A tin-based catalyst anchored with oxygen vacancies to form a surface hindered lewis acid-base pair for one-step synthesis of formic acid

Abstract

This invention belongs to the field of nanomaterial preparation technology, specifically a tin-based catalyst that utilizes oxygen vacancies to anchor copper to form a surface-hindered Lewis acid-base pair for the one-step synthesis of formic acid. Cu / SnO2(O vs A material with surface-hindered Lewis acid-base pairs is constructed. Copper is uniformly anchored on the catalyst surface using light enhancement and the characteristics of oxygen vacancies on the SnO2 surface. The Cu / SnO2(O) material... vs The structure was obtained by vacancy anchoring Cu in Cu:SnO2 at mass ratios of 0%, 5%, 10%, and 15% under xenon lamp irradiation. This material exhibits excellent catalytic performance in photocatalytic carbon dioxide reduction and can be used for one-step electrocatalytic desorption of carbon dioxide to formic acid.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of nanomaterial preparation, and particularly relates to a tin-based catalyst for synthesizing formic acid in one step. BACKGROUND

[0002] At present, the energy structure in the development of human society is fossil energy such as coal, oil and natural gas. With the continuous improvement of productivity, our dependence on fossil energy is increasing. However, the uncontrolled use of fossil energy has accelerated the depletion of resources, causing environmental problems such as global warming and rising sea levels. Therefore, it is urgent to adjust the current energy structure. Although renewable energy has the characteristics of environmental friendliness, it is difficult to achieve continuous high-density concentrated development and utilization due to its regional and intermittent nature. Therefore, intermittent renewable energy can be converted into electrical energy, thermal energy, etc., and stored by chemical bond energy for convenient transportation and reuse. The method of converting carbon dioxide into high-value chemical products in the chemical industry by electrochemical reduction using renewable energy can realize the resource utilization of carbon dioxide and achieve the closed-loop cycle of carbon. Among the many catalysts for electrocatalytic carbon dioxide, tin-based electrocatalysts have appropriate adsorption energy for CO2RR intermediates, which can convert CO2 into C1 products such as formic acid (HCOOH) and carbon monoxide (CO), so they are widely used in the field of CO2RR.

[0003] At present, the catalysts for producing formic acid are mostly metal-based catalysts, especially Sn, Bi, Pb, In and other main group metals. The outermost layer of these metals is a p orbital, which is more likely to adsorb O to generate OCHO intermediates when it is adsorbed with CO2, and further generate formic acid. Because tin-based materials have good selectivity for formic acid and low cost. ＊ OCHO intermediate, and further generate formic acid. Because tin-based materials have good selectivity for formic acid and low cost. SUMMARY

[0004] The purpose of the present application is to provide a simple method for constructing a hindered Lewis acid-base pair on the surface of a catalyst to achieve efficient production of formic acid. At the same time, the material is also used for photocatalytic reduction of carbon dioxide and shows excellent catalytic performance.

[0005] In order to achieve the above purposes, the specific technical solutions of the present application are as follows:

[0006] A Cu / SnO2(O vs ) material for constructing a surface hindered Lewis acid-base pair, which uses a light-adding method and the characteristics of oxygen vacancies on the surface of SnO2 to uniformly anchor copper on the surface of the catalyst, the catalyst being SnO2(O vs ) material; the Cu / SnO2(O vs) The structure is obtained by anchoring Cu vacancies under xenon lamp irradiation with Cu: SnO2 at a mass ratio of 5%-15%.

[0007] Another object of the present application is to protect a Cu / SnO2(O vs ) The preparation method of the surface blocked Lewis acid-base pair comprises the following steps:

[0008] In the first step, SnCl2 and Na3C6H5O7·2H2O are added into deionized water, and after magnetic stirring, NaOH is added dropwise, and magnetic stirring is performed again.

[0009] In the second step, the obtained substance in the first step is sent into a high-pressure reaction kettle for heating reaction.

[0010] In the third step, the product after the reaction in the second step is washed with deionized water and anhydrous ethanol respectively, and vacuum drying is performed to obtain a sample.

[0011] In the fourth step, the sample obtained in the third step is annealed in a tube furnace to obtain SnO2(O vs ) material.

[0012] In the fifth step, the SnO2(O vs ) material obtained in the fourth step is added into deionized water and magnetic stirring is performed, and CuCl2 solution is added during the magnetic stirring and in a dark environment, and the solution is continuously stirred to be fully mixed.

[0013] In the sixth step, the substance in the fifth step is subjected to xenon lamp light irradiation reaction while magnetic stirring is performed to obtain a product.

[0014] In the seventh step, the product obtained after the sixth step is washed with deionized water and anhydrous ethanol, and vacuum drying is performed to obtain a Cu / SnO2(O vs ) surface blocked Lewis acid-base pair.

[0015] As a preferred embodiment in the present application, in the first step of the above-mentioned preparation method of Cu / SnO2(O vs ) material, the molar ratio of SnCl2 and Na3C6H5O7·2H2O is between 1 / 3 and 1 / 2; the ratio of the amount of substance (mmol) of SnCl2 to the volume (ml) of deionized water is less than 1 / 5 and greater than 1 / 6 (i.e. 1 / 6-1 / 5, which can be determined according to the actual production requirement), and the deionized water is added and stirred magnetically until it is uniform; the ratio of the amount of substance (mmol) of SnCl2 to the volume (μL) of NaOH is 5-7:500; the concentration of NaOH is not less than 1M (preferably 1-1.2M); and the magnetic stirring after the addition of NaOH is performed for more than 20min (preferably 20-30min).

[0016] As a preferred embodiment in the present application, in the second step of the above-mentioned preparation method of Cu / SnO2 (O vs ), the high-pressure reaction kettle is a polytetrafluoroethylene high-pressure reaction kettle; the temperature of the heating reaction is 180-220 DEG C, and the heating time is 12-14 hours.

[0017] As a preferred embodiment in the present application, in the third step of the above-mentioned preparation method of Cu / SnO2 (O vs ), the vacuum drying temperature is 80-100 DEG C, and the drying time is more than 8 hours.

[0018] As a preferred embodiment in the present application, in the fourth step of the above-mentioned preparation method of Cu / SnO2 (O vs ), the temperature of the tube furnace is increased to 800±50 DEG C at a rate of 5 DEG C / min-10 DEG C / min, and annealing is performed under the condition for 6-8 hours.

[0019] As a preferred embodiment in the present application, in the fifth step of the above-mentioned preparation method of Cu / SnO2 (O vs ), 10 ml of deionized water is taken, 0.0011 mg-0.0032 mg of CuCl2 is added, the concentration of CuCl2 in the obtained solution is 0.08 mM-0.24 mM, and the stirring time is more than 30 min until the solution is uniform.

[0020] As a preferred embodiment in the present application, in the sixth step of the above-mentioned preparation method of Cu / SnO2 (O vs ), the wavelength of the xenon lamp is 420 nm-520 nm, the power of the xenon lamp is 20 W, and the illumination time is 1-3 h.

[0021] Another object of the present application is to protect the Cu / SnO2 (O vs ) material constructed by a surface hindered Lewis acid-base pair prepared by any of the above-mentioned methods or a suitable combination of method steps, which is an electrocatalytic carbon dioxide catalyst.

[0022] The last object of the present application is to protect the Cu / SnO2 (O vs ) material constructed by a surface hindered Lewis acid-base pair for photocatalytic reduction of carbon dioxide to synthesize formic acid in one step.

[0023] Compared with the prior art, the present application has the following beneficial effects:

[0024] (1) After the oxygen vacancy is anchored to Cu, the structural stability of the oxygen vacancy-containing tin oxide is greatly improved, and the improvement cost is low;

[0025] (ii) The material exhibits excellent catalytic performance for photocatalytic reduction of carbon dioxide.

[0026] (iii) The material exhibits a microstructure of SnO2(O vs ) nanosheet anchoring Cu to form a composite structure, which exhibits good catalytic activity for electrocatalytic reduction of carbon dioxide to formic acid. When the mass ratio of Cu / SnO2 is 5%, the faradic efficiency of the prepared electrocatalyst for formic acid reaches 94% at a voltage of -0.98 V (vs RHE), which is much higher than the faradic efficiency of 35% of SnO2(O vs ). The improvement in the performance of electrocatalytic reduction of carbon dioxide is due to the suitable steric hindrance between Cu(-OH) and SnO2(O vs ) and the difference in electronegativity, which forms a hindered Lewis acid-base pair on the surface of the catalyst. The hindered Lewis acid-base pair can efficiently activate carbon dioxide molecules, and the addition of Cu can greatly improve the conductivity of SnO2(O vs ), thereby improving the reaction rate. The surface reconstruction process forms Cu-OH with suitable steric hindrance and lack of mobility between the adjacent Sn-O vs , thereby forming a Lewis acid-base pair. After the oxygen on Cu-OH and the unsaturated Sn site are modified by protons, the adsorption of CO2 becomes easy, and CO2 can realize one-step desorption to form formic acid after combining with the surface hindered Lewis acid-base pair. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 SEM images of the samples prepared in the examples and comparative examples of the present application:

[0028] Among them, (a) is Example 1, (b) is Example 2, (c) is Example 3, (d) is Comparative Example 1, (e) is Comparative Example 2, and (f) is Comparative Example 3.

[0029] Figure 2 X-ray diffraction patterns of the material samples prepared in Examples 1-3 and Comparative Examples 1-3 of the present application.

[0030] Figure 3 EPR spectra of the material samples prepared in Examples 1-2 and Comparative Examples 1-2 of the present application.

[0031] Figure 4 Formic acid faradic efficiency and electrochemical impedance spectroscopy of the materials prepared in Examples 1-3 and Comparative Examples 1-3;

[0032] Among them, (a) is the formic acid faradic efficiency comparison chart of each material at different potentials; (b) is the electrochemical impedance spectroscopy of each material.

[0033] Figure 5Cu / SnO2(O vs ) constructed surface hindered Lewis acid-base pair material one-step carbon dioxide electrocatalytic desorption to produce formic acid mechanism diagram.

[0034] Figure 6 Raman spectrum obtained by quasi-in-situ Raman test immediately after i-t test of examples 1-3 at-0.98 vs.RHE voltage for half an hour.

[0035] Figure 7 Cyclic voltammetry (CV) data diagram of the material prepared in example 1 at-0.38 to-0.68 V (vs.RHE) voltage. DETAILED DESCRIPTION

[0036] All features disclosed in this specification, and / or all steps of any methods or processes disclosed in this specification, can be combined in any combination, except combinations where at least some of such features and / or steps are mutually exclusive.

[0037] Any feature disclosed in this specification, unless stated otherwise, can be replaced by any equivalent or similar feature, or by a feature that is technically equivalent or similar in function, effect or purpose. That is, unless stated otherwise, each feature is one of a number of equivalent or similar features that can be substituted for it.

[0038] The features and properties of the present application will be further described using the following examples, together with the comparison examples.

[0039] In the following examples and comparison examples, the wavelength of the xenon lamp is 420-520 nm, and the power of the xenon lamp is 20 W.

[0040] Example 1:

[0041] Cu / SnO2(O vs ) constructed surface hindered Lewis acid-base pair material (tin-based catalyst with oxygen vacancies anchoring copper to form surface hindered Lewis acid-base pair Cu / SnO2(O vs )

[0042] Firstly, 5 mmol SnCl2 and 10 mmol Na3C6H5O7·2H2O were added to 30 ml of deionized water, and magnetically stirred for 10 min, then 500 μL of 1 M NaOH was added dropwise, and magnetically stirred for 20 min;

[0043] Secondly, the solution after magnetic stirring in the first step was sent into a 50 ml polytetrafluoroethylene high-pressure reaction kettle, and heated at 180℃ for 12 hours;

[0044] Thirdly, the product after reaction in the second step was washed with deionized water and anhydrous ethanol respectively, and vacuum dried;

[0045] Fourth step, the obtained sample is heated to 800℃ in a tube furnace at a heating rate of 5℃ / min, and annealed at this temperature for 6 hours, and then ground to collect SnO2(O vs ) material sample.

[0046] Fifth step, the SnO2(O vs ) material sample prepared in the fourth step is added into 30ml deionized water, and 14.06mg CuCl2·2H2O is added during magnetic stirring, and the solution is fully mixed by stirring in the dark environment for 30min;

[0047] Sixth step, the mixed solution obtained in the fifth step is irradiated by a xenon lamp for 1h while magnetic stirring to obtain the product;

[0048] Seventh step, the product obtained in the sixth step is washed with deionized water and anhydrous ethanol, and vacuum dried to prepare 1-Cu / SnO2(O vs ).

[0049] Example 2:

[0050] A Cu / SnO2(O vs ) material for constructing a surface hindered Lewis acid-base pair, the preparation method is as follows:

[0051] Fifth step, the SnO2 prepared in the previous step is added into 30ml deionized water, and 30.15mg CuCl2·2H2O is added during magnetic stirring, and the solution is fully mixed by stirring in the dark environment for 30min;

[0052] Sixth step, the mixed solution obtained in the fifth step is irradiated by a xenon lamp for 1h while magnetic stirring;

[0053] Seventh step, the product obtained in the sixth step is washed with deionized water and anhydrous ethanol, and vacuum dried to prepare 2-Cu / SnO2(O vs ).

[0054] Example 3:

[0055] A Cu / SnO2(O vs ) material for constructing a surface hindered Lewis acid-base pair, the preparation method is as follows:

[0056] Fifth step, the SnO2 prepared in the previous step is added into 30ml deionized water, and 47.15mg CuCl2·2H2O is added during magnetic stirring, and the solution is fully mixed by stirring in the dark environment for 30min;

[0057] Step 6: The mixed solution obtained in step 5 was irradiated with a xenon lamp for 1 h while being magnetically stirred.

[0058] Step 7: The product of step 6 was washed with deionized water and anhydrous ethanol and dried in vacuum to obtain 3-Cu / SnO2(O vs ).

[0059] Comparative Example 1:

[0060] Step 1: 5 mmol of SnCl2and 10 mmol of Na3C6H5O7·2H2O were added to 30 ml of deionized water and magnetically stirred for 10 min, after which 500 μL of 1 M NaOH was added dropwise and magnetically stirred for 20 min;

[0061] Step 2: The mixed solution was placed in a 50 ml Teflon autoclave and heated at 180 °C for 12 h;

[0062] Step 3: The product of step 2 was washed with deionized water and anhydrous ethanol and dried in vacuum; Step 4: The obtained sample was annealed in a tube furnace at 800 °C at a rate of 5 °C / min for 6 h, after which the sample SnO2was collected by grinding.

[0063] Comparative Example 2:

[0064] Step 1: SnO2obtained in Comparative Example 1 was added to 30 ml of deionized water, and 14.06 mg of CuCl2·2H2O was added during magnetic stirring, and the solution was mixed thoroughly under dark conditions for 30 min;

[0065] Step 2: The dark treatment was continued for 1 h while being magnetically stirred;

[0066] Step 3: The product of step 2 was washed with deionized water and anhydrous ethanol and dried in vacuum to obtain Cu-SnO2(O vs ). Comparative Example 3:

[0067] Step 1: Commercial SnO2was added to 30 ml of deionized water, and 14.06 mg of CuCl2·2H2O was added during magnetic stirring, and the solution was mixed thoroughly under dark conditions for 30 min;

[0068] Step 2: Step 1 was irradiated with a xenon lamp for 1 h while being magnetically stirred;

[0069] Step 3: The product of step 2 was washed with deionized water and anhydrous ethanol and dried in vacuum to obtain Cu / SnO2(O vs ).

[0070] Test:

[0071] The materials finally obtained in Examples 1-3 and Comparative Examples 1-3 were subjected to electrochemical carbon dioxide reduction at different voltages to obtain formic acid faradic efficiency and EIS test, see Figure 4 .

[0072] From Figure 4 (a) it can be seen that the formic acid faradic efficiency of the materials obtained in Examples 1-3 is significantly higher than that of Comparative Examples 1-3, indicating that the addition of Cu significantly improves the ability of the catalyst to reduce carbon dioxide to formic acid, and Comparative Example 1 has the best performance. From Figure 4 (b) it can be seen that with the addition of Cu and the presence of oxygen vacancies, the electrochemical performance of the materials in the examples is significantly improved compared to the materials in the comparative examples.

[0073] Figure 6 For surface monitoring in the quasi-in-situ Raman test of Examples 1-3, the successful monitoring of M-OH bonds indicates the successful anchoring of Cu elements to form Cu-SnO(O vs ) surface blocked Lewis acid-base pairs (Cu-OH, Sn-O vs ) during the electrochemical process, which further adsorbs carbon dioxide in the next step of electrocatalytic carbon dioxide reduction, thereby realizing one-step desorption to produce formic acid.

[0074] The 1-Cu / SnO2(O vs ) material prepared in Example 1 was subjected to CV test at -0.38 to -0.68 V (vs. RHE) immediately after different intervals i-t, see Figure 7 .

[0075] Figure 7 For cyclic voltammetry test (CV) at -0.38 to -0.68 V (vs. RHE), it can be seen from Figure 7 that with the increase of i-t test time, the reduction peak shifts to the right, indicating that the reduction reaction is promoted, and electrons overcome the interface barrier to inject into the surface of the particles to attract positively charged protons, that is, a large number of surface states are generated, that is Figure 5 the mechanism experiment of adding H + to Cu(-OH) and Sn sites.

[0076] The above examples only express the specific embodiments of the present application, and the description is more specific and detailed, but it cannot be understood as a limitation on the protection scope of the present application. It should be noted that for ordinary skilled persons in the art, without departing from the technical concept of the present application, a number of modifications and improvements can be made, which are within the protection scope of the present application.

[0077] This Background section is intended to provide a general overview of the context of the application, the work of the current named inventors, to the extent the work is associated with the present application, and the work of others in the field of the application to the extent the work is associated with the present application, and to the extent the work described in this section is associated with the present application, neither expressly nor impliedly, is admitted to be prior art to the present application.

Claims

1. A Cu / SnO2-O vs The application of materials that construct surface-hindered Lewis acid-base pairs in the one-step electrocatalytic reduction of carbon dioxide to formic acid is characterized by: This material utilizes light enhancement and the characteristics of oxygen vacancies on the SnO2 surface to uniformly anchor copper onto the catalyst surface, wherein the catalyst is SnO2-O. vs The Cu / SnO2-O vs The structure was obtained by vacancy anchoring Cu in Cu:SnO2 at a mass ratio of 5-15% under xenon lamp irradiation; The specific preparation method of this material includes the following steps: First, add SnCl2 and Na3C6H5O7·2H2O to deionized water, stir magnetically, then add NaOH dropwise, and stir magnetically again. The second step is to send the substance obtained in the first step into a high-pressure reactor for heating and reaction. The third step is to wash the product after the reaction in the second step with deionized water and anhydrous ethanol, and then dry it under vacuum to obtain the sample. The fourth step is to anneal the obtained sample in a tube furnace to obtain SnO2-O. vs ; Fifth step, SnO2-O vs Add the solution to deionized water and stir magnetically. While stirring magnetically and in the dark, add CuCl2 solution and continue stirring to mix the solution thoroughly. The sixth step involves irradiating the substance from the fifth step with a xenon lamp while simultaneously stirring it magnetically to obtain the product. Step 7: The product obtained after step 6 is washed with deionized water and anhydrous ethanol, and then dried under vacuum to obtain Cu / SnO2-O. vs ; In the fifth step, SnO2-O vs When added to deionized water, the concentration of CuCl2 in the resulting solution is 0.08 mM to 0.24 mM. In step six, the wavelength of the xenon lamp is 420nm to 520nm, the power of the xenon lamp is 20W, and the illumination time is 1-3 hours.

2. The application according to claim 1, characterized in that: In the first step, the molar ratio of SnCl2 to Na3C6H5O7·2H2O is between 1 / 3 and 1 / 2; the ratio of the amount of SnCl2 (mmol) to the volume of deionized water (ml) is less than 1 / 5 and greater than 1 / 6, and the mixture is added to the deionized water and magnetically stirred until homogeneous; the ratio of the amount of SnCl2 (mmol) to the volume of NaOH (μL) is 5-7:500; the concentration of NaOH is 1-1.2M; and the magnetic stirring time after adding NaOH is 20-30 minutes.

3. The application according to claim 1, characterized in that: In the second step, the high-pressure reactor is a polytetrafluoroethylene high-pressure reactor; the heating temperature is 180℃~220℃, and the heating time is 12~14 hours.

4. The application according to claim 1, characterized in that, In the third step, the vacuum drying temperature is 80~100℃; the drying time is more than 8 hours.

5. The application according to claim 1, characterized in that, The annealing conditions in the fourth step are as follows: the temperature of the tube furnace is raised to 800±50℃ at a rate of 5-10℃ / min, and annealed under these conditions for 6-8 hours.

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