ABO3 Type High-entropy Perovskite Bax(FeCoNiZrY)0.2O3-delta Electrocatalytic Material and Preparation Method Thereof

Abstract

The present disclosure discloses an ABO.sub.3 type high-entropy perovskite Ba.sub.x(FeCoNiZrY).sub.0.2O.sub.3-δ electrocatalytic material and a preparation method thereof, belonging to the technical field of electrocatalytic materials. The electrocatalytic material is prepared by taking hydrated cobalt nitrate, hydrated ferric nitrate, hydrated nickel nitrate, barium nitrate, hydrated yttrium nitrate, hydrated zirconium nitrate and polyacrylonitrile staple fibers as raw materials through processes of liquid phase chelation, gelation, calcination, etc. The prepared high-entropy perovskite Ba.sub.x(FeCoNiZrY).sub.0.2O.sub.3-δ electrocatalytic material can release more electrochemical active sites due to its special nanostructure, thus showing better electrocatalytic activity. Meanwhile, by adjusting the stoichiometric ratio of A/B-site metals, the electronic structure change of five metals in a catalytic center and the change of an oxygen vacancy content are realized, and the purpose of adjusting and optimizing the nitrogen reduction performance is achieved, so that the electrocatalytic material has excellent electrocatalytic conversion of nitrogen gas into ammonia gas.

Claims

1. An electrocatalyst for ammonia synthesis, wherein the electrocatalyst is an ABO.sub.3 type high-entropy perovskite Ba.sub.x(FeCoNiZrY).sub.0.2O.sub.3-δ electrocatalytic material, wherein A-site metal of the ABO.sub.3 type is Ba, B-site metals comprise the metals Fe, Co, Ni, Zr and Y, x is 0.9 and 1, and 0<δ<3.

2. The electrocatalyst for ammonia synthesis according to claim 1, wherein the atomic ratio of the metals is as follows: Ba:Fe:Co:Ni:Zr:Y=1:0.2:0.2:0.2:0.2:0.2, or Ba:Fe:Co:Ni:Zr:Y=0.9:0.2:0.2:0.2:0.2:0.2.

3. A method for preparing the electrocatalyst for ammonia synthesis according to claim 1, wherein the method comprises the following steps: (1) dissolving polyacrylonitrile powder in N, N-dimethylformamide to obtain a polyacrylonitrile solution, and then carrying out electrospinning; pre-oxidizing a membrane obtained by electrospinning at high temperature, then breaking the pre-oxidized membrane and dispersing the pre-oxidized membrane in water to form a pre-oxidized polyacrylonitrile staple fiber dispersion; (2) dissolving barium salt, ferric salt, cobalt salt, nickel salt, zirconium salt and yttrium salt in water to form an aqueous solution; after that, adding a certain amount of ethylene glycol and citric acid to chelate the metal salts so as to form a clear solution, adjusting the pH to 7-9 with ammonia water, heating and concentrating to form gel and then adding the pre-oxidized polyacrylonitrile staple fiber dispersion obtained in step (1), continuing to concentrate to form gel, and then removing the solvent at high temperature to prepare a precursor powder; and (3) calcining the precursor powder obtained in step (2) to obtain the ABO.sub.3 type high-entropy perovskite Ba.sub.x(FeCoNiZrY).sub.0.2O.sub.3-δ electrocatalytic material.

4. The method according to claim 3, wherein in step (1), the concentration of the polyacrylonitrile solution is 0.08-0.12 g/mL, and the condition of electrospinning is 15-20 kV.

5. The method according to claim 3, wherein in step (1), the pre-oxidation temperature is 150-200° C., and the pre-oxidation time is 2-5 hours.

6. The method according to claim 3, wherein in step (2), the cobalt salt comprises: Co(NO.sub.3).sub.2.Math.6H.sub.2O, with a concentration of 1.0-1.5 mg/mL; the nickel salt comprises: Ni(NO.sub.3).sub.2.Math.6H.sub.2O, with a concentration of 1.0-1.5 mg/mL; the ferric salt comprises: Fe(NO.sub.3).sub.3.Math.9H.sub.2O, with a concentration of 1.5-2.0 mg/mL; the zirconium salt comprises: Zr(NO.sub.3).sub.4.Math.5H.sub.2O, with a concentration of 1.5-2.0 mg/mL; the yttrium salt comprises: Y(NO.sub.3).sub.3.Math.6H.sub.2O, with a concentration of 1.5-2.0 mg/mL; and the barium salt comprises: Ba(NO.sub.3).sub.2, when x=0.9, the concentration of the barium salt is 4.0-5.0 mg/mL (excluding 5.0 mg/mL), and when x=1, the concentration of the barium salt is 5.0-5.5 mg/mL.

7. The method according to claim 3, wherein the concentration of the citric acid in the aqueous solution of step (2) is 10.0-15.0 mg/mL, and the concentration of the ethylene glycol is 5.0-10.0 mg/mL.

8. The method according to claim 3, wherein in step (3), the calcination temperature is 800-1200° C., and the calcination time is 5-10 hours.

9. A method for preparing ammonia gas, wherein the method comprises employing the electrocatalyst for ammonia synthesis according to claim 1 as an electrocatalyst.

Description

BRIEF DESCRIPTION OF FIGURES

[0037] FIG. 1 is a schematic diagram of an ABO.sub.3 type high-entropy perovskite Ba.sub.x(FeCoNiZrY).sub.0.2O.sub.3-δ electrocatalytic material and a preparation method thereof according to the present disclosure.

[0038] FIG. 2A is a scanning electron microscope (SEM) photograph of an ABO.sub.3 type high-entropy perovskite Ba.sub.x(FeCoNiZrY).sub.0.2O.sub.3-δ electrocatalytic material (x=0.9) prepared according to Example 1 of the present disclosure; and FIG. 2B is a scanning electron microscope (SEM) photograph of the ABO.sub.3 type high-entropy perovskite Ba.sub.x(FeCoNiZrY).sub.0.2O.sub.3-δ electrocatalytic material (x=1) prepared according to Example 2 of the present disclosure.

[0039] FIG. 3 is an X-ray diffractometer (XRD) spectrogram of the ABO.sub.3 type high-entropy perovskite Ba.sub.x(FeCoNiZrY).sub.0.2O.sub.3-δ electrocatalytic material prepared according to Examples land 2 of the present disclosure.

[0040] FIG. 4A shows the energy dispersive X-ray analysis (EDX) and inductively coupled plasma spectroscopy test (ICP) results of the ABO.sub.3 type high-entropy perovskite Ba.sub.x(FeCoNiZrY).sub.0.2O.sub.3-δ electrocatalytic material (x=0.9) prepared according to Example 1 of the present disclosure; and FIG. 4B shows the energy dispersive X-ray analysis (EDX) and inductively coupled plasma spectroscopy test (ICP) results of the ABO.sub.3 type high-entropy perovskite Ba.sub.x(FeCoNiZrY).sub.0.2O.sub.3-δ electrocatalytic material (x=1) prepared according to Example 2 of the present disclosure.

[0041] FIG. 5 is an X-ray photoelectron spectroscopy (XPS) curve of the ABO.sub.3 type high-entropy perovskite Ba.sub.x(FeCoNiZrY).sub.0.2O.sub.3-δ electrocatalytic material prepared according to Examples 1 and 2 of the present disclosure.

[0042] FIG. 6 is a performance diagram of the electrocatalytic reduction of nitrogen gas to ammonia gas of the ABO.sub.3 type high-entropy perovskite Ba.sub.x(FeCoNiZrY).sub.0.2O.sub.3-δ electrocatalytic material prepared according to Examples 1 and 2 of the present disclosure.

DETAILED DESCRIPTION

[0043] The present disclosure will be further described below in conjunction with specific examples. It should be understood that these examples are only used to illustrate the present disclosure and not to limit the scope of the present disclosure. In addition, it should be understood that after reading the contents taught in the present disclosure, those skilled in the art can make various changes or modifications to the present disclosure, and these equivalent forms also fall within the scope defined by the appended Claims of the present application.

Example 1

[0044] 1 g of polyacrylonitrile powder was dissolved in 10 mL of N, N-dimethylformamide for carrying out electrospinning under a voltage of 17 kV. The obtained membrane was pre-oxidized for 2 h at 200° C. Finally, the pre-oxidized membrane was broken for 0.5 h at 13000 rpm and then disposed in water to form a dispersion, and the concentration of the dispersion was 4.5 mg/mL.

[0045] 470.4 mg of Ba(NO.sub.3).sub.2, 116.4 mg of Co(NO.sub.3).sub.2.Math.6H.sub.2O, 116.3 mg of Ni(NO.sub.3).sub.2.Math.6H.sub.2O, 161.6 mg of Fe(NO.sub.3).sub.3.Math.9H.sub.2O, 171.7 mg of Zr(NO.sub.3).sub.4.Math.5H.sub.2O and 153.2 mg of Y(NO.sub.3).sub.3.Math.6H.sub.2O were dissolved in 100 mL of deionized water while stirring so as to obtain a clear and transparent solution. Subsequently, 1095.2 mg of citric acid and 707.6 mg of ethylene glycol were added, and the pH was adjusted to 9 with ammonia water. The above solution was concentrated into gel at 80° C. and then added with the pre-oxidized polyacrylonitrile dispersion with a mass concentration of 4.5 mg/L in an amount of 5 mL. After mixing, the solution was continued to be concentrated to form a uniformly dispersed gel-like precursor. The precursor was heated to 200° C. and dried for 5 h to obtain solid powder. Finally, the solid powder was calcined at 1000° C. for 5 h to obtain ABO.sub.3 type high-entropy perovskite Ba.sub.0.9(FeCoNiZrY).sub.0.2O.sub.3-δ.

[0046] The relevant process parameters in an electrochemical test method were as follows: ink was formed by uniformly mixing 6 mg of Ba.sub.x(FeCoNiZrY).sub.0.2O.sub.3-δ and an ethanol (1940 μL) solution of Nafion (5 wt %, 60 μL). 1×1 cm.sup.2 carbon paper was coated with 40 μL of the above ink and dried to prepare an electrode slice.

[0047] According to experimental testing, Ba.sub.0.9(FeCoNiZrY).sub.0.2O.sub.3-δ has nitrogen electric reduction performance. Within a certain overpotential range, the highest ammonia gas production and the highest Faraday efficiency are 24.37 μg h.sup.−1 mg.sup.−1.sub.cat and 11.70%.

[0048] 1 g of polyacrylonitrile powder was dissolved in 10 mL of N, N-dimethylformamide for carrying out electrospinning under a voltage of 17 kV. The obtained membrane was pre-oxidized for 2 h at 200° C. Finally, the pre-oxidized membrane was broken for 0.5 h at 13000 rpm and then disposed in water to form a dispersion, and the concentration of the dispersion was 4.5 mg/mL.

[0049] 522.7 mg of Ba(NO.sub.3).sub.2, 116.4 mg of Co(NO.sub.3).sub.2.Math.6H.sub.2O, 116.3 mg of Ni(NO.sub.3).sub.2.Math.6H.sub.2O, 161.6 mg of Fe(NO.sub.3).sub.3.Math.9H.sub.2O, 171.7 mg of Zr(NO.sub.3).sub.4.Math.5H.sub.2O and 153.2 mg of Y(NO.sub.3).sub.3.Math.6H.sub.2O were dissolved in 100 mL of deionized water while stirring so as to obtain a clear and transparent solution. Subsequently, 1152.8 mg of citric acid and 744.8 mg of ethylene glycol were added, and the pH was adjusted to 9 with ammonia water. The above solution was concentrated into gel at 80° C. and then added with the pre-oxidized polyacrylonitrile dispersion with a mass concentration of 4.5 mg/L in an amount of 5 mL. After mixing, the solution was continued to be concentrated to form a uniformly dispersed gel-like precursor. The precursor was heated to 200° C. and dried for 5 h to obtain solid powder. Finally, the solid powder was calcined at 1000° C. for 5 h to obtain ABO.sub.3 type high-entropy perovskite Ba(FeCoNiZrY).sub.0.2O.sub.3-δ.

[0050] According to the experimental testing described in Example 1, Ba(FeCoNiZrY).sub.0.2O.sub.3-δ has nitrogen electric reduction performance. Within a certain overpotential range, the highest ammonia gas production and the highest Faraday efficiency are 16.11 μg h.sup.−1 mg.sup.−1.sub.cat and 6.01%.

[0051] FIG. 1 is a schematic diagram of a preparation process of ABO.sub.3 type high-entropy perovskite Ba(FeCoNiZrY).sub.0.2O.sub.3-δ.

[0052] SEM, XRD, EDX, ICP, XPS, and electrochemical workstations were used to characterize the morphology features, electronic structure, and performance as a nitrogen gas reduction electrocatalyst of the ABO.sub.3 type high-entropy perovskite Ba(FeCoNiZrY).sub.0.2O.sub.3-δ electrocatalytic material obtained according to the present disclosure. The determination results were as follows:

[0053] (1) The SEM test results show (see FIG. 2) that the high-entropy perovskite Ba.sub.x(FeCoNiZrY).sub.0.2O.sub.3-δ has a lava-like morphology, and the pore size is about 300 nm.

[0054] (2) XRD test results show again (see FIG. 3) that the crystal structure of the high-entropy perovskite Ba.sub.x(FeCoNiZrY).sub.0.2O.sub.3-δ is a cubic phase structure, which conforms to the general structure of perovskite materials.

[0055] (3) EDX analysis and ICP analysis show (see FIG. 4) that the Ba, Fe, Co, Ni, Zr, Y and O elements on the surface of the high-entropy perovskite Ba.sub.x(FeCoNiZrY).sub.0.2O.sub.3-δ material are uniformly distributed, and the ratio of the surface metals conforms to a feed ratio. It further illustrates the successful synthesis of high-entropy perovskite.

[0056] (4) XPS test results further prove that the surface of the high-entropy perovskite Ba.sub.x(FeCoNiZrY).sub.0.2O.sub.3-δ material has Ba, Fe, Co, Ni, Zr, Y and O elements, as shown in FIG. 5.

[0057] (5) The electrochemical test results show that the prepared ABO.sub.3 type high-entropy perovskite Ba.sub.x(FeCoNiZrY).sub.0.2O.sub.3-δ materials all have excellent nitrogen reduction performance. When x=0.9, the Ba.sub.x(FeCoNiZrY).sub.0.2O.sub.3-δ has the highest ammonia gas production and the highest Faraday efficiency, which are 24.37 μg.Math.h.sup.−1.Math.mg.sup.−1.sub.cat and 11.70%, respectively, as shown in FIG. 6.

Example 3

[0058] 1.2 g of polyacrylonitrile powder was dissolved in 10 mL of N, N-dimethylformamide for carrying out electrospinning under a voltage of 17 kV. The obtained membrane was pre-oxidized for 5 h at 150° C. Finally, the pre-oxidized membrane was broken for 0.5 h at 13000 rpm and then disposed in water to form a dispersion, and the concentration of the dispersion was 4.5 mg/mL.

[0059] 522.7 mg of Ba(NO.sub.3).sub.2, 116.4 mg of Co(NO.sub.3).sub.2.Math.6H.sub.2O, 116.3 mg of Ni(NO.sub.3).sub.2.Math.6H.sub.2O, 161.6 mg of Fe(NO.sub.3).sub.3.Math.9H.sub.2O, 171.7 mg of Zr(NO.sub.3).sub.4.Math.5H.sub.2O and 153.2 mg of Y(NO.sub.3).sub.3.Math.6H.sub.2O were dissolved in 100 mL of deionized water while stirring so as to obtain a clear and transparent solution. Subsequently, 1152.8 mg of citric acid and 744.8 mg of ethylene glycol were added, and the pH was adjusted to 9 with ammonia water. The above solution was concentrated into gel at 80° C. and then added with the pre-oxidized polyacrylonitrile dispersion with a mass concentration of 4.5 mg/L in an amount of 5 mL. After mixing, the solution was continued to be concentrated to form a uniformly dispersed gel-like precursor. The precursor was heated to 150° C. and dried for 10 h to obtain solid powder. Finally, the solid powder was calcined at 850° C. for 5 h to obtain ABO.sub.3 type high-entropy perovskite Ba(FeCoNiZrY).sub.0.2O.sub.3-δ.

[0060] The morphology of the prepared Ba(FeCoNiZrY).sub.0.2O.sub.3-δ is similar to that of Example 2, and the electrocatalytic performance thereof is similar to that of Example 2.

Example 4

[0061] 1 g of polyacrylonitrile powder was dissolved in 10 mL of N, N-dimethylformamide for carrying out electrospinning under a voltage of 17 kV. The obtained membrane was pre-oxidized for 2 h at 200° C. Finally, the pre-oxidized membrane was broken for 0.5 h at 13000 rpm and then disposed in water to form a dispersion, and the concentration of the dispersion was 4.5 mg/mL.

[0062] 470.4 mg of Ba(NO.sub.3).sub.2, 116.4 mg of Co(NO.sub.3).sub.2.Math.6H.sub.2O, 116.3 mg of Ni(NO.sub.3).sub.2.Math.6H.sub.2O, 161.6 mg of Fe(NO.sub.3).sub.3.Math.9H.sub.2O, 171.7 mg of Zr(NO.sub.3).sub.4.Math.5H.sub.2O and 153.2 mg of Y(NO.sub.3).sub.3.Math.6H.sub.2O were dissolved in 100 mL of deionized water while stirring so as to obtain a clear and transparent solution. Subsequently, 1152.8 mg of citric acid and 744.8 mg of ethylene glycol were added, and the pH was adjusted to 9 with ammonia water. The above solution was concentrated into gel at 80° C. and then added with the pre-oxidized polyacrylonitrile dispersion with a mass concentration of 4.5 mg/L in an amount of 10 mL. After mixing, the solution was continued to be concentrated to form a uniformly dispersed gel-like precursor. The precursor was heated to 200° C. and dried for 5 h to obtain solid powder. Finally, the solid powder was calcined at 1100° C. for 5 h to obtain ABO.sub.3 type high-entropy perovskite Ba.sub.0.9(FeCoNiZrY).sub.0.2O.sub.3-δ.

[0063] The morphology of the prepared Ba.sub.0.9(FeCoNiZrY).sub.0.2O.sub.3-δ is similar to that of Example 1, and the electrocatalytic performance thereof is similar to that of Example 1.

Comparative Example 1

[0064] When the concentration of the polyacrylonitrile in step 1 was further increased, or the calcination temperature in step 2 was lower than 800° C., the high-entropy perovskite phase will be impure.

Comparative Example 2

[0065] When there was no step (1), the remaining operating parameters were the same as in those in Example 1 (the pre-oxidized polyacrylonitrile staple fiber dispersion was not needed in step (2)), and the prepared Ba.sub.x(FeCoNiZrY).sub.0.2O.sub.3-δ electrocatalytic material did not have the morphological structure as shown in FIG. 2, and was very poor in electrocatalytic performance.

[0066] Although the present disclosure has been disclosed as above with exemplary examples, it is not intended to limit the present disclosure. Anyone who is familiar with this technology can make various changes and modifications without departing from the spirit and scope of the present disclosure. Therefore, the protection scope of the present disclosure shall prevail as defined in the claims.