Cuprous oxide-based composite material, and preparation method and application thereof

Abstract

This invention belongs to the field of photoelectrocatalysis technology, specifically relating to a cuprous oxide-based composite material, its preparation method, and its applications. The invention provides a cuprous oxide-based composite material comprising a p-type cuprous oxide layer and an n-type cuprous oxide layer sequentially stacked; the p-type and n-type cuprous oxide layers form a heterojunction. By stacking the p-type and n-type cuprous oxide layers and forming a heterojunction between them, this invention can further improve the photostability and charge separation efficiency of the composite material.

Description

Technical Field

[0001] This invention belongs to the field of photoelectrocatalysis technology, specifically relating to a cuprous oxide-based composite material, its preparation method, and its application. Background Technology

[0002] Since the Industrial Revolution, the concentration of carbon dioxide in the atmosphere has increased from 275 ppm to 400 ppm. In recent years, it has been discovered that carbon dioxide can be reduced to chemical fuels through photoelectrocatalysis. Photoelectrochemical conversion of carbon dioxide using solar energy can effectively achieve carbon neutrality.

[0003] In solar photoelectrochemical (PEC) systems, the photocathode is primarily a p-type semiconductor. However, semiconductors capable of absorbing visible light and possessing high charge separation efficiency are few in number. Furthermore, carbon dioxide, with its linear and centrosymmetric structure, is very stable, requiring approximately 750 kJ / mol to break the initial C=O bond.

[0004] The main challenges of photoelectrocatalytic carbon dioxide reduction (CCO) lie in the inherent stability of carbon dioxide, the low potential of the CCO reduction reaction, and the low selectivity of the reduction products. In a typical photoelectrocatalytic CCO reduction reaction, electrons reduce carbon dioxide to various carbon fuels, such as carbon monoxide and methane. During the reaction, the catalyst plays a crucial role in providing high energy to the charge carrier and breaking the C=O bonds of carbon dioxide. Several factors are typically considered when selecting catalysts for photoelectrocatalytic CCO reduction, such as the absorption efficiency of sunlight, a sufficiently negative conduction band for CCO reduction, and photostability. Therefore, photoelectrocatalysts with high selectivity, high stability, and excellent activity are desired.

[0005] Cuprous oxide is a p-type semiconductor with a direct band gap of 2–2.2 eV, high carrier mobility, and a sufficient number of copper active sites for carbon dioxide activation. Furthermore, cuprous oxide can absorb a wide range of visible light and exhibits low toxicity, low processing cost, and high natural abundance. These advantages make it a primary catalyst material for photoelectrochemical carbon dioxide reduction. However, the slow charge transfer, low charge separation efficiency, and poor stability of cuprous oxide also limit its practical application in photoelectrochemical carbon dioxide reduction. Summary of the Invention

[0006] The purpose of this invention is to provide a cuprous oxide-based composite material, its preparation method, and its application. The cuprous oxide-based composite material provided by this invention has high photostability and excellent charge separation efficiency of photogenerated electron / hole pairs.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] This invention provides a cuprous oxide-based composite material, comprising a substrate and a p-type cuprous oxide layer and an n-type cuprous oxide layer sequentially stacked on the substrate surface;

[0009] The p-type cuprous oxide layer and the n-type cuprous oxide layer form a heterojunction;

[0010] The cuprous oxide-based composite material is used for photoelectrocatalytic carbon dioxide reduction.

[0011] Preferably, the thickness of the p-type cuprous oxide layer is 1.16~2.7 μm; the thickness of the n-type cuprous oxide layer is 0.15~0.29 μm.

[0012] The mass ratio of the p-type cuprous oxide layer to the n-type cuprous oxide layer is 15:2 to 35:1.

[0013] This invention also provides a method for preparing the cuprous oxide-based composite material described above, comprising the following steps:

[0014] The first water-soluble copper salt solution, the first complexing agent solution, and the first pH adjuster are mixed to obtain a first sedimentation solution with a pH value of 9-11;

[0015] The second water-soluble copper salt solution, the second complexing agent solution, and the second pH adjuster are mixed to obtain a second sedimentation solution with a pH value of 4.5~5.4;

[0016] Using the first deposition solution as the deposition solution, a first electrochemical deposition is performed on the substrate surface to obtain a substrate with a p-type cuprous oxide layer deposited on it;

[0017] Using the second deposition solution as the deposition solution, a second electrochemical deposition is performed on the surface of the p-type cuprous oxide layer to obtain the cuprous oxide-based composite material.

[0018] Preferably, the water-soluble copper salt in the first water-soluble copper salt solution includes copper sulfate;

[0019] The complexing agent in the first complexing agent solution includes lactic acid.

[0020] Preferably, the concentration of the water-soluble copper salt in the first water-soluble copper salt solution is 0.18~0.22 mol / L; and the concentration of the complexing agent in the first complexing agent solution is 1.35~1.65 mol / L.

[0021] The volume ratio of the first water-soluble copper salt solution to the first complexing agent solution is 1:1.

[0022] Preferably, the water-soluble copper salt in the second water-soluble copper salt solution includes copper acetate;

[0023] The complexing agent in the second complexing agent solution includes acetic acid.

[0024] Preferably, the concentration of the water-soluble copper salt in the second water-soluble copper salt solution is 0.035~0.045 mol / L; and the concentration of the complexing agent in the second complexing agent solution is 0.15~0.17 mol / L.

[0025] The volume ratio of the second water-soluble copper salt solution to the second complexing agent solution is 1:1.

[0026] Preferably, the conditions for the first electrochemical deposition include:

[0027] Using a substrate as the working electrode, a platinum sheet electrode as the counter electrode, and a silver / silver chloride electrode as the reference electrode, a constant voltage mode was employed, with a fixed voltage of -0.45 to -0.55 V vs. the reference electrode, and a deposited charge of 0.3 to 0.7 mAh / cm³. 2 ;

[0028] The temperature of the first electrochemical deposition is 55~65 ℃.

[0029] Preferably, the conditions for the second electrochemical deposition include:

[0030] Using a substrate with deposited p-type cuprous oxide as the working electrode, a platinum sheet electrode as the counter electrode, and a silver / silver chloride electrode as the reference electrode, a constant voltage mode was employed, with a fixed voltage of 0.018–0.022 V vs. the reference electrode, and a deposited charge of 0.02–0.04 mAh / cm³. 2 ;

[0031] The temperature of the second electrochemical deposition is 68~72 ℃.

[0032] The present invention also provides the application of the cuprous oxide-based composite material described in the above technical solution or the cuprous oxide-based composite material prepared by the preparation method described in the above technical solution as a photoelectrocatalytic material in photoelectrocatalytic carbon dioxide reduction.

[0033] This invention provides a cuprous oxide-based composite material, comprising a substrate and p-type and n-type cuprous oxide layers sequentially stacked on the substrate surface; the p-type and n-type cuprous oxide layers form a heterojunction; the cuprous oxide-based composite material is used for photoelectrocatalytic carbon dioxide reduction. This invention improves the high electron / hole recombination rate by stacking p-type and n-type cuprous oxide layers and forming a heterojunction between them. This heterojunction allows photogenerated electrons to move from the internal electric field to the n-type cuprous oxide layer, while holes move to the p-type cuprous oxide layer. The n-type cuprous oxide layer covering the surface of the p-type cuprous oxide layer forms a two-layer structure, preventing the p-type cuprous oxide layer from being directly exposed to light and directly contacting the electrolyte, thus mitigating problems such as photocorrosion. In practical applications, the cuprous oxide-based composite material is used in photoelectrocatalytic carbon dioxide reduction. In the p / n heterojunction, the electron-rich n-type semiconductor directly contacts CO2, thereby achieving efficient charge transfer and improving photocatalytic activity. This further enhances the photostability and charge separation efficiency of the composite material. Attached Figure Description

[0034] Figure 1 A flowchart of the preparation method provided by this invention;

[0035] Figure 2 The XRD (X-ray diffraction) patterns of p-type cuprous oxide and p / n heterojunction cuprous oxide obtained in Example 1 are shown.

[0036] Figure 3 The images shown are SEM (scanning electron microscope) images of p-type cuprous oxide and p / n heterojunction cuprous oxide obtained in Example 1; where... Figure 3 ac is p-type cuprous oxide. Figure 3 df is a p / n heterojunction cuprous oxide;

[0037] Figure 4 ab are HRTEM (high-resolution transmission electron microscopy) images of p-type cuprous oxide obtained in Example 1;

[0038] Figure 4 ce is the EDS (energy-dispersive X-ray diffraction) spectrum of p-type cuprous oxide obtained in Example 1;

[0039] Figure 5 a is an HRTEM (high-resolution transmission electron microscope) image of cuprous oxide in a p / n heterojunction obtained in Example 1;

[0040] Figure 5 bd is the EDS (energy-dispersive X-ray diffraction) spectrum of the p / n heterojunction cuprous oxide obtained in Example 1;

[0041] Figure 6ac represents the XPS (X-ray photoelectron spectroscopy) images of p-type cuprous oxide and p / n heterojunction cuprous oxide obtained in Example 1;

[0042] Figure 6 d represents the UV-Vis absorption spectra of p-type cuprous oxide and p / n heterojunction cuprous oxide obtained in Example 1;

[0043] Figure 7 a shows the photocurrent density test results of p-type cuprous oxide and p / n heterojunction cuprous oxide obtained in Example 1 at different potentials;

[0044] Figure 7 b is the photocurrent density test diagram of p-type cuprous oxide and p / n heterojunction cuprous oxide obtained in Example 1 at a constant potential of 0.65 V vs. RHE;

[0045] Figure 8 The Mott-Schottky curves are for the p-type cuprous oxide and the p / n heterojunction cuprous oxide obtained in Example 1.

[0046] Figure 9 a represents the wavelength-photocurrent curves of p-type cuprous oxide and p / n heterojunction cuprous oxide obtained in Example 1;

[0047] Figure 9 b is the incident photon current conversion efficiency (IPCE) curve of p-type cuprous oxide and p / n heterojunction cuprous oxide obtained in Example 1;

[0048] Figure 9 c represents the bandgap curves of p-type cuprous oxide and p / n heterojunction cuprous oxide obtained in Example 1;

[0049] Figure 9 d represents the electrochemical impedance curves of p-type cuprous oxide and p / n heterojunction cuprous oxide obtained in Example 1;

[0050] Figure 10 a is the current-time curve and yield-time curve of the CO2 reduction reaction of the p / n heterojunction cuprous oxide electrode obtained in Example 1, which are continuous electrocatalytic-photoelectrocatalytic CO2 reduction reactions.

[0051] Figure 10 b is the product yield-time curve of the photocatalytic CO2 reduction reaction obtained by the p / n heterojunction cuprous oxide electrode obtained in Example 1 under the condition of no external bias voltage;

[0052] Figure 10 c represents the p / n heterojunction cuprous oxide obtained in Example 1 at 0.75 V in the absence of light. RHE 0.45 V RHE and 0.15 V RHEThree sets of product yield-time curves for electrocatalytic reduction of CO2 under applied bias;

[0053] Figure 10 d represents the p / n heterojunction cuprous oxide electrode obtained in Example 1 under illumination and in the presence of 0.15V. RHE Current-time curves and related product (CH4 and CO) yield / yield-time curves for the photoelectrocatalytic CO2 reduction reaction under applied bias. Detailed Implementation

[0054] This invention provides a cuprous oxide-based composite material, comprising a substrate and a p-type cuprous oxide layer and an n-type cuprous oxide layer sequentially stacked on the substrate surface;

[0055] The p-type cuprous oxide layer and the n-type cuprous oxide layer form a heterojunction;

[0056] The cuprous oxide-based composite material is used for photoelectrocatalytic carbon dioxide reduction.

[0057] In this invention, the thickness of the p-type cuprous oxide layer is preferably 1.16~2.7 μm, more preferably 1.5~2.5 μm, and even more preferably 1.8~2.0 μm; the thickness of the n-type cuprous oxide layer is preferably 0.15~0.29 μm, more preferably 0.18~0.25 μm, and even more preferably 0.20~0.23 μm.

[0058] In this invention, the preferred mass ratio of the p-type cuprous oxide layer to the n-type cuprous oxide layer is 15:2-35:1.

[0059] This invention also provides a method for preparing the cuprous oxide-based composite material described above, comprising the following steps:

[0060] The first water-soluble copper salt solution, the first complexing agent solution, and the first pH adjuster are mixed to obtain a first sedimentation solution with a pH value of 9-11;

[0061] The second water-soluble copper salt solution, the second complexing agent solution, and the second pH adjuster are mixed to obtain a second sedimentation solution with a pH value of 4.5~5.4;

[0062] Using the first deposition solution as the deposition solution, a first electrochemical deposition is performed on the substrate surface to obtain a substrate with a p-type cuprous oxide layer deposited on it;

[0063] Using the second deposition solution as the deposition solution, a second electrochemical deposition is performed on the surface of the p-type cuprous oxide layer to obtain the cuprous oxide-based composite material.

[0064] In this invention, unless otherwise specified, all raw materials used in the preparation are commercially available products well known to those skilled in the art.

[0065] The present invention mixes a first water-soluble copper salt solution, a first complexing agent solution and a first pH adjuster to obtain a first sedimentation solution with a pH value of 9 to 11.

[0066] In this invention, the water-soluble copper salt in the first water-soluble copper salt solution preferably includes copper sulfate; the complexing agent in the first complexing agent solution preferably includes lactic acid. In this invention, the solvents in both the first water-soluble copper salt solution and the first complexing agent solution are preferably ultrapure water.

[0067] In this invention, the concentration of water-soluble copper salt in the first water-soluble copper salt solution is preferably 0.18~0.22 mol / L; the concentration of complexing agent in the first complexing agent solution is preferably 1.35~1.65 mol / L; and the volume ratio of the first water-soluble copper salt solution to the first complexing agent solution is 1:1.

[0068] In this invention, the pH adjuster preferably comprises a sodium hydroxide solution; the molar concentration of the sodium hydroxide solution is preferably 0.4 mol / L. This invention does not impose a specific limit on the amount of the pH adjuster used, as long as a sediment with the desired pH value is obtained.

[0069] The present invention does not have any special limitations on the first mixing process, and any process known to those skilled in the art can be used.

[0070] The present invention mixes a second water-soluble copper salt solution, a second complexing agent solution and a second pH adjuster to obtain a second sedimentation solution with a pH value of 4.5 to 5.4.

[0071] In this invention, the water-soluble copper salt in the second water-soluble copper salt solution preferably includes copper acetate; the complexing agent in the second complexing agent solution preferably includes acetic acid. In this invention, the solvents in both the second water-soluble copper salt solution and the second complexing agent solution are preferably ultrapure water.

[0072] In this invention, the concentration of the water-soluble copper salt in the second water-soluble copper salt solution is preferably 0.035~0.045 mol / L; the concentration of the complexing agent in the second complexing agent solution is preferably 0.15~0.17 mol / L; and the volume ratio of the second water-soluble copper salt solution to the second complexing agent solution is preferably 1:1.

[0073] In this invention, the pH adjuster preferably comprises a sodium hydroxide solution; the molar concentration of the sodium hydroxide solution is preferably 0.4 mol / L. This invention does not impose a specific limit on the amount of the pH adjuster used, as long as a sediment with the desired pH value is obtained.

[0074] The present invention does not have any special limitations on the second mixing process, and any process known to those skilled in the art can be used.

[0075] In this invention, there is no restriction on the order of the first mixing and the second mixing.

[0076] After obtaining the first deposition solution, the present invention uses the first deposition solution as the deposition solution to perform a first electrochemical deposition on the substrate surface to obtain a substrate with a p-type cuprous oxide layer deposited.

[0077] In this invention, the substrate preferably comprises conductive glass.

[0078] Prior to the first electrochemical deposition, the present invention preferably includes pretreatment of the substrate; the pretreatment preferably includes:

[0079] The conductive glass was ultrasonically washed with acetone, deionized water and anhydrous ethanol in sequence, with each ultrasonic wash lasting no less than 30 minutes. Then it was rinsed with deionized water and anhydrous ethanol at least 3 times. After being purged with nitrogen and dried, it was placed in an oven to dry for no less than 15 minutes to obtain the pretreated conductive glass.

[0080] In this invention, the conditions for the first electrochemical deposition preferably include:

[0081] Using a substrate as the working electrode, a platinum sheet electrode as the counter electrode, and a silver / silver chloride electrode as the reference electrode, a constant voltage mode was employed, with a fixed voltage of -0.45 to -0.55 V vs. the reference electrode, and a deposited charge of 0.3 to 0.7 mAh / cm³. 2 ;

[0082] The temperature of the first electrochemical deposition is 55~65 ℃.

[0083] In this invention, the first electrochemical deposition is preferably performed using an electrochemical workstation CHI-760E.

[0084] Following the first electrochemical deposition, the present invention preferably further includes washing and drying the obtained deposited material. The present invention does not have specific limitations on the washing and drying process; any process well known to those skilled in the art can be used.

[0085] After obtaining a substrate with a p-type cuprous oxide layer deposited thereon, the present invention uses the second deposition solution as the deposition solution to perform a second electrochemical deposition on the surface of the p-type cuprous oxide layer to obtain the cuprous oxide-based composite material.

[0086] In this invention, the conditions for the second electrochemical deposition preferably include:

[0087] Using a substrate with deposited p-type cuprous oxide as the working electrode, a platinum sheet electrode as the counter electrode, and a silver / silver chloride electrode as the reference electrode, a constant voltage mode was employed, with a fixed voltage of 0.018–0.022 V vs. the reference electrode, and a deposited charge of 0.02–0.04 mAh / cm³. 2 ;

[0088] The temperature of the second electrochemical deposition is 68~72 ℃.

[0089] In this invention, the second electrochemical deposition is preferably performed using an electrochemical workstation CHI-760E.

[0090] Following the second electrochemical deposition, the present invention preferably further includes washing and drying the obtained deposited material. The present invention does not have specific limitations on the washing and drying process; any process well known to those skilled in the art can be used.

[0091] The process flow diagram of the preparation method provided by this invention is as follows: Figure 1 As shown.

[0092] This invention also provides the application of the cuprous oxide-based composite material described in the above-described technical solutions, or the cuprous oxide-based composite material prepared by the preparation method described in the above-described technical solutions, as a photoelectrocatalytic material in the photoelectrocatalytic reduction of carbon dioxide. This invention does not impose any particular limitation on the specific implementation of the application; any method well-known to those skilled in the art can be used. In this invention, the photoelectrocatalytic material is preferably used in the photoelectrocatalytic reduction of carbon dioxide.

[0093] To further illustrate the present invention, a cuprous oxide-based composite material, its preparation method, and its application are described in detail below with reference to the accompanying drawings and embodiments. However, these descriptions should not be construed as limiting the scope of protection of the present invention.

[0094] Example 1

[0095] The conductive glass was ultrasonically washed with acetone, deionized water and anhydrous ethanol in sequence, with each ultrasonic wash lasting 30 min. Then it was rinsed three times with deionized water and anhydrous ethanol, purged with nitrogen and dried, and then placed in an oven to dry for 15 min to obtain the pretreated conductive glass.

[0096] A 100 mL solution of copper sulfate with a concentration of 0.2 mol / L and a 100 mL solution of lactic acid with a concentration of 1.5 mol / L were mixed. The pH of the mixture was adjusted to 10 using a 0.4 mol / L sodium hydroxide solution to obtain the first sediment.

[0097] A 100 mL solution of copper acetate with a concentration of 0.04 mol / L and a 100 mL solution of acetic acid with a concentration of 0.16 mol / L were mixed. The pH of the mixture was adjusted to 4.9 using a 0.4 mol / L sodium hydroxide solution to obtain the second sedimentation solution.

[0098] Using pretreated conductive glass as the working electrode, a platinum sheet electrode as the counter electrode, and a silver / silver chloride electrode as the reference electrode, and with the first deposition solution as the deposition solution, the first electrochemical deposition was performed using an electrochemical workstation CHI-760E. A constant voltage mode was employed, with a fixed voltage of -0.5 V vs. the reference electrode, controlling the deposition charge at 0.5 mAh / cm². 2 The temperature of the first electrochemical deposition is 60 °C. After the first electrochemical deposition, the deposited material is rinsed with deionized water and dried at room temperature to obtain a substrate with a p-type cuprous oxide layer deposited on it.

[0099] A conductive glass electrode with a p-type cuprous oxide layer was used as the working electrode, a platinum sheet electrode as the counter electrode, and a silver / silver chloride electrode as the reference electrode. A second electrochemical deposition was performed using a CHI-760E electrochemical workstation in constant voltage mode, with a fixed voltage of 0.02 V vs. the reference electrode, and the deposition charge was controlled at 0.03 mAh / cm³. 2 The temperature of the second electrochemical deposition is 72 °C. After the second electrochemical deposition, the deposited material is rinsed with deionized water and dried at room temperature to obtain the cuprous oxide-based composite material (p / n heterojunction cuprous oxide).

[0100] Performance testing

[0101] Test Example 1

[0102] X-ray diffraction (XRD) was performed on the p-type cuprous oxide and p / n heterojunction cuprous oxide obtained in Example 1. The XRD patterns are shown below. Figure 2 As shown;

[0103] from Figure 2 It can be seen that the XRD peaks are mainly caused by the cuprous oxide and tin oxide substrates. Specifically, the diffraction peaks at 29.9°, 36.72°, 42.56°, and 73.8° are attributed to the (110), (111), (200), and (311) crystal planes of cuprous oxide, respectively. The p-type cuprous oxide and p / n heterojunction cuprous oxide samples have crystalline phases and no obvious peak positions or intensity changes.

[0104] Test Example 2

[0105] Scanning electron microscopy (SEM) was performed on the p-type cuprous oxide and p / n heterojunction cuprous oxide obtained in Example 1. The SEM images are shown below. Figure 3 As shown, where Figure 3 ac is p-type cuprous oxide. Figure 3 df is a p / n heterojunction cuprous oxide;

[0106] from Figure 3 As can be seen from ab, p-type cuprous oxide nanoparticles are uniformly and densely deposited on the relatively smooth conductive glass FTO surface, and the p-type cuprous oxide film is composed of tiny crystals with sharp pyramid shapes.

[0107] from Figure 3 As can be seen from the diagram, the ultrathin n-type cuprous oxide protective layer on the p-type cuprous oxide surface makes the p-type cuprous oxide film surface smoother; the cross-section is shown in the diagram. Figure 3 c and 3f show that by controlling the amount of deposited charge, the average thicknesses of p-type and n-type cuprous oxide are 1.93 μm and 0.22 μm, respectively. In addition, the grain size of p / n heterojunction cuprous oxide is smaller than that of the original p-type cuprous oxide, exposing more active crystal faces and retaining sufficient carbon dioxide adsorption sites for carbon dioxide reduction.

[0108] Test Example 3

[0109] Figure 4 ab are HRTEM images of p-type cuprous oxide obtained in Example 1; it can be seen that the lattice spacing of 0.308 nm corresponds to the (110) crystal plane of cuprous oxide;

[0110] Figure 5 a is the HRTEM image of the p / n heterojunction cuprous oxide obtained in Example 1. It can be seen that the HRTEM results of the p / n heterojunction cuprous oxide show that the lattice spacing is 0.301 nm, which corresponds to the (110) crystal plane of cuprous oxide.

[0111] p-type cuprous oxide ( Figure 4 ce) and p / n heterojunction cuprous oxide ( Figure 5 The EDS mapping results of bd also confirmed the uniform distribution of copper and oxygen elements.

[0112] Test Example 4

[0113] Figure 6 ac represents the XPS spectra of p-type cuprous oxide and p / n heterojunction cuprous oxide obtained in Example 1;

[0114] like Figure 6 As shown in the full spectrum, copper and oxygen are the fundamental components of p-type cuprous oxide and p / n heterojunction cuprous oxide, which has been verified by XRD and EDS mapping results; in the Cu 2p spectrum, as... Figure 6As shown in b, the p-type cuprous oxide sample has two peaks at 952.2 eV and 932.4 eV, with a binding energy difference of 19.8 eV, corresponding to Cu + 2p1 / 2 and Cu + 2p3 / 2; in addition, the two satellite peaks at 954.6 eV and 935.1 eV are attributed to Cu, respectively. 2+ 2p 1 / 2 and Cu 2+ 2p 3 / 2 ;

[0115] The p / n heterojunction cuprous oxide exhibits two peaks at 952.4 eV and 932.5 eV, with a binding energy difference of 19.9 eV, originating from Cu. + 2p 1 / 2 and Cu + 2p 3 / 2 Furthermore, the two satellite peaks at 954.8 eV and 934.6 eV are attributed to Cu, respectively. 2+ 2p 3 / 2 and Cu 2+ 2p 3 / 2 Clearly, p-type cuprous oxide and p / n heterojunction cuprous oxide contain primary-state Cu. + and a small amount of Cu 2+ ;

[0116] like Figure 6 As shown in Figure c, in the O 1s spectrum, p-type cuprous oxide exhibits two peaks at 535.5 eV and 531.7 eV, attributed to chemisorbed oxygen and lattice oxygen, respectively. However, the p / n heterojunction cuprous oxide sample displays three peaks at 535.5 eV, 531.4 eV, and 530.5 eV, attributed to chemisorbed oxygen, cuprous oxide lattice oxygen, and copper oxide lattice oxygen, respectively.

[0117] Test Example 5

[0118] Figure 6 Figure d shows the UV-Vis absorption spectra of the p-type cuprous oxide and the p / n heterojunction cuprous oxide obtained in Example 1. It can be seen that both p-type and p / n heterojunction cuprous oxide exhibit visible light response. Furthermore, the light absorption of the p / n heterojunction cuprous oxide is stronger than that of the p-type cuprous oxide in the wavelength range of 350–600 nm. Clearly, the p / n heterojunction of cuprous oxide improves light utilization and extends the absorption edge to 641 nm.

[0119] Test Example 6

[0120] Figure 7 Photocurrent density test diagrams of p-type cuprous oxide and p / n heterojunction cuprous oxide obtained in Example 1 at different potentials;

[0121] The test was conducted using a three-electrode system. The counter electrode was platinum, the reference electrode was silver / silver chloride, and the working electrodes were conductive glass loaded with p-type cuprous oxide and conductive glass loaded with p / n heterojunction cuprous oxide. The electrolyte was a mixture of 0.1 mol / L tetrabutylammonium hexafluorophosphate / acetonitrile and 0.1 mol / L triethanolamine / acetonitrile solution.

[0122] from Figure 7 As can be seen, the photocurrent density of p / n heterojunction cuprous oxide is significantly higher than that of p-type cuprous oxide. The p / n heterojunction cuprous oxide exhibits the maximum photocurrent density of -0.35 mA / cm² at 0.15 V vs. RHE. 2 It is p-type cuprous oxide (-0.2 mA / cm). 2 The photocurrent of cuprous oxide in the p / n heterojunction is 1.75 times that of the previous generation, and the significant increase is mainly due to efficient charge separation.

[0123] Figure 7 b shows the photocurrent density test at a constant potential of 0.65 V vs. RHE, which confirms the excellent stability of cuprous oxide.

[0124] Test Example 7

[0125] Figure 8 The Mott-Schottky curves are for the p-type cuprous oxide and the p / n heterojunction cuprous oxide obtained in Example 1.

[0126] The test was conducted using a three-electrode system, with conductive glass loaded with p-type cuprous oxide and conductive glass loaded with p / n heterojunction cuprous oxide as working electrodes, platinum as the counter electrode, silver / silver chloride as the reference electrode, and 0.1 mol / L tetrabutylammonium hexafluorophosphate / acetonitrile as the electrolyte.

[0127] from Figure 8 It can be seen that the flat-band potentials of p-type cuprous oxide and p / n heterojunction cuprous oxide are 0.802 V and 0.882 V, respectively. The flat-band potentials are infinitely close to the bottom of the valence band of the semiconductor material, indicating the valence band positions of p-type and p / n heterojunction cuprous oxide. The p / n heterojunction cuprous oxide possesses a flat-band position that is more conducive to photoelectron transport.

[0128] Test Example 8

[0129] Figure 9 a represents the wavelength-photocurrent curves of p-type cuprous oxide and p / n heterojunction cuprous oxide obtained in Example 1. Figure 9It can be seen that the p-type cuprous oxide and p / n heterojunction cuprous oxide samples have photocurrent response in the range of 300 nm to 600 nm, and the photocurrent density of p-type cuprous oxide and p / n heterojunction cuprous oxide increases with the increase of applied bias voltage.

[0130] Figure 9 b represents the incident photon current conversion efficiency (IPCE) curves for p-type cuprous oxide and p / n heterojunction cuprous oxide obtained in Example 1, as shown below. Figure 9 As shown in b, the photocurrent density of p / n heterojunction cuprous oxide is significantly greater than that of p-type cuprous oxide. This is because the n-type cuprous oxide protective layer on the p-type cuprous oxide improves the charge separation efficiency of photogenerated electron / hole pairs in the p / n heterojunction cuprous oxide. The IPCE values ​​of both p-type and p / n heterojunction cuprous oxide gradually increase with increasing voltage.

[0131] Figure 9 c represents the bandgap curves of p-type cuprous oxide and p / n heterojunction cuprous oxide obtained in Example 1, as shown below. Figure 9 As shown in Figure c, the IPCE value of p / n heterojunction cuprous oxide is greater than that of p-type cuprous oxide. The band gaps of p-type and p / n heterojunction cuprous oxide can be evaluated using the Tauc plotting method; the band gap of the p-type cuprous oxide sample is 2.24 eV, while the band gap of the p / n heterojunction cuprous oxide sample is narrower at 2.2 eV. The narrow band gap of p / n heterojunction cuprous oxide is beneficial for visible light absorption, which has potential benefits for practical applications of solar energy conversion.

[0132] Test Example 9

[0133] Figure 9 Figure d shows the electrochemical impedance spectroscopy (EIS) curves of p-type cuprous oxide and p / n heterojunction cuprous oxide obtained in Example 1. It can be seen that due to the formation of the p / n heterojunction, the charge transfer resistance in the p / n heterojunction cuprous oxide is reduced, holes and electrons are far away from the interface, the space charge region is widened, and the internal electric field is enhanced. Therefore, the internal electric field increases the resistance to electron diffusion, while the diffusion current is significantly reduced. At this time, under the action of the internal electric field, a minority carrier drift current is formed in the p / n heterojunction region, and the drift current is greater than the diffusion current, which can be ignored. Therefore, the p / n heterojunction exhibits low resistance.

[0134] Test Case 10

[0135] Figure 10 The graph shows the relationship between the yield and production rate of the CO2 reduction reaction of the p / n heterojunction cuprous oxide obtained in Example 1.

[0136] in, Figure 10a is the current-time curve and the yield-time curve of the related reaction products (CH4 and CO) for the continuous electrocatalytic-photoelectrocatalytic CO2 reduction reaction of the prepared p / n heterojunction cuprous oxide electrode. Figure 10 b is the product yield-time curve of the photocatalytic CO2 reduction reaction of the p / n heterojunction cuprous oxide electrode without external bias voltage; Figure 10 c represents the p / n heterojunction cuprous oxide electrode under no light illumination, with three sets of applied bias voltages (0.75 V). RHE 0.45 V RHE 0.15V RHE Product yield-time curve of electrocatalytic CO2 reduction reaction; Figure 10 d represents the cuprous oxide electrode in a p / n heterojunction under illumination and in the presence of 0.15 V. RHE Current-time curves and related product (CH4 and CO) yield / yield-time curves for the photoelectrocatalytic CO2 reduction reaction under applied bias.

[0137] The equipment used in the experiment was an automated online trace gas analysis system (Labsolar-6A) and a gas chromatograph (GC9790).

[0138] like Figure 10 As shown in Figure a, in the first three hours, no obvious products were produced when only bias voltage (0.75 V vs. RHE, 0.45 V vs. RHE, 0.15 V vs. RHE) was applied without illumination. Starting from the fourth hour, with a bias voltage of -0.6 V vs. RHE maintained and illumination from a light source added, product formation was clearly visible.

[0139] Figure 10 b shows that, under illumination alone, without the application of a bias voltage, no obvious product is produced.

[0140] Figure 10 c shows that when only a bias voltage is applied, without illumination, no obvious product is produced.

[0141] Figure 10 As shown in Figure d, during the test, the CO2 reduction rate of cuprous oxide in the p / n heterojunction increased cumulatively with the production of CO and CH4 products, with CO being the main product. The results indicate that the product yield continuously increased with the progress of the reaction within the first 11 hours. When the reaction time reached 11 hours, the sample was essentially deactivated, with almost no product regeneration. Furthermore, Figure 10 The right side of d shows that the p / n heterojunction cuprous oxide exhibits excellent reduction performance within 6 hours. The CO2 reduction rate is highest at 6 hours and gradually decreases with increasing time.

[0142] In summary, by generating more efficient charge separation and transfer and increasing CO2 adsorption active sites, p / n heterojunction cuprous oxide exhibits better photoelectrocatalytic CO2 reduction efficiency, which is crucial for converting CO2 into valuable compounds. Therefore, we believe that in the current system, electrons and photons play a synergistic role, and relying solely on the redox performance of electron transfer from external circuits or photogenerated electron-hole redox mechanisms cannot achieve the desired effect.

[0143] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. Other embodiments can be obtained based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A cuprous oxide-based composite material, characterized in that, Includes a substrate and a p-type cuprous oxide layer and an n-type cuprous oxide layer sequentially stacked on the substrate surface; The p-type cuprous oxide layer and the n-type cuprous oxide layer form a heterojunction; The cuprous oxide-based composite material is used for photoelectrocatalytic carbon dioxide reduction.

2. The cuprous oxide-based composite material according to claim 1, characterized in that, The thickness of the p-type cuprous oxide layer is 1.16~2.7 μm; the thickness of the n-type cuprous oxide layer is 0.15~0.29 μm. The mass ratio of the p-type cuprous oxide layer to the n-type cuprous oxide layer is 15:2 to 35:

1.

3. The method for preparing the cuprous oxide-based composite material according to any one of claims 1 to 2, characterized in that, Includes the following steps: The first water-soluble copper salt solution, the first complexing agent solution, and the first pH adjuster are mixed to obtain a first sedimentation solution with a pH value of 9-11; The second water-soluble copper salt solution, the second complexing agent solution, and the second pH adjuster are mixed to obtain a second sedimentation solution with a pH value of 4.5~5.4; Using the first deposition solution as the deposition solution, a first electrochemical deposition is performed on the substrate surface to obtain a substrate with a p-type cuprous oxide layer deposited on it; Using the second deposition solution as the deposition solution, a second electrochemical deposition is performed on the surface of the p-type cuprous oxide layer to obtain the cuprous oxide-based composite material.

4. The preparation method according to claim 3, characterized in that, The water-soluble copper salt in the first water-soluble copper salt solution includes copper sulfate; The complexing agent in the first complexing agent solution includes lactic acid.

5. The preparation method according to claim 3 or 4, characterized in that, The concentration of the water-soluble copper salt in the first water-soluble copper salt solution is 0.18~0.22 mol / L; the concentration of the complexing agent in the first complexing agent solution is 1.35~1.65 mol / L. The volume ratio of the first water-soluble copper salt solution to the first complexing agent solution is 1:

1.

6. The preparation method according to claim 3, characterized in that, The water-soluble copper salt in the second water-soluble copper salt solution includes copper acetate; The complexing agent in the second complexing agent solution includes acetic acid.

7. The preparation method according to claim 3 or 6, characterized in that, The concentration of the water-soluble copper salt in the second water-soluble copper salt solution is 0.035~0.045 mol / L; the concentration of the complexing agent in the second complexing agent solution is 0.15~0.17 mol / L. The volume ratio of the second water-soluble copper salt solution to the second complexing agent solution is 1:

1.

8. The preparation method according to claim 3, characterized in that, The conditions for the first electrochemical deposition include: With the base as the working electrode, the platinum sheet electrode as the counter electrode, and the silver / silver chloride electrode as the reference electrode, a constant voltage mode is adopted, the fixed voltage is-0.45~-0.55 V vs. the reference electrode, and the deposited charge quantity is 0.3~0.7 mAh / cm 2 ; The temperature of the first electrochemical deposition is 55~65 ℃.

9. The preparation method according to claim 3, characterized in that, The conditions for the second electrochemical deposition include: Using a substrate with deposited p-type cuprous oxide as the working electrode, a platinum sheet electrode as the counter electrode, and a silver / silver chloride electrode as the reference electrode, a constant voltage mode was employed, with a fixed voltage of 0.018–0.022 V vs. the reference electrode, and a deposited charge of 0.02–0.04 mAh / cm³. 2 ; The temperature of the second electrochemical deposition is 68~72 ℃.

10. The application of the cuprous oxide-based composite material according to any one of claims 1 to 2 or the cuprous oxide-based composite material prepared by the preparation method according to any one of claims 3 to 9 as a photoelectrocatalytic material in photoelectrocatalytic carbon dioxide reduction.

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