A cadmium vanadium acid bismuth sulfide composite photothermal catalyst containing sulfur vacancies, a preparation method and application thereof

Abstract

The application discloses a kind of sulphur vacancy's cadmium sulfide bismuth vanadate composite photo-thermal catalyst and preparation method and application, the method includes the following steps: in nitric acid solution, add bismuth nitrate pentahydrate and ammonium metavanadate and mix uniformly, the mass ratio of bismuth nitrate pentahydrate and ammonium metavanadate is 97:23, obtain mixed solution;Hexadecyltrimethylammonium bromide and NaHCO3 are added in mixed solution and mix uniformly, keep warm at 80~140 ℃, then collect product, dry again to obtain bismuth vanadate;Bismuth vanadate, thioacetamide and cadmium source are mixed uniformly in deionized water, the molar ratio of thioacetamide and cadmium source is (0.5~1.5):1, keep warm and treat at 140~200 ℃, then collect product, dry again to obtain sulphur vacancy's cadmium sulfide bismuth vanadate composite photo-thermal catalyst, easy to operate, raw material is easy to obtain, low in cost, less in energy consumption, good in stability, high in activity, high in the efficiency of photo-thermal reforming PLA hydrolysate.

Description

Technical Field

[0001] This invention belongs to the field of photothermal catalyst preparation and environmental remediation technology, specifically relating to a bismuth cadmium vanadate sulfide composite photothermal catalyst containing sulfur vacancies, its preparation method, and its application. Background Technology

[0002] Since plastics were first synthesized in 1907, their excellent stability, low price, and high plasticity have led to their widespread application in all aspects of human production and daily life. However, with large quantities of plastics accumulating in landfills or being discarded into the environment without being recycled or upgraded, this poses a significant threat to natural ecosystems. Despite rapid advancements in industrially implemented methods, current solutions are unable to recycle waste plastics in an environmentally friendly and economical manner. For example, in mechanical recycling, most recycled plastics processed through melting and re-extrusion have a smaller molecular weight than virgin plastics, resulting in a decrease in both thermal and mechanical mass. Therefore, there is an urgent need to explore environmentally friendly and low-cost value-added pathways for plastics to achieve a transition to a circular carbon economy.

[0003] In recent years, the conversion of plastics into various commercial chemicals (e.g., alkanes, aromatics, and olefins) using thermocatalysis and photocatalysis has shown great potential for upgrading and recycling plastics. While thermocatalysis can transform plastic waste into value-added chemicals, the conditions are often harsh, including high temperature, high pressure, and the use of expensive catalysts, which is considered a major obstacle to the economic feasibility of thermocatalysis. Compared to thermocatalysis, photoreforming technology using pretreated plastic waste as raw material can also convert plastics into valuable chemicals, but its low photocatalytic efficiency has been a major factor limiting its industrial application. Photothermal catalysis effectively combines photocatalysis and thermocatalysis technologies, fully leveraging their synergistic effects. A prerequisite for photothermal catalysis technology is the efficient utilization of light. Ultraviolet-visible light can excite photogenerated carriers, transferring electrons to higher energy states through interband transitions. These photogenerated electrons and holes activate target molecules or intermediates, leading to redox reactions. Near-infrared light, absorbed by semiconductor materials, can convert photon energy into heat energy, generating a localized thermal effect and achieving a self-heating effect. This photoinduced self-heating simplifies the composition of the reaction system, eliminating the need for additional heating and meeting the requirements of energy conservation and emission reduction. Photocatalysis promotes the formation of strong redox reaction sites by adjusting adsorption sites and adsorption energy, thereby lowering activation energy and reaction temperature. Thermal catalysis provides the energy required to overcome the activation energy barrier, promoting the thermal activation and reaction of reactants. Furthermore, increasing the reaction temperature can accelerate mass transfer of reactant molecules on the catalyst surface.

[0004] Polylactic acid (PLA) is one of the most commonly used plastic products in daily life, generally used in the production of various packaging boxes and clothing. Therefore, the photoreforming of PLA has high practical value. PLA is usually hydrolyzed to lactic acid (LA) under alkaline conditions. For example, Reisner et al. converted LA molecules in PLA hydrolysate into pyruvic acid (PA), while simultaneously reducing H2O to hydrogen gas (H2). Compared with photocatalytic water splitting, the potential energy required for photoreforming the alkaline hydrolysis products of PLA is almost energy neutral. This is because LA can be regarded as a sacrificial agent and is preferentially oxidized in the photocatalytic water splitting reaction. Therefore, the photoreforming of PLA should mainly use narrow bandgap photocatalysts.

[0005] BiVO4 and CdS, as common narrow-bandgap photocatalysts, possess advantages such as high visible light response, low cost, and good chemical stability, and are considered to have great application potential. However, their poor carrier transport performance and lack of response to infrared light limit their photothermal catalytic performance and their role in the photoreforming of PLA. Summary of the Invention

[0006] To overcome the shortcomings of the existing technology, this invention discloses a bismuth cadmium vanadate sulfide composite photothermal catalyst containing sulfur vacancies, its preparation method, and its application. It is simple to operate, the raw materials are readily available, the cost is low, the energy consumption is low, the stability is good, the activity is high, and the efficiency of photothermal reforming PLA hydrolysate is high.

[0007] This invention is achieved through the following technical solution:

[0008] A method for preparing a bismuth cadmium vanadate-cadmium sulfide composite photothermal catalyst containing sulfur vacancies includes the following steps:

[0009] S1, add bismuth nitrate pentahydrate and ammonium metavanadate to nitric acid solution and mix thoroughly. The mass ratio of bismuth nitrate pentahydrate to ammonium metavanadate is 97:23 to obtain a mixed solution.

[0010] S2, add hexadecyltrimethylammonium bromide and NaHCO3 to the mixed solution and mix evenly to obtain precursor solution a. Keep precursor solution a at 80-140℃, collect the product, and then dry it to obtain bismuth vanadate.

[0011] S3, bismuth vanadate, thioacetamide and cadmium source are mixed evenly in deionized water, the molar ratio of thioacetamide to cadmium source is (0.5-1.5):1, and the mass ratio of thioacetamide to ammonium metavanadate in S1 is (45-75):230, to obtain precursor solution b. Precursor solution b is kept at 140-200℃, and then the product is collected and dried to obtain bismuth vanadate cadmium sulfide composite photothermal catalyst containing sulfur vacancies.

[0012] Preferably, the molar concentration of nitric acid in the nitric acid solution in S1 is 0.5 to 1, and the ratio of the nitric acid solution to ammonium metavanadate is 40 mL: 0.23 g.

[0013] Preferably, in step S2, hexadecyltrimethylammonium bromide and NaHCO3 are added sequentially to the mixed solution and mixed evenly. The ratio of hexadecyltrimethylammonium bromide, NaHCO3 and ammonium metavanadate in step S1 is 1g:(2-3)g:0.23g to obtain precursor solution a.

[0014] Preferably, in S2, the precursor solution a is kept at 80-140°C for 8-14 hours, and then the product is collected.

[0015] Preferably, the cadmium source mentioned in S3 is cadmium nitrate or cadmium acetate.

[0016] Preferably, the ratio of deionized water in S3 to ammonium metavanadate in S1 is 60 mL: 0.23 g, and the concentration of thioacetamide in precursor solution b is 0.75–1.25 mg / mL.

[0017] Preferably, in step S3, the precursor solution b is kept at 140–200°C for 16–24 h, and then the product is collected.

[0018] Preferably, in step S3, deionized water is added to the reaction solution obtained after heat treatment of the precursor solution b. Then, the solution is centrifuged at a speed of 8000-12000 r / min to remove the supernatant. This process is repeated 3-5 times, and the resulting precipitate is dried to obtain a bismuth cadmium vanadate composite photothermal catalyst containing sulfur vacancies.

[0019] A bismuth cadmium vanadate composite photothermal catalyst containing sulfur vacancies, obtained by the preparation method of the bismuth cadmium vanadate composite photothermal catalyst containing sulfur vacancies described in any of the above claims.

[0020] Application of bismuth cadmium vanadate composite photothermal catalyst containing sulfur vacancies in photothermal reforming PLA hydrolysate.

[0021] Compared with the prior art, the present invention has the following beneficial technical effects:

[0022] This invention discloses a method for preparing a sulfur-vacancy-containing cadmium sulfide-bismuth vanadate composite photothermal catalyst. Utilizing the in-situ growth of cadmium sulfide on the surface of bismuth vanadate, not only is an S-type heterojunction formed, but also a large number of sulfur vacancies are created. This promotes the efficient separation of photogenerated carriers between bismuth vanadate and cadmium sulfide. If the molar ratio of sulfur to cadmium is too low, cadmium sulfide cannot be formed; conversely, if it is too high, sufficient sulfur vacancies cannot be formed. This method also extends the light absorption range of the composite material to the near-infrared region, generating a self-heating effect, thereby achieving highly efficient PLA photothermal synergistic reforming. By utilizing the photothermal synergistic effect of the sulfur-vacancy-containing cadmium sulfide-bismuth vanadate composite photothermal catalyst to increase pyruvate yield, this method significantly solves the problems of high energy consumption and low photocatalytic performance in traditional thermocatalysis. The preparation process is simple, low-cost, and the raw materials are readily available.

[0023] Furthermore, if the molar concentration of nitric acid solution is too low, the synthesis time of bismuth vanadate will be too long and its purity will be insufficient; conversely, if the molar concentration of nitric acid is too high, the particle size of the synthesized bismuth vanadate will be too large.

[0024] Furthermore, if the hydrothermal temperature of the precursor solution a (first time) is too high or the time is too long, the resulting bismuth vanadate particles will be too large; conversely, if the hydrothermal temperature is too low or the time is too short, pure phase bismuth vanadate cannot be formed.

[0025] Furthermore, if the hydrothermal temperature of the precursor liquid b (secondary) is too high or the time is too long, too many sulfur vacancies will be formed, which will become recombination centers of charge carriers. If the hydrothermal temperature is too low or the time is too short, cadmium sulfide containing sulfur vacancies will not be formed.

[0026] The present invention provides a sulfur-vacancy-containing bismuth vanadate-cadmium sulfide composite photothermal catalyst prepared by the above preparation method. The bismuth vanadate and cadmium sulfide are monoclinic and hexagonal phase crystals, respectively. It has the characteristics of high temperature resistance and acid and alkali corrosion resistance, and is a photothermal catalytic material with good stability.

[0027] The present invention also discloses the application of the above-mentioned composite photocatalyst in the photothermal reforming PLA hydrolysate. Compared with unmodified bismuth vanadate, the activity of the sulfur-vacancy-containing cadmium vanadate composite photothermal catalyst of the present invention is significantly improved, and its pyruvate yield is increased by about 30 times. Attached Figure Description

[0028] Figure 1 XRD patterns of the sulfur-vacant cadmium sulfide and bismuth vanadate composite photothermal catalyst prepared in this invention, as well as pure phase bismuth vanadate and cadmium sulfide.

[0029] Figure 2 The electron paramagnetic resonance spectra of the sulfur-vacant cadmium sulfide and bismuth vanadate composite photothermal catalysts prepared in Examples 1-4 of this invention are shown.

[0030] Figure 3The images show the UV-Vis absorption spectra of the sulfur-vacant cadmium sulfide and bismuth vanadate composite photothermal catalysts prepared in Examples 1-4 of this invention.

[0031] Figure 4 The images show the photothermal reforming PLA activity diagrams of the cadmium sulfide and bismuth vanadate composite photothermal catalysts containing sulfur vacancies prepared in Examples 1-4 of this invention. Detailed Implementation

[0032] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. These descriptions are intended to explain the invention and not to limit it.

[0033] This invention discloses a method for preparing a bismuth vanadate-cadmium sulfide composite photothermal catalyst, comprising the following steps:

[0034] Step 1: Prepare 40 mL of nitric acid solution with a molar concentration of 0.5–1;

[0035] Step 2: Add 0.97g of bismuth nitrate pentahydrate and 0.23g of ammonium metavanadate to the nitric acid solution obtained in Step 1, and stir until homogeneous at room temperature to obtain a mixed solution;

[0036] Step 3: Add 1g of hexadecyltrimethylammonium bromide (CTAB) and 2-3g of NaHCO3 to the mixed solution obtained in Step 2 in sequence, stir evenly, and then place it in a 100mL polytetrafluoroethylene liner and hydrothermally heat it at 80-140℃ for 8-14h. After cooling to room temperature, centrifuge to collect the pale yellow product, and then dry it at 60℃ for 6 hours to obtain pure bismuth vanadate.

[0037] Step 4: Prepare a 60 mL aqueous solution of sulfur and cadmium sources, with a molar ratio of sulfur to cadmium of (0.5–1.5):1. The sulfur source is thioacetamide, and the cadmium source is cadmium nitrate or cadmium acetate. If cadmium acetate is used, its concentration can be 2.1 mg / mL, and the concentration of thioacetamide can be 0.75–1.25 mg / mL. Add the bismuth vanadate obtained in Step 3 to the aqueous solution of sulfur and cadmium sources, stir well, and then place it in a 100 mL polytetrafluoroethylene-lined container. Incubate at 140–200 °C. The hydrothermal reaction was carried out for 16–24 hours, then cooled to room temperature. Deionized water was added, and the reaction solution was centrifuged 3–5 times at 8000–12000 r / min for 8–10 min each time (and then centrifuged for 10 min each time). 40–50 mL of deionized water was added each time, and the product was dried (dried at 60℃ for 6 hours) to obtain a composite photocatalyst of cadmium sulfide and bismuth vanadate containing sulfur vacancies. Bismuth vanadate is a monoclinic phase crystal BiVO4, and cadmium sulfide is a hexagonal crystal system rich in sulfur vacancies, which can photothermally reform PLA hydrolysate.

[0038] Example 1

[0039] Weigh 0.97g of bismuth nitrate pentahydrate and 0.23g of ammonium metavanadate and dissolve them in 40mL of 0.5M HNO3 aqueous solution. Stir well at room temperature to obtain a mixed solution.

[0040] 1 g of hexadecyltrimethylammonium bromide (CTBA) and 3 g of NaHCO3 were slowly added sequentially to the above solution, and the mixture was stirred for 0.5 h. The mixed solution was then placed in a 100 mL polytetrafluoroethylene liner and hydrothermally heated at 80 °C for 8 h. After cooling to room temperature, deionized water was added, and the product was centrifuged to obtain a light yellow precipitate, which was then dried in a 60 °C oven for 6 h to obtain bismuth vanadate solid powder.

[0041] The prepared bismuth vanadate powder was placed in 60 mL of a mixed aqueous solution with a cadmium acetate concentration of 2.1 mg / mL and a thioacetamide concentration of 1.25 mg / mL. After stirring evenly, the solution was placed in a 100 mL polytetrafluoroethylene liner and hydrothermally reacted at 140 °C for 14 h. After cooling to room temperature, deionized water was added, and the reaction solution was centrifuged 5 times at 8000 r / min, with 40 mL of deionized water added each time. The product was then dried to obtain a cadmium sulfide and bismuth vanadate composite photocatalyst containing sulfur vacancies.

[0042] Example 2

[0043] Weigh 0.97g of bismuth nitrate pentahydrate and 0.23g of ammonium metavanadate and dissolve them in 40mL of 0.5M HNO3 aqueous solution. Stir well at room temperature to obtain a mixed solution.

[0044] 1 g of hexadecyltrimethylammonium bromide (CTBA) and 3 g of NaHCO3 were slowly added sequentially to the above solution, and the mixture was stirred for 0.5 h. The mixed solution was placed in a 100 mL polytetrafluoroethylene liner and hydrothermally heated at 90 °C for 10 h. After cooling to room temperature, deionized water was added and the product was centrifuged to obtain a light yellow precipitate, which was then dried in a 60 °C oven for 6 h to obtain bismuth vanadate solid powder.

[0045] The prepared bismuth vanadate powder was placed in 60 mL of the mixed aqueous solution from step 1. The concentration of cadmium acetate was 2.1 mg / mL and the concentration of thioacetamide was 1 mg / mL. After stirring evenly, the solution was placed in a 100 mL polytetrafluoroethylene liner and hydrothermally reacted at 160 °C for 16 h. After cooling to room temperature, deionized water was added, and the reaction solution was centrifuged 4 times at 8000 r / min, with 50 mL of deionized water added each time. The product was then dried to obtain a composite photocatalyst of cadmium sulfide and bismuth vanadate containing sulfur vacancies.

[0046] Example 3

[0047] Weigh 0.97g of bismuth nitrate pentahydrate and 0.23g of ammonium metavanadate and dissolve them in 40mL of 1M HNO3 aqueous solution. Stir well at room temperature to obtain a mixed solution.

[0048] 1 g of hexadecyltrimethylammonium bromide (CTBA) and 2 g of NaHCO3 were slowly added sequentially to the above solution, and the mixture was stirred for 0.5 h. The mixed solution was placed in a 100 mL polytetrafluoroethylene liner and hydrothermally heated at 100 °C for 12 h. After cooling to room temperature, deionized water was added and the product was centrifuged to obtain a light yellow precipitate, which was then dried in a 60 °C oven for 6 h to obtain bismuth vanadate solid powder.

[0049] The prepared bismuth vanadate powder was placed in 60 mL of the mixed aqueous solution from step 1. The concentration of cadmium acetate was 2.1 mg / mL and the concentration of thioacetamide was 1 mg / mL. After stirring evenly, the solution was placed in a 100 mL polytetrafluoroethylene liner and hydrothermally reacted at 180 °C for 18 h. After cooling to room temperature, deionized water was added, and the reaction solution was centrifuged three times at 10000 r / min, with 45 mL of deionized water added each time. The product was then dried to obtain a composite photocatalyst of cadmium sulfide and bismuth vanadate containing sulfur vacancies.

[0050] Example 4

[0051] Weigh 0.97g of bismuth nitrate pentahydrate and 0.23g of ammonium metavanadate and dissolve them in 40mL of 1M HNO3 aqueous solution. Stir well at room temperature to obtain a mixed solution.

[0052] 1 g of hexadecyltrimethylammonium bromide (CTBA) and 2 g of NaHCO3 were slowly added sequentially to the above solution, and the mixture was stirred for 0.5 h. The mixed solution was placed in a 100 mL polytetrafluoroethylene liner and hydrothermally heated at 120 °C for 12 h. After cooling to room temperature, deionized water was added and the product was centrifuged to obtain a light yellow precipitate, which was then dried in a 60 °C oven for 6 h to obtain bismuth vanadate solid powder.

[0053] The prepared bismuth vanadate powder was placed in 60 mL of the mixed aqueous solution from step 1. The concentration of cadmium acetate was 2.1 mg / mL and the concentration of thioacetamide was 0.75 mg / mL. After stirring evenly, the mixture was placed in a 100 mL polytetrafluoroethylene liner and hydrothermally reacted at 200 °C for 24 h. After cooling to room temperature, deionized water was added, and the reaction solution was centrifuged three times at 12000 r / min, with 50 mL of deionized water added each time. The product was then dried to obtain a composite photocatalyst of cadmium sulfide and bismuth vanadate containing sulfur vacancies.

[0054] Take 300 mg of the samples prepared in Examples 1-4, and perform X-ray diffraction to obtain the following results. Figure 1 The XRD diffraction pattern shown is from... Figure 1 It can be seen that the composite material has two crystal phases: monoclinic bismuth vanadate crystal and hexagonal CdS crystal.

[0055] Take 100 mg of the samples prepared in Examples 1-4 and equal amounts of bismuth vanadate and cadmium sulfide, and perform electron paramagnetic resonance (EPR) testing. Figure 2As shown, neither pure bismuth vanadate nor cadmium sulfide exhibited electron paramagnetic resonance signals, while the composite catalysts of Examples 1-4 all showed signals of varying degrees at g=2.004, which were attributed to signal peaks caused by sulfur vacancies. This further proves that composite photothermal catalysts containing sulfur vacancies of cadmium sulfide and bismuth vanadate can be prepared by the above method.

[0056] Take 200 mg of the samples prepared in Examples 1-4 of this paper and equal amounts of bismuth vanadate and cadmium sulfide, and perform ultraviolet-visible diffuse reflectance testing. Figure 3 As shown, the light absorption of pure-phase bismuth vanadate and cadmium sulfide is cut off at 520 nm and 600 nm, respectively, while the composite catalysts of Examples 1-4 exhibit light absorption in the range of 200-800 nm. This is because sulfur vacancies can introduce new defect energy levels, thereby expanding the light absorption range. Furthermore, after near-infrared light is absorbed by the semiconductor material cadmium sulfide, it can convert photon energy into heat energy and generate a localized thermal effect, achieving a self-heating effect and providing thermal energy for the reaction process of the cadmium sulfide / bismuth vanadate composite photothermal catalyst.

[0057] Preparation of PLA hydrolysate: 1.5g of commercial PLA particles were chopped and placed in 40mL of 1MKOH solution. The mixture was stirred at 50℃ for 48h and the supernatant was taken as the photothermal reforming reactant.

[0058] The activity testing process is as follows:

[0059] 50 mg of samples from Examples 1 to 4, and 50 mg each of bismuth vanadate and cadmium sulfide were weighed out respectively, thus a total of six experiments were set up;

[0060] Six samples were dispersed in a photocatalytic reactor containing 40 mL of PLA hydrolysate, and argon gas was introduced to purge the air. The samples were then irradiated with a 300 W xenon lamp for 5 hours. The product concentration in the photocatalytic reactor was then determined by liquid chromatography. Figure 4 The bar chart shown. From Figure 4 It can be seen that, compared with unmodified bismuth vanadate and cadmium sulfide, the samples of Examples 1 to 4 significantly improved the efficiency of photo-reforming PLA hydrolysate and significantly increased the yield of pyruvate. Example 3 was the best, with its activity increased by 30.3 times.

[0061] This invention utilizes the in-situ growth of cadmium sulfide on the surface of bismuth vanadate, forming not only an S-shaped heterojunction but also a large number of sulfur vacancies. This promotes the efficient separation of photogenerated carriers between bismuth vanadate and cadmium sulfide, and extends the light absorption range of the composite material to the near-infrared region, generating a self-heating effect, thereby achieving highly efficient PLA photothermal synergistic reforming. By utilizing the photothermal synergistic effect of the sulfur-vacancy-containing cadmium sulfide and bismuth vanadate composite photothermal catalyst, the goal of increasing pyruvate yield is achieved, significantly solving the problems of high energy consumption and low photocatalytic performance in traditional thermocatalysis. The preparation process of this method is simple, low-cost, and uses readily available raw materials.

Claims

1. The application of a bismuth cadmium vanadate composite photothermal catalyst containing sulfur vacancies in photothermal reforming polylactic acid hydrolysate, characterized in that, The preparation method of the bismuth vanadate-cadmium sulfide composite photothermal catalyst is as follows: S1, add bismuth nitrate pentahydrate and ammonium metavanadate to nitric acid solution and mix thoroughly. The molar concentration of nitric acid in the nitric acid solution is 0.5~1, the mass ratio of bismuth nitrate pentahydrate to ammonium metavanadate is 97:23, and the ratio of nitric acid solution to ammonium metavanadate is 40 mL:0.23 g, to obtain a mixed solution; S2, add hexadecyltrimethylammonium bromide and NaHCO3 to the mixed solution and mix evenly to obtain precursor solution a. Keep precursor solution a at 80~140 ℃ for 8~14 h, then collect the product and dry it to obtain bismuth vanadate. S3, bismuth vanadate, thioacetamide and cadmium source are mixed evenly in deionized water, the molar ratio of thioacetamide to cadmium source is (0.5~1.5):1, and the mass ratio of thioacetamide to ammonium metavanadate in S1 is (45~75):230, to obtain precursor solution b. Precursor solution b is kept at 140~200℃ for 16~24 h, then the product is collected and dried to obtain bismuth vanadate cadmium sulfide composite photothermal catalyst containing sulfur vacancies.

2. The application of the sulfur-vacancy-containing bismuth cadmium vanadate sulfide composite photothermal catalyst according to claim 1 in photothermal reforming polylactic acid hydrolysate, characterized in that, S2 is added sequentially to the mixed solution with hexadecyltrimethylammonium bromide and NaHCO3 and mixed evenly. The ratio of hexadecyltrimethylammonium bromide, NaHCO3 and ammonium metavanadate in S1 is 1g: (2~3)g: 0.23g to obtain precursor solution a.

3. The application of the sulfur-vacancy-containing bismuth cadmium vanadate sulfide composite photothermal catalyst according to claim 1 in photothermal reforming polylactic acid hydrolysate, characterized in that, The cadmium source mentioned in S3 is cadmium nitrate or cadmium acetate.

4. The application of the sulfur-vacancy-containing bismuth cadmium vanadate sulfide composite photothermal catalyst according to claim 1 in photothermal reforming polylactic acid hydrolysate, characterized in that, The ratio of deionized water in S3 to ammonium metavanadate in S1 is 60 mL: 0.23g, the concentration of thioacetamide in precursor solution b is 0.75~1.25 mg / mL.

5. The application of the sulfur-vacancy-containing bismuth cadmium vanadate sulfide composite photothermal catalyst according to claim 1 in photothermal reforming polylactic acid hydrolysate, characterized in that, S3 added deionized water to the reaction solution obtained after heat treatment of precursor solution b, then centrifuged at 8000~12000 r / min to remove the supernatant, repeated 3~5 times, and then dried the precipitate to obtain the bismuth cadmium vanadate composite photothermal catalyst containing sulfur vacancies.

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