ZnCdS / APF composite photocatalyst, and preparation method and application thereof
By in-situ polymerization of aminophenol formaldehyde resin (APF) on the surface of ZnCdS to form a composite photocatalyst, the problems of photocorrosion, selectivity and carrier recombination of ZnCdS photocatalyst in the photocatalytic oxygen reduction process were solved, and the H2O2 yield was improved with high efficiency and low cost.
Patent Information
- Application Number
- CN202610466228.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-04-10
- Publication Date
- 2026-07-10
AI Technical Summary
Existing ZnCdS photocatalysts suffer from problems such as photocorrosion, low selectivity of two-electron oxygen reduction, severe recombination of photogenerated carriers, and insufficient surface active sites during the photocatalytic reduction of oxygen to H2O2. Furthermore, existing modification strategies are either costly or have limited effectiveness.
A composite photocatalyst was formed by in-situ polymerization of aminophenol formaldehyde resin (APF) on the surface of ZnCdS. APF, as a multifunctional interface layer, promotes oxygen adsorption and stabilization of ·OOH intermediates, consumes photogenerated holes, optimizes charge separation, and improves electron concentration and H2O2 selectivity.
It significantly improves H2O2 yield, reduces costs, and is a green process suitable for large-scale production, achieving efficient photocatalytic oxygen reduction to H2O2.
Smart Images
Figure CN122352344A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of photocatalysis technology, specifically relating to a ZnCdS / aminophenol formaldehyde resin (APF) composite photocatalyst and its preparation method, as well as the application of the composite photocatalyst in visible light catalytic oxygen reduction to hydrogen peroxide. Background Technology
[0002] Hydrogen peroxide (H2O2), as an environmentally friendly green oxidant, is widely used in pulp bleaching, wastewater treatment, chemical synthesis, disinfection, and fuel cells. With increasing global focus on green chemistry and sustainable development, the market demand for H2O2 continues to grow. Currently, the anthraquinone process is the main industrial method for producing H2O2. While this process is mature, it suffers from high energy consumption, complex operation, reliance on precious metal catalysts, numerous byproducts, and significant organic waste emissions, contradicting the principles of green chemistry. Therefore, developing a new, mild, environmentally friendly, and economically feasible route for H2O2 synthesis is of great significance.
[0003] In recent years, the synthesis of H2O2 via solar-driven photocatalytic oxygen reduction reaction (ORR) has emerged as a promising alternative due to its advantages of being green, sustainable, and energy-efficient, requiring only light, water, and oxygen. The key to this process lies in developing highly efficient and selective photocatalytic materials that can effectively promote the two-electron ORR pathway and suppress the four-electron water-generating side reaction, thereby improving the yield and selectivity of H2O2.
[0004] Among numerous photocatalytic materials, metal sulfide semiconductors have attracted widespread attention due to their suitable band structure, good visible light response, and tunable electronic properties. Zn0 x Cd 1-x By adjusting the Zn / Cd ratio, ZnCdS solid solutions can achieve continuously tunable band structures, combining the broad spectral absorption capacity of CdS in the visible light region with the high structural integrity of ZnS. However, pure-phase ZnCdS still faces several key challenges in photocatalysis:
[0005] 1. Significant photocorrosion phenomenon: Under illumination, the S on the ZnCdS surface... 2- It is easily oxidized by photogenerated holes, leading to material structure degradation and affecting long-term catalytic performance.
[0006] 2. Insufficient ORR path selectivity: ZnCdS surfaces tend to undergo four-electron ORR to generate water, but have low selectivity for two-electron ORR to generate H2O2, which limits the accumulation efficiency of H2O2.
[0007] 3. Severe recombination of photogenerated carriers: Electron-hole pairs generated by photoexcitation recombine rapidly in the bulk phase and on the surface, resulting in a decrease in the effective electron concentration participating in the surface oxygen reduction reaction.
[0008] 4. Limited surface active sites: The original ZnCdS surface lacks functional sites that are conducive to O2 adsorption and the stability of the ·OOH intermediate, which further restricts the ORR reaction kinetics.
[0009] To address the aforementioned issues, researchers have proposed various modification strategies, including loading noble metals (such as Pt and Au), compositing with carbon materials, constructing heterostructures, or introducing surface modification layers. These methods have improved photocatalytic performance to some extent, but generally suffer from drawbacks such as high cost, weak interfacial interactions, complex processes, or limited selectivity improvement. In particular, the use of noble metals significantly increases catalyst costs, limiting their large-scale application. Furthermore, traditional carbon material composites or heterostructures often struggle to simultaneously achieve both electron separation efficiency and surface reaction selectivity.
[0010] Therefore, there is an urgent need to develop a novel composite photocatalyst that is low-cost, structurally controllable, and can simultaneously improve the activity and selectivity of ZnCdS photocatalytic ORR for H2O2 production. An ideal modified layer should possess the following characteristics: good electron conduction and hole trapping capabilities, abundant surface functional groups to promote O2 adsorption and ·OOH stabilization, and the formation of tight interfacial contacts on the ZnCdS surface to optimize charge separation. Based on this, this invention proposes using aminophenol formaldehyde resin (APF) as a multifunctional interfacial layer and constructing a ZnCdS / APF composite photocatalyst through an in-situ polymerization strategy, aiming to synergistically improve the efficiency and practicality of photocatalytic ORR for H2O2 production. Summary of the Invention
[0011] The purpose of this invention is to overcome the technical defects of existing ZnCdS photocatalysts, such as low selectivity of two-electron oxygen reduction, severe recombination of photogenerated carriers, and insufficient surface active sites during H2O2 production, and to provide a ZnCdS / APF composite photocatalyst, its preparation method, and its application.
[0012] This invention involves in-situ polymerization to coat the surface of ZnCdS with aminophenol-formaldehyde resin (APF). APF is a three-dimensional network polymer rich in phenolic hydroxyl, amino, and aromatic rings. Its unique electron-rich properties facilitate the adsorption of oxygen and the ·OOH intermediate, thereby promoting the two-electron oxygen reduction reaction (ORR) pathway and improving H2O2 selectivity. Simultaneously, APF can act as a hole transfer layer, promptly consuming photogenerated holes and promoting the migration of photogenerated electrons to the surface. Furthermore, the tight heterojunction interface formed by the two facilitates the separation of photogenerated electron-hole pairs and interfacial charge transfer, increasing the effective electron concentration participating in oxygen reduction.
[0013] To achieve the above objectives, the technical solution adopted by the present invention is as follows:
[0014] 1. ZnCdS / APF composite photocatalyst
[0015] The composite photocatalyst provided by this invention uses a ZnCdS solid solution as the core for light absorption and electron generation, and APF resin as a multifunctional interface layer. APF is tightly attached to the ZnCdS surface through chemical bonding or physical coating, forming a stable core-shell or semi-encapsulated structure. The mass fraction of APF in this composite structure is 40–70 wt%. Under optimized conditions, the composite catalyst exhibits the best photocatalytic H2O2 production performance when the APF mass fraction is approximately 60–65% (corresponding to a 35% Z / A sample).
[0016] 2. Preparation method
[0017] (1) Synthesis of ZnCdS:
[0018] 5 mmol cadmium acetate, 10 mmol zinc acetate, and 12.5 mmol thioacetamide were dissolved sequentially in 25 mL of deionized water. 5 mL of ethylenediamine was added to the mixture, and the mixture was stirred for 30 min. The solution was transferred to a 50 mL stainless steel reactor lined with polytetrafluoroethylene (PTFE) and reacted at 230 °C for 4 h. After naturally cooling to room temperature, the mixture was centrifuged, washed three times with deionized water, and the resulting sample was vacuum-dried at 40 °C for 24 h to obtain the ZnCdS sample (ZCS).
[0019] (2) In-situ recombination:
[0020] 20 mg of the above ZCS was ultrasonically dispersed in a round-bottom flask containing 30 mL of deionized water (ultrasonic power 200 W, time 10 min). A certain amount of 3-aminophenol, 300 μL of formaldehyde solution (37 wt%), and 100 μL of ammonia solution (28 wt%) were added sequentially. The mixture was magnetically stirred at 30 ℃ for 24 h. By changing the amount of 3-aminophenol (0.1 mmol, 0.2 mmol, 0.3 mmol, 0.4 mmol), composite catalysts with different APF loadings were prepared, corresponding to ZCS mass percentages of approximately 30%, 35%, 45%, and 60% (i.e., 30% Z / A, 35% Z / A, 45% Z / A, 60% Z / A).
[0021] (3) Post-processing: After the reaction was completed, the solid was separated by centrifugation and washed three times each with deionized water and anhydrous ethanol. The obtained sample was vacuum dried at 60 °C for 48 h to obtain the ZnCdS / APF composite photocatalyst.
[0022] 3. Application Method
[0023] The above-mentioned composite photocatalyst was used for photocatalytic production of H₂O₂. Typical test conditions: 10 mg of the catalyst was dispersed in 50 mL of deionized water and placed in a photocatalytic reaction flask. A 300 W xenon lamp (equipped with a 420 nm cutoff filter) was used as the visible light source, with the lamp 10 cm away from the liquid surface. Before the reaction, high-purity oxygen (200 mL / min) was bubbled for 30 min to remove dissolved oxygen and establish an oxygen-saturated environment. Oxygen was continuously bubbled during the reaction. After 1 h of reaction, a sample was taken, and the H₂O₂ concentration was determined using the potassium titanium oxalate standardization method.
[0024] Beneficial effects:
[0025] Significantly improved photocatalytic H2O2 production activity: The ZnCdS / APF composite photocatalyst prepared in this invention exhibits an H2O2 yield that first increases and then decreases with increasing APF loading under visible light irradiation. The 35% Z / A sample achieves an H2O2 yield of 5318 μmol g. -1 h -1 Compared to pure ZnCdS (2983 μmol g), -1 h -1 The efficiency was increased by 78.3%. The introduction of an appropriate amount of APF effectively promoted the transfer of photogenerated electrons to the surface and the selective reduction of oxygen to H2O2.
[0026] Low cost and green process: This invention does not require any precious metals (such as Pt, Au) or toxic organic reagents. It uses only common metal salts, sulfur sources, and phenolic monomers as raw materials, with water and ethylenediamine as solvents, and the reaction conditions are mild. The entire process is simple, highly reproducible, suitable for large-scale production, and meets the requirements of green chemistry and sustainable development.
[0027] Tunable structure: The loading of APF can be precisely controlled by simply changing the amount of 3-aminophenol, thereby optimizing the catalytic performance and providing a new approach for designing efficient ORR photocatalysts. Attached Figure Description Figure 1 Flowchart of the preparation process of ZnCdS / APF composite photocatalyst. Figure 2 Bar chart comparing the visible light catalytic hydrogen peroxide production performance of ZnCdS / APF composite photocatalysts with different proportions. Figure 3 SEM images of pure ZnCdS, pure APF, and the optimal composite ratio (35% Z / A). Figure 4 XRD images of pure ZnCdS, pure APF and 35% Z / A samples. Figure 5 UV-vis DRS of pure ZnCdS, pure APF and 35% Z / A composite samples. Figure 6 Kubelka-Munk conversion diagrams of pure ZnCdS and pure APF are used to estimate the bandgap energy (Eg). Figure 7 Mott-Schottky curves of pure ZnCdS and pure APF samples (test frequency 1~3 kHz, 0.5 M Na2SO4 solution, pH=7) were used to calculate the conduction band (CB) of the samples. Figure 8 EIS plots of pure ZnCdS, pure APF and 35% Z / A composite samples (frequency range 0.01 Hz~1000 kHz, bias voltage 0.2 V vs. open circuit potential). Figure 9 Transient photocurrent response curves of pure ZnCdS, pure APF and 35% Z / A composite samples (in 0.5 M Na2SO2 electrolyte, intermittent visible light irradiation, bias voltage 0.2 V vs. Ag / AgCl). Detailed Implementation
[0028] Example 1: Preparation of ZnCdS
[0029] 5 mmol (1.333 g) of cadmium acetate, 10 mmol (2.195 g) of zinc acetate, and 12.5 mmol (0.939 g) of thioacetamide were dissolved sequentially in 25 mL of deionized water. 5 mL of ethylenediamine was added to the mixture, and the mixture was stirred for 30 min. The solution was transferred to a 50 mL stainless steel reactor lined with polytetrafluoroethylene and reacted at 230 °C for 4 h. After naturally cooling to room temperature, the mixture was centrifuged, washed three times with deionized water, and the resulting sample was vacuum-dried at 40 °C for 24 h to obtain the ZnCdS sample (ZCS).
[0030] Example 2: Preparation of ZnCdS / APF composite photocatalysts with different APF loadings
[0031] 20 mg of ZCS prepared in Example 1 was ultrasonically dispersed in a round-bottom flask containing 30 mL of deionized water. 3-Aminophenol (10.9–43.7 mg) was added according to different loading ratios, followed by 300 μL of formaldehyde solution (37 wt%) and 100 μL of ammonia solution (28 wt%). The mixture was magnetically stirred at 30 °C for 24 h. After the reaction was complete, the mixture was centrifuged, washed three times each with deionized water and anhydrous ethanol, and dried under vacuum at 60 °C for 48 h to obtain the composite photocatalyst.
[0032] Example 3: Preparation of pure APF (Comparative Example)
[0033] 1 mmol (109 mg) of 3-aminophenol was ultrasonically dispersed in a round-bottom flask containing 30 mL of deionized water. 300 μL of formaldehyde solution (37 wt%) and 100 μL of ammonia solution (28 wt%) were added, and the mixture was stirred at 30 °C for 24 h. After centrifugation to separate the solid sample, it was washed three times each with deionized water and ethanol. The resulting sample was then vacuum-dried at 60 °C for 48 h to obtain pure APF resin.
[0034] Example 4: Performance test of the prepared catalyst for photocatalytic hydrogen peroxide production from pure water.
[0035] 10 mg of each of the different catalysts prepared in Examples 1-3 were weighed and dispersed in 50 mL of deionized water, then placed in a photoreaction flask. A 300 W xenon lamp (equipped with a 420 nm cutoff filter) was used as the visible light source, with the lamp 10 cm above the liquid surface. High-purity oxygen (200 mL / min) was bubbled for 30 min before the reaction, and oxygen was continuously bubbled during the reaction. After 1 h of reaction, a 3 mL sample was taken, and the H2O2 concentration was determined using the potassium titanium oxalate standardization method. Each sample was tested in triplicate, and the average value was taken. The results showed that the 35% Z / A composite catalyst had the highest H2O2 yield (5318 μmol g). -1 h -1 (This represents a 73.8% improvement compared to pure ZCS).
[0036] Example 5: Characterization tests of pure ZnCdS, pure APF and 35% Z / A catalysts
[0037] The catalysts prepared in Examples 1-3 were characterized by physicochemical methods, and the test results are as follows:
[0038] SEM characterization: The morphology of pure ZCS, pure APF, and 35% Z / A composite samples was observed using field emission scanning electron microscopy. (See attached image) Figure 3 As shown, pure ZCS consists of irregular nanoparticles with a size distribution of 50–150 nm and slight agglomeration between particles; pure APF exhibits a smooth spherical structure; in the 35% Z / A composite sample, APF is uniformly dispersed on the surface of ZCS particles, and there are no obvious free particles of the pure sample, proving that in-situ polymerization has successfully achieved close composite.
[0039] XRD characterization: Phase analysis of pure ZCS, pure APF, and 35% Z / A was performed using X-ray diffraction. (See attached image) Figure 4As shown, pure ZCS exhibits three diffraction peaks at different positions, corresponding to the (111), (220), and (311) crystal planes of the cubic zincblende structure. Pure APF shows only one broad, diffuse peak between 2θ = 15 and 25°. The XRD pattern of the 35% Z / A composite sample clearly retains all the characteristic peaks of ZCS, with the peak positions and full width at half maximum (FWHM) remaining essentially unchanged, and no impurity peaks appearing, indicating that the introduction of APF did not alter the crystal structure of ZCS.
[0040] UV-vis DRS testing and band gap calculation: The diffuse reflectance spectrum of the sample was measured using a UV-Vis spectrophotometer, with BaSO4 as the reference. (See attached image) Figure 5 As shown, pure ZCS exhibits strong absorption in the ultraviolet to visible region (<480 nm); pure APF shows relatively gradual absorption in the 300–800 nm range; the 45% Z / A composite sample shows significantly higher absorption intensity in the 400–500 nm region than pure ZCS, indicating improved light utilization efficiency after composite formation. This was confirmed by Kubelka-Munk function conversion (see attached diagram). Figure 6 The calculated band gaps for pure ZCS and pure APF are 2.29 eV and 2.38 eV, respectively.
[0041] Mott-Schottky assay: In a three-electrode system (working electrode: conductive glass with a drop-coated catalyst film; counter electrode: Pt wire; reference electrode: Ag / AgCl), Mott-Schottky assays were performed on pure ZnCdS and pure APF samples at frequencies ranging from 1 to 3 kHz in 0.5 M Na₂SO₄ (pH=7) electrolyte. (See attached image) Figure 7 As shown, all samples exhibit a positive slope, indicating the characteristics of an n-type semiconductor. The intersection of the tangents drawn at the three frequencies with the X-axis is the flat band potential.
[0042] Electrochemical impedance spectroscopy (EIS) testing: A three-electrode system was used in 0.5 M Na₂SO₄ electrolyte, with a frequency range of 0.01 Hz to 1000 kHz, AC amplitude of 5 mV, open-circuit bias, and continuous irradiation with visible light (λ≥420 nm). (See attached image.) Figure 8 As shown in the EIS diagram, the semicircular diameter in the high-frequency region corresponds to the charge transfer resistance (Rct). The Rct decreases significantly at 35% Z / A, indicating that the recombination interface promotes the separation and migration of photogenerated carriers.
[0043] Transient photocurrent response test: In 0.5 M Na2SO4 electrolyte, a three-electrode system was used, intermittently irradiated with visible light (λ≥420 nm) (on / off cycle 60 s), with the bias voltage being the open-circuit potential. (See attached...) Figure 9As shown, the photocurrent response of the 35% Z / A composite sample is fast and stable with good repeatability, further confirming that the APF loading effectively suppresses the recombination of photogenerated electrons and holes and prolongs the lifetime of photogenerated electrons.
Claims
1. A ZnCdS / APF composite photocatalyst, characterized in that: Using ZnCdS solid solution as the photocatalytic active component, aminophenol formaldehyde resin (APF) is loaded on the ZnCdS surface, and the two form a heterojunction interface.
2. A method for preparing a ZnCdS / APF composite photocatalyst, characterized in that, Includes the following steps: (1) Synthesis of ZnCdS: Cadmium acetate, zinc acetate and thioacetamide were dissolved in deionized water in sequence, with the mass ratio of zinc source to cadmium source being 2:
1. Ethylenediamine was added, and after stirring, the mixture was transferred to a reactor for hydrothermal reaction. After the reaction was completed, the mixture was cooled, washed and dried to obtain ZnCdS solid solution. (2) In-situ composite: ZnCdS obtained in step (1) was ultrasonically dispersed in deionized water, and 3-aminophenol, formaldehyde solution and ammonia solution were added in sequence. The mixture was stirred at 25~35 ℃ for 20~30 hours. The mass percentage of APF in the composite catalyst was 40~70 wt%. (3) Post-treatment: After the reaction was completed, the mixture was centrifuged, washed with deionized water and ethanol, and dried under vacuum to obtain ZnCdS / APF composite photocatalyst.
3. The preparation method according to claim 2, characterized in that: In step (1), the amount of cadmium acetate used is 4-6 mmol, the amount of zinc acetate is 9-11 mmol, the amount of thioacetamide is 10-15 mmol, the amount of deionized water is 20-30 mL, and the amount of ethylenediamine is 3-8 mL; the hydrothermal reaction temperature is 220-240 ℃, and the reaction time is 3-6 h.
4. The preparation method according to claim 2, characterized in that: The mass ratio of ZnCdS to 3-aminophenol in step (2) is 20:1 to 5:1; The formaldehyde solution is a 37-40 wt% aqueous solution, and the volume used is 200-400 μL; the ammonia solution is a 25-28 wt% aqueous solution, and the volume used is 50-150 μL; the volume of deionized water is 25-35 mL.
5. An application of a ZnCdS / APF composite photocatalyst, characterized in that: The composite photocatalyst is used for photocatalytic production of hydrogen peroxide. Under visible light irradiation, with oxygen or air as the oxygen source and pure water or an aqueous solution containing a water-soluble sacrificial agent as the reaction medium, hydrogen peroxide is generated through a two-electron oxygen reduction reaction.
6. The application according to claim 5, characterized in that: In the photocatalytic hydrogen peroxide production reaction, the catalyst dosage is 5-25 mg, the light source is simulated sunlight or visible light (λ≥420 nm), the reaction temperature is 15-50 °C, and the hydrogen peroxide yield is 5000-6500 μmol g. -1 h -1 .