CN102527187B - Method for removing SO2 from air by using external voltage - Google Patents

Abstract

The invention relates to a method for removing foreign gas SO2 from the air by using external voltage. The air passes through a battery-like structural device and then enters a proton exchange membrane fuel cell (PEMFC). Certain voltage is applied onto the battery-like structural device to remove SO2 from the air. By the method, the negative effect of the foreign gas SO2 in the air on the performance of the PEMFC can be effectively eliminated, and the environmental adaptability of the fuel battery can be improved.

Description

A kind of applied voltage that utilizes removes SO in air 2method

Technical field

The present invention relates to a kind of applied voltage that utilizes and remove SO in air ₂method, be specially adapted to Proton Exchange Membrane Fuel Cells field.

Background technology

Proton Exchange Membrane Fuel Cells (PEMFC) is a kind of energy conversion device that chemical energy is directly changed into electric energy, there is the multiple advantages such as power density is high, energy conversion efficiency is high, room temperature starts fast, noiseless is pollution-free, be considered to be hopeful to be widely used in automobile power, disperse the fields such as power station.Because Proton Exchange Membrane Fuel Cells adopts surrounding air as oxidant conventionally, thus battery performance and air quality closely related.SO in air ₂can be adsorbed on electrode surface, reduce battery performance, and irrecoverable after battery performance decay.Therefore, numerous scholars have done deep research to this problem, have also proposed corresponding countermeasure.

The people such as Motadi (R. Motadi, et al. J. Power Sources 138 (2004) 216-225) study discovery, when passing into battery 2.5 ppm SO ₂air 45 h after, battery performance has declined 53%.The researcher of U.S. Los Alamos National Laboratory (E. Brosha, et al. 2005 Mid Year DOE Fuel Cell Program Review) has studied and has contained SO ₂the impact of dry humid air on battery performance, find the former more obvious to the poisoning effect of battery; Also studied variable concentrations SO ₂on battery performance impact, find SO ₂cause the poisoning initial concentration of battery between 0.1 ~ 0.25ppm.The people such as Jing (F. Jing, et al, J. Power Sources 166 (2007) 172-176) have studied 1 ppm SO ₂impact on battery performance, after long-play (100 h), cell voltage is reduced to 0.44V by 0.68V, has declined 35%.For SO ₂poison the mechanism of PEMFC catalyst, many scholars also inquire into.The Mepsted of Britain defence assessment office (G. Mepsted. Defense and Evalution Research Agency, 2001) thinks SO ₂be polar molecule, be easy to adsorb on Pt, cause cell catalyst poisoning, and this adsorption process is irreversible.Brosha etc. (E. Brosha, et al. 2005 Mid Year DOE Fuel Cell Program Review) think SO ₂be adsorbed on Pt catalyst surface, covered catalyst activity position, affect electric charge and shift, hindered proton conduction, cause battery performance to decline.The people such as Fu Jie (Fu Jie etc. power technology 31(2007) 864-913) find that ohmic resistance does not have significant change in the process of battery performance decay, charge transfer resistance obviously increases, and illustrates that battery performance decline mainly ascribes SO to ₂hindered oxygen reduction reaction.Further research is found, SO ₂absorption behavior on Pt catalyst shows great potential dependent.When cell potential is during in 0.65V left and right, SO ₂on Pt catalyst, with molecular forms, exist; When current potential is during higher than 0.65V, SO ₂can be oxidized; And when current potential is during lower than 0.65V, SO ₂can reduce (J. Fu, et al. J. Power Sources 187 (2009) 32-39).At present, solve SO in air ₂the method that battery is poisoned to problem mainly contains two kinds: current potential recovers and external purifying.Mohtadi etc. (R. Motadi, et al. J. Power Sources 138 (2004) 216-225) adopt the method for cyclic voltammetric, and poisoning battery performance is afterwards recovered completely.Brosha etc. (E. Brosha, et al. 2006 Annual DOE Fuel Cell Program Review) adopt 1.4V pulse 5 seconds and maintain the method for battery open circuit a period of time and recover poisoning battery.The essence that current potential recovers is absorption S oxidized removing under high potential, and Pt active sites is again out exposed, and battery performance recovers.But this method cannot be implemented when battery normally moves.(the F. Uribe such as the experiment Uribe of U.S. Los Alamos country; et al. DOE Hydrogen Program, FY 2004 Progress Report:315-320) before cell cathode import, use the mode of commercialization desulfurizing filter to protect cathod catalyst.Result shows, battery can be basicly stable in 1000 hours.(the X. Ma such as the Ma Xiaowei of Tongji University; et al. J. Power Sources 175 (2008) 383-389) adopt KOH modified activated carbon as external purifying material, protected well the stable operation 130 hours in the air of the NOx that contains 1.1 ppm and 0.25 ppm SO2 of a pile.In other patent, also mentioned external purifying method.In CIPO Patent CA 2550875, adopt porous mass and some alkaline matter absorbing acid gases SO2 such as active carbon, activated alumina.In US Patent 2007009338, adopt the molecular sieve of alkali metal containing and alkaline-earth metal to reach the effect of desulfurization.These external purifying methods are all to rely on the pure adsorption process of foreign gas on adsorbent to reach the object removing, and an inevitable problem is adsorbed saturated exactly.And the alkaline matter using may enter battery with air-flow, affects battery performance.

Summary of the invention

The object of this invention is to provide a kind of applied voltage that utilizes and remove foreign gas SO in air ₂external purifying method.

For achieving the above object, the technical solution used in the present invention is:

A kind of applied voltage that utilizes removes SO in air ₂method, adopt class battery structure device to operate, described class battery structure device comprises two end plates that play fixations, provide remove the porous material layer, film of gas occasion, to electrode layer, porous material layer, film, be held between two end plates after electrode layer is superimposed together successively, form class battery structure device; Wherein film with electrode layer is hot pressed into membrane electrode;

On two end plates of class battery structure device, apply voltage, air stream, through porous material layer, can remove airborne foreign gas SO ₂, and then application time can be avoided SO ₂reduce battery performance.

Described film be Nafion class film, described to electrode, be Pt/C electrode or carbon paper class;

Nafion class film with first electrode layer is hot pressed into membrane electrode, then membrane electrode is superimposed with each other with porous material layer again; Nafion class film is 212Nafion or 115Nafion film.

Described porous material is carbon felt class or carbon fiber polyporous materials, and this kind of material is to SO ₂there is certain adsorption capacity and have certain conductive capability.

Described porous material has carried out hydrophobisation before being assembled into class battery structure device to be processed and protonated processing;

Hydrophobisation processing procedure is that porous material is immersed in PTFE solution, obtains PTFE content and be 5% ~ 30% porous material, then dries, and finally, in the calcining of tube furnace the inside, calcining heat is 200 ~ 400 ℃;

Protonated processing procedure is the porous material dipping Nafion solution after hydrophobic is processed, and making Nafion content on porous material is 5% ~ 30%, and room temperature is dried.

Described device is for to assemble porous material, membrane electrode and stainless steel end plate with bolt; Described voltage range is 0.6V ~ 2.0V.

Specific operation process is,

1) porous material and membrane electrode assembly are dressed up class battery structure device;

2) on said apparatus, apply voltage, then this device is connected with fuel battery cathode with proton exchange film inlet end;

3) contain SO ₂air first pass into said apparatus, air stream, through porous material layer, can remove airborne foreign gas SO ₂, from said apparatus air out, enter into fuel cell, and then application time can be avoided SO ₂reduce battery performance, computer is automatically recorded cell voltage and is changed.

Described Proton Exchange Membrane Fuel Cells is common battery, by cell voltage, changes to detect SO ₂removal effect, also can detect SO by other method ₂removal effect is as gas-chromatography etc.

Airborne SO ₂can poison Proton Exchange Membrane Fuel Cells (PEMFC) catalyst, reduce battery performance.The present invention can eliminate foreign gas SO in air effectively ₂negative effect to PEMFC performance, avoids SO ₂poison cell catalyst, improve the environmental suitability of fuel cell.

advantage of the present invention:

1) the present invention can remove airborne SO effectively ₂.

2) the present invention has solved effectively because absorption is saturated and frequently change the problem of sorbing material.

Accompanying drawing explanation

Fig. 1, class proton exchange membrane fuel cell structure device schematic diagram; 1-end plate; 2-Pt/C electrode; 3-Nafion 212 films; 4-polyacrylonitrile carbon felt;

Fig. 2, whole process chart: I-for removing air SO ₂class battery structure device; II-for detection of SO ₂the PEM battery of removal effect.5-power supply; 6-load; 7-SO ₂air Mixture; The air inlet of 8-cell cathode; 9-cell cathode tail row; 10-galvanic anode fuel (hydrogen); 11-galvanic anode tail row;

Fig. 3, battery are containing 1ppm SO ₂air in move the life curve of 200 h, saturated humidification, battery temperature is 30 ℃, 400mAcm ^-2lower operation.

The specific embodiment

First assemble a class battery structure device, and this device is linked with a battery; On said apparatus, apply certain voltage; Contain SO ₂air by this device, from then on device enters into battery after out again.

Its concrete operation step is as follows:

1), with bolt fixedly porous material, membrane electrode and stainless steel end plate, form class battery structure device.

2) on class battery structure device, apply 0.6V ~ 2.0V voltage, and this device and battery are linked.

3) contain finite concentration SO ₂air by class battery structure device, from then on device out enters into battery afterwards.Record cell voltage over time.

The processing procedure of described porous material is:

1) hydrophobisation is processed: porous material floods a certain amount of PTFE, and PTFE content is 5% ~ 30%, in water-bath or drying box, dries, and dried porous material is respectively calcined to 30min respectively with at 240 ℃, 340 ℃;

2) protonated processing: porous material is flooded to a certain amount of Nafion solution, and Nafion content is 5% ~ 30%, and room temperature is dried.

The preparation process of described membrane electrode is: Nafion film is with to electrode, hot pressing under uniform temperature, pressure forms.

Embodiment 1

The polyacrylonitrile carbon felt (a kind of porous material) that the wide height of one block length is respectively to 3.5cm*2.5cm*0.6cm floods the PTFE solution of about 8mL 25%, dry 6h at 80 ℃ of water-baths.Then, carbon felt is put into tube furnace the inside, under nitrogen protection, calcines, calcination procedure is to keep 30min at 240 ℃, keeps 30min at 340 ℃, and the mass ratio of carbon felt and PTFE is 70:30.The carbon felt of surging after processing is flooded to a certain amount of 5% Nafion solution, is that 10:1 carries out protonated processing according to carbon felt and Nafion mass ratio.Pt/C electrode and Nafion 212 films are kept to 1 min under 140 ℃, 1 MPa pressure, be hot pressed into membrane electrode.Finally with bolt, carbon felt, membrane electrode and stainless steel end plate are fixed up, are assembled into class battery structure device, for SO ₂remove.

Device schematic diagram as shown in Figure 1.Class battery structure device and a monocell are linked, and apply 1.1V voltage on class battery structure device.Contain 1 ppm SO ₂air by this device, specifically refer to that the carbon felt from install flows through, then enter into monocell, whole process flow diagram as shown in Figure 2.Computer records cell voltage over time automatically, as shown in red curve in Fig. 3.In Fig. 3, black curve is containing 1 ppm SO ₂air voltage temporal evolution curve while directly entering into battery.The basic parameter of battery operation: saturated humidification, battery temperature is 30 ℃, and air velocity is 1000 mL/min, and air pressure is 0.1 4MPa.

Test result: can obviously find out from Fig. 3, when containing 1 ppm SO ₂air while directly entering into battery cell voltage in less than 20 h, declined more than 200 millivolt; When containing 1 ppm SO ₂air first through being applied in the device of 1.1 V voltages, then while entering into battery, cell voltage surpasses 200 h and does not all significantly decrease.Illustrate that the class battery structure device outside battery can effectively remove airborne SO ₂, avoid SO ₂battery performance is caused to negative effect.

Claims (2)

1. one kind is utilized applied voltage to remove SO in air ₂method, it is characterized in that: adopt class battery structure device to operate, described class battery structure device comprises two end plates that play fixations, provide remove the porous material layer, film of gas occasion, to electrode layer, porous material layer, film, be held between two end plates after electrode layer is superimposed together successively, form class battery structure device; Wherein film with electrode layer is hot pressed into membrane electrode;

On two end plates of class battery structure device, apply voltage, contain SO ₂air stream through porous material layer, foreign gas SO ₂be removed, during application, can avoid SO ₂reduce battery performance;

Described film be Nafion class film, described to electrode, be Pt/C electrode or carbon paper;

Nafion class film with first electrode layer is hot pressed into membrane electrode, then membrane electrode is superimposed with each other with porous material layer again;

Described porous material is carbon felt class or carbon fiber polyporous materials;

Described porous material has carried out hydrophobisation before being assembled into class battery structure device to be processed and protonated processing;

Hydrophobisation processing procedure is that porous material is immersed in PTFE solution the inside, obtains PTFE content and be 5% ~ 30% porous material, then dries, and finally, in the calcining of tube furnace the inside, calcining heat is 200 ~ 400 ℃;

Protonated processing procedure is the porous material dipping Nafion solution after hydrophobic is processed, and making Nafion content on porous material is 5% ~ 30%, and room temperature is dried;

Described class battery structure device is for to assemble porous material layer, membrane electrode and stainless steel end plate with bolt;

Described voltage range is 0.6V ~ 2.0V;

Specific operation process is,

1) porous material layer and membrane electrode assembly are dressed up class battery structure device;

2) on said apparatus, apply voltage, then this device is connected with fuel battery cathode with proton exchange film inlet end;

3) contain SO ₂air first pass into said apparatus, air stream, through porous material layer, can remove airborne foreign gas SO ₂, from said apparatus air out, enter into fuel cell, and then application time can be avoided SO ₂reduce battery performance, computer is automatically recorded cell voltage and is changed.

2. it is characterized in that in accordance with the method for claim 1: Nafion class film is 212Nafion or 115Nafion film.

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