Method for controlling photo-driven co2 reduction reaction path by plasma effect and application thereof

Abstract

The present application relates to a kind of methods for controlling light-driven CO2 reduction reaction path using plasma effect and its application, belong to photocatalysis technical field.The present application is based on in-depth study plasma effect on reaction path regulation field, first propose to use plasma effect control light-driven CO2 reduction reaction path method, can change product selectivity, realize the effect of product CO selectivity greatly increase.Inventor also provides a kind of plasma effect characterization method, can first realize plasma to the quantitative characterization of reaction molecule polarization degree.The present application has the following advantages and beneficial effects:1) the catalyst Ag / Co2V2O7 prepared by the present application has simple process, high repeatability, and can realize large-scale production.In the test of light-driven carbon dioxide hydrogenation, it shows superior activity and 100% selectivity to CO, realizes the regulation of plasma effect on reaction path.2) the present application also provides a kind of plasma effect characterization method, can first realize plasma to the quantitative characterization of reaction molecule polarization degree.

Description

TECHNICAL FIELD

[0001] The application relates to a method for controlling a light-driven CO2 reduction reaction path by using a plasma effect and application thereof, and belongs to the technical field of photocatalysis. BACKGROUND

[0002] Excessive use of fossil energy discharges a large amount of CO2, which is one of the main driving factors causing energy crisis and global climate change. Climate change threatens the balance of the natural ecosystem and poses a serious challenge to the sustainable development of human society. At present, reducing CO2 emission has become the consensus of the international community. Countries actively respond to this global challenge by formulating emission reduction targets and policies, promoting clean energy technologies and improving energy efficiency.

[0003] Through effective utilization of solar energy, fixing and converting CO2 into CO is one of the favorable ways to solve the current energy crisis and environmental deterioration. However, in the process of CO2 reduction and conversion, there are two competitive reactions, i.e. reverse water-gas shift reaction and Sabatier reaction, which seriously affect the selectivity of the reaction and are the main factors restricting the efficient reaction.

[0004] So far, there is still a lack of systematic guiding theory in the field of regulation of CO2 reduction reaction path.

[0005] The plasma effect has good application effect in the light-driven reaction using solar energy. The reaction driven by the plasma effect has high reaction efficiency. However, there is still a lack of in-depth research on the regulation of reaction path by the plasma effect, which is also a challenging topic. So far, there is no related report. SUMMARY

[0006] The purpose of the application is to fill the gap in the prior art, and provide a method for controlling a light-driven CO2 reduction reaction path by using a plasma effect and application thereof.

[0007] The main idea of the application is as follows: based on the in-depth research on the regulation of reaction path by the plasma effect, the inventors first propose a method for controlling a light-driven CO2 reduction reaction path by using a plasma effect, which can change the product selectivity and realize the effect of greatly improving the selectivity of product CO. The inventors also provide a method for characterizing the plasma effect, which can first realize the quantitative characterization of the polarization degree of the reaction molecules by the plasma.

[0008] To achieve the above-mentioned purpose, the technical scheme of the application is as follows:

[0009] In the first aspect of the present application, a method for controlling the light-driven CO2 reduction reaction path by plasma effect is provided, which can be used to improve the selectivity of CO product in the CO2 reduction reaction, and the method comprises the preparation of a catalyst and the light-driven CO2 reduction:

[0010] The preparation of the catalyst comprises the following steps:

[0011] (1) Dissolve cobalt nitrate crystals and ammonium metavanadate in water respectively to obtain a cobalt nitrate solution and an ammonium metavanadate solution, then add the cobalt nitrate solution dropwise into the ammonium metavanadate solution, and heat and stir the mixed solution until the water is completely evaporated;

[0012] (2) After the sample obtained in step (1) is uniformly ground, it is first calcined at 350°C for 2h, and then placed for calcination at 650°C for 2h to obtain a Co2V2O7 catalyst;

[0013] (3) The sample obtained in step (2) is uniformly dispersed in deionized water, silver nitrate solution and methanol are added, and then it is placed under a 300W xenon lamp for 6h, and after the obtained sample is centrifuged, washed and dried, an Ag / Co2V2O7 catalyst with a loading of 0.5-5wt% Ag is obtained (here, the loading refers to the mass ratio of Ag to the Co2V2O7 carrier);

[0014] The light-driven CO2 reduction is carried out using the obtained Ag / Co2V2O7 catalyst with a loading of 0.5-5wt% Ag as the light-driven catalyst.

[0015] Further, in step (1), the molar ratio of cobalt nitrate to metavanadic acid in the mixed solution is 1:1.

[0016] Further, in step (3), the Co2V2O7 catalyst sample is dispersed in deionized water to form a solution with a concentration of 10mg / ml, the concentration of the silver nitrate solution is 10mg / ml, and the weight ratio of silver nitrate to Co2V2O7 in the Ag / Co2V2O7 catalyst is 0.5-5:100.

[0017] Further, the specific method for carrying out the light-driven CO2 reduction reaction using the obtained Ag / Co2V2O7 as the light-driven catalyst is as follows:

[0018] (1) Uniformly disperse the Ag / Co2V2O7 catalyst in a quartz reactor;

[0019] (2) In the dark state, the flow rate of CO2 and H2 is 10 ml / min, and the first blowing is 30 min, and only the mixed gas of CO2 and H2 is obtained, and the light is turned on, and the light conditions are as follows: 300W xenon lamp, light intensity is 10 suns, and reaction time is 5 hours.

[0020] The inventors accidentally found that: after the modification of Ag nanoclusters, the local surface plasma effect can produce a polarization field around the Ag clusters, which can polarize the reaction molecules and intermediates, regulate the reaction path, and increase the CO selectivity of the product from 36% to nearly 100%.

[0021] In the second aspect of the present application, the present application also provides a method for characterizing plasma effect.

[0022] Since the regulation of the reaction path is related to the polarization effect of the plasma effect, quantitative characterization can prove the polarization effect of the plasma, but there is still a lack of test means for the plasma effect, so a method for characterizing plasma effect is provided. The specific steps of the method are as follows:

[0023] (1) Put the sample to be tested in the light excitation test equipment, first use 30ml / min of Ar gas to blow for 50min in the dark state, and blow away the residual impurity gas on the surface;

[0024] (2) Switch the test gas (CO2 or CO) to control the flow rate to be 30ml / min, so that the catalyst is saturatedly adsorbed to the test gas;

[0025] (3) Switch the Ar gas again, after the system is stable, turn on the light, and realize the quantitative characterization of the plasma effect by comparing and analyzing the signals of the reference TCD and the test TCD.

[0026] In the method for characterizing plasma effect of the present application, the polarization degree of the plasma to the reaction molecules can be quantitatively characterized for the first time by introducing a molecular probe.

[0027] Compared with the prior art, the present application has the following advantages and beneficial effects:

[0028] 1) The catalyst Ag / Co2V2O7 prepared by the present application has simple process and high repeatability, and can realize large-scale production. In the light-driven carbon dioxide hydrogenation test, it shows superior activity and 100% selectivity to CO, and realizes the regulation of the reaction path by the plasma effect.

[0029] 2) The present application also provides a method for characterizing plasma effect, which can quantitatively characterize the polarization degree of the plasma to the reaction molecules for the first time. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 XRD patterns of Ag / Co2V2O7 with different loading amounts.

[0031] Figure 2 This is a transmission electron microscope photo of Ag / Co2V2O7.

[0032] Figure 3 EDX images of Ag / Co2V2O7, where (a)-(d) represent the element distribution of Co, V, O, and Ag, respectively.

[0033] Figure 4 This is a comparison chart of the CO2 hydrogenation reaction activity of samples under xenon lamp irradiation.

[0034] Figure 5 This is the electromagnetic field simulation diagram of the Ag / Co2V2O7 model.

[0035] Figure 6 This is a test diagram of the stability of CO2 hydrogenation reaction of Ag / Co2V2O7 sample under xenon lamp irradiation.

[0036] Figure 7 CO2 photoexcitation adsorption and desorption test of the sample.

[0037] Figure 8 CO photoexcitation adsorption-desorption test of the sample. DETAILED DESCRIPTION

[0038] The present invention will be further described in detail below using specific examples with reference to the accompanying drawings. The following examples will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any way. It should be noted that for those skilled in the art, the optimal data in the present invention are specific to the present invention only, and that reasonable adjustments and improvements without departing from the scope of the present invention are within the scope of protection of the present invention.

[0039] Example 1

[0040] Weigh 1 mmol of Co(NO₃)₂·6H₂O and 1 mmol of NH₄VO₃, respectively, and dissolve them in 50 mL of double-distilled water. Slowly add the Co(NO₃)₂ solution dropwise to the NH₄VO₃ solution, then heat to 80°C until the solution evaporates to dryness. The evaporated sample is transferred to a muffle furnace and sintered at 350°C for 2 hours to obtain a precursor. The precursor is then transferred to a muffle furnace and sintered at 650°C for 2 hours to obtain the Co₂V₂Oₐ sample.

[0041] Example 2

[0042] The Co2V2O7 sample obtained in Example 1 was weighed at 1 g, added to 100 mL of deionized water, ultrasonically dispersed and stirred, and 30 mL of methanol and different volumes (0.5 ml, 1 ml, 2 ml, and 5 ml, respectively) of an AgNO3 solution (concentration of 10 mg / ml) were added dropwise. Then it was placed under a 300 W xenon lamp (420 nm cutoff filter) and irradiated for 6 h. The obtained sample was centrifuged and washed, and vacuum dried for 12 h, to obtain four Ag / Co2V2O7 catalysts (loading of 0.5 wt% Ag, 1 wt% Ag, 2 wt% Ag, and 5 wt% Ag, respectively).

[0043] Figure 1 For the XRD patterns of all samples, it can be reflected that all the prepared samples have good crystallinity.

[0044] In combination with Figure 2 With Figure 3 TEM and EDX tests, the lattice fringes and element distribution of the Ag / Co2V2O7 (1 wt% Ag) catalyst can be clearly seen, and the Ag clusters are uniformly loaded on the surface of the sample.

[0045] Example 3

[0046] During the performance test, 50 mg of the Co2V2O7 sample of Example 1 and the Ag / Co2V2O7 samples containing 0.5 wt% Ag, 1 wt% Ag, 2 wt% Ag, and 5 wt% Ag of Example 2 were weighed each time, and the performance test of the photocatalytic reduction of CO2 in the flow phase was carried out.

[0047] Specific test method:

[0048] (1) 50 mg of Co2V2O7 catalyst or Ag / Co2V2O7 (loading of 0.5 wt% Ag, 1 wt% Ag, 2 wt% Ag, and 5 wt% Ag, respectively) catalyst was uniformly dispersed in a quartz reactor, and then installed in a photo-thermal flow phase test device for performance test.

[0049] (2) The flow rates of CO2 and H2 were both controlled at 10 ml / min in the dark state, and the gas was purged for 30 min. A gas chromatograph (GC) was used to detect the mixed gas of CO2 and H2 in the tail gas. The light was turned on, and the light conditions were as follows: 300 W xenon lamp, light intensity of 10 suns, and reaction time of 5 hours. The GC program was controlled to detect the products in real time, and the changes in reaction selectivity were analyzed and compared.

[0050] Figure 4As can be seen, the Co2V2O7 catalyst in the light-driven CO2 reduction test, the product is mostly CH4, CO only accounts for about 36%, and after the loading of Ag cluster, the CO selectivity of the reaction product is greatly improved, close to 100%, and the CO yield of the sample of Ag / Co2V2O7 with 1wt% Ag reaches the highest.

[0051] As can be seen from the FDTD simulation of Figure 5 It can be seen that Ag will produce a significant plasma effect under light excitation, and the electromagnetic field strength around the silver particles will be greatly improved, which will cause a local potential difference. The existence of the polarization field will regulate the reaction path and promote the adjustment of selectivity. Figure 6 As shown in the figure, and in the flow phase test for more than 100h, the Ag / Co2V2O7 catalyst shows significant stability, and still maintains nearly 100% selectivity for product CO during the test.

[0052] Example 4

[0053] To quantitatively characterize the polarization field generated by the plasma effect, the light excitation adsorption and desorption test method is used, and the specific process is as follows:

[0054] (1) Respectively, 40mg Co2V2O7 and Ag / Co2V2O7 (1wt% Ag) samples are placed in the light excitation test equipment, and first purged with Ar gas (30ml / min) for 50min to remove the impurity gas remaining on the surface.

[0055] (2) Switch the test gas (CO2 or CO), control the flow rate to 30ml / min, and make the catalyst saturated adsorption to the test gas.

[0056] (3) Switch to Ar gas again, after the system is stable, turn on the light, and realize the quantitative characterization of the plasma effect by comparing the signals of the reference TCD and the test TCD.

[0057] As Figure 7 And Figure 8 As shown, CO2 and CO gas molecules are used as probes respectively, and the signals of the reference TCD and the test TCD are compared to realize the characterization of the plasma effect. As Figure 7 And Figure 8 As shown, the plasma effect generated by Ag / Co2V2O7 under light excitation can be significantly observed, which has a greater polarization force on CO2 and CO molecules. The significant enhancement of this polarization force will cause a great change in the reaction intermediate path. In addition, the comparison of the polarization molecule quantity also realizes the quantitative characterization of the plasma.

[0058] The above merely illustrates the embodiments of the present application, and does not limit the patent scope of the present application, and any equivalent transformation or direct or indirect application in other related technical fields based on the content of the present application is also included in the patent protection scope of the present application.

Claims

1. A method for controlling the light-driven CO2 reduction reaction path using the plasma effect, characterized in that: The method is used to improve the selectivity of CO production in a CO2 reduction reaction, and the method includes preparing a catalyst and light-driven CO2 reduction: The preparation of the catalyst comprises the following steps: (1) Dissolving cobalt nitrate crystals and ammonium metavanadate in water to obtain a cobalt nitrate solution and an ammonium metavanadate solution, respectively, then adding the cobalt nitrate solution dropwise to the ammonium metavanadate solution, and heating and stirring the mixed solution until the water is completely evaporated; (2) Grinding the sample obtained in step (1) uniformly, calcining it at 350°C for 2 h, and then calcining it at 650°C for 2 h to obtain a Co2V2O7 catalyst; (3) The sample obtained in step (2) was uniformly dispersed in deionized water, and silver nitrate solution and methanol were added, and then placed under a 300W xenon lamp for 6 hours. The obtained sample was centrifuged, washed, and dried to obtain an Ag / Co2V2O7 catalyst with an Ag loading of 0.5-5wt%; The light-driven CO2 reduction is carried out using the Ag / Co2V2O7 catalyst with a loading amount of 0.5-5wt% Ag as a light-driven catalyst to perform mobile phase light-driven CO2 reduction.

2. The method according to claim 1, characterized in that In the step (1), the molar ratio of cobalt nitrate to metavanadic acid in the mixed solution is 1:

1.

3. The method according to claim 1, characterized in that In the step (3), the concentration of the solution formed by dispersing the Co2V2O7 catalyst sample in deionized water is 10 mg / ml, the concentration of the silver nitrate solution is 10 mg / ml, and the weight ratio of silver nitrate to Co2V2O7 in the Ag / Co2V2O7 catalyst is 0.5-5:

100.

4. The method according to claim 1, wherein The specific method of using the obtained Ag / Co2V2O7 as a light-driven catalyst to carry out a light-driven CO2 reduction reaction is as follows: (1) Ag / Co2V2O7 catalyst is evenly dispersed in a quartz reactor; (2) Under dark conditions, control the flow rates of CO2 and H2 to 10 ml / min, purge for 30 minutes to obtain a mixture of only CO2 and H2, and then turn on the light.

5. The method according to claim 4, characterized in that The illumination conditions are as follows: 300W xenon lamp, illumination intensity of 10 suns, and reaction time of 5 hours.

6. A method for characterizing plasma effects, characterized in that: The specific steps of the method are as follows: (1) Place the sample to be tested in a light excitation test device and purge it in the dark with 30 ml / min of Ar gas for 50 minutes to purge the impurity gas remaining on the surface; wherein the sample to be tested is the Ag / Co2V2O7 catalyst used in the method according to any one of claims 1 to 4; (2) Switch the test gas to CO2 or CO, control the flow rate to 30 ml / min, and make the catalyst saturated with the test gas; (3) Switch to Ar gas again. After the system is stable, turn on the light and quantitatively characterize the plasma effect by comparing and analyzing the signals of the reference TCD and the test TCD.

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