Selenium-doped cadmium sulfide photoelectrode and preparation method thereof
Se-doping CdS electrodes address the low photocurrent density and instability of CdS by enhancing charge separation and reducing photocorrosion, achieving improved photocurrent density and stability.
Patent Information
- Application Number
- CN202510482222.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-17
- Publication Date
- 2025-07-15
AI Technical Summary
The existing cadmium sulfide photoelectrodes have problems with low photocurrent density and insufficient stability, especially when they are prone to failure during photocorrosion.
Using selenium-doped cadmium sulfide photoelectrode, the preparation method includes hydrothermal reaction and annealing to ensure the stability and photoelectric properties of the crystal.
The photocurrent density is significantly improved, the photocurrent density of the photoelectrode doubles at high bias voltage, and the stability is significantly improved, which can maintain high-efficiency photoelectrocatalytic performance for a long time.
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Figure CN120309191A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to a selenium-doped cadmium sulfide photoanode, and also relates to a preparation method of the above cadmium sulfide photoanode. Background Art
[0002] Photocatalysis, electrocatalysis, and photoelectrochemical systems are several emerging high-value technologies that have been prominent in recent years. For pure photocatalysis, incident light irradiates a semiconductor catalyst, causing the semiconductor to be excited to generate holes and electrons. The holes have strong oxidizing properties and can oxidize substrates at the valence band. Correspondingly, reduction reactions can occur at the conduction band. However, due to the recombination of photo-generated charges in photocatalysis, its significant drawbacks are low reaction rate and low quantum efficiency. In an electrocatalytic system, all electrons are induced by an external bias voltage, which determines the current density of the circuit. In actual application, the applied voltage is often higher than the theoretically required voltage to compensate for overpotential or other energy losses. The semiconductor-based photoelectrochemical system that absorbs and converts solar energy can reduce the dependence on pure electricity, and the wire can effectively separate electrons and holes, thereby achieving a more energy-saving and efficient catalytic effect.
[0003] Photoelectrochemistry has a wide range of applications in fields such as water splitting, pollutant degradation, and biomass high-value conversion. Cadmium sulfide is an attractive semiconductor material due to its good visible light response and suitable band edge positions. However, when cadmium sulfide is fabricated into a photoanode, there are problems of low photocurrent density and insufficient stability (photo-corrosion exists). Summary of the Invention
[0004] Object of the Invention: The object of the present invention is to provide a selenium-doped cadmium sulfide photoanode that can significantly improve the photocurrent density and stability of the cadmium sulfide photoanode (effectively suppressing the photo-corrosion problem of the cadmium sulfide photoanode during application); another object of the present invention is to provide a preparation method of the above cadmium sulfide photoanode.
[0005] Technical Solution: The selenium-doped cadmium sulfide photoanode described in the present invention includes a conductive glass substrate and cadmium sulfide doped with selenium grown on the conductive glass substrate; selenium is doped into the lattice of cadmium sulfide.
[0006] Among them, the chemical formula of the cadmium sulfide doped with selenium is CdS 1-x Se x ; 0 < X < 1.
[0007] Among them, the preparation method of the above cadmium sulfide photoanode includes the following steps:
[0008] (1) Lean the cleaned conductive glass against the inner wall of the reaction device with the conductive surface facing down to facilitate the growth of cadmium sulfide crystals;
[0009] (2) Prepare a mixed solution containing selenium salt and cadmium sulfide precursor; pour the mixed solution into the reaction device in step (1), seal it, and conduct a hydrothermal reaction at high temperature;
[0010] (3) After the reaction, take out the conductive glass on which the conductive crystal has grown, wash and dry it, and then perform annealing treatment on the side with the grown conductive crystal to make the grown crystal not easy to peel off. After treatment, a selenium-doped cadmium sulfide photoanode is obtained.
[0011] Among them, in step (1), the conductive glass is FTO or ITO. Selenium-doped cadmium sulfide grows on the conductive glass.
[0012] Among them, in step (2), the solvent of the mixed solution is a mixed solvent composed of ethanol and deionized water.
[0013] Among them, in the mixed solvent, the mixing volume ratio of ethanol to deionized water is 1 - 3:1 - 3.
[0014] Among them, in step (2), the reaction materials corresponding to the cadmium sulfide precursor are: thiourea, cadmium nitrate tetrahydrate, and cysteine, and the molar ratio of the addition of thiourea, cadmium nitrate tetrahydrate, and cysteine is 1:1:0.6 - 0.7.
[0015] Among them, in step (2), the molar ratio of the addition of the selenium salt to thiourea is 0.5 - 5:100.
[0016] Among them, in step (2), the hydrothermal reaction temperature is 160 - 200 °C, and the time is 8 - 32 h.
[0017] Among them, in step (3), the atmosphere for the quenching treatment is nitrogen or hydrogen; the quenching temperature is 300 - 800 °C, and the time is 1 - 3 h.
[0018] Beneficial effects: Compared with the prior art, the present invention has the following remarkable advantages: The selenium-doped cadmium sulfide photoanode of the present invention can greatly improve the photocurrent density of the cadmium sulfide photoanode. In the acetonitrile solution of 1 mM tetrabutylammonium hexafluorophosphate, the photocurrent density of the photoanode can reach 280 - 300 μA / cm 2 , in the same solution, the photocurrent density of a single cadmium sulfide photoanode is 150 - 170 μA / cm 2 , therefore, compared with a single cadmium sulfide photoanode, the photocurrent density of the present invention is almost doubled; the selenium-doped cadmium sulfide photoanode of the present invention can also greatly improve the stability of the cadmium sulfide photoanode, and can effectively inhibit the photocorrosion problem of the cadmium sulfide photoanode during application. When reacting continuously for 1400 s under a bias voltage of 1 V vs Ag / AgCl, when the photocurrent of the cadmium sulfide photoanode decays to 50 μA / cm 2 , the photocurrent of the selenium-doped cadmium sulfide photoanode still remains at 100 μA / cm2 Above. Description of the Drawings
[0019] Figure 1 XRD patterns of the selenium-doped cadmium sulfide photoanodes obtained in Examples 1 to 5; in the figure, the CH3CH2OH, CH3CH2OH:H2O = 3:1, CH3CH2OH:H2O = 1:1, CH3CH2OH:H2O = 1:3, and H2O curves are the photoanodes obtained in Examples 1 to 5, respectively;
[0020] Figure 2 XRD patterns of the selenium-doped cadmium sulfide photoanodes obtained in Examples 4 and 6 to 10;
[0021] Figure 3 XRD patterns of the selenium-doped cadmium sulfide photoanodes obtained in Examples 8 and 11 to 16;
[0022] Figure 4 SEM images of the selenium-doped cadmium sulfide photoanodes prepared in Examples 4 and 5; in the figure, a is the SEM image of the selenium-doped cadmium sulfide photoanode prepared in Example 5; b is the SEM image of the selenium-doped cadmium sulfide photoanode prepared in Example 4; c is the SEM image of the selenium-doped cadmium sulfide photoanode prepared in Example 8;
[0023] Figure 5 Transient current-time curves of the selenium-doped cadmium sulfide photoanodes prepared under different solvents, different synthesis times, and different selenium doping amounts; among them, (a) is the transient current-time curve of the selenium-doped cadmium sulfide photoanodes obtained in Examples 1 to 5, (b) is the transient current-time curve of the selenium-doped cadmium sulfide photoanodes obtained in Examples 4 and 6 to 10, and (c) is the transient current-time curve of the selenium-doped cadmium sulfide photoanodes obtained in Examples 8 and 11 to 16.
[0024] Figure 6 EIS diagrams, LSV diagrams, and transient current-time curves of the selenium-doped cadmium sulfide photoanode and the cadmium sulfide photoanode prepared by the present invention; among them, test conditions: the light source is an AM1.5 xenon lamp (light intensity is 100 mW / cm 2 ), the solvent is acetonitrile, the supporting electrolyte is 1 M tetrabutylammonium hexafluorophosphate, and the bias voltage for the transient current-time test is 1 V vs Ag / AgCl;
[0025] Figure 7 Stability comparison diagram of a single cadmium sulfide photoanode and the selenium-doped cadmium sulfide photoanode obtained in Example 8. Detailed Description of the Invention
[0026] Example 1
[0027] A method for preparing a selenium-doped cadmium sulfide photoelectrode, comprising the following steps:
[0028] (1) After cleaning the surface of the FTO conductive glass with acetone, isopropanol, and deionized water respectively, lean it obliquely against the inner wall of the polytetrafluoroethylene inner liner of the hydrothermal reactor;
[0029] (2) Weigh 0.0005 mol of thiourea, 0.0005 mol of cadmium nitrate tetrahydrate, and 0.0003 mol of cysteine (the molar ratio of thiourea: cadmium nitrate tetrahydrate: cysteine is 1:1:0.6), and dissolve them in 10 mL of ethanol; add 0.000025 mol (i.e., 5 wt%) of sodium selenite to the solution, stir for 1 h, and then pour the mixed solution into the inner liner of the hydrothermal reactor; react at 180 °C for 12 h in a forced-air drying oven. After the reaction, take out the FTO, and then wash the electrode piece with ethanol and deionized water in sequence;
[0030] (3) After the electrode piece is dried in a vacuum drying oven, place it in a tubular furnace, keep the side with the grown conductive crystal facing up, anneal it at 400 °C for 1 h in a nitrogen atmosphere to obtain a selenium-doped cadmium sulfide photoelectrode.
[0031] Example 2
[0032] The preparation method of Example 2 is exactly the same as that of Example 1, and the only difference is that in step (2), it is dissolved in 10 mL of a mixed solvent; in the mixed solvent, the mixing volume of ethanol and deionized water is 3:1; a selenium-doped cadmium sulfide photoelectrode is prepared.
[0033] Example 3
[0034] The preparation method of Example 3 is exactly the same as that of Example 1, and the only difference is that in step (2), it is dissolved in 10 mL of a mixed solvent; in the mixed solvent, the mixing volume of ethanol and deionized water is 1:1; a selenium-doped cadmium sulfide photoelectrode is prepared.
[0035] Example 4
[0036] The preparation method of Example 4 is exactly the same as that of Example 1, and the only difference is that in step (2), it is dissolved in 10 mL of a mixed solvent; in the mixed solvent, the mixing volume of ethanol and deionized water is 1:3; a selenium-doped cadmium sulfide photoelectrode is prepared.
[0037] Example 5
[0038] The preparation method of Example 5 is exactly the same as that of Example 1, and the only difference is that in step (2), it is dissolved in 10 mL of deionized water; a selenium-doped cadmium sulfide photoelectrode is prepared.
[0039] Figure 1XRD patterns of the selenium-doped cadmium sulfide photoanodes obtained in Examples 1-5 are as follows. Figure 1 As shown, the structures of all selenium-doped cadmium sulfide photoanodes are not damaged, and they are all in the hexagonal crystal phase (PDF card number: 41-1049). Figure 1 The detailed pattern in the range of 20-55° in Figure 1 shows that CdS 0.33 Se 0.67 characteristic peaks are generated when ethanol is used as the solvent, indicating that the phase of cadmium sulfide changes significantly when ethanol is used as the solvent. Figure 1 The detailed pattern in the range of 20-55° in Figure 1 shows that CdS 0.42 Se 0.58 and CdS 0.75 Se 0.25 characteristic peaks are generated when the volume ratio of ethanol to deionized water is 3:1 and 1:1 respectively, indicating that the change in the ratio of ethanol to deionized water will cause a significant change in the phase of cadmium sulfide. When the solvent is pure deionized water, the growth of the (002) plane of cadmium sulfide is particularly prominent, and finally grows into flaky crystals, as shown in Figure 4 (a). As the proportion of ethanol increases, the change in phase caused by selenium doping becomes more prominent, resulting in a gradual decrease in the intensity of the characteristic peaks of cadmium sulfide. When the ratio of ethanol to deionized water is 1:3, the flaky crystals will agglomerate to form a flower-like structure, as shown in Figure 4 (b).
[0040] The photocurrent density curves of the photoanodes with different solvent ratios show that, as shown in Figure 5 (a), the photocurrent density is the highest when the ratio of ethanol to deionized water is 1:1, but it is not stable and will rapidly decay from 380 μA / cm 2 to below 150 μA / cm 2 within 300 s, so it is not suitable for application. Correspondingly, when the ratio of ethanol to deionized water is 1:3, the photocurrent is relatively the highest and more stable, about 170 μA / cm 2 . The photocurrent densities of other ratios are all lower than 170 μA / cm 2 . Except for the photoanode with a ratio of ethanol to deionized water of 1:1, the stabilities of other photoanodes are consistent within 300 s.
[0041] Example 6
[0042] The preparation method of Example 6 is exactly the same as that of Example 4, and the only difference is that in step (2), the reaction is carried out at 180 °C for 16 h in a forced-air drying oven; a selenium-doped cadmium sulfide photoanode is prepared.
[0043] Example 7
[0044] Example 7 has the exact same preparation method as Example 6, and the only difference is that in step (2), the reaction is carried out in a forced air drying oven at 180 °C for 20 h; a selenium-doped cadmium sulfide photoanode is prepared.
[0045] Example 8
[0046] Example 8 has the exact same preparation method as Example 6, and the only difference is that in step (2), the reaction is carried out in a forced air drying oven at 180 °C for 24 h; a selenium-doped cadmium sulfide photoanode is prepared.
[0047] Compared with a single cadmium sulfide electrode, the impedance of selenium-doped cadmium sulfide is lower (as shown in Figure 6 (a)), and the photocurrent density of the selenium-doped cadmium sulfide photoanode increases more rapidly under a bias voltage greater than 0.2 V vs Ag / AgCl (as shown in Figure 6 (b)). At a bias voltage of 1 V vs Ag / AgCl, the photocurrent density also increases from 160 μA / cm 2 of single cadmium sulfide to about 300 μA / cm 2 of selenium-doped cadmium sulfide, and the photocurrent density almost doubles, as shown in Figure 6 (c). Compared with a single cadmium sulfide photoanode, the stability of selenium-doped cadmium sulfide has also been greatly improved, as shown in Figure 7 . At a light intensity of 100 mW / cm 2 , the photocurrent increases for both the cadmium sulfide photoanode and the selenium-doped cadmium sulfide photoanode under the action of self-decomposition. Due to the unique phase (CdS 1-n Se 0<n<0.25 ) of the selenium-doped cadmium sulfide photoanode, the increase in photocurrent is greater than that of the cadmium sulfide photoanode. The photocurrent reaches its peak at around 350 - 400 s and then decays slowly. As the semiconductor continuously decomposes and peels off, when the photocurrent is lower than 50 μA / cm 2 , it can be considered that the photoanode is no longer suitable for catalytic conversion applications. When the photocurrent of the cadmium sulfide photoanode decays to 50 μA / cm 2 , the photocurrent of the selenium-doped cadmium sulfide photoanode is still greater than 100 μA / cm 2 , so this photoanode can still continue to be used for photoelectrocatalytic conversion applications. Compared with a single cadmium sulfide photoanode, the stability of the selenium-doped cadmium sulfide photoanode has been significantly improved.
[0048] Example 9
[0049] Example 9 has the exact same preparation method as Example 6, and the only difference is that in step (2), the reaction is carried out in a forced air drying oven at 180 °C for 28 h; a selenium-doped cadmium sulfide photoanode is prepared.
[0050] Example 10
[0051] Example 10 was prepared in exactly the same manner as Example 6, with the only difference being that in step (2), the reaction was carried out at 180 °C for 32 h in a forced-air drying oven; a selenium-doped cadmium sulfide photoanode was prepared.
[0052] Figure 2 XRD patterns of the selenium-doped cadmium sulfide photoanodes obtained in Examples 4 and 6 - 10 are shown in Figure 2 As shown, the structures of all selenium-doped cadmium sulfide photoanodes did not destroy the structure of cadmium sulfide, and they were all hexagonal phase (PDF card number: 41 - 1049), without obvious characteristic peaks of selenium doping. When the hydrothermal reaction time was 24 h, a nanoparticle structure was formed, as shown in Figure 4 (c).
[0053] The photocurrent density curves at different synthesis times showed that, as shown in Figure 5 (b), although the photocurrent densities at the initial 16 h and 24 h were similar, the photoanode at 16 h was unstable and prone to peeling. As the reaction time increased, the photocurrent rapidly decayed from 300 μA / cm 2 to 200 μA / cm 2 or less, while the photoanode at 24 h could be stably maintained at around 280 μA / cm 2 . Compared with other photoanodes, the photoanode synthesized at 24 h had a relatively higher and more stable photocurrent. The photocurrent densities that could be achieved by the photoanodes at 12 h, 20 h, 28 h, and 32 h were 160 μA / cm 2 , 200 μA / cm 2 , 135 μA / cm 2 , and 210 μA / cm 2 respectively. Although the stability could be maintained, the photocurrent density was lower than that of the photoanode at 24 h.
[0054] Example 11
[0055] Example 11 was prepared in exactly the same manner as Example 8, with the only difference being that in step (2), 0.0000025 mol (i.e., 0.5 wt%) of sodium selenite was further added to the solution; a selenium-doped cadmium sulfide photoanode was prepared.
[0056] Example 12
[0057] Example 12 was prepared in exactly the same manner as Example 11, with the only difference being that in step (2), 0.000005 mol (i.e., 1 wt%) of sodium selenite was further added to the solution; a selenium-doped cadmium sulfide photoanode was prepared.
[0058] Example 13
[0059] Example 13 has the exact same preparation method as Example 11. The only difference is that in step (2), 0.00001 mol (i.e., 2 wt%) of sodium selenite is further added to the solution; a selenium-doped cadmium sulfide photoanode is prepared.
[0060] Example 14
[0061] Example 14 has the exact same preparation method as Example 11. The only difference is that in step (2), 0.00005 mol (i.e., 10 wt%) of sodium selenite is further added to the solution; a selenium-doped cadmium sulfide photoanode is prepared.
[0062] Example 15
[0063] Example 15 has the exact same preparation method as Example 11. The only difference is that in step (2), 0.000075 mol (i.e., 15 wt%) of sodium selenite is further added to the solution; a selenium-doped cadmium sulfide photoanode is prepared.
[0064] Example 16
[0065] Example 16 has the exact same preparation method as Example 11. The only difference is that in step (2), 0.0001 mol (i.e., 20 wt%) of sodium selenite is further added to the solution; a selenium-doped cadmium sulfide photoanode is prepared.
[0066] Figure 3 XRD patterns of the selenium-doped cadmium sulfide photoanodes obtained in Example 8 and Examples 11 - 16; as Figure 3 shown, the cadmium sulfide structures of the selenium-doped cadmium sulfide photoanodes with selenium doping amounts of 0.5 wt%, 1 wt%, 2 wt%, and 5 wt% are not damaged, and they are all hexagonal crystal phases (PDF card number: 41 - 1049); however, when the selenium doping amount is greater than 5 wt% (10 wt%, 15 wt%, and 20 wt%), the structure of cadmium sulfide is damaged, the crystallinity is greatly reduced, and the diffraction peak intensity rapidly decreases. As the selenium doping amount increases from 0.5 wt% to 5 wt%, the characteristic peaks of cadmium sulfide continuously increase. When the selenium doping amount is 5 wt%, the selenium-doped cadmium sulfide photoanode forms a nanoparticle structure, as Figure 4 (c) shown. The photocurrent density curves of different selenium doping amounts show that, as Figure 5 (c) shown, the crystallinity of the 5 wt% selenium doping is relatively higher than that of other doping amounts, the charge transfer efficiency is also stronger, and the photocurrent density of the 5 wt% selenium doping is also higher than that of the photoanodes with other doping amounts, reaching 270 μA / cm 2or so. All other selenium-doped cadmium sulfide photoanodes can maintain a stable photocurrent within 300 s. The photocurrent densities at doping levels of 0.5 wt%, 1 wt%, 2 wt%, 10 wt%, 15 wt%, and 20 wt% are 52 μA / cm 2 、75 μA / cm 2 、127 μA / cm 2 、200 μA / cm 2 、160 μA / cm 2 and 220 μA / cm 2 .
Claims
1. A selenium-doped cadmium sulfide photoanode, characterized in that: It includes a conductive glass substrate and cadmium sulfide crystals doped with selenium grown on the conductive glass substrate.
2. The cadmium sulfide photoelectrode doped with selenium according to claim 1, wherein: The chemical formula of selenium-doped cadmium sulfide is CdS 1-x Se x ; where 0 < X < 1.
3. The preparation method of the cadmium sulfide photo - electrode according to claim 1, characterized in that, It includes the following steps: (1) Lean the cleaned conductive glass against the inner wall of the reaction device; (2) Prepare a mixed solution containing a selenium salt and a cadmium sulfide precursor; pour the mixed solution into the reaction device in step (1), seal it, and carry out a hydrothermal reaction at a high temperature; (3) After the reaction, take out the conductive glass on which the conductive crystals have grown, clean and dry it, and then perform quenching treatment on the side where the conductive crystals have grown to obtain a selenium-doped cadmium sulfide photoanode.
4. The preparation method according to claim 3, wherein: In step (1), the conductive glass is FTO or ITO.
5. The preparation method according to claim 3, characterized in that: In step (2), the solvent of the mixed solution is a mixed solvent composed of ethanol and deionized water.
6. The preparation method according to claim 5, characterized in that: In the mixed solvent, the mixing volume ratio of ethanol to deionized water is 1-3:1-3.
7. The preparation method according to claim 3, wherein: In step (2), the reaction materials corresponding to the cadmium sulfide precursor are: thiourea, cadmium nitrate tetrahydrate, and cysteine, and the molar ratio of the addition of thiourea, cadmium nitrate tetrahydrate, and cysteine is 1:1:0.6-0.
7.
8. The preparation method according to claim 3, characterized in that: In step (2), the molar ratio of the addition of the selenium salt to thiourea is 0.5-5:
100.
9. The preparation method according to claim 3, wherein: In step (2), the hydrothermal reaction temperature is 160-200 °C, and the time is 8-32 h.
10. The preparation method according to claim 3, characterized in that: In step (3), the atmosphere for quenching treatment is nitrogen or hydrogen; the quenching temperature is 300-800 °C, and the time is 1-3 h.