ultrasonic 1 hour, get 10 microlitre suspension-turbid liquids and be coated on clean rotating circular disk glass-carbon electrode surface, dry under the air at room temperature, make the thin film work electrode; Be the Pt silk to electrode, reference electrode is Ag/AgCl, and test solution is the HClO of 0.1 mol 4
Fig. 2 c is the Pd/TiO of preparation 2The X-ray diffraction spectrogram of/G, similar to sample synthetic among the embodiment 1, by finding out the characteristic diffraction peak that obvious Pd is arranged among the figure, there is not TiO 2Characteristic diffraction peak, the TiO that hydrolysis generates is described 2It is amorphous state.Transmission electron microscope photo is similar to embodiment 1, and Pd is dispersed in carrier surface, and particle diameter is distributed in about 3 nanometers.Fig. 5 is Pd/TiO 2The power spectrum face scanning analysis figure of/G, C, O, Pd, four kinds of elements of Ti evenly distribute, and further show unformed TiO 2Evenly cover the Graphene surface.Electrochemical results such as Fig. 6 c, Fig. 7 c, Fig. 8, shown in Figure 9 compare with Comparative Examples 1, and not only current potential is shuffled, and the limiting diffusion current value increases.Carry out hydrogen reduction test under different rotating speeds, along with the increase of rotating speed, limiting diffusion current increases thereupon, by the K-L formula calculate n=3.97, close to 4 electron reactions.Have good anti-methyl alcohol performance simultaneously, take-off potential and limiting diffusion current value all remain unchanged substantially in methanol solution.The hydrogen reduction polarization curve of Figure 11 after voltage range is for 50 weeks of 0.6-1.2 volt circulation and 1000, as can be seen from the figure, after the circulation through 1000 weeks, hydrogen reduction take-off potential and the limiting diffusion current density of catalyst all do not have significant change, show through amorphous TiO 2Load after, catalyst has good stable, efficiently solves the etching problem of carbon carrier in cyclic process.
Embodiment 3
(1) preparation of graphite oxide: taking by weighing 2 gram graphite is the graphite H of 50 grams per liters with the preparation graphite concentration 2SO 40.04 liter of suspension takes by weighing 0.1 gram KMnO then 4Under ice bath, slowly join above-mentioned H 2SO 4In the suspension, 40 oStirring reaction is 1 hour under the C; Adding deionized water in above-mentioned suspension, is 1.2 grams per liters with the graphite concentration dilution, and temperature is risen to 100 oC reaction 10 minutes; Take by weighing 0.333 gram mass mark and be 0.75% H 2O 2Solution adds in the above-mentioned reactant liquor with cessation reaction; With the HCl solution washing of 1.5 mol, supernatant is removed in centrifugation under 5000 rev/mins the rotating speed, can not detect SO repeatedly for several times in supernatant 4 2-With the sample collected 40 oC vacuumize 14 hours can obtain graphite oxide.
(2) Pd/TiO 2The preparation of/G: take by weighing 0.1 gram graphite oxide and be scattered in the glycerol solvent 0.1 liter of the suspension that preparation graphite oxide concentration is 1 grams per liter, ultrasonic dispersion obtained graphene oxide suspension in 2 hours; Take by weighing 171.0 milligrams and add in the above-mentioned graphene oxide suspension, behind hydrolysis, obtain TiO 2/ graphene oxide carrier suspension; The NaOH solution that drips concentration in the above-mentioned suspension and be 0.2 mol is 14 to regulate pH; Take by weighing 285.0 milligrams of K 2PdCl 4Join in the above-mentioned suspension, 130 oRefluxed under the C nitrogen protection 3 hours, the reduction of utilizing glycerol with the Pd particulate load at TiO 2On/graphene oxide the carrier; Cool the temperature to 90 then oC also adds 0.11 milliliter of hydrazine hydrate, reacts 20 minutes, in order to graphene oxide is reduced to Graphene; Temperature is down to that to add concentration after the room temperature be that the HCl solution of 0.2 mol is 4 to regulate pH, leaves standstill after 8 hours under 8000 rev/mins the rotating speed centrifugation then and removes supernatant; With deionized water cyclic washing, centrifugal in supernatant, the detection less than Cl -Existence; With sample 40 oC vacuumize 14 hours can obtain catalyst P d/TiO 2/ G.
Take by weighing 5.0 milligrams and adopt the synthetic Pd/TiO of the inventive method 2/ G catalyst powder, with 1 milliliter of isopropyl alcohol, 100 microlitre mass fractions are 5% Nafion alcoholic solution dispersion, ultrasonic 1 hour, get 10 microlitre suspension-turbid liquids and be coated on clean rotating circular disk glass-carbon electrode surface, dry under the air at room temperature, make the thin film work electrode; Be the Pt silk to electrode, reference electrode is Ag/AgCl, and test solution is the HClO of 0.1 mol 4
Fig. 2 d is the Pd/TiO of preparation 2The X-ray diffraction spectrogram of/G by finding out the characteristic diffraction peak that obvious Pd is arranged among the figure, does not have TiO 2Characteristic diffraction peak, the TiO that hydrolysis generates is described 2It is amorphous state.Transmission electron microscope photo is similar to embodiment 1, and Pd is dispersed in carrier surface, and particle size is 4 nanometers, mainly is that grain diameter increases to some extent because the load capacity of Pd increases.Electrochemical results is shown in Fig. 6 d, Fig. 7 d, because TiO 2Content increase, cause conductivity to descend, catalytic performance descends to some extent.
Comparative Examples 1
With Pd/G as a comparison, its synthetic method is:
(1) preparation of graphite oxide: taking by weighing 2.174 gram graphite is the graphite H of 43.48 grams per liters with the preparation graphite concentration 2SO 40.05 liter of suspension takes by weighing 0.145 gram KMnO then 4Under ice bath, slowly join above-mentioned H 2SO 4In the suspension, 35 oStirring reaction is 2 hours under the C; Adding deionized water in above-mentioned suspension, is 0.9 grams per liter with the graphite concentration dilution, and temperature is risen to 95 oC reaction 15 minutes; Take by weighing 0.403 gram mass mark at last and be 0.6% H 2O 2Solution adds in the above-mentioned reactant liquor with cessation reaction; With the HCl solution washing of 1.25 mol, supernatant is removed in centrifugation under 4000 rev/mins the rotating speed, can not detect SO repeatedly for several times in supernatant 4 2-With the sample collected 50 oC vacuumize 12 hours can obtain graphite oxide.
(2) preparation of Pd/G: take by weighing 0.1 gram graphite oxide and be scattered in the ethylene glycol solvent 0.125 liter of the suspension that preparation graphite oxide concentration is 0.8 grams per liter, ultrasonic dispersion obtained graphene oxide suspension in 1.5 hours; The NaOH solution that drips concentration in the above-mentioned suspension and be 0.1 mol is 12 to regulate pH; Take by weighing 49.8 milligrams of PdCl 2Join in the above-mentioned suspension, 125 oBack flow reaction is 3.5 hours under the C nitrogen protection, the reduction of utilizing ethylene glycol with the Pd particulate load on the graphene oxide carrier; Cool the temperature to 95 then oC also adds 0.09 milliliter of hydrazine hydrate, reacts 40 minutes, in order to graphene oxide is reduced to Graphene; Temperature is down to that to add concentration after the room temperature be that the HCl solution of 0.1 mol is 3 to regulate pH, leaves standstill after 10 hours under 9000 rev/mins the rotating speed centrifugation then and removes supernatant; With detecting less than Cl in deionized water cyclic washing, the centrifuged supernatant -Existence; With sample 50 oC vacuumize 12 hours can obtain catalyst P d/G.
Take by weighing 5.0 milligrams and adopt the synthetic Pd/G catalyst powder of the inventive method, with 1 milliliter of isopropyl alcohol, 100 microlitre mass fractions are 5% Nafion alcoholic solution dispersion, ultrasonic 1 hour, get 10 microlitre suspension-turbid liquids and be coated on clean rotating circular disk glass-carbon electrode surface, dry under the air at room temperature, make the thin film work electrode; Be the Pt silk to electrode, reference electrode is Ag/AgCl, and test solution is the HClO of 0.1 mol 4
Fig. 2 a is for the X-ray diffraction spectrogram of the Pd/G of preparation, by finding out the characteristic diffraction peak that obvious Pd is arranged among the figure.Fig. 4 is the high-resolution-ration transmission electric-lens photo of Pd/G, and the Pd particle is obviously reunited at carrier surface.Electrochemical results such as Fig. 6 a, Fig. 7 a, shown in Figure 10, take-off potential is more negative, and limiting diffusion current is less than normal simultaneously.Do not have tangible methanol oxidation peak under the condition that methyl alcohol exists, but starting voltage and limiting diffusion current density reducing all, mainly is because methyl alcohol has occupied some catalytic activity sites, and the anti-methyl alcohol poor performance of Pd/G is described.

Claims (5)

1. palladium/titanium dioxide/graphen catalyst, it is characterized in that: the chemical composition of this catalyst is described as Pd/TiO 2/ G, wherein, G is Graphene; TiO 2/ G is catalyst carrier, amorphous state TiO 2Evenly cover the G surface; Catalytic activity constituent element Pd particle diameter is 2～4 nanometers, is evenly distributed on TiO 2/ G carrier surface; Catalytic activity constituent element Pd accounts for 10%～50% of catalyst gross mass, TiO 2Account for 5%～15% of catalyst gross mass, G accounts for 35%～85% of catalyst gross mass.
2. the preparation method of the described palladium/titanium dioxide of claim 1/graphen catalyst is characterized in that, may further comprise the steps:
(1) preparation of graphite oxide: the preparation graphite concentration is the H of 40～50 grams per liters 2SO 4Suspension is then according to KMnO 4With the mass ratio of graphite be the ratio of 1:10～1:20 under ice bath with KMnO 4Join above-mentioned H 2SO 4In the suspension, 30～40 oStirring reaction is 1～3 hour under the C; Adding deionized water in above-mentioned suspension, is 0.6～1.2 grams per liter with the graphite concentration dilution, and temperature is risen to 90～100 oC reaction 10～20 minutes; According to H 2O 2With the mass ratio of graphite be that the ratio of 1:1000～1:800 is 0.5%～0.75% H with mass fraction 2O 2Solution adds in the above-mentioned reactant liquor with cessation reaction; With the HCl solution washing of 1～1.5 mol, supernatant is removed in centrifugation under 3000～5000 rev/mins the rotating speed, can not detect SO repeatedly for several times in supernatant 4 2-With the sample collected 40～60 oC vacuumize 10～14 hours obtains graphite oxide;
(2) Pd/TiO 2The preparation of/G: it is the suspension of 0.5～1 grams per liter that graphite oxide is scattered in the low-carbon alcohols solvent preparation graphite oxide concentration, and ultrasonic dispersion obtained graphene oxide suspension in 1～2 hour; According to TiO 2The ratio that accounts for catalyst gross mass 5%～15% is calculated and is measured titanium compound and adds in the above-mentioned graphene oxide suspension, obtains TiO behind hydrolysis 2/ graphene oxide carrier suspension; To TiO 2Dropping concentration is that the NaOH solution of 0.05～0.2 mol is 10～14 to regulate pH in the/graphene oxide carrier suspension; The ratio that accounts for catalyst gross mass 10%～50% according to Pd is calculated and is taken by weighing palladium compound and joins TiO 2In/graphene oxide carrier the suspension, 120～130 oBack flow reaction is 3～4 hours under the C nitrogen protection, the reduction of utilizing low-carbon alcohols with the Pd particulate load at TiO 2On/graphene oxide the carrier; Cool the temperature to 80～95 then oC also adds hydrazine hydrate, and wherein the mass ratio of the volume/graphene oxide of hydrazine hydrate is 9～11 milliliters/10 grams, reacts 20～40 minutes, and graphene oxide is reduced to Graphene; Temperature is down to that to add concentration after the room temperature be that the HCl solution of 0.05～0.2 mol is 2～4 to regulate pH, leaves standstill after 8～12 hours under 7000～9000 rev/mins the rotating speed centrifugation then and removes supernatant; With deionized water cyclic washing, centrifugal in supernatant, the detection less than Cl -Existence; With sample 40～60 oC vacuumize 10～14 hours obtains catalyst P d/TiO 2/ G.
3. preparation method according to claim 2 is characterized in that, the low-carbon alcohols in the step (2) is a kind of in methyl alcohol, ethylene glycol or the glycerol.
4. preparation method according to claim 2 is characterized in that, the titanium compound in the step (2) is a kind of in titanium tetraisopropylate, titanium tetrachloride or the nine hydration titanium sulfates.
5. preparation method according to claim 2 is characterized in that, palladium compound is PdCl in the step (2) 2Or K 2PdCl 4In a kind of.
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CN104437475A (en) * 2014-11-27 2015-03-25 北京化工大学 Electro-catalyst Pt/amTiO2/rGO and preparation method
CN110560147A (en) * 2019-07-31 2019-12-13 广东工业大学 Sub-nano Pd particle loaded Ti-SBA-15 catalyst, and preparation method and application thereof
CN111584844A (en) * 2020-05-20 2020-08-25 佛山科学技术学院 Titanium dioxide nano composite electrode material and preparation method thereof
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