CN102800481A - Surface passivation method of iron oxide photoelectrode - Google Patents
Surface passivation method of iron oxide photoelectrode Download PDFInfo
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- CN102800481A CN102800481A CN2012101370308A CN201210137030A CN102800481A CN 102800481 A CN102800481 A CN 102800481A CN 2012101370308 A CN2012101370308 A CN 2012101370308A CN 201210137030 A CN201210137030 A CN 201210137030A CN 102800481 A CN102800481 A CN 102800481A
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- iron oxide
- optoelectronic pole
- surface passivation
- passivation method
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Abstract
The invention discloses a surface passivation method of an iron oxide photoelectrode, and the method comprises the steps of: using an iron oxide film material photoelectrode as an anode, soaking the anode in the aqueous solution of saturated NaCl, and scanning the light current-time curve of the anode under a strong illumination condition, wherein the thickness of the iron oxide photoelectrode is 400-500 nm, and the treatment time is 2-10hours. The surface passivation method of an iron oxide photoelectrode disclosed by the invention is simple and efficient, the equipment is simple, the surface passivation method is liable to be applied in a mass scale, and the quantum conversion efficiency of the photoelectrode with a treated surface is greatly improved.
Description
Technical field
The present invention relates to a kind of surface passivation method of iron oxide optoelectronic pole.
Background technology
Solar energy is a kind of inexhaustible, the natural resources that energy is huge, and each hour shines upon enough human a whole year that uses of energy of the earth.Directly utilizing sunlight to obtain the energy is a yearning method that obtains clean energy resource, and its influence to environment is very little.Along with the concern of countries in the world to carbon emission reduction, and solar power generation---photovoltaic technology (photovoltaic, PV)---the method as a kind of acquisition clean energy resource of comparative maturity is just receiving increasing attention.Yet, compare with other generation technology, though solar cell with the operation of 70% theoretical efficiency, cost of its generating now is still high.In addition, photovoltaic generation has only solved the problem of catching in the solar energy utilization, and the problem of storage of solar energy is also unresolved.Because can change and rise and fall sunshine in every day, when solar irradiation was not enough, solar power generation just can be affected.If so do not have a kind of effective and cheap storage of solar energy method, just can not utilize solar energy fully.So how the utilization to solar energy reduces the photovoltaic manufacturing cost except paying close attention to, how also to pay close attention to effectively conversion of solar energy with store.
Photoelectrochemical cell (photoelectrochemical cells; PEC) be a kind of wet chemical method that utilizes; Photosynthesis of plants in simulating nature circle; Solar energy is directly changed into the system of chemical energy (Hydrogen Energy), and it utilizes semiconductor and electrolyte directly contacts the solid/liquid knot that forms (semiconductor-liquid junction SCLJ) reaches the purpose of conversion of solar energy and storage.This solid/liquid knot has following advantage: (1) is compared with solid-state p-n junction; Only need directly insert semiconductor and just can form the solid/liquid knot that is used for separating the photoproduction electron hole pair in the electrolyte; Therefore semiconductor can be selected more cheap polycrystalline sample for use, and preparation technology also simplifies greatly; (2) owing to be that solid phase-liquid phase knot has freely " ideal " structure; The shortcoming that does not have the mechanical stress that causes owing to not matching of two contacted solid phase lattices; Thereby greatly reduce the recombination velocity of free carrier, improved conversion efficiency at the interface.
The key of utilization photoelectrochemical cell hydrogen production by water decomposition is to find suitable optoelectronic pole.Desirable optoelectronic pole material will have advantages such as suitable band gap (can absorb most of sunlight), fast light corrosivity, cheapness.(iron oxide of being mentioned among the present invention is α-Fe to iron oxide
2O
3) be an outstanding semiconductor photoelectrode material that can satisfy above-mentioned three conditions simultaneously.Certainly, iron oxide itself has many deficiencies, and like poorly conductive, surface recombination rate is high.To the shortcoming of its poorly conductive, improve through other ion that mixes usually.Up to the present, Si
4+And Ti
4+Be considered to comparatively effectively dopant ion.Before us the matching relationship through ionic radius has been proposed, with Si
4+And Ti
4+Be doped in the iron oxide method [M. Zhang, W. Luo, Z. Li, Y. Tao and Z. Zou, Appl. Phys. Lett. 97,042105 (2010)] simultaneously with its carrier concentration of further raising and photoelectrochemical behaviour.To the high shortcoming of iron oxide surface recombination rate, solve through surface passivation usually.The present invention is intended to the method through the electrochemical surface processing, reaches the purpose of iron oxide surface passivation, and part is eliminated its surperficial dangling bonds and oxygen defect etc. and fallen into into attitude, in the hope of reducing surface recombination rate, improves electricity conversion.The present invention is very routine with unadulterated iron oxide photoelectricity, carries out electrochemical surface and handles.
Summary of the invention
The present invention seeks to, a kind of surface passivation method of iron oxide optoelectronic pole is provided, can significantly improve its IPCE (conversion quantum efficiency).
The surface passivation method of said sull material optoelectronic pole is: as anode, be immersed in sull material optoelectronic pole in the aqueous solution of saturated NaCl, under the intense light irradiation condition, scan its photoelectric current-time graph.The thickness of said iron oxide optoelectronic pole is 400-500 nm.Processing time is 2 hours-10 hours.Room temperature condition can, preferably with 20-35 ℃.
Described sull material optoelectronic pole optical thin film is obtained by ultrasonic spray pyrolysis (USP) prepared.Concrete steps are: the alcoholic solution with the ferric acetyl acetonade of 0.02 M is a precursor liquid, with the ultrasonic atomizer atomizing, is carrier gas with compressed air, sprays in the already heated quartz ampoule, is deposited on the Conducting Glass that is placed in the quartz ampoule.Depositing temperature 500-550 ℃.
The present invention uses it for decomposing water with solar energy and produces hydrogen through after the sull material being carried out the electrochemical surface processing.The photoelectric current of the sull optoelectronic pole after the processing significantly increases, and is nearly 6 times before handling, and the IPCE value under 365 nm wavelength and 1.23 V vs. RHE (reversible hydrogen electrode) bias voltage reaches 13%.
Advantage beneficial effect of the present invention is: the surface passivation method of handling the iron oxide optoelectronic pole is simple, efficient, and equipment is simple, is easy to extensive use, and the optoelectronic pole conversion quantum efficiency significantly improves after the surface treatment.
Description of drawings
Fig. 1 be (a) sull optoelectronic pole under the saturated NaCl aqueous solution and strong illumination through photoelectric current-time graph of 9 hours (illustration is a some circle part enlarged drawing); (b) be through 2 hours, handled in 4 hours and 9 hours and the photoelectric current-potential curve (illustration be the untreated and quiet 9 hour iron oxide IPCE value handled) of untreated sull optoelectronic pole in the 1 M NaOH aqueous solution.
Fig. 2 is the transient state photoelectric current along with the sull of time variation.Bias voltage is illustrated respectively among the figure for RHE, is 1.0,1.2 and 1.5 V.In 4 s, there are 2 s to open the light, close light At All Other Times.Red line is represented the transient current of handling through 9 hours, and blue representative is untreated.
Fig. 3 be the following differential capacitance of the different bias voltages that record through electrochemical impedance spectroscopy (illustration be based on analog circuit figure.
R S Be series resistance,
R SC Be the semi-conductor electricity electrode resistance,
R CT Be charge transfer resistance).Triangle is represented depletion-layer capacitance
C SC ,, box-shaped is represented Helmholtz's layer capacitance
C H Result before blue representative is handled, the red result who represents after handling in 9 hours.
Fig. 4 is the fluorescence emission spectrum (excitation wavelength 520 nm) of sull, the sample before the black line representative is handled, after the red line representative is handled.
Embodiment
Fig. 1 (a) has shown the concrete grammar of the surface passivation of iron oxide optoelectronic pole.Utilize the CHI600B electrochemical analyser, under 1.4 V vs. RHE bias voltages with strong illumination under three-electrode system in, with the saturated NaCl aqueous solution photoelectric current-time graph that is the sull of electrolyte.In the time of beginning, photoelectric current sharply is raised to a peak value (1.5 mA cm
-2), about 5000 s, drop to a lowest point (1.0 mA cm then
-2).Again then, photoelectric current promotes in ensuing 30000 s steadily, reaches a platform (4.0 mA cm at last
-2).Can find out that from the illustration of Fig. 1 (a) photoelectric current of rising is not the influence that comes from dark current, photoelectric current is negligible because dark current is compared, and no matter is at 30000 s or in end.Certainly, in 9 hours so long time, the pH value of saturated NaCl is certain to change; Change influence in order to eliminate the pH value to photoelectric current; Fig. 1 (b) has compared in the 1 M NaOH aqueous solution, before handling, through 2 hours, 4 hours and the Fe that handled in 9 hours
2O
3The photoelectricity flow valuve of film.For all Fe
2O
3Film photoelectric electrode, dark current all is negligible being lower than under the 1.6 V vs. RHE bias voltages, photoelectric current all rises when 1.0 V vs. RHE.The photoelectricity flow valuve of the sull after the processing is all big than what do not handle.Under 1.23 V vs. RHE bias voltages, for 2 hours, 4 hours, 9 hours and untreated Fe
2O
3The photoelectric current of film is respectively 0.79,1.01,1.89 and 0.33 mA cm
-2For the Fe that surpasses processing in 9 hours
2O
3Film, photoelectric current can not continue to increase again.The illustration of Fig. 1 (b) has provided the employing light intensity meter, and (Newport, 840-C) test light intensity is with the IPCE value under the monochromatic filter test different wave length.Can find out that the sample IPCE value after the processing significantly increases, untreated and be respectively 5% and 13% through the IPCE value of the sample handled in 9 hours under 365 nm and 1.23 V vs. RHE bias voltages, promptly through 9 hours processing, the IPCE value increased by 1.6 times.
In order to estimate the water oxidation that taken place on treated and undressed sull-electrolyte interface and the dynamics of charge recombination, the transient state photoelectric current is recorded in the 1M NaOH aqueous solution, and is as shown in Figure 2.Handled through 9 hours with undressed film under three crucial bias voltages, along with the Kai Heguan of lamp, time-resolved photoelectric current goes on record.The shape of transient state photoelectric current is similar and typical: when opening the light, an anode photoelectric current peak occurring, is to go out oxygen reaction (OER, oxygen evolution reaction) dynamics and accumulate slowlyer because photohole is moved on the interface; Close the light time, the cathode photo current peak occurs, be because from external circuit migration electronics that comes and the hole of gathering compound at the interface.Under higher biased, there is enough electromotive force deoxidation water in most of hole, thereby transient performance weakens., disclosed the film of handling and made less hole accumulate at the interface obviously than a little less than not handling through the transient state photoelectric current of the film handled in 9 hours.
As in foreword, saying, the surface trap attitude is considered to be present on the sull electrode.Energy trapping possibly be to come from a unordered plane of crystal, on this surface, has dangling bonds or oxygen room.Long time treatment Fe in NaCl
2O
3Film possibly cause Fe
3+Perhaps Fe
2+Dissolving, be similar to document [M. Gr tzel, J. Kiwi, C. L. Morrison, R. S. Davidson, and A. C. C. Tseung, J. Chem. Soc., Faraday Trans. I 81,1883 (1985)] and say.Fe
3+Perhaps Fe
2+Dissolving mean that (dangling bonds possibly be because surperficial Fe for the minimizing in dangling bonds or oxygen room
3+Existence and oxygen room usually in iron oxide with Fe
2+Form exists), or in other words, the passivation of surface state.
Electrochemical impedance spectroscopy (EIS; Electrochemical impedance spectroscopy) and fluorescence spectrum (PL; What photoluminescence spectroscopy) be used to that further support surface attitude is passivated guesses, said by Fig. 3 and Fig. 4 respectively.Fig. 3 compared before the film with handle after the semiconductor depletion-layer capacitance (
C SC ) and Helmholtz's layer capacitance (
C H ).Because electrode described herein is unadulterated, thus can expect be
C H Value approximately than
C SC A high one magnitude.Along with the rising of bias voltage, because the change of depletion width is big,
C SC Reduce;
C H Reduce, but concrete reason is still not clear along with the rising of bias voltage yet.Yet the treatment effect that Fig. 3 shows is conspicuous:
C SC Raise and
C H Reduce.
C H The reason that reduces is a film surface because be passivated the minimizing of the charge density that causes,
C SC The reason that raises is the minimizing because of the surface trap attitude, and electric charge more concentrates in the depletion layer.Therefore, the variation of surface capacitance is a solid evidence of surface passivation.
The iron oxide fluorescence spectrum derives from the directly compound of electron hole pair, depends on surface quality strongly, especially the surface trap density of states.Since the surface trap attitude plays an important role in the non-radiation recombination of iron oxide surface exciton, if surface state has been passivated so, fluorescence spectrum should be enhanced.Fig. 4 showed in air with no applying bias condition under processing before with processing after the fluorescence emission spectrum of sull.Visible by figure; Untreated sample do not have fluorescence to occur, and a tangible fluorescence emission peak has appearred in the sample after handling in 9 hours with 520 nm injection optical excitation the time; Start from 580 nm (promptly corresponding to the band gap of sull; 2.1 eV), reach peak value, trail at 700 nm places at 610 nm places.This presentation of results the part of photoproduction exciton through radiation recombination.Sample through handling has shown fluorescent emission, and this is the vaild evidence that another surface state is passivated.
Claims (4)
1. the surface passivation method of iron oxide optoelectronic pole is characterized in that: sull material optoelectronic pole as anode, is immersed in the aqueous solution of saturated NaCl, under the intense light irradiation condition, scans its photoelectric current-time graph; The thickness of said iron oxide optoelectronic pole is 400-500 nm; Processing time is 2 hours-10 hours.
2. the surface passivation method of iron oxide optoelectronic pole as claimed in claim 1 is characterized in that, during photoelectric current-time sweep, platinum Pt is as negative electrode, and the Ag/AgCl electrode is as reference electrode.
3. the surface passivation method of iron oxide optoelectronic pole as claimed in claim 1 is characterized in that, described iron oxide photoelectricity is thin-film material very, is obtained by ultrasonic spray pyrolysis (USP) prepared.
4. the surface passivation method of iron oxide optoelectronic pole as claimed in claim 3; It is characterized in that preparation sull material optoelectronic pole concrete steps are: the alcoholic solution with the ferric acetyl acetonade of 0.02 M is a precursor liquid, atomizes with ultrasonic atomizer; With compressed air is carrier gas; Spray in the already heated quartz ampoule, be deposited on the Conducting Glass that is placed in the quartz ampoule depositing temperature 500-550 ℃.
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105039938A (en) * | 2015-06-19 | 2015-11-11 | 许昌学院 | Method for preparing photoelectrode of alpha-iron oxide film by single-source precursor |
| CN107268020A (en) * | 2017-06-06 | 2017-10-20 | 中国矿业大学 | A kind of Ta3N5The preparation method and Ta of film3N5The application of film |
| CN109252179A (en) * | 2018-09-19 | 2019-01-22 | 苏州大学 | A kind of double absorption layer light anode and preparation method for photocatalytic water |
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| US20030011965A1 (en) * | 2001-01-09 | 2003-01-16 | Lih-Ren Shiue | Electrochemical capacitor with electrode material for energy storage |
| CN102304738A (en) * | 2011-07-22 | 2012-01-04 | 南京大学 | Surface treatment method of InGaN-based photo-electrode |
| CN102423706A (en) * | 2011-11-02 | 2012-04-25 | 西南交通大学 | Preparation method of micro/nano alpha-Fe2O3 photoelectrode |
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2012
- 2012-05-04 CN CN2012101370308A patent/CN102800481A/en active Pending
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
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| US20030011965A1 (en) * | 2001-01-09 | 2003-01-16 | Lih-Ren Shiue | Electrochemical capacitor with electrode material for energy storage |
| CN102304738A (en) * | 2011-07-22 | 2012-01-04 | 南京大学 | Surface treatment method of InGaN-based photo-electrode |
| CN102423706A (en) * | 2011-11-02 | 2012-04-25 | 西南交通大学 | Preparation method of micro/nano alpha-Fe2O3 photoelectrode |
Non-Patent Citations (2)
| Title |
|---|
| MICHAEL GRATZEL ET AL.: "Visible-light-induced photodissolution of α-Fe2O3 powder in the presence of chloride anions", 《JOURNAL OF THE CHEMICAL SOCIETY, FARADAY TRANSACTIONS 1: PHYSICAL CHEMISTRY IN CONDENSED PHASES》 * |
| 袁洪春等: "α-Fe2O3纳米薄膜的超声喷雾热解制备及其表征", 《淮北煤师院学报：自然科学版》 * |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105039938A (en) * | 2015-06-19 | 2015-11-11 | 许昌学院 | Method for preparing photoelectrode of alpha-iron oxide film by single-source precursor |
| CN105039938B (en) * | 2015-06-19 | 2018-10-02 | 许昌学院 | The method that a kind of list source presoma prepares the optoelectronic pole of α-ferric oxide film |
| CN107268020A (en) * | 2017-06-06 | 2017-10-20 | 中国矿业大学 | A kind of Ta3N5The preparation method and Ta of film3N5The application of film |
| CN109252179A (en) * | 2018-09-19 | 2019-01-22 | 苏州大学 | A kind of double absorption layer light anode and preparation method for photocatalytic water |
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