Preparation method and use of thickness-controllable bismuth nanosheet and bismuth alloy nanosheet

Abstract

The present disclosure relates to a preparation method and use of a thickness-controllable bismuth nanosheet and its alloy, in order to solve the technical problems that the existing metal catalysts for the conversion of carbon dioxide to formic acid exhibit a low efficiency, a high overpotential, a relatively positive hydrogen evolution potential, and a poor stability. In the present disclosure, a bismuth nanosheet of a single atom layer thickness with a thickness of only 0.7 nm is obtained through an aqueous solution reduction method by using a bismuth salt compound as a raw material, using ethylene glycol ethyl ether as a solvent, and using a highly reductive aqueous solution containing NaBH.sub.4, LiBH.sub.4 or the like as a reducing agent, under a protection atmosphere of an inert gas.

Claims

1. A method for preparing a bismuth-containing nanosheet, comprising the steps of: adding 0.5 mmol of bismuth salt compound as a raw material into 200 mL of ethylene glycol ethyl ether as a solvent, stirring with sonication to homogenization until a clear solution is obtained, subsequently stirring the solution at 25° C. for 30 min, under a protection of an inert gas, cooling the resultant to ambient temperature, then adding an aqueous reducing solution containing 20 mmol NaBH.sub.4 dropwise thereto under an inert gas atmosphere, and stirring for another 15 min, and after completion of the reaction, allowing the reaction product to be sonicated, filtered, washed with ethanol and water, collected, and dried, to obtain the bismuth-containing nanosheet with a thickness of 0.7 nm.

2. The method according to claim 1, wherein the raw material further comprises a palladium, nickel, zinc, gold, or copper salt compound, and the bismuth-containing nanosheet is a bismuth alloy nanosheet.

3. A method, comprising reducing carbon dioxide in the presence of the bismuth-containing nanosheet prepared by the method of claim 1.

4. The method according to claim 1, wherein the bismuth-containing nanosheet is supported on a carbon-based carrier to form a supported bismuth-containing nanosheet, wherein the carbon-based carrier is GO, reduced GO, or carbon black.

5. A method, comprising reducing carbon dioxide in the presence of the supported bismuth-containing nanosheet prepared by the method of claim 4.

6. The method according to claim 2, wherein the bismuth salt compound is bismuth chloride or bismuth nitrate, and the palladium, nickel, zinc, gold, or copper salt compound has an amount of 0.5 mmol-5 mmol.

7. A method, comprising reducing carbon dioxide in the presence of the bismuth alloy nanosheet prepared by the method of claim 2.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) The present disclosure is further described in detail below with reference to the drawings and the particular embodiments.

(2) FIG. 1 is a transmission electron microscopy image of the bismuth nanosheet prepared in Example 1 in the present disclosure;

(3) FIG. 2 is an atomic force microscopy image of the bismuth nanosheet prepared in Example 1 in the present disclosure;

(4) FIG. 3 is an atomic force microscopy image of the bismuth nanosheet prepared in Example 1 in the present disclosure after treating at a temperature of 300° C. for 4 h;

(5) FIG. 4 is an atomic force microscopy image of the bismuth nanosheet prepared in Example 2 in the present disclosure;

(6) FIG. 5 is a Faradic efficiency graph for the reduction of CO.sub.2 to formic acid at different potentials with the bismuth nanosheet prepared in Example 1 in the present disclosure;

(7) FIG. 6 is a comparison linear scanning voltammogram for the reduction of CO.sub.2 with the bismuth nanosheets prepared in Examples 1, 2 and 3 in the present disclosure;

(8) FIG. 7 is a linear scanning voltammogram for the reduction of CO.sub.2 with the supported bismuth nanosheet prepared in Example 4 in the present disclosure;

(9) FIG. 8 is a linear scanning voltammogram for the reduction of CO.sub.2 with the palladium-bismuth alloy nanosheet prepared in Example 5 in the present disclosure;

(10) FIG. 9 is a comparison Faradic efficiency graph for the reduction of CO.sub.2 to formic acid with the bismuth nanosheets prepared in Examples 1, 2, and 3 in the present disclosure;

(11) FIG. 10 is a current efficiency graph for the bismuth nanosheet prepared in Example 1 in the present disclosure operated at −0.58 V for 75 h; and

(12) FIG. 11 is a nuclear magnetic detection spectrum for the catalytic reduction of CO.sub.2 to produce formic acid at −0.58 V with the bismuth nanosheet prepared in Example 1 in the present disclosure.

DETAILED DESCRIPTION

(13) The present disclosure is described in detail below with reference to the drawings.

(14) The present disclosure provides a method for preparing a thickness-controllable bismuth nanosheet, comprising the steps of:

(15) dissolving a bismuth salt compound as a raw material in ethylene glycol ethyl ether as a solvent, and

(16) performing a reduction through an aqueous solution reduction method to obtain the bismuth nanosheet.

(17) A specific embodiment of the method for preparing a thickness-controllable bismuth nanosheet comprises the steps of:

(18) adding 0.5 mmol to 5 mmol of bismuth salt compound into 200-300 mL of ethylene glycol ethyl ether, stirring with sonication to homogenization until a clear solution is obtained,

(19) subsequently stirring the solution at 25-120° C. for 30-60 min, under a protection of an inert gas,

(20) cooling the resultant to ambient temperature,

(21) then adding an aqueous reducing solution containing 20-40 mmol of NaBH.sub.4 or LiBH.sub.4 dropwise thereto under an inert gas atmosphere, and stirring for another 15-30 min, and

(22) after completion of the reaction, allowing the reaction product to be sonicated, filtered, washed with ethanol and water, collected, and dried, to obtain the bismuth nanosheet.

(23) The bismuth nanosheet preferably has a thickness of 0.7 nm-50 nm, and more preferably has a thickness of 0.7 nm-4 nm. The bismuth salt compound is bismuth chloride or bismuth nitrate. The bismuth nanosheet prepared may also be supported on a carbon-based carrier, wherein the carbon-based carrier is GO, reduced GO, or carbon back such as BLACK PEARLS® 2000 (available from Asian-Pacific Specialty Chemicals Ltd, Kuala Lumpur, Malaysia) or VULCAN® XC-72 (available from CABOT Corporation, USA).

(24) The present disclosure further provides a method for preparing a thickness-controllable bismuth alloy nanosheet, comprising the steps of:

(25) dissolving a bismuth salt compound and a palladium, nickel, zinc, gold, or copper salt compound as raw materials in ethylene glycol ethyl ether as a solvent, and

(26) performing a reduction through an aqueous solution reduction method to obtain the bismuth alloy nanosheet.

(27) A specific embodiment of the method for preparing a thickness-controllable bismuth alloy nanosheet comprises the steps of:

(28) dissolving 0.5 mmol to 5 mmol of palladium, nickel, zinc, gold, or copper salt compound in 200-300 mL of ethylene glycol ethyl ether, stirring with sonication to homogenization,

(29) subsequently stirring the solution at 25-120° C. for 30-60 min, under a protection atmosphere of an inert gas,

(30) cooling the resultant to ambient temperature, then adding 0.5 mmol to 5 mmol of bismuth salt compound thereto, mixing and stirring the mixture to homogenization,

(31) then adding an aqueous reducing solution containing 20-40 mmol of NaBH.sub.4 or LiBH.sub.4 dropwise thereto under an inert gas atmosphere, and stirring for another 15-30 min,

(32) after completion of the reaction, allowing the reaction product to be filtered, washed with ethanol and water, collected, and dried,

(33) placing the dried sample in a tube furnace into which hydrogen gas is injected, and calcinating the sample at 300-600° C. for 1-3 h, to obtain the bismuth alloy nanosheet.

(34) The bismuth salt compound is bismuth chloride or bismuth nitrate.

(35) The present disclosure further provides use a bismuth nanosheet, a supported bismuth nanosheet, or a bismuth alloy nanosheet prepared by the above preparation method for an efficient electrocatalytic reduction of carbon dioxide.

EXAMPLE 1

(36) Preparation of a Bismuth Nanosheet Having a Thickness of 0.7 nm

(37) 0.5 mmol of bismuth chloride was added into 200 mL of ethylene glycol ethyl ether, and was stirred with sonication to homogenization until a clear solution was obtained. Subsequently, the solution was stirred at 25° C. for 30 min under a protection atmosphere of an inert gas. After the resultant was cooled to ambient temperature, an aqueous reducing solution containing 20 mmol of NaBH.sub.4 was dropwise added thereto under an inert gas atmosphere and was stirred for another 15 min. After the reaction was completed, the reaction product was sonicated, filtered, washed with ethanol and water, collected, and dried, to obtain the bismuth nanosheet having a thickness of 0.7 nm.

(38) FIG. 1 is a transmission electron microscopy image of the bismuth nanosheet prepared in Example 1 in the present disclosure. It can be seen from this figure that the bismuth nanosheet prepared in this example exhibits an ultra-thin lamellar structure.

(39) FIG. 2 is an atomic force microscopy image of the bismuth nanosheet prepared in Example 1 in the present disclosure. It can be seen from this figure that its average thickness is 0.70 nm.

(40) FIG. 3 is an atomic force microscopy image of the bismuth nanosheet prepared in Example 1 in the present disclosure after treating at a temperature of 300° C. for 4 h. It can be seen from this figure that its average thickness is 0.72 nm, substantially consistent with the thickness prior to the high temperature treatment.

(41) FIG. 5 is a Faradic efficiency graph for the reduction of CO.sub.2 to formic acid at different potentials with the bismuth nanosheet prepared in Example 1 in the present disclosure. It can be seen from this figure that when the potential is at −0.58 V, the Faradic efficiency for producing formic acid reaches 98% at most while it is merely less than 1% for hydrogen gas; and when the initial overpotential is only at 0.13 V, the Faradic efficiency for producing formic acid can still reach 33%.

(42) FIG. 10 is a current efficiency graph for the bismuth nanosheet prepared in Example 1 in the present disclosure operated at −0.58 V for 75 h. It can be seen from this figure that during the 75 h operating period of the bismuth nanosheet catalyst, the current substantially does not show any attenuation, and the Faradic efficiency for producing formic acid remains unchanged and is 98%. This also demonstrates the ultrahigh stability of the bismuth nanosheet catalyst.

(43) FIG. 11 is a nuclear magnetic detection spectrum for the catalytic reduction of CO.sub.2 to produce formic acid at −0.58 V with the bismuth nanosheet prepared in Example 1 in the present disclosure. This figure indicates that: as shown by the designation in the figure, formic acid is actually detected through the detection of H-NMR (AV 500) spectrum, and is quantified with DMSO as an internal standard.

EXAMPLE 2

(44) Preparation of a Bismuth Nanosheet Having a Thickness of 4 nm

(45) 2.5 mmol of bismuth nitrate compound was added into 250 mL of ethylene glycol ethyl ether, and was stirred with sonication to homogenization until a clear solution was obtained. Subsequently, the solution was stirred at 70° C. for 45 min under a protection atmosphere of an inert gas. After the resultant was cooled to ambient temperature, an aqueous reducing solution containing 30 mmol of LiBH.sub.4 was dropwise added thereto under an inert gas atmosphere and was stirred for another 20 min. After the reaction was completed, the reaction product was sonicated, filtered, washed with ethanol and water, collected, and dried, to obtain the bismuth nanosheet having a thickness of 4 nm.

(46) FIG. 4 is an atomic force microscopy image of the bismuth nanosheet prepared in Example 2 in the present disclosure. It can be seen from this figure that the sheet of the bismuth nanosheet has a thickness of 4 nm.

EXAMPLE 3

(47) Preparation of a Bismuth Nanosheet Having a Thickness of 13 nm

(48) 5 mmol of bismuth nitrate was added into 300 mL of ethylene glycol ethyl ether, and was stirred with sonication to homogenization until a clear solution was obtained. Subsequently, the solution was stirred at 120° C. for 60 min under a protection atmosphere of an inert gas. After the resultant was cooled to ambient temperature, an aqueous reducing solution containing 40 mmol of NaBH.sub.4 was dropwise added thereto under an inert gas atmosphere and was stirred for another 30 min. After the reaction was completed, the reaction product was sonicated, filtered, washed with ethanol and water, collected, and dried, to obtain the bismuth nanosheet having a thickness of 13 nm.

(49) Carbon dioxide was electrocatalytically reduced to formic acid with the bismuth nanosheets prepared in the above Examples 1-3. In the process of the reduction, the potential during the constant potential reduction was controlled in a range of −0.38 V to −1.08 V (vs.RHE). The time for electroreduction was 75 h.

(50) FIG. 6 is a comparison linear scanning voltammogram for the reduction of CO.sub.2 with the bismuth nanosheets prepared in Examples 1, 2 and 3 in the present disclosure. This figure demonstrates that the bismuth nanosheets having different thicknesses have different responses to CO.sub.2, and the less the thickness is, the larger the response is. The sheet having a thickness of 0.7 nm exhibits the largest current and the lowest initial potential.

(51) FIG. 9 is a comparison Faradic efficiency graph for the reduction of CO.sub.2 to formic acid with the bismuth nanosheets prepared in Examples 1, 2, and 3 in the present disclosure. It can be seen from this figure that the bismuth nanosheet having a thickness of 0.7 nm shows the best CO.sub.2 reduction property. The peak overpotential (330 mV) of the bismuth nanosheet having a thickness of 0.7 nm is lower than those of the bismuth nanosheets having thicknesses of 4 nm (430 mV) and 13 nm (530 mV), and its Faradic efficiency for producing formic acid is also significantly higher than the other two bismuth nanosheets having different thicknesses. This further proves that the thinner the sheet of the bismuth nanosheet is, the better the CO.sub.2 catalytic reduction property is.

EXAMPLE 4

(52) The bismuth nanosheet having a thickness of 0.7 nm prepared in Example 1 was supported on GO to prepare a supported bismuth nanosheet.

(53) Here, the GO may also be replaced with reduced GO, or carbon back such as BLACK PEARLS® 2000 or VULCAN® XC-72.

(54) The bismuth nanosheet prepared in Example 1 can still maintain a relatively high catalytic property after complexation with a carbon-based carrier.

(55) FIG. 7 is a linear scanning voltammogram for the reduction of CO.sub.2 with the supported bismuth nanosheet prepared in Example 4 in the present disclosure. It can be seen from this figure that the supported bismuth nanosheet has a larger response to CO.sub.2.

EXAMPLE 5

(56) Preparation of a Palladium-Bismuth Alloy Nanosheet

(57) 0.5 mmol of palladium chloride was dissolved in 200 mL of ethylene glycol ethyl ether, and was stirred with sonication to homogenization. Subsequently, the solution was stirred at 25° C. for 30 min under a protection atmosphere of an inert gas. After the resultant was cooled to ambient temperature, 0.5 mmol of bismuth chloride was added thereto, and was mixed and stirred to homogenization. Then, an aqueous reducing solution containing 20 mmol of NaBH.sub.4 was dropwise added thereto under an inert gas atmosphere and was stirred for another 15 min. After the reaction was completed, the reaction product was filtered, washed with ethanol and water, collected, and dried. The dried sample was placed in a tube furnace into which hydrogen gas was injected, and calcinated at 300° C. for 1 h, to obtain the palladium-bismuth alloy nanosheet.

(58) The palladium-bismuth alloy nanosheet prepared in Example 5 can still maintain a relative high catalytic property.

(59) FIG. 8 is a linear scanning voltammogram for the reduction of CO.sub.2 with the palladium-bismuth alloy nanosheet prepared in Example 5 in the present disclosure. It can be seen from this figure that the palladium-bismuth alloy nanosheet in a CO.sub.2 saturated electrolyte exhibits a current and an initial potential both superior to those in a N.sub.2 saturated electrolyte, demonstrating that the palladium-bismuth alloy nanosheet has a larger response to CO.sub.2.

EXAMPLE 6

(60) Preparation of a Nickel-Bismuth Alloy Nanosheet

(61) 5 mmol of nickel nitrate was dissolved in 300 mL of ethylene glycol ethyl ether, and was stirred with sonication to homogenization. Subsequently, the solution was stirred for 60 min at 120° C. under a protection atmosphere of an inert gas. After the resultant was cooled to ambient temperature, 5 mmol of bismuth nitrate was added thereto, and was mixed and stirred to homogenization. Then, an aqueous reducing solution containing 40 mmol of LiBH.sub.4 was dropwise added thereto under an inert gas atmosphere and was stirred for another 30 min. After the reaction was completed, the reaction product was filtered, washed with ethanol and water, collected, and dried. The dried sample was placed in a tube furnace into which hydrogen gas was injected, and calcinated at 600° C. for 3 h, to obtain the nickel-bismuth alloy nanosheet.

(62) The nickel nitrate in Example 6 was replaced with zinc nitrate, gold trichloride, or copper chloride to prepare zinc-bismuth alloy nanosheet, gold-bismuth alloy nanosheet, or copper-bismuth alloy nanosheet respectively.

(63) The nickel-bismuth alloy nanosheet prepared in Example 6 can still maintain a relatively high catalytic property.

(64) It is apparent that the above examples are merely intended for illustration in order for a clear explanation, rather than limitation to the embodiments. Other variations or modifications of different forms can also be made by one of ordinary skill in the art on the basis of the above description. There is no need or no way to exhaustively recite all the embodiments. Obvious variations or modifications derived therefrom still fall within the protection scope of the present disclosure.