Application of a co-catalytic electrolyte in photoelectrocatalytic hydrogen evolution

Abstract

The application discloses application of a co-catalytic electrolyte in photoelectrocatalytic hydrogen evolution, and the application comprises the following steps: placing a photoelectrocatalytic medium in the co-catalytic electrolyte, and catalyzing hydrogen production under the action of a voltage and light source irradiation, wherein the electrolyte comprises a co-catalyst and a dispersion liquid, and the co-catalyst comprises a room-temperature ionic liquid. The application has the advantages of realizing the interdisciplinary of photoelectrochemistry, semiconductor physics and material science, and being innovative and forward-looking. The application is favorable for deep understanding of the co-catalytic effect and mechanism of the room-temperature ionic liquid in the field of photoelectrochemical catalysis, and provides a research idea and a reliable means for realizing large-scale green hydrogen production.

Description

Technical Field

[0001] This invention relates to the field of photoelectrocatalysis technology, and in particular to the application of a co-catalytic electrolyte in photoelectrocatalytic hydrogen evolution. Background Technology

[0002] With increasingly serious environmental pollution and energy shortages, the search for and utilization of clean and renewable energy sources has become an urgent priority. Hydrogen energy, with its high energy density and clean, pollution-free characteristics, is widely used as an energy carrier and fuel in energy transition and industrial production. The photoelectrocatalytic hydrogen evolution reaction using semiconductor materials under sunlight irradiation has been extensively studied. However, many semiconductor catalysts suffer from low solar energy conversion efficiency (STH), complex preparation processes, and low stability, severely hindering their application in photoelectrocatalytic hydrogen production and increasing production costs. Therefore, developing photoelectrocatalytic hydrogen production catalysts with high catalytic activity, high stability, and scalable production capabilities has remained a research hotspot.

[0003] Improving the efficiency of photoelectrocatalytic hydrogen evolution while reducing costs hinges on the design of the catalytic system, primarily focusing on enhancing the catalytic performance of semiconductor catalysts. In addition, the properties of the electrolyte solution and co-catalysts should be studied and designed. Room-temperature ionic liquids (RTILs) are non-aqueous liquids composed entirely of organic cations and organic / inorganic anions with melting points below 100°C. Compared to traditional aqueous solutions, they exhibit higher thermodynamic and chemical stability, better ionic conductivity, higher electrocatalytic performance, a wider electrochemical window, and lower melting point and volatility. Rosen et al. reported the use of imidazolium-based RTILs, specifically 1-ethyl-3-methylimidazolium tetrafluoroborate (also known as [EMIM][BF4] or [C2mim][BF4]), as a supporting electrolyte in the electrochemical CO2 reduction reaction in aqueous solution. The presence of [EMIM][BF4] reduced the overpotential for CO2 reduction to CO at the Ag electrode, demonstrating the co-catalytic role of [EMIM][BF4] in the electrochemical reduction reaction. It is worth noting that, due to the presence of aromatic rings, most imidazole-based RTILs exhibit strong absorption capabilities for ultraviolet light, which can help the catalytic system capture photons, improve solar energy conversion efficiency, and facilitate their application in photoelectrocatalytic reactions. However, existing literature contains very few studies on the use of imidazole-based ionic liquids in photoelectrocatalysis, and almost no research has been reported on the application of imidazole-based RTILs in photoelectrocatalytic hydrogen production. Furthermore, the high viscosity and low mass transfer rate of most pure RTILs limit their application as both solvents and supporting electrolytes.

[0004] Therefore, it is important to design an electrolyte based on RTILs and couple it with a photoelectrocatalyst to improve the hydrogen evolution efficiency of existing photoelectrocatalysts. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention provides an application of a co-catalytic electrolyte in photoelectrocatalytic hydrogen evolution, the application including,

[0006] By placing the photoelectrocatalytic medium in a co-catalytic electrolyte, hydrogen production is catalytically achieved under applied voltage and light source irradiation.

[0007] The electrolyte comprises a cocatalyst and a dispersion, wherein the cocatalyst comprises a room-temperature ionic liquid.

[0008] Furthermore, the co-catalyst comprises an imidazolium-based room-temperature ionic liquid with the following general formula:

[0009]

[0010] Where n is 2 or 4.

[0011] Furthermore, the dispersion comprises water.

[0012] Furthermore, the volume concentration of the cocatalyst in the cocatalytic electrolyte is 25-50%.

[0013] Furthermore, the photoelectrocatalytic medium includes a photoelectrocatalyst and a photoelectrocatalyst support.

[0014] Furthermore, the photocatalyst comprises a P-type semiconductor containing copper.

[0015] Furthermore, the copper-containing P-type semiconductor also contains bismuth.

[0016] Furthermore, the light source includes ultraviolet light or visible light.

[0017] Furthermore, the step of placing the photoelectrocatalytic medium in a co-catalytic electrolyte and then catalytically producing hydrogen under light source irradiation further includes,

[0018] Remove oxygen from the co-catalytic electrolyte.

[0019] Furthermore, the removal of oxygen from the co-catalytic electrolyte includes,

[0020] An inert gas is passed into the cocatalytic electrolyte to remove oxygen from the cocatalytic electrolyte.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] (1) [C2mim] in the co-catalytic electrolyte of this invention +This approach bridges the photoelectrocatalytic reaction process, significantly reducing the overpotential required for the photoelectrochemical reduction of H2O to H2. Furthermore, the system requires no additional supporting electrolyte.

[0023] (2) In addition, due to the presence of the aromatic ring of [C2mim][BF4], it has a strong absorption capacity for ultraviolet light, which can help the catalytic system capture photons, improve the light conversion efficiency, and facilitate its application in photoelectrocatalytic reactions.

[0024] (3) Since its conduction band potential and hydrogen evolution potential are more negative than the potential required for Cu ions in the lattice to be reduced to metallic Cu, Cu-based materials are reduced before the catalytic hydrogen evolution reaction occurs, resulting in the degradation or deactivation of the photocatalyst. This invention uses [C2mim][BF4] to quickly capture electrons and carry out a reduction reaction, which effectively promotes the separation of photogenerated electrons and holes and inhibits their recombination.

[0025] (4) This invention enables the integration of multiple disciplines such as photoelectrochemistry, semiconductor physics, and materials science, demonstrating innovation and forward-looking vision. It facilitates a deeper understanding of the co-catalytic effects and mechanisms of room-temperature ionic liquids in photoelectrochemical catalysis. It provides research ideas and reliable methods for achieving large-scale green hydrogen production.

[0026] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the steps or processes indicated in the description and the drawings. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 The image shows a graph of the photocurrent (Z-axis) of the substrate electrode immersed in the cocatalytic electrolyte of Example 1 of the present invention as a function of the optical fiber position (XY-axis);

[0029] Figure 2 The image shows a graph of the photocurrent (Z-axis) of the substrate electrode immersed in the cocatalytic electrolyte of Example 2 of the present invention as a function of the optical fiber position (XY-axis);

[0030] Figure 3 The diagram shows the ΔI value of the substrate electrode measured in the co-catalytic electrolyte of Example 1;

[0031] Figure 4 The diagram shows the ΔI values ​​at different potentials when the substrate electrode is immersed in the cocatalytic electrolyte of Example 1 and Example 2 and the electrolyte of the comparative example, respectively. Detailed Implementation

[0032] The technical solutions of the present invention will be clearly and completely described below with reference to specific embodiments and accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] The design concept of this invention is as follows: the aromatic rings contained in imidazole-based room-temperature ionic liquids (RTILs) can help the catalytic system capture photons, improve solar energy conversion efficiency, and facilitate the application of the catalytic system in photoelectrocatalytic reactions. However, most pure RTILs have high viscosity and low mass transfer rates, which limits their application as solvents and supporting electrolytes, even making them less suitable than conventional electrolytes. Therefore, it is necessary to find suitable RTILs and dispersions to prepare electrolytes of appropriate concentrations, which can then work together with the photoelectrocatalytic system to effectively improve the catalytic hydrogen evolution efficiency of the system.

[0034] Therefore, the present invention provides an application of a co-catalytic electrolyte in photoelectrocatalytic hydrogen evolution, the application comprising the following steps.

[0035] By placing the photoelectrocatalytic medium in a co-catalytic electrolyte, hydrogen production is catalytically achieved under applied voltage and light source irradiation.

[0036] The electrolyte comprises a cocatalyst and a dispersion, wherein the cocatalyst comprises a room-temperature ionic liquid.

[0037] In this invention, the volume concentration of the co-catalyst in the co-catalytic electrolyte is 25-50%. The co-catalyst comprises an imidazole-based room-temperature ionic liquid with the following general formula:

[0038]

[0039] Where n is 2 or 4, i.e., 1-ethyl-3-methylimidazolium tetrafluoroborate or 1-butyl-3-methylimidazolium tetrafluoroborate.

[0040] The dispersion includes water.

[0041] The photoelectrocatalytic medium includes a photoelectrocatalyst and a photoelectrocatalyst support. The photoelectrocatalyst includes a copper-containing P-type semiconductor, which also contains bismuth.

[0042] The light source includes ultraviolet light or visible light.

[0043] The step of placing the photoelectrocatalytic medium in a cocatalytic electrolyte, before catalytically producing hydrogen under applied voltage and light source irradiation, further includes removing oxygen from the cocatalytic electrolyte. This removal of oxygen from the cocatalytic electrolyte includes passing an inert gas into the cocatalytic electrolyte to remove oxygen.

[0044] The application of the present invention will be described in detail below with reference to specific embodiments.

[0045] It should be noted that the chemical reagents mentioned in the examples, such as 1-ethyl-3-methylimidazolium tetrafluoroborate ([C2mim][BF4]), 1-butyl-3-methylimidazolium tetrafluoroborate ([C4mim][BF4]), and KHCO3, are purchased and used directly without further processing, and their purity is at or above analytical grade. This is not intended to limit the invention. The FTO mentioned in the examples is fluorinated tin dioxide, a commonly used photoelectrophotocatalyst carrier. The photoelectrophotocatalyst used in the examples is a p-type semiconductor CuBi2O4 dot array. Of course, the co-catalyst electrolyte of this invention can also be used in conjunction with other photoelectrophotocatalysts. The substrate electrode mentioned in the examples is a shorthand for a fluorine-doped tin dioxide electrode with a p-type semiconductor CuBi₂O₄ dot array. The preparation method of the substrate electrode follows existing techniques, such as the paper "Screening of transition and post-transition metals to incorporate into copper oxide and copper bismuth oxide for photoelectrochemical hydrogen evolution" published by Sean P. Berglund et al. in 2013 in *Physical Chemistry & Chemical Physics*, Vol. 4554, No. 15. The potentials in the chronoamperometry characterization results in the test examples are all relative to the Ag / AgCl reference electrode. The light source mentioned in the examples is a xenon lamp, model HPX-2000-HP-DUV, with a power of 75W. The illumination in the examples was also performed under this xenon lamp. These details will not be elaborated further.

[0046] Example 1

[0047] An application of a co-catalytic electrolyte in photoelectrocatalytic hydrogen evolution includes,

[0048] The substrate electrode was placed in a 25 vol.% aqueous solution of [C2mim][BF4] and irradiated with a light source. The substrate electrode continuously catalyzed hydrogen production.

[0049] The 25 vol.% aqueous solution of [C2mim][BF4] needs to be continuously purged with argon gas for 30 min before catalytic hydrogen production to remove the oxygen it contains. The pH value of the 25 vol.% aqueous solution of [C2mim][BF4] after removing oxygen is approximately 4.

[0050] Example 2

[0051] An application of a co-catalytic electrolyte in photoelectrocatalytic hydrogen evolution includes,

[0052] The substrate electrode was placed in a 25 vol.% aqueous solution of [C4mim][BF4] and irradiated with a light source. The substrate electrode continuously catalyzed hydrogen production.

[0053] The 25 vol.% aqueous solution of [C4mim][BF4] needs to be continuously purged with argon gas for 30 min before catalytic hydrogen production to remove the oxygen it contains. The pH value of the 25 vol.% aqueous solution of [C4mim][BF4] after removing oxygen is approximately 4.

[0054] Comparative Example

[0055] An application of an electrolyte in photoelectrocatalytic hydrogen evolution includes,

[0056] The substrate electrode was placed in a 0.1 mol / L KHCO3 aqueous solution and irradiated with a light source, and the substrate electrode continuously catalyzed hydrogen production.

[0057] In particular, the 0.1 mol / L KHCO3 aqueous solution needs to be continuously purged with argon gas for 30 minutes before catalytic hydrogen production to remove the oxygen it contains.

[0058] Test case

[0059] Scanning photoelectrochemical microscopy (SPECM) characterization uses microprobe electrodes or optical fibers to scan and probe redox currents and potentials within micro-regions to analyze photoelectrochemical reactions. It is widely used in electrochemical and photoelectrochemical reaction analysis. This method can also be used to study the influence of substances in the electrolyte on the performance of photoelectrocatalysts.

[0060] This test example uses SPECM to study the photoelectrocatalytic hydrogen evolution activity of the substrate electrodes placed in the co-catalytic electrolytes of Examples 1 and 2. The two substrate electrodes were immersed in their respective electrolytes. An optical fiber was used as a scanning probe, suspended vertically 150 μm above the substrate electrodes, allowing the fiber to scan along the XY plane of the substrate electrodes and introduce illumination, thus controlling local irradiation of each point on the CuBi₂O₄ array. Simultaneously, a series of different potentials were applied to the substrate electrodes, with the applied potential being greater than their open-circuit potential. CuBi₂O₄ generated photogenerated holes (h₁, h₂, h₃) under photon excitation. + ) and photogenerated electrons (e - Under the influence of the built-in electric field and the external potential, the two separate and migrate to the semiconductor surface, and the H in the electrolyte... + Capture e - The photocatalyst is reduced to H2. At this point, the SPECM records the current change during the photoelectrocatalytic reaction and outputs an image of the photoreduction current versus the fiber position to evaluate the catalytic activity of the catalyst.

[0061] Figure 1 The image shows a graph of the photocurrent (Z-axis) of the substrate electrode immersed in the co-catalytic electrolyte of Example 1 of the present invention as a function of the fiber position (XY-axis). Figure 1 The upper center plot is a three-dimensional photocurrent-fiber position function graph. Except for the FTO background current, the darker the color in the graph, the greater the photocurrent and the higher the catalytic activity. The lower planar plot is a two-dimensional projection of the upper plot. The darker the color in the middle annular current circle, the greater the photocurrent and the higher the catalytic activity. The darker part on the outside is the FTO background current.

[0062] Figure 2 The image shows a graph of the substrate electrode photocurrent (Z-axis) versus the fiber position (XY-axis) when the substrate electrode is immersed in the co-catalytic electrolyte of Example 2 of the present invention. Figure 1 and Figure 2 The comparison shows that, for the same photoelectrocatalytic medium, the co-catalytic electrolyte of Example 1 has higher catalytic activity than that of Example 2.

[0063] When p-type semiconductor photocatalysts operate under illumination, they generate a negative reduction current. This reduction current is an effective way to evaluate the catalytic activity of photocatalysts; generally, a larger reduction current indicates higher catalytic activity. However, if the applied potential is too negative, the photocatalyst may undergo self-reduction, resulting in photocorrosion and deactivation.

[0064] Chronoamperometry allows for the application of a constant potential to the substrate electrode and the recording of current-time changes. The reduction current of the substrate electrode can be altered by changing the applied voltage, removing the light source, and applying light to irradiate the substrate electrode. The substrate electrode was immersed in the co-catalytic electrolytes of Examples 1 and 2, and the electrolyte of the comparative example, respectively. An electrochemical workstation was connected, and different potentials were applied to control the duration of UV-Vis irradiation of the CuBi₂O₄ photocatalyst. Simultaneously, the photocurrent-time response was collected. First, a certain potential was applied to the substrate electrode without illumination. After the current recorded by the electrochemical workstation stabilized, the first current value was recorded. Subsequently, the substrate electrode was irradiated with ultraviolet-visible light, and the second current value, i.e., the photocurrent, was recorded. The light source is removed after a certain period of illumination. The average difference between the second and first current values ​​is ΔI, i.e. and The difference between ΔI and ΔI can be used to evaluate the catalytic performance of photocatalysts at different potentials. By comparing ΔI at different electrode potentials in different solvent media, the photoelectrocatalytic hydrogen evolution performance in different electrolyte environments can be evaluated.

[0065] For example, Figure 3 The figure shows ΔI measured at the substrate electrode in the co-catalytic electrolyte of Example 1, from... Figure 3 It can be seen that at potentials of 0.15V (a), 0.1V (b), 0.05V (c), and 0.01V (d), ΔI increases as the potential becomes more negative.

[0066] Figure 4 The diagram shows the ΔI values ​​when the substrate electrode is immersed in the cocatalytic electrolytes of Examples 1 and 2, and the electrolyte of the comparative example, at potentials of 0.15V, 0.10V, 0.05V, 0.01V, -0.05V, and -0.1V. It can be seen that at potentials of 0.15V, 0.10V, 0.05V, 0.01V, and -0.05V, Example 1 exhibits the highest photoreduction current, exceeding that of Examples 2 and the comparative example. This is because [C2mim] + The presence of [C4mim][BF4] acts as a bridge in the reaction process, significantly reducing the overpotential required for the photoelectric reduction of H2O to H2, thus promoting the hydrogen evolution reaction. The lowest photoreduction current in Example 2 is mainly due to the physical properties of [C4mim][BF4]. Compared to [C2mim][BF4] (viscosity: 25.7 cp, conductivity: 14 mS / cm), [C4mim][BF4] has a higher viscosity and lower conductivity (viscosity: 180 cp, conductivity: 3.5 mS / cm), reducing charge carriers and mass transfer rates, thereby decreasing the activity and efficiency of the photocatalytic hydrogen evolution reaction.

[0067] In addition, from Figure 4As can be seen, in the co-catalytic electrolyte of Example 1, the substrate electrode exhibits a rapid change in ΔI at potentials of 0.15V, 0.10V, and 0.05V, while the change in ΔI is very gradual at potentials of 0.05V, 0.01V, and -0.05V. This change process is exactly the opposite of that in the comparative example. These results also indicate that the co-catalytic electrolyte of Example 1 of the present invention has a higher photoreduction current than the electrolyte of the comparative example at potentials of at least 0.15V, 0.10V, 0.05V, 0.01V, and -0.05V, and is more stable at lower potentials of 0.05V, 0.01V, and -0.05V.

[0068] In summary, the application of a co-catalytic electrolyte of the present invention in photoelectrocatalytic hydrogen evolution is based on [C2mim] in the co-catalytic electrolyte. + This invention bridges the gap in photoelectrocatalytic reactions, significantly reducing the overpotential required for the photoelectrochemical reduction of H₂O to H₂. Simultaneously, the system requires no additional supporting electrolyte. Because its conduction band potential and hydrogen evolution potential are more negative than those required for the reduction of Cu ions in the crystal lattice to metallic Cu, Cu-based materials are reduced before the hydrogen evolution reaction occurs, leading to degradation or deactivation of the photocatalyst. This invention utilizes [C₂mim][BF₄] to rapidly capture electrons for reduction, effectively promoting the separation of photogenerated electrons and holes and inhibiting their recombination. This invention enables interdisciplinary collaboration between photoelectrochemistry, semiconductor physics, and materials science, demonstrating innovation and forward-looking vision. It contributes to a deeper understanding of the co-catalytic effects and mechanisms of room-temperature ionic liquids in photoelectrochemical catalysis. It provides research ideas and reliable methods for large-scale green hydrogen production.

[0069] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An application of a co-catalytic electrolyte in photoelectrochemical hydrogen evolution, characterized in that, The applications include, By placing the photoelectrocatalytic medium in a co-catalytic electrolyte, hydrogen production is catalytically achieved under applied voltage and light source irradiation. The electrolyte comprises a cocatalyst and a dispersion, wherein the cocatalyst comprises a room-temperature ionic liquid; The cocatalyst comprises an imidazole-based room-temperature ionic liquid with the following general formula: Where n has a value of 2 or 4; The dispersion includes water.

2. The application according to claim 1, characterized in that, The volume concentration of the cocatalyst in the cocatalytic electrolyte is 25-50%.

3. The application according to claim 1, characterized in that, The photoelectrocatalytic medium includes a photoelectrocatalyst and a photoelectrocatalyst support.

4. The application according to claim 3, characterized in that, The photocatalyst comprises a P-type semiconductor containing copper.

5. The application according to claim 4, characterized in that, The copper-containing P-type semiconductor also contains bismuth.

6. The application according to claim 1, characterized in that, The light source includes ultraviolet light or visible light.

7. The application according to claim 1, characterized in that, The step of placing the photoelectrocatalytic medium in a co-catalytic electrolyte, before catalytic hydrogen production under light source irradiation, further includes: Remove oxygen from the co-catalytic electrolyte.

8. The application according to claim 7, characterized in that, The removal of oxygen from the co-catalytic electrolyte includes, An inert gas is passed into the cocatalytic electrolyte to remove oxygen from the cocatalytic electrolyte.

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