A photothermal bubble regulation device and method based on liquid phase microstructure effect

Abstract

The application provides a kind of photothermal bubble regulation device and method based on liquid phase microstructure effect, it relates to electrochemical hydrogen production and light / electrocatalytic reaction bubble management technical field.The device includes support frame, semiconductor laser, beam expander, optical lens, high-precision three-dimensional displacement platform, test platform, high-speed camera and electrochemical workstation;Laser is irradiated after expansion and focusing The surface of photoactive electrode forms photothermal temperature gradient;Under the action of electrochemical bias, bubbles are generated on the surface of the electrode, and the temperature gradient is used to excite the thermal capillary force at the three-phase contact line to drive the liquid film to converge and form a liquid phase microstructure;By adjusting the displacement platform to change the defocus distance or adjusting the laser power, the competition between the thermal capillary force and the separation pressure is changed, the liquid phase microstructure is switched between the pulsation and collapse state, the bubble is driven to be driven, oscillated or directionally slipped, and the non-contact bubble control and mass transfer enhancement are realized.The application has low energy consumption and high precision, and can significantly improve the efficiency of electrochemical reaction.

Description

Technical Field

[0001] This invention relates to the field of electrochemical hydrogen production and photo / electrocatalytic reaction bubble management technology, and particularly to a photothermal bubble control device and method based on liquid phase microstructure effects. Background Technology

[0002] In catalytic reactions involving gas-liquid-solid multiphase interfaces, such as electrochemical and photoelectric water splitting, bubbles generated in situ on the electrode surface are often firmly pinned to the solid-liquid interface, masking catalytic active sites, hindering ion mass transfer, significantly increasing the system's ohmic resistance and concentration polarization, and consequently drastically reducing reaction efficiency and operational stability. Therefore, effectively overcoming the interfacial pinning effect of bubbles and achieving efficient and controllable bubble desorption is a key bottleneck that urgently needs to be overcome in the field of energy catalysis.

[0003] Currently, the mainstream bubble desorption strategies are mainly divided into two categories: one is the external physical field-assisted method, such as introducing ultrasound, magnetic field or microgravity field, etc. This type of method relies on external energy input, which not only increases the energy consumption and complexity of the system, but also easily causes violent fluctuations in local flow field and potential; the other is the electrode surface structure design method, such as constructing a conical electrode with Laplace pressure gradient or constructing an asymmetric wettability interface. Although this type of method can drive the directional migration of bubbles to a certain extent, it is still subject to the strong pinning effect of the bubble three-phase contact line at the mesoscale, making it difficult to achieve controllable and active regulation of the entire process of bubble self-nucleation, growth to desorption.

[0004] Research indicates that the essence of bubble pinning lies in the evolution of the microscopic mechanical behavior of the interface at the three-phase contact line. Thermocapillary effects and separation pressure act on the accumulated liquid phase during bubble diffusion, inducing complex topological evolution and thus dominating the pinning state. However, existing technologies largely focus on overcoming global adhesion forces at the macroscopic scale, neglecting the dynamic contribution of the interfacial liquid phase structure, thus making it difficult to overcome the pinning bottleneck of anchored bubbles. Therefore, there is an urgent need to develop a scheme that can actively control the liquid phase structure behavior at the mesoscopic scale, thereby achieving bubble depinning, oscillation, and directional transport control, to achieve efficient and controllable bubble management with lower energy consumption. Summary of the Invention

[0005] This invention provides a photothermal bubble control device and method based on the liquid phase microstructure effect. The aim is to induce the formation of liquid phase microstructures based on the photothermal effect, thereby mediating bubble destacking, oscillation, and directional transport control. Specifically, by modulating the spatial distribution of laser light, the periodic pulsation and collapse of liquid ridges are driven by the competitive mechanism of thermocapillary force and separation pressure, thereby driving the bubble to change between oscillating or sliding states and steady state, achieving non-contact bubble manipulation.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: In a first aspect, the present invention provides a photothermal bubble control device based on liquid phase microstructure effect, including a support frame, a semiconductor laser, a beam expander, an optical lens, a high-precision three-dimensional displacement platform, a testing platform, a high-speed camera, and an electrochemical workstation. The semiconductor laser, beam expander, and optical lens are sequentially fixed and assembled on the support frame along the optical path direction, together forming the laser emission optical path; The high-precision three-dimensional displacement platform is arranged on the light-emitting side of the laser emission path and is used to mount the photoactive electrode and adjust the defocus distance of the electrode relative to the laser focal plane. The test platform is used to place an electrolytic cell containing electrolyte, and the photoactive electrode mounted on a high-precision three-dimensional displacement platform can extend into the electrolytic cell. The high-speed camera is positioned towards the electrolytic cell and the photoactive electrode for in-situ synchronous observation of the evolution of bubble and liquid phase microstructures. The electrochemical workstation is electrically connected to a photoactive electrode, which is used to apply a constant bias voltage to the electrolysis system, driving an electrochemical reaction on the electrode surface and generating bubbles.

[0007] Furthermore, the high-precision three-dimensional displacement platform includes an x-axis adjustment platform, a y-axis adjustment platform, and a z-axis adjustment base; the x-axis adjustment platform is the bottom support component of the displacement platform and can move along the x-axis direction; the y-axis adjustment platform is slidably mounted above the x-axis adjustment platform and can move along the y-axis direction; the z-axis adjustment base is fixedly mounted on the y-axis adjustment platform and is used to support the photoactive electrode and realize displacement adjustment in the z-axis direction.

[0008] Furthermore, the test platform includes a height-adjustable auxiliary fixing platform, an electrode fixing and observation base, and a reflector; the electrode fixing and observation base is installed on the height-adjustable auxiliary fixing platform; and the reflector is embedded inside the electrode fixing and observation base.

[0009] Furthermore, it also includes an image processing and analysis unit; the image processing and analysis unit is communicatively connected to the high-speed camera and the semiconductor laser, respectively, and receives image data acquired by the high-speed camera and operating parameters of the semiconductor laser; the image processing and analysis unit is configured as follows: The image data is acquired, and dynamic parameters are extracted from the image data using a threshold segmentation algorithm. The dynamic parameters include bubble displacement, contact angle, contact diameter, and projected area of ​​liquid phase microstructure. Based on the dynamic parameters and / or operating parameters, the laser propagation path and the secondary focusing effect of the bubble are simulated by Monte Carlo ray tracing, and the actual light intensity distribution and temperature gradient of the electrode surface and bubble interface are calculated according to the simulation results.

[0010] Furthermore, the high-speed camera has a detachable filter mounted on the front end of its lens; the device is also equipped with a background illumination optical path, in which a diffuser is provided, which is arranged facing the electrolytic cell and the observation area to provide uniform supplementary light.

[0011] Secondly, the present invention provides a method for controlling photothermal bubbles based on liquid-phase microstructure effects, and based on the photothermal bubble control device described above, the method comprising: When the semiconductor laser is turned on, the laser beam passes through the beam expander and optical lens in sequence and irradiates the surface of the photoactive electrode, forming a light intensity field with a preset spatial distribution, and creating a photothermal temperature gradient in the local area of ​​the electrode. A constant bias voltage is applied to the photoactive electrode by an electrochemical workstation to generate bubbles on the electrode surface. The photothermal temperature gradient is used to excite thermocapillary force at the three-phase contact line of the bubbles, driving the surface liquid film to converge or collapse, forming a ridge-like or thin-film liquid phase microstructure. By adjusting the high-precision three-dimensional displacement platform to change the defocus distance of the electrode relative to the laser focal plane to adjust the shape of the laser spot, or by adjusting the output power of the semiconductor laser to change the spatial distribution and magnitude of the photothermal temperature gradient, the competitive relationship between thermocapillary force and interfacial separation pressure is adjusted, causing the liquid phase microstructure to switch between a periodic pulsating state and a collapsed spreading state, driving the bubbles to complete destacking, periodic oscillation, or directional sliding, thereby achieving non-contact manipulation of bubbles and enhanced reaction mass transfer.

[0012] Furthermore, adjusting the defocus distance of the electrode relative to the laser focal plane by adjusting the high-precision three-dimensional displacement platform to adjust the shape of the laser spot includes: By controlling the sign and size of the defocus distance, the electrode surface can be positioned in front of the laser focal plane to form a pre-focal zone bubble, in the Rayleigh zone to form a Rayleigh zone bubble, or behind the focal plane to form an over-focal zone bubble. Among these, the pre-focal zone bubble undergoes a brief period of vibration during its growth before transitioning to stable growth, the Rayleigh zone bubble exhibits a growth pattern of gradually decreasing vibration within a specific diameter range, and the over-focal zone bubble mainly grows stably.

[0013] Furthermore, when the bubble is in a periodic oscillation state under the competition between the thermocapillary force and the interfacial separation pressure, the output bias voltage of the electrochemical workstation is cut off at the moment when the bubble and the flow field reach resonance, so that the bubble stops growing and detaches from the electrode surface, thus obtaining an isolated bubble with inherent amplitude-frequency characteristics.

[0014] Furthermore, the optical path position of the semiconductor laser is translated, causing the isolated bubble and its surrounding liquid-phase microstructure system to move along a preset planar trajectory. After moving to the target position, the system relaxes and resumes stable oscillation.

[0015] Furthermore, when the electrochemical workstation applies a constant bias voltage, the electrolyte used is a 0.1~0.5 mol / L neutral Na2SO4 solution, and the photoactive electrode is a TiO2 nanorod array thin film electrode.

[0016] The photothermal bubble control device and method based on liquid phase microstructure effect provided by this invention have at least the following beneficial effects: 1. This invention constructs a photothermal bubble control device using a support frame, a semiconductor laser, a beam expander, an optical lens, a high-precision three-dimensional displacement platform, a testing platform, a high-speed camera, and an electrochemical workstation. When the semiconductor laser is turned on, the laser beam passes through the beam expander and optical lens and irradiates the surface of the photoactive electrode, forming a light intensity field with a preset spatial distribution, creating a photothermal temperature gradient in a localized region of the electrode. A constant bias voltage is applied to the photoactive electrode through the electrochemical workstation, causing bubbles to form on the electrode surface. The photothermal temperature gradient is used to excite thermocapillary forces at the three-phase contact line of the bubbles, driving the surface liquid film to converge or collapse, forming ridge-like or thin-film liquid-phase microstructures. By adjusting the defocus distance of the high-precision three-dimensional displacement platform to adjust the laser spot morphology, or by adjusting the output power of the semiconductor laser, the spatial distribution and magnitude of the photothermal temperature gradient are changed, thereby regulating the competitive relationship between the thermocapillary forces and the interfacial separation pressure. This allows the liquid-phase microstructure to switch between a periodic pulsating state and a collapsed spreading state, driving the bubbles to complete depinning, periodic oscillation, or directional sliding. The above process achieves the pinning state transformation of bubbles under non-contact conditions.

[0017] 2. This invention achieves bubble motion mode control by adjusting the defocus distance or laser output power using a high-precision three-dimensional displacement platform, requiring only a low-power laser of tens of milliwatts. Image data acquired by a high-speed camera is obtained through an image processing and analysis unit. Dynamic parameters such as bubble displacement, contact angle, contact diameter, and projected area of ​​the liquid phase microstructure are extracted using a threshold segmentation algorithm. Monte Carlo ray tracing is then used to simulate the laser propagation path and the bubble's secondary focusing effect. Based on the simulation results, the actual light intensity distribution and temperature gradient on the electrode surface and bubble interface are calculated, thereby predicting the bubble's motion mode and trajectory. This process does not rely on external physical field devices such as ultrasound, magnetic fields, or microgravity fields, nor does it depend on complex surface structure designs.

[0018] 3. In the electrochemical water splitting reaction, when the bubbles are in a periodic oscillation state, the periodic pulsation of the liquid phase microstructure can reduce the reaction overpotential. This oscillation process periodically renews the catalytic active sites covered by the bubbles, suppresses concentration polarization, enhances the mass transfer process, and thus improves the reaction efficiency.

[0019] 4. This invention can also cut off the output bias voltage of the electrochemical workstation at the moment when the bubble and the flow field reach resonance, causing the bubble to stop growing and detach from the electrode surface, thus obtaining an isolated bubble with inherent amplitude-frequency characteristics. By translating the optical path position of the semiconductor laser, the isolated bubble and its surrounding liquid-phase microstructure system are moved along a preset planar trajectory. After moving to the target position, the bubble relaxes and recovers stable oscillation, thereby realizing the directional transport of the bubble. Attached Figure Description

[0020] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0021] Figure 1 A structural diagram of a photothermal bubble control device based on liquid phase microstructure effect provided in an embodiment of the present invention; Figure 2 This is a structural diagram of a test platform in a photothermal bubble control device based on liquid phase microstructure effect, provided in an embodiment of the present invention. Figure 3 A schematic diagram of a high-precision three-dimensional displacement platform in a photothermal bubble control device based on liquid phase microstructure effect provided in an embodiment of the present invention; Figure 4 A schematic diagram of the separation state of the test platform in a photothermal bubble control device based on liquid phase microstructure effect provided for an embodiment of the present invention; Figure 5 This is a schematic diagram of the image processing and analysis process provided in an embodiment of the present invention; Figure 6 The present invention provides a schematic diagram of the principle of photothermal bubble control and the bubble-laser optical simulation; wherein, (a) is a schematic diagram of the evolution of laser spot in different propagation regions; (b) is a schematic diagram of the core principle of photothermal bubble control; and (c) is a flowchart of Monte Carlo ray tracing in bubble-laser optical simulation. Figure 7 A flowchart of a photothermal bubble control method based on liquid phase microstructure effect provided for an embodiment of the present invention; Figure 8 This is a schematic diagram of the liquid phase microstructure obtained by observing bubbles generated based on an example platform, provided in an embodiment of the present invention. Figure 9 The diagram shows the bubble oscillation modes under spatial light field modulation and their impact on electrocatalytic performance, provided for embodiments of the present invention. Among them, (a) are the displacement curves of three bubble modes as a function of time: bubble with reaction site located in the laser pre-focus region (UFB), bubble with reaction site located in the laser Rayleigh region (RLB), and bubble with reaction site located in the laser post-focus region (OFB); (b) are the overall curve and a magnified view of the overpotential as a function of time. Figure 10 The following are the bubble control test results provided by the example platform in this embodiment of the invention: (a) the change curve of the lateral displacement of the bubble over time; and (b) the evolution curve of the position of the bubble and the three-phase contact line over time.

[0022] Figure label: 1. Support frame; 2. Semiconductor laser; 3. Beam expander; 4. Optical lens; 5. High-precision three-dimensional displacement platform; 5-1. Z-axis adjustment base; 5-2. Y-axis adjustment platform; 5-3. X-axis adjustment platform; 6. Test platform; 6-1. Height adjustment auxiliary fixing platform; 6-2. Electrode fixing and observation base; 6-2-1. Reflector; 7. Bottom glass of reaction cell.

[0023] The accompanying drawings have illustrated specific embodiments of the invention, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the invention in any way, but rather to illustrate the concept of the invention to those skilled in the art through reference to specific embodiments. Detailed Implementation

[0024] The technical solution of the present invention and how the technical solution of the present invention solves the above-mentioned technical problems are described in detail below with specific embodiments. These specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments. The embodiments of the present invention will now be described with reference to the accompanying drawings.

[0025] Example 1: This invention provides a photothermal bubble control device based on liquid-phase microstructure effects, such as... Figure 1 and Figure 2 As shown ( Figure 1 and Figure 2 (A partial perspective view is used to illustrate the device, which includes a support frame 1, a semiconductor laser 2, a beam expander 3, an optical lens 4, a high-precision three-dimensional displacement platform 5, a testing platform 6, a high-speed camera, and an electrochemical workstation. The semiconductor laser 2, beam expander 3, and optical lens 4 are sequentially fixed and assembled on the support frame 1 along the optical path, forming a laser emission optical path. The high-precision three-dimensional displacement platform 5 is arranged on the light-emitting side of the laser emission optical path to mount the photoactive electrode and adjust the defocus distance of the electrode relative to the laser focal plane. The testing platform 6 is used to place the electrolytic cell containing the electrolyte, and the photoactive electrode mounted on the high-precision three-dimensional displacement platform 5 can extend into the electrolytic cell. The high-speed camera is positioned facing the electrolytic cell and the photoactive electrode to observe the evolution of bubble and liquid phase microstructure in situ synchronously. The electrochemical workstation is electrically connected to the photoactive electrode to apply a constant bias voltage to the electrolytic system, driving an electrochemical reaction on the electrode surface and generating bubbles.

[0026] In use, the photoactive electrode is mounted on a high-precision three-dimensional displacement platform 5 and inserted into the electrolytic cell placed on the test platform 6. The semiconductor laser 2 is activated, and the laser beam is emitted sequentially through the beam expander 3 and the optical lens 4, irradiating the surface of the photoactive electrode. By adjusting the displacement of the high-precision three-dimensional displacement platform 5 along the optical axis, the defocus distance of the electrode surface relative to the laser focal plane is changed, thereby forming a light intensity field with a preset radial distribution on the electrode surface. Under the action of this light intensity field, a photothermal temperature gradient is generated in a local area of ​​the electrode due to photothermal conversion.

[0027] A constant anodic bias is applied to the photoactive electrode via an electrochemical workstation, driving a photoelectrochemical reaction that generates a single bubble on the electrode surface. At the three-phase contact line of the bubble, the photothermal temperature gradient excites thermocapillary forces, which point towards the cooler region, driving the liquid film on the electrode surface to converge or collapse towards the contact line, thereby forming a ridge-like or thin-film liquid-phase microstructure near the contact line. The dynamic behavior of this liquid-phase microstructure is jointly determined by the competitive relationship between the thermocapillary forces and the interfacial separation pressure.

[0028] By further adjusting the defocus distance of the high-precision three-dimensional displacement platform 5 to change the laser spot morphology, or by adjusting the output power of the semiconductor laser 2, the spatial distribution and magnitude of the photothermal temperature gradient can be altered, thereby controlling the competitive relationship between thermocapillary force and interfacial separation pressure. When this competitive relationship changes, the liquid-phase microstructure can switch between a periodic pulsating state and a collapsed spreading state, thereby driving the bubble to achieve destacking, periodic oscillation, or directional sliding. During this process, a high-speed camera can capture real-time images of the evolution of the bubble and the liquid-phase microstructure, which can be used to provide feedback for adjusting laser parameters or the position of the displacement platform, achieving precise control of the bubble's motion behavior.

[0029] Based on the above working process, this device can actively control the pinning state of bubbles under non-contact conditions with only low-power laser excitation, without relying on ultrasound, external magnetic fields, or complex micro / nano structures. It boasts advantages such as low energy consumption, high control precision, and fast response speed. Simultaneously, the periodic oscillation of the bubbles continuously updates the catalytic active sites on the electrode surface, suppresses concentration polarization, and enhances the mass transfer process, thereby effectively improving the electrochemical reaction efficiency. Furthermore, by controlling the moment when the bubbles and the flow field reach resonance and cutting off the output bias voltage of the electrochemical workstation, a device with inherent amplitude can be obtained. An isolated bubble with specific frequency characteristics is guided to move along a preset trajectory by translating a laser optical path, thereby achieving customized separation and directional transport of the bubble.

[0030] In an exemplary embodiment, the laser wavelength of the semiconductor laser 2 is preferably the excitation wavelength corresponding to the photoelectrode; for example, the semiconductor laser wavelength of the TiO2 nanorod array thin film electrode is preferably 375 nm. The excitation light from the semiconductor laser is expanded by the beam expander 3 and then focused by the optical lens 4. The precise movement of the working electrode along the optical axis is controlled by a high-precision three-dimensional displacement platform 5 to change the defocus distance of the electrode surface relative to the laser focal plane, thereby constructing a light intensity field with a specific spatial distribution on the electrode surface. The laser power is preferably 5–20 mW to form a suitable temperature gradient locally. The bubble and liquid phase structure are observed in situ synchronously from the side and bottom using a high-speed camera, preferably at an imaging frame rate of 1000–20,000 fps.

[0031] The working electrode is a photoactive electrode, preferably a thin-film electrode material grown in situ on the surface of indium tin oxide (ITO) / fluorine-doped tin oxide (FTO) conductive glass, including but not limited to thin-film electrodes such as TiO2 nanoarray films that can effectively absorb laser light to generate a localized photothermal effect. Under light irradiation, this electrode can undergo a photoelectrochemical reaction and generate a single oxygen bubble, while simultaneously achieving effective photothermal conversion and driving a change in the liquid phase structure. The electrolyte is preferably a 0.1~0.5 mol / L Na2SO4 neutral solution. A constant bias voltage is applied by an electrochemical workstation to drive the nucleation and growth of bubbles on the electrode surface.

[0032] In some embodiments, such as Figure 3 As shown, the high-precision three-dimensional displacement platform 5 includes an x-axis adjustment platform 5-3, a y-axis adjustment platform 5-2, and a z-axis adjustment base 5-1. The x-axis adjustment platform 5-3 is the bottom support of the displacement platform and can move along the x-axis direction. The y-axis adjustment platform 5-2 is slidably mounted above the x-axis adjustment platform 5-3 and can move along the y-axis direction. The z-axis adjustment base 5-1 is fixedly mounted on the y-axis adjustment platform 5-2 and is used to support the photoactive electrode and achieve displacement adjustment in the z-axis direction. Through the above three-axis displacement adjustment, the spatial position of the photoactive electrode in the laser optical path can be precisely controlled, especially the defocus distance along the optical axis (z-axis). Specifically, when the z-axis adjustment base 5-1 moves the electrode upward or downward, the position of the electrode surface relative to the laser focal plane changes, thereby obtaining different defocus amounts (positive defocus or negative defocus) and absolute values ​​of defocus distance. By combining the horizontal movement of the x-axis adjustment platform 5-3 and the y-axis adjustment platform 5-2, the target area of ​​the nucleated bubble on the electrode surface can be precisely aligned with the center of the laser spot, ensuring the symmetry and repeatability of the photothermal temperature gradient.

[0033] As an example only, the x-axis adjustment platform 5-3 and y-axis adjustment platform 5-2 can employ a linear displacement stage driven by a precision cross roller guide and a differential head, such as a dovetail slide with a stroke of 25 mm and a resolution of 10 μm; the z-axis adjustment base 5-1 can employ a high-precision lifting stage with a built-in stepper motor and ball screw, combined with a grating ruler to achieve closed-loop control, with a minimum step distance of 1 μm. To adapt to the electrochemical environment, all surfaces of components that may come into contact with the electrolyte are treated with polytetrafluoroethylene or ceramic coating for insulation and corrosion resistance. The high-precision three-dimensional displacement platform 5 is fixed on an optical vibration isolation platform to reduce the interference of environmental vibration on electrode positioning and bubble observation.

[0034] In some embodiments, such as Figure 4 As shown, the test platform 6 includes a height-adjustable auxiliary fixing platform 6-1, an electrode fixing and observation base 6-2, a reflector 6-2-1, and a bottom glass 7 of the reaction cell.

[0035] The electrode fixing and observation base 6-2 is installed above the height-adjustable auxiliary fixing platform 6-1. The bottom glass 7 of the reaction cell is positioned above the electrode fixing and observation base 6-2, serving as the direct bearing surface for the electrolytic cell, allowing it to rest stably on the bottom glass 7. The bottom glass 7 has good light transmittance, allowing images of bubbles and liquid phase microstructures from the bottom viewpoint to pass through and propagate downwards. The reflector 6-2-1 is embedded inside the electrode fixing and observation base 6-2, located below the bottom glass 7. The reflector's surface is arranged at a preset angle, facing both upwards toward the bottom glass 7 and horizontally toward the observation direction, used to reflect the images of bubbles and liquid phase microstructures at the bottom of the electrolytic cell that have passed through the bottom glass 7 back to the observation direction.

[0036] When the photoactive electrode, mounted on the high-precision three-dimensional displacement platform 5, extends into the electrolytic cell and is positioned above the bottom glass 7 of the reaction cell, bubbles nucleate and grow on the electrode surface. The high-speed camera lens is aimed at the reflective surface of the reflector 6-2-1 and takes a side view. The image of the bubble and the surrounding liquid phase microstructure is transmitted sequentially through the electrolyte and the bottom glass 7 of the reaction cell, propagating downwards to the reflector 6-2-1. After being reflected by the reflector 6-2-1, the image is directed towards a horizontal observation direction and enters the high-speed camera, thus achieving in-situ synchronous observation of the liquid phase microstructure at the three-phase contact line of the bubble from a bottom perspective.

[0037] The height-adjustable auxiliary fixing platform 6-1 can adjust the vertical height of the electrode fixing and observation base 6-2 according to the height of the electrolytic cell and the working position of the electrode, ensuring that the reflected light path of the reflector 6-2-1 is precisely matched with the optical axis of the high-speed camera, thus ensuring the clarity of the observed image and the alignment of the light path.

[0038] In some embodiments, a filter is detachably mounted on the front end of the lens of the high-speed camera; the device is also equipped with a background illumination optical path, in which a diffuser is provided, the diffuser being arranged toward the electrolytic cell and the observation area to provide uniform supplementary light.

[0039] When semiconductor laser 2 illuminates the electrode surface, some of the laser light may be reflected by the bottom of the electrolytic cell or the bubble interface and enter the high-speed camera, causing overexposure or interfering with the accuracy of bubble edge recognition. A detachable filter mounted on the front of the high-speed camera lens is used to cut off or attenuate light signals near the laser wavelength while allowing visible light to pass through, effectively suppressing interference from reflected laser light on the acquisition of bubble and liquid phase microstructure images. A diffuser is placed in the background illumination optical path to convert point light sources or parallel beams into large-area uniform surface light sources. The diffuser is positioned facing the electrolytic cell and the observation area, providing diffused illumination to the observation area from the side or below, avoiding specular reflection or shadow areas on the bubble surface caused by unidirectional illumination, and making the outlines of the bubble three-phase contact line and the ridged liquid phase microstructure clearer.

[0040] In some embodiments, the photothermal bubble control device based on liquid-phase microstructure effect further includes an image processing and analysis unit; the image processing and analysis unit is communicatively connected to a high-speed camera and a semiconductor laser 2, respectively, and receives image data acquired by the high-speed camera and operating parameters of the semiconductor laser 2; the image processing and analysis unit is configured to perform, for example, Figure 5 The steps S501-S502 are shown.

[0041] S501: Acquire image data and extract dynamic parameters from the image data using a threshold segmentation algorithm. The dynamic parameters include bubble displacement, contact angle, contact diameter, and projected area of ​​liquid phase microstructure.

[0042] In practice, a high-speed camera continuously acquires grayscale images of bubbles and liquid microstructures at the bottom of the electrolytic cell at a set frame rate, and transmits the image data to the image processing and analysis unit in real time. The image processing and analysis unit first performs median filtering on the original images to remove speckle and sensor noise; then, it uses a threshold segmentation algorithm to separate the bubble region, liquid microstructure region, and background electrolyte region. Based on the segmented binary images, edge detection and ellipse fitting are used to extract the bubble's centroid displacement, left / right contact angle, contact line diameter, and the projected area of ​​the liquid microstructure on the horizontal plane. Taking bubble displacement as an example, the oscillation amplitude and frequency of the bubble can be calculated by the change in centroid coordinates between consecutive frames; the contact angle is obtained by measuring the angle between the tangent of the bubble profile at the three-phase contact point and the electrode surface.

[0043] S502: Based on dynamic parameters and / or operating parameters, the laser propagation path and bubble secondary focusing effect are simulated using the Monte Carlo ray tracing method, and the actual light intensity distribution and temperature gradient on the electrode surface and bubble interface are calculated based on the simulation results.

[0044] In practical implementation, the image processing and analysis unit inputs the dynamic parameters extracted in step S501, such as bubble diameter, contact angle, and projected area of ​​the liquid phase microstructure, along with the operating parameters of the semiconductor laser 2, such as preset output power and defocus distance, into the optical simulation module. This optical simulation module, based on the Monte Carlo ray tracing method, discretizes the incident laser into a large number of light beams. Each beam passes sequentially through the optical lens 4, the electrolyte, and the bottom glass 7 of the reaction tank, undergoing refraction and reflection at the bubble interface. The simulation considers the focusing effect of the bubble as a secondary microlens, recording the energy deposition position and intensity of each light beam reaching the electrode surface, and finally accumulating them to obtain the actual light intensity distribution on the electrode surface. Furthermore, based on the light intensity distribution combined with the photothermal conversion efficiency of the electrode material and the thermal diffusivity of the electrolyte, the finite difference method is used to solve the heat conduction equation, calculating the two-dimensional temperature gradient field of the electrode surface and the bubble interface. The obtained simulation results can quantify the magnitude and direction of the thermocapillary force, used to explain or predict the oscillation behavior of the bubble at different defocus distances, and provide a quantitative basis for operators to adjust the displacement platform or laser power.

[0045] like Figure 6 The diagram shown illustrates the principle of photothermal bubble control and the flowchart of bubble-laser optical simulation provided in this embodiment of the invention. Figure 6 Figure (a) shows a schematic diagram of the evolution of the laser spot in different propagation regions. Along the incident direction of the laser, the propagation path can be divided into the pre-focal region, the Rayleigh region, and the post-focal region. In the pre-focal region, the laser spot gradually shrinks as the propagation distance increases, the energy converges towards the center, and the spot brightness gradually increases with the propagation process. After entering the Rayleigh region, the spot maintains a stable Gaussian distribution shape, the energy concentration reaches its peak, and it is the region with the strongest photothermal effect. After entering the post-focal region, the spot begins to diverge, the energy density gradually decreases as the propagation distance increases, and the spot brightness weakens accordingly. Figure 6 The multiple frames in (a) from top to bottom show the changes in the laser spot outline at different propagation stages. The center of the laser spot gradually moves downward with the propagation direction, clearly demonstrating the spatial distribution differences of laser energy on the defocus path, providing a direct physical reference for the regulation of photothermal effects at different defocus distances.

[0046] Figure 6Figure (b) illustrates the core principle of photothermal bubble control. An incident laser beam is irradiated onto the TiO2 / FTO electrode surface at a set incident angle. The position and shape of the laser spot change with the defocusing distance, and it interacts with bubbles at different locations, including bubbles above the electrode, bubbles attached to the electrode surface, and bubbles passing through the electrode. The bubbles act as secondary microlenses, producing a secondary focusing effect on the incident laser, altering the local light intensity distribution, and thus creating a non-uniform temperature field on the electrode surface, driving the bubbles to oscillate and slide. Figure 6 The microscopic images in the upper right corner of (b) show the morphological features of the bubble and the light intensity distribution under laser irradiation. The upper image is a bright spot image of the bubble, with a scale bar showing 200 μm and a magnification of 14x, clearly showing the overall outline of the bubble. The lower image shows the light intensity distribution stripes under laser irradiation, reflecting the modulation effect of the bubble on the laser. By adjusting the high-precision three-dimensional displacement platform to change the defocus distance, the relative position of the laser spot and the bubble can be precisely controlled, thereby regulating the magnitude and direction of the thermocapillary force and achieving active control over the bubble's pinning state and oscillation behavior.

[0047] Figure 6 Figure (c) shows the Monte Carlo ray tracing flowchart for the bubble-laser optical simulation, corresponding to the simulation steps in the aforementioned image processing and analysis unit. The specific implementation process is as follows: First, parameter initialization is performed by inputting operating parameters such as laser power, wavelength, and defocus distance, as well as material parameters such as electrolyte refractive index and electrode photothermal conversion efficiency. Then, the ray tracing function is called to discretize the incident laser into a large number of ray beams, generating initial simulated rays. Next, the propagation path of each ray is determined to see if it intersects with the interface of different media. If the ray intersects with the interface, the interface parameters are read, and the reflection and refraction behavior of the ray at the interface is calculated. If the ray does not intersect with the interface, the simulation continues with straight-line propagation. By recording the propagation path, reflection and refraction angles, and energy attenuation of each ray, a complete beam path distribution is obtained, ultimately generating the simulation results of laser propagation at the electrolyte, bubble, and electrode interfaces, providing reliable data support for calculating the actual light intensity distribution and temperature gradient on the electrode surface and bubble interface.

[0048] Example 2: This invention provides a method for controlling photothermal bubbles based on liquid-phase microstructure effects, applicable to the device described in any embodiment of Example 1, such as... Figure 7 The diagram shown is a flowchart of a photothermal bubble control method based on liquid phase microstructure effect provided in an embodiment of this application. The method includes the following steps S701-S703.

[0049] S701: Turn on the semiconductor laser 2. The laser beam passes through the beam expander 3 and the optical lens 4 in sequence and is emitted to irradiate the surface of the photoactive electrode, forming a light intensity field with a preset spatial distribution, and forming a photothermal temperature gradient in the local area of ​​the electrode.

[0050] S702: A constant bias voltage is applied to the photoactive electrode through an electrochemical workstation, causing bubbles to be generated on the electrode surface. The photothermal temperature gradient is used to excite thermocapillary force at the three-phase contact line of the bubbles, driving the surface liquid film to converge or collapse, forming a ridge-like or thin-film liquid phase microstructure.

[0051] S703: By adjusting the high-precision three-dimensional displacement platform 5 to change the defocus distance of the electrode relative to the laser focal plane to adjust the shape of the laser spot, or to adjust the output power of the semiconductor laser 2, the spatial distribution and magnitude of the photothermal temperature gradient are changed, thereby adjusting the competitive relationship between thermocapillary force and interface separation pressure, so that the liquid phase microstructure switches between periodic pulsation state and collapse and spreading state, driving the bubble to complete destacking, periodic oscillation or directional sliding, so as to realize non-contact manipulation of the bubble and enhanced reaction mass transfer.

[0052] In some embodiments, adjusting the defocus distance of the electrode relative to the laser focal plane by adjusting the high-precision three-dimensional displacement platform 5 to adjust the shape of the laser spot includes: controlling the sign and size of the defocus distance so that the electrode surface is located in front of the laser focal plane to form a pre-focal zone bubble, located in the Rayleigh region to form a Rayleigh region bubble, or located behind the focal plane to form an over-focal zone bubble; wherein, the pre-focal zone bubble undergoes a brief vibration during growth and then transitions to stable growth, the Rayleigh region bubble exhibits a growth mode of gradually attenuating vibration within a specific diameter range, and the over-focal zone bubble mainly grows stably.

[0053] In some embodiments, when the bubble is in a periodic oscillation state under the competition of thermocapillary force and interfacial separation pressure, the output bias voltage of the electrochemical workstation is cut off at the moment when the bubble and the flow field reach resonance, so that the bubble stops growing and detaches from the electrode surface, thereby obtaining an isolated bubble with inherent amplitude-frequency characteristics.

[0054] In some embodiments, the optical path position of the semiconductor laser 2 is shifted so that the isolated bubble and its surrounding liquid microstructure system move along a preset planar trajectory, and after moving to the target position, it relaxes and recovers stable oscillation.

[0055] Based on the above embodiments 1 and 2, the beneficial effects of the present invention are verified by the following embodiments 3-5.

[0056] Example 1: Taking the TiO2 / FTO thin film electrode as an example, the fluorine-doped tin oxide (FTO) conductive glass substrate was ultrasonically cleaned sequentially with deionized water, acetone, and ethanol, and then dried with nitrogen. A precursor solution containing 30 mL of deionized water, 30 mL of hydrochloric acid (36 wt%), and 1 mL of tetrabutyl titanate (0.05 mol / L) was prepared. The substrate was immersed in this solution and placed in an autoclave lined with polytetrafluoroethylene, and heated at 160 °C for 2 hours in a vacuum drying oven. After cooling to room temperature, the sample was removed and annealed in a muffle furnace at 400 °C for 30 minutes to obtain the TiO2 nanorod array thin film electrode.

[0057] based on Figure 1 and Figure 2 The described apparatus, with different defocus distances, forms UFB-type bubbles in the front-focus region, RLB-type bubbles in the Rayleigh region, and OFB-type bubbles in the overfocus region, respectively. Using a high-speed camera to photograph from the bottom of the test electrode, it is clearly observed that the differentiation process of the liquid-phase microstructure is related to the spatial distribution of the laser at the bubble movement contact line, such as... Figure 8 As shown. This embodiment demonstrates that the formation of liquid-phase microstructures is directly related to the spatial modulation of laser light. Based on this, through... Figure 6 The bubble-laser optical simulation method described can directly obtain the influence of bubble sites and growth parameters on the laser intensity distribution.

[0058] Example 2: (1) Under a laser power of 10mW, with different defocus distances, RLB-type bubbles in the Rayleigh region exhibit a growth mode with gradually decreasing vibration within a specific diameter range; UFB-type bubbles in the pre-focal region transition to stable growth after a brief vibration process; while OFB-type bubbles in the over-focal region mainly exhibit stable growth. During the vibration stage, both RLB-type and UFB-type bubbles undergo simple harmonic vibration, and the vibration frequency of UFB-type bubbles is higher than that of RLB-type bubbles. When RLB-type bubbles begin to vibrate, the degree of liquid ridge aggregation is very high. The evolution of displacement over time and vibration details of the above three bubble modes are as follows: Figure 9 As shown in Figure (a), the figure illustrates the variation of bubble displacement Δx with time t in three modes: UFB, RLB, and OFB, along with magnified details of the corresponding vibration stages, verifying the differences in bubble vibration behavior at different defocus distances. A ridge-like liquid phase structure continuously develops and forms during the vibration of the RLB-type bubble, and a stable liquid phase structure characterizes the cessation of bubble vibration. This example demonstrates that the method of this invention can effectively control the bubble vibration process and confirms the mediating role of the liquid phase structure in the bubble vibration process.

[0059] (2) Under a bias voltage of 0.1 V, the system was controlled to generate RLB-type bubbles. The overpotential change curve of the reaction process was recorded using an electrochemical workstation, and the results are as follows: Figure 9As shown in (b), the RLB bubble in a stable oscillating state exhibits the lowest reaction overpotential among the three bubble modes. Within its oscillation time window, the overpotential fluctuation frequency perfectly matches the bubble oscillation frequency, with an amplitude of only 1.5 mV, and shows an overall decreasing trend; once the oscillation stops, the overpotential rises sharply. This embodiment demonstrates that the method of the present invention can effectively improve the catalytic efficiency of the photoelectrochemical reaction process.

[0060] Example 3: At a specific moment of bubble-flow field resonance, the bias voltage of the electrochemical workstation is rapidly cut off. At this point, due to the cessation of the electrochemical reaction, bubble growth stops, but the oscillation state of the bubble itself and the surrounding liquid ridge is preserved. The separated bubble, under the sole action of a 15 mW laser, continues to maintain its original amplitude-frequency characteristics and oscillates stably, as shown below. Figure 10 As shown in (a), by translating the laser beam path, the bubble-microstructure liquid phase system can be guided to move along a preset planar trajectory. After moving to the new position, it resumes stable oscillation after a relaxation time of approximately 0.8 s, as shown in (a). Figure 10 As shown in (b), this embodiment demonstrates the ability of the method of the present invention to precisely control the customized separation of bubble size and free-path transport.

[0061] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A photothermal bubble control device based on liquid-phase microstructure effect, characterized in that, It includes a support frame (1), a semiconductor laser (2), a beam expander (3), an optical lens (4), a high-precision three-dimensional displacement platform (5), a testing platform (6), a high-speed camera, and an electrochemical workstation; The semiconductor laser (2), beam expander (3), and optical lens (4) are sequentially fixed and assembled on the support frame (1) along the optical path direction, together forming the laser emission optical path; The high-precision three-dimensional displacement platform (5) is arranged on the light-emitting side of the laser emission path and is used to mount the photoactive electrode and adjust the defocus distance of the electrode relative to the laser focal plane. The test platform (6) is used to place an electrolytic cell containing electrolyte, and the photoactive electrode mounted on the high-precision three-dimensional displacement platform (5) can extend into the electrolytic cell; The high-speed camera is positioned towards the electrolytic cell and the photoactive electrode for in-situ synchronous observation of the evolution of bubble and liquid phase microstructures. The electrochemical workstation is electrically connected to a photoactive electrode, which is used to apply a constant bias voltage to the electrolysis system, driving an electrochemical reaction on the electrode surface and generating bubbles.

2. The photothermal bubble control device based on liquid-phase microstructure effect according to claim 1, characterized in that, The high-precision three-dimensional displacement platform (5) includes an x-axis adjustment platform (5-3), a y-axis adjustment platform (5-2), and a z-axis adjustment base (5-1). The x-axis adjustment platform (5-3) is the bottom support of the displacement platform and can move along the x-axis direction. The y-axis adjustment platform (5-2) is slidably installed above the x-axis adjustment platform (5-3) and can move along the y-axis direction. The z-axis adjustment base (5-1) is fixedly installed on the y-axis adjustment platform (5-2) and is used to support the photoactive electrode and realize displacement adjustment in the z-axis direction.

3. The photothermal bubble control device based on liquid-phase microstructure effect according to claim 1, characterized in that, The test platform (6) includes a height-adjustable auxiliary fixing platform (6-1), an electrode fixing and observation base (6-2), and a reflector (6-2-1); the electrode fixing and observation base (6-2) is installed on the height-adjustable auxiliary fixing platform (6-1); the reflector (6-2-1) is embedded in the inner side of the electrode fixing and observation base (6-2).

4. The photothermal bubble control device based on liquid-phase microstructure effect according to claim 1, characterized in that, It also includes an image processing and analysis unit; the image processing and analysis unit is communicatively connected to the high-speed camera and the semiconductor laser (2), respectively, and receives image data acquired by the high-speed camera and operating parameters of the semiconductor laser (2); the image processing and analysis unit is configured as follows: The image data is acquired, and dynamic parameters are extracted from the image data using a threshold segmentation algorithm. The dynamic parameters include bubble displacement, contact angle, contact diameter, and projected area of ​​liquid phase microstructure. Based on the dynamic parameters and / or operating parameters, the laser propagation path and the secondary focusing effect of the bubble are simulated by Monte Carlo ray tracing, and the actual light intensity distribution and temperature gradient of the electrode surface and bubble interface are calculated according to the simulation results.

5. The photothermal bubble control device based on liquid-phase microstructure effect according to claim 1, characterized in that, The high-speed camera has a detachable filter mounted on the front end of its lens; the device is also equipped with a background illumination optical path, in which a diffuser is provided, which is arranged facing the electrolytic cell and the observation area to provide uniform supplementary light.

6. A method for controlling photothermal bubbles based on liquid-phase microstructure effects, characterized in that, Based on the photothermal bubble control device according to any one of claims 1 to 5, the method includes: When the semiconductor laser (2) is turned on, the laser beam passes through the beam expander (3) and the optical lens (4) in sequence and is emitted to irradiate the surface of the photoactive electrode, forming a light intensity field with a preset spatial distribution, and forming a photothermal temperature gradient in the local area of ​​the electrode. A constant bias voltage is applied to the photoactive electrode by an electrochemical workstation to generate bubbles on the electrode surface. The photothermal temperature gradient is used to excite thermocapillary force at the three-phase contact line of the bubbles, driving the surface liquid film to converge or collapse, forming a ridge-like or thin-film liquid phase microstructure. By adjusting the high-precision three-dimensional displacement platform (5) to change the defocus distance of the electrode relative to the laser focal plane to adjust the shape of the laser spot, or by adjusting the output power of the semiconductor laser (2), the spatial distribution and magnitude of the photothermal temperature gradient are changed, thereby adjusting the competitive relationship between thermocapillary force and interface separation pressure, so that the liquid phase microstructure switches between periodic pulsation state and collapse and spreading state, driving the bubble to complete de-nailing, periodic oscillation or directional sliding, so as to realize non-contact manipulation of the bubble and enhanced reaction mass transfer.

7. The photothermal bubble control method based on liquid-phase microstructure effect according to claim 6, characterized in that, The method of adjusting the shape of the laser spot by changing the defocus distance of the electrode relative to the laser focal plane by adjusting the high-precision three-dimensional displacement platform (5) includes: By controlling the sign and size of the defocus distance, the electrode surface can be positioned in front of the laser focal plane to form a pre-focal zone bubble, in the Rayleigh zone to form a Rayleigh zone bubble, or behind the focal plane to form an over-focal zone bubble. Among these, the pre-focal zone bubble undergoes a brief period of vibration during its growth before transitioning to stable growth, the Rayleigh zone bubble exhibits a growth pattern of gradually decreasing vibration within a specific diameter range, and the over-focal zone bubble mainly grows stably.

8. The photothermal bubble control method based on liquid-phase microstructure effect according to claim 6, characterized in that, When the bubble is in a periodic oscillation state under the competition between the thermocapillary force and the interfacial separation pressure, the output bias voltage of the electrochemical workstation is cut off at the moment when the bubble and the flow field reach resonance, so that the bubble stops growing and detaches from the electrode surface, thus obtaining an isolated bubble with inherent amplitude-frequency characteristics.

9. The photothermal bubble control method based on liquid-phase microstructure effect according to claim 8, characterized in that, The optical path position of the semiconductor laser (2) is translated so that the isolated bubble and its surrounding liquid phase microstructure system move along a preset plane trajectory and then relax to restore stable oscillation after moving to the target position.

10. The photothermal bubble control method based on liquid-phase microstructure effect according to claim 6, characterized in that, When the electrochemical workstation applies a constant bias voltage, the electrolyte used is a neutral Na2SO4 solution of 0.1~0.5 mol / L, and the photoactive electrode is a TiO2 nanorod array thin film electrode.

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