CN103022521A

CN103022521A - Palladium-cobalt/graphene nano electro-catalyst and preparation method thereof

Info

Publication number: CN103022521A
Application number: CN2012105161439A
Authority: CN
Inventors: 银凤翔; 李国儒; 陈标华; 王亮
Original assignee: Changzhou Institute for Advanced Materials Beijing University of Chemical Technology
Current assignee: Changzhou Institute for Advanced Materials Beijing University of Chemical Technology
Priority date: 2012-12-05
Filing date: 2012-12-05
Publication date: 2013-04-03

Abstract

The invention discloses a palladium-cobalt/graphene nano electro-catalyst and a preparation method thereof. According to the palladium-cobalt/graphene nano electro-catalyst, palladium serves as an active ingredient, cobalt serves as a cocatalyst, and graphene serves as a carrier; and in the catalyst, the mass fraction of the palladium is 10-40%, the mass fraction of the cobalt is 5-30%, and the balance is the carrier. According to the preparation method of the catalyst, graphite oxide nanosheets are ultrasonically dispersed into polylol, palladium salt liquid, cobalt salt liquid and sodium acetate liquid are then added and fully mixed uniformly, the mixture is then transferred into a microwave hydrothermal reaction kettle, and the filtering, washing and drying processes are carried out after reaction, thereby obtaining the palladium-cobalt/graphene nano electro-catalyst. The preparation method disclosed by the invention has the advantages of energy saving, high speed, simple process and the like; and the particle sizes of palladium and cobalt nanoparticles in the prepared palladium-cobalt/graphene nano electro-catalyst are uniform. The catalyst has high electro-catalytic activity to the electrooxidation of formic acid and is widely applied to fuel cells.

Description

A kind of palladium-cobalt/graphene nano electro-catalyst and preparation method thereof

Technical field

The present invention relates to a kind of eelctro-catalyst and preparation method thereof, particularly a kind of palladium-cobalt/graphene nano electro-catalyst and preparation method thereof.

Background technology

Proton Exchange Membrane Fuel Cells take hydrogen as fuel is considered to one of fuel cell technology of tool prospect, however since at present the extensive preparation of hydrogen and storage safe problem etc. do not solve so that Proton Exchange Membrane Fuel Cells is failed industrialization always.Direct methanol fuel cell can be avoided the preparation of hydrogen and storage safe problem, but methyl alcohol is difficult for catalytic oxidation and battery performance is descended.Studies show that recently with formic acid to be that the direct methanoic acid fuel cell of fuel has overcome above-mentioned these shortcomings to a certain extent, and formic acid almost there is not toxicity.Therefore, direct methanoic acid fuel cell is considered to a kind of very promising fuel cell system.

In the catalyst of direct methanoic acid fuel cell, Pt and Pd are the anode catalysts of most study, but Pt easily poisons because of CO absorption as the catalyst of formic acid catalytic oxidation, so that its catalytic activity reduces greatly.Studies show that recently, Pd has preferably formic acid catalytic oxidation activity and anti-CO poisoning performance.Studies show that simultaneously, usually in catalyst, add second or the third element, can further improve the performance of Pd catalyst, and add the Co co-catalyst in the catalyst and can obviously improve catalytic activity and the anti-CO poisoning performance of Pd, thereby make its anode catalyst as direct methanoic acid fuel cell have high activity and stable.

The preparation method traditional at the supported on carbon surface precious metal nano-particle catalyst mainly is based on dipping-reduction technique, but this method is difficult to the size of control load palladium metal particle on carbon carrier, and the dispersion of noble metal granule on carbon carrier neither be very even, especially for the Pt/C catalyst of preparation high capacity amount.Recently, polyxol method is proved to be to prepare a kind of effective ways of high dispersion metal nano particle.In this method, polyalcohol is as solvent and the reducing agent of slaine, and at high temperature polyalcohol makes the metal ion in the solution be reduced into metal nanoparticle.Microwave heating technique is owing to having fast, and evenly, energy-conservation and high efficiency advantage is used widely in the synthesizing of organic chemical synthesis and nano material recently.

Summary of the invention

The purpose of this invention is to provide a kind of palladium-cobalt/graphene nano electro-catalyst and preparation method thereof.

A kind of palladium-cobalt of the present invention/graphene nano electro-catalyst is take palladium as active component, and cobalt is co-catalyst, and Graphene is carrier; The mass fraction of palladium is 10～40% in the catalyst, and the mass fraction of cobalt is 5～30%, and surplus is carrier.

The preparation method of a kind of palladium-cobalt/graphene nano electro-catalyst mainly may further comprise the steps:

1) with in the ultrasonic ethylene glycol that is dispersed in liquid of graphite oxide nanometer sheet, then add palladium salting liquid, cobalt salt solution and SAS, fully mix, graphite oxide nanometer sheet content is 0.25～1.2g/L in the mixture, the concentration of palladium salt is 0.0005～0.05mol/L, the concentration of cobalt salt is 0.0001～0.01mol/L, and the concentration of sodium acetate is 0.05～0.1mol/L;

2) said mixture is transferred in the microwave hydrothermal reaction kettle, microwave heating reaction is after 5～10 minutes, after filtration, washing, oven dry, obtains palladium-cobalt/graphene nano electro-catalyst.

Among the present invention, described palladium salt is palladium bichloride or palladium.

Compared with the prior art, the present invention adopts polyalcohol method and microwave technology, Pd nano particle has tiny and uniform particle diameter in the catalyst that is synthesized, and average grain diameter can be regulated and control about 3.0nm, and Pd nano particle high degree of dispersion on graphene nanometer sheet is even; In the catalyst preparation, add the co-catalyst cobalt chloride, can obviously improve the catalytic activity of platinum selective oxidation CO, reduced reaction temperature, also reduced the content of noble metal platinum simultaneously; The preparation method has fast, evenly, and the energy-conservation and high advantage of efficient.

Embodiment

EXAMPLE l:

The ultrasonic processing of 200mg graphite oxide nanometer sheet is dispersed in the ethylene glycol of 400mL, then adds the palladium chloride solution of 20mL 0.04M, the cobalt chloride solution of 10mL 0.1M and the SAS of 20mL 1M, and fully mix.Should transfer in the microwave hydrothermal reaction kettle by uniform mixture carry out microwave radiation heating reaction 10min.After the cooling, after filtration, with acetone and deionized water fully wash, 90 ℃ of oven dry, obtain palladium-cobalt/graphene nano electro-catalyst.As a comparison, synthesize in the same way palladium/graphene catalyst (mass fraction of palladium is 24.6%).

To Oxidation of Formic Acid electrocatalysis characteristic test and relatively: a small amount of eelctro-catalyst (palladium-cobalt/Graphene, palladium/graphene nano electro-catalyst) and an amount of 5% Nafion solution and absolute ethyl alcohol are mixed under ul-trasonic irradiation, should be coated on the glassy carbon electrode by uniform mixture, rear as measuring work electrode 80 ℃ of lower oven dry.Reference electrode is saturated calomel electrode (SCE) during measurement, and electrolyte is lM CHOOH+lMHClO ₄, platinized platinum is to electrode.Estimate nanometer electrical catalyst to the electro catalytic activity of formic acid electrochemical oxidation with cyclic voltammetry, sweep speed is 20mV/s.On the Pd-Co/ Graphene that records in above-mentioned preparation, the Pd/ graphene nano electro-catalyst, the peak current of formic acid electroxidation is respectively 18.3mA and 10.7mA, shows that Pd-Co/ Graphene eelctro-catalyst has the higher electro catalytic activity to Oxidation of Formic Acid than Pd/ graphen catalyst.

Embodiment 2

The ultrasonic processing of 600mg graphite oxide nanometer sheet is dispersed in the ethylene glycol of 500mL, then adds the palladium chloride solution of 28mL 0.1M, the cobalt chloride solution of 15mL 0.1M and the SAS of 25mL 1M, and fully mix.Should transfer in the microwave hydrothermal reaction kettle by uniform mixture carry out microwave radiation heating reaction 8min.After the cooling, after filtration, with acetone and deionized water fully wash, 90 ℃ of oven dry, obtain palladium-cobalt/graphene nano electro-catalyst.As a comparison, synthesize in the same way palladium/graphene catalyst (mass fraction of palladium is 30%).

The method test of pressing embodiment 1 relatively Pd-Co/ Graphene and Pd/ graphen catalyst to the catalytic performance of formic acid electroxidation.The peak current of formic acid electroxidation is respectively 25.6mA and 15.3mA on the Pd-Co/ Graphene that records under the same terms in above-mentioned preparation and the Pd/ graphen catalyst, illustrates that Pd-Co/ Graphene eelctro-catalyst has the higher electro catalytic activity to Oxidation of Formic Acid than Pd/ graphen catalyst.

Example 3

The ultrasonic processing of 400mg graphite oxide nanometer sheet is dispersed in the ethylene glycol of 600mL, then adds the palladium chloride solution of 20mL 0.05M, the cobalt chloride solution of 20mL 0.1M and the SAS of 30mL 1M, and fully mix.Should transfer in the microwave hydrothermal reaction kettle by uniform mixture carry out microwave radiation heating reaction 6min.After the cooling, after filtration, with acetone and deionized water fully wash, 90 ℃ of oven dry, obtain palladium-cobalt/graphene nano electro-catalyst.As a comparison, synthesize in the same way palladium/graphene catalyst (mass fraction of palladium is 17%).

The method test of pressing embodiment 1 relatively Pd/ Graphene and palladium/graphene catalyst to the catalytic performance of formic acid electroxidation.The peak current of formic acid electroxidation is respectively 9.2mA and 5.3mA on the Pd/ Graphene that records under the same terms in above-mentioned preparation and the palladium/graphene catalyst, illustrates that Pd-Co/ Graphene eelctro-catalyst has the higher electro catalytic activity to Oxidation of Formic Acid than Pd/ Graphene eelctro-catalyst.

Claims

1. palladium-cobalt/graphene nano electro-catalyst comprises active component palladium and carrier Graphene, it is characterized in that this catalyst is take cobalt as the group catalyst; The mass fraction of palladium is 10～40% in the catalyst, and the mass fraction of cobalt is 5～30%, and surplus is carrier.

2. the method for preparing palladium-cobalt claimed in claim 1/graphene nano electro-catalyst is characterized in that preparation process is as follows:

1) is dispersed in the ethylene glycol the graphite oxide nanometer sheet is ultrasonic, then add palladium salting liquid, cobalt salt solution and SAS, fully mix, graphite oxide nanometer sheet content is 0.25～1.2g/L in the mixture, the concentration of palladium salt is 0.0005～0.05mol/L, the concentration of cobalt salt is 0.0001～0.01mol/L, and the concentration of sodium acetate is 0.05～0.1mol/L;

2) said mixture is transferred in the microwave hydrothermal reaction kettle, microwave heating reaction is after 5～10 minutes, after filtration, washing, oven dry, obtains palladium/graphene nano electro-catalyst.

3. the preparation method of a kind of palladium-cobalt according to claim 2/graphene nano electro-catalyst is characterized in that described palladium salt is palladium bichloride or palladium.

4. the preparation method of a kind of palladium-cobalt according to claim 2/graphene nano electro-catalyst is characterized in that described cobalt salt is cobalt chloride, cobalt nitrate, cobalt carbonate or cobalt acetate.