CN114261956A

CN114261956A - Photo-anode water-splitting electrolyte solution based on amino acid carbon dots

Info

Publication number: CN114261956A
Application number: CN202111498068.3A
Authority: CN
Inventors: 王红艳; 王纳; 张永帅
Original assignee: Shaanxi Normal University
Current assignee: Shaanxi Normal University
Priority date: 2021-12-09
Filing date: 2021-12-09
Publication date: 2022-04-01
Anticipated expiration: 2041-12-09
Also published as: CN114261956B

Abstract

The invention discloses a photoanode water decomposition electrolyte solution based on amino acid carbon dots, which is prepared by taking amino acid as a precursor and synthesizing a carbon dot aqueous solution by a hydrothermal method, wherein the raw materials are cheap and easy to obtain, the synthesis method is simple and quick, the product does not need a complex purification process, the obtained carbon dot aqueous solution can be directly used as the electrolyte solution and applied to the photoanode water decomposition, a traditional supporting electrolyte is not required to be additionally added, the system has excellent performance and good stability, the photocurrent value is greatly increased, the water decomposition efficiency of the photoanode is improved, and the photoanode water decomposition electrolyte solution is beneficial to actual production application and further mechanism exploration.

Description

Photo-anode water-splitting electrolyte solution based on amino acid carbon dots

Technical Field

The invention belongs to the technical field of carbon dot synthesis and water decomposition by a photoelectric anode, and particularly relates to a photo-anode water decomposition electrolyte solution based on amino acid carbon dots.

Background

With the rapid increase of population, the global consumption of fossil energy is faster and faster, and the problem of serious environmental pollution is solved, so that scientists accelerate the development of renewable clean energy. Solar energy has attracted great attention as an inexhaustible green energy source, and scientists are actively studying how to widely utilize and convert solar energy. Currently, hydrogen production by solar energy decomposition of water is considered as one of the most promising ways to obtain green energy. The photoelectrocatalysis water decomposition is mainly based on the research of hydrogen production and oxygen production by water cracking of a semiconductor photoelectrode. Among them, the oxygen generation process occurring in the photo-anode is one of the key bottlenecks for limiting the photoelectrocatalysis water decomposition to realize high efficiency, because the process needs to transfer 4 electrons and protons, so how to break through the photoelectrocatalysis water oxidation is the hotspot and difficulty of the current research. The traditional method is to modify the photoelectrode by strategies such as heteroatom doping, nano construction, heterojunction construction and the like so as to improve the effective separation of photogenerated electrons and holes in the system. However, the important composition of the electrolyte system in the photoelectrocatalytic process is often ignored.

In order to improve the performance of the photoanode, it seems more convenient and efficient to explore suitable novel electrolyte solutions. This is because the interaction of the electrolyte with the metal oxide interface can adjust the position of the conduction band edge of the photoelectrode, which plays a crucial role in determining the magnitude of the charge injection and current density of the photocurrent. The carbon dot is a nano structure containing a large number of oxygen atoms and hydrogen atoms, has excellent electrochemical properties as an electron donor and an electron acceptor, leads to chemiluminescence and electrochemiluminescence, and has wide application prospects in the fields of photoelectricity, catalysis, sensing and the like. The photoluminescent and photochemical properties of the carbon dots also make it an effective catalyst. The carbon dots are generally functionalized with COOH, COOR, OH groups, and the like on the surface and can be highly dispersed in water in a colloidal state. The colloidal nature of the carbon dots enables the establishment of an electron shell around the surface associated with the PEC process, which can induce specific motion of the carbon dots in the electron field. Thus, aqueous solutions of carbon dots have the potential to be used directly as electrolytes. The previous work of the subject group firstly uses EDTA-2 Na as a precursor to synthesize a carbon dot solution as an electrolyte solution for the photo-anode water decomposition, and the photocurrent value can reach 0.64mA/cm at the position of the applied voltage of 1.23V vs RHE²(Wang，H.Y.,Hu,R.,Wang,N.,Hu,G.L.,Wang,K.,Xie,W.H.,Cao R.Boosting photoanodic activity for water splitting in carbon dots aqueous solution without any traditional supporting electrolyte.Applied Catalysis B:Environmental.2021,296,120378.)。

Disclosure of Invention

The invention aims to provide a photoanode water-splitting electrolyte solution based on amino acid carbon points.

Aiming at the purposes, the photoanode water-splitting electrolyte solution based on amino acid carbon points is prepared by adding amino acid serving as a precursor into deionized water, performing ultrasonic treatment to completely dissolve the amino acid, transferring the solution into a reaction kettle, performing hydrothermal reaction at 160-250 ℃ for 6-10 hours, and performing centrifugation and filtration after the reaction is finished to obtain a carbon point water-splitting electrolyte solution, namely the photoanode water-splitting electrolyte solution.

The amino acid is any one of 3-aminopropionic acid, 4-aminobutyric acid, 5-aminopentanoic acid, 6-aminocaproic acid, 7-aminoheptanoic acid, 8-aminocaprylic acid, 9-aminononanoic acid, 10-aminoyeric acid, 11-aminoundecanoic acid, 12-aminododecanoic acid, glycine, alanine, valine, leucine, isoleucine, methionine, proline, tryptophan, serine, tyrosine, cysteine, phenylalanine, asparagine, glutamine, threonine, aspartic acid, glutamic acid, lysine, arginine, histidine, selenocysteine and pyrrolysine, and preferably any one of 3-aminopropionic acid, 4-aminobutyric acid, 6-aminocaproic acid, 7-aminoheptanoic acid and 8-aminocaprylic acid.

The concentration of amino acid in deionized water is preferably controlled to be 1-6 mol/L.

The photo-anode water-splitting electrolyte solution based on the amino acid carbon points is preferably subjected to a hydrothermal reaction at 180-200 ℃ for 6-8 hours.

The pH range of the carbon dot aqueous solution is 6-8.

The invention has the following beneficial effects:

according to the invention, amino acid is used as a precursor, a hydrothermal method is adopted to synthesize the carbon dot aqueous solution, the raw materials are cheap and easy to obtain, the synthesis method is simple and rapid, the product does not need a complex purification process, the obtained carbon dot aqueous solution can be directly used as an electrolyte solution and applied to water decomposition of the photoelectric anode, no traditional supporting electrolyte is additionally added, the system has excellent performance and good stability, the photocurrent value is greatly increased, the water decomposition efficiency of the photoelectric anode is improved, and the method is beneficial to practical production application and further mechanism exploration.

Drawings

FIG. 1 is a data showing the characterization of XRD of carbon spots synthesized from 3-aminopropionic acid as a precursor in example 1.

FIG. 2 is the IR characterization data of the carbon spots synthesized in example 1 using 3-aminopropionic acid as a precursor.

FIG. 3 is a C1S spectrum of XPS of carbon spots synthesized using 3-aminopropionic acid as a precursor in example 1.

FIG. 4 is a spectrum of XPS N1S showing the carbon point obtained by using 3-aminopropionic acid as a precursor in example 1.

FIG. 5 is a spectrum of XPS O1S showing the carbon point obtained by using 3-aminopropionic acid as a precursor in example 1.

FIG. 6 is an XPS survey of carbon spots synthesized using 3-aminopropionic acid as a precursor in example 1.

FIG. 7 is a fluorescence test chart of a carbon dot synthesized using 3-aminopropionic acid as a precursor in example 1.

FIG. 8 is a graph of the LSV curve of the carbon dot aqueous solution synthesized by using 3-aminopropionic acid as a precursor in example 1.

FIG. 9 is a graph of the LSV curve of the carbon dot solution synthesized by using 4-aminobutyric acid as a precursor in example 3.

FIG. 10 is a graph of the LSV curve of the carbon dot solution synthesized from 6-aminocaproic acid in example 5.

FIG. 11 is a graph of the LSV curve of the carbon dot solution synthesized by using 8-aminocaprylic acid as a precursor in example 7.

FIG. 12 is a graph of electrochemical On-Off I-T curve test of carbon dot solution synthesized by using 3-aminopropionic acid as a precursor in example 1.

FIG. 13 is a graph of electrochemical On-Off I-T curve test of carbon dot solution synthesized by using 4-aminobutyric acid as a precursor in example 3.

FIG. 14 is a graph of electrochemical On-Off I-T curve test of carbon dot solution synthesized with 6-aminocaproic acid as a precursor in example 5.

FIG. 15 is a graph of electrochemical On-Off I-T curve test of carbon dot solution synthesized by using 8-aminocaprylic acid as a precursor in example 7.

Detailed Description

The invention will be described in more detail below with reference to the following figures and specific examples, but the scope of the invention is not limited to these examples.

Example 1

Weighing 0.891g (10mmol) of 3-aminopropionic acid in a beaker, adding 10mL of deionized water for dissolving, carrying out ultrasonic treatment for 20min, transferring the obtained solution into a reaction kettle with a polytetrafluoroethylene lining, sealing the reaction kettle, carrying out hydrothermal reaction at 180 ℃ for 8h, centrifuging the reaction product for 10min at 10000r/min by using a centrifuge after the reaction is finished, and filtering the supernatant by using a filter membrane with the pore diameter of 220nm to obtain clear and transparent yellow liquid, namely a carbon dot aqueous solution, namely a photoanode aqueous decomposition electrolyte solution. The pH of the aqueous solution at the carbon point was measured to be 6.94 by a pH meter.

Freeze-drying the obtained carbon dot aqueous solution to obtain powder, and performing XRD characterization by using an X-ray powder diffractometer, wherein the result is shown in figure 1, a wide diffraction peak appears at 2 theta of 23.7 degrees, and the result is the result of stacking a large number of irregular carbon atoms; characterizing by an ultraviolet visible near-infrared spectrometer to obtain an infrared spectrogram shown in figure 2, wherein the periphery of the carbon point contains O-H, -COOH, N-H, O-C-N and other groups; and (3) characterizing by using a multifunctional imaging photoelectron spectrometer to obtain an XPS spectrum of the element C, N, O in figures 3-5 and a full spectrum in figure 6, and analyzing to obtain the valence state of each element in the carbon dots.

The fluorescence test chart of the obtained carbon dot aqueous solution is shown in FIG. 7, and it can be seen from the chart that the excitation-dependent photoluminescence of the carbon dot aqueous solution indicates that the carbon dot can be excited by irradiation of visible light.

Example 2

In the present example, hydrothermal reaction was carried out at 200 ℃ for 8 hours, and the other steps were the same as in example 1, to obtain a clear and transparent yellow liquid, i.e., a carbon dot aqueous solution, i.e., a photoanode aqueous electrolyte solution.

Example 3

In this example, 1.03g (10mmol) of 4-aminobutyric acid was used in place of 3-aminopropionic acid in example 1, and the other steps were the same as in example 1 to obtain a clear and transparent yellow liquid-an aqueous carbon dot solution, i.e., a photoanode aqueous electrolyte solution. The pH of the aqueous solution at the carbon point was measured to be 7.83 with a pH meter.

Example 4

In the present example, hydrothermal reaction was carried out at 200 ℃ for 8 hours, and the other steps were the same as in example 3, to obtain a clear and transparent yellow liquid, i.e., a carbon dot aqueous solution, i.e., a photoanode aqueous electrolyte solution.

Example 5

In this example, 1.31g (10mmol) of 6-aminocaproic acid was used in place of 3-aminopropionic acid in example 1, and the other steps were the same as in example 1 to obtain a clear and transparent yellow liquid-an aqueous solution of carbon dots, i.e., a photoanode aqueous electrolyte solution. The pH of the aqueous solution at the carbon point was measured by a pH meter to be 6.82.

Example 6

In the present example, hydrothermal reaction was carried out at 200 ℃ for 8 hours, and the other steps were the same as in example 5, to obtain a clear and transparent yellow liquid, i.e., a carbon dot aqueous solution, i.e., a photoanode aqueous electrolyte solution.

Example 7

In this example, 1.59g (10mmol) of 8-aminocaprylic acid was used in place of 3-aminopropionic acid in example 2, and the other steps were the same as in example 2 to obtain a clear and transparent yellow liquid-an aqueous solution of carbon dots, i.e., a photoanode aqueous splitting electrolyte solution. The pH of the aqueous solution at the carbon point was measured to be 6.10 with a pH meter.

Electrochemical tests were carried out using the aqueous solutions of carbon dots synthesized in examples 1, 3, 5 and 7, respectively, as electrolyte solutions, using an electrochemical workstation CHI660E, using Ag/AgCl as a reference electrode and a Pt electrode as a counter electrode, and using a 4 cm-length electrode²FTO plate coverage 2cm² WO₃And constructing a three-electrode system as a working electrode, inserting the three-electrode system into an electrolyte solution, connecting the electrode with an electrochemical workstation according to a wiring sequence, and applying a certain external voltage to perform photoelectrochemical test by taking light with wavelength of 420nm as a light source. LSV tests are respectively carried out under dark and light conditions, and the results are shown in FIGS. 8-11; the voltage is controlled at 0.75V, an On-Off I-T test is carried out,the lamp was turned on/off for 10 seconds, and the cycle was 10 times, as shown in FIGS. 12 to 15. From the LSV chart, the photocurrent of the aqueous solution of each carbon spot was sharply increased under the light irradiation, indicating that the carbon spot was excited under the light irradiation to promote the water decomposition. As can be seen from the On-Off I-T test chart, after light is added, the photocurrent is increased instantly, which indicates that the holes and the electrons are effectively and rapidly separated at the moment of illumination of the carbon dot aqueous solution, thereby improving the photoelectric water oxidation efficiency.

Claims

1. A photoanode water-splitting electrolyte solution based on amino acid carbon dots is characterized in that: adding amino acid serving as a precursor into deionized water, performing ultrasonic treatment to completely dissolve the amino acid, transferring the amino acid into a reaction kettle, performing hydrothermal reaction for 6-10 hours at 160-250 ℃, centrifuging and filtering after the reaction is finished to obtain a carbon dot aqueous solution, namely a photoanode aqueous decomposition electrolyte solution;

the amino acid is any one of 3-aminopropionic acid, 4-aminobutyric acid, 5-aminopentanoic acid, 6-aminocaproic acid, 7-aminoheptanoic acid, 8-aminocaprylic acid, 9-aminononanoic acid, 10-aminoyeric acid, 11-aminoundecanoic acid, 12-aminododecanoic acid, glycine, alanine, valine, leucine, isoleucine, methionine, proline, tryptophan, serine, tyrosine, cysteine, phenylalanine, asparagine, glutamine, threonine, aspartic acid, glutamic acid, lysine, arginine, histidine, selenocysteine and pyrrolysine.

2. The photoanode water-splitting electrolyte solution based on amino acid carbon dots of claim 1, wherein: the concentration of the amino acid in the deionized water is controlled to be 1-6 mol/L.

3. The photoanode water-splitting electrolyte solution based on amino acid carbon dots of claim 1, wherein: the amino acid is any one of 3-aminopropionic acid, 4-aminobutyric acid, 6-aminocaproic acid, 7-aminoheptanoic acid and 8-aminocaprylic acid.

4. The photoanode water-splitting electrolyte solution based on amino acid carbon dots of claim 3, wherein: carrying out hydrothermal reaction for 6-8 hours at 180-200 ℃.

5. The photoanode water-splitting electrolyte solution based on amino acid carbon dots of claim 1, wherein: the pH range of the carbon dot aqueous solution is 6-8.