A catalyst surface potential testing device and method with microsecond time resolution

Abstract

The application discloses a catalyst surface potential testing device and method with microsecond time resolution, and the testing device comprises a circuit control unit, a surface potential testing unit and a signal acquisition unit which are connected in sequence. The disclosed device can read the potential on a nanosecond time interval, and the fastest response of the surface potential signal reading is 10 microseconds, thus breaking the limitation of the electrochemical workstation as a detector on the time interval of the sampling point. In addition, the field effect transistor is controlled by using a signal generator, so that the on-off of the circuit can be realized, and the time zero point is determined. The method has important significance for the research on catalyst kinetics.

Description

Technical Field

[0001] This application relates to a catalyst surface potential testing device and method with microsecond-level time resolution, belonging to the field of transient optical / photoelectric / electrocatalytic reaction kinetics measurement. Background Technology

[0002] In traditional catalytic reactions, the relationship between the back electrode potential (the applied electrode potential) and the surface catalytic reaction current is typically studied to evaluate catalyst performance. However, due to the potential for additional potential values ​​caused by partial voltages and applied light, the actual surface potential is not necessarily equal to the potential applied to the back electrode. Since the surface potential is the physical quantity directly related to the catalytic reaction, its study is crucial. Furthermore, because the reaction process is dynamic, a deeper understanding of the catalytic mechanism requires monitoring changes in its structure and surface catalytically active species across different time scales. Surface potential measurement techniques can characterize the redox state of the catalyst surface, providing information on surface structural changes; therefore, research into surface potential measurement techniques with ultra-high time resolution is of significant importance.

[0003] Currently, electrochemical workstations are primarily used to simultaneously read surface current and surface potential values. However, only a few modes (such as cyclic voltammetry, linear sweep voltammetry, and chronoamperometry) have the capability to simultaneously read surface potential. In these modes, the sampling time interval of the electrochemical workstation is limited, making it suitable only for measuring potential changes on the order of milliseconds. It cannot accurately read potential changes on the order of microseconds or nanoseconds. Furthermore, since reading surface potential requires circuit testing, once the test is closed, the electrochemical workstation cannot further read the decay value of the surface potential, limiting the investigation of catalyst structural changes. Therefore, for time-resolved potential studies, it is crucial to reduce dependence on electrochemical workstation readings. In addition, using an electrochemical workstation as a switch for circuit on / off operations results in inaccurate determination of the time starting point, affecting kinetic analysis. Summary of the Invention

[0004] The purpose of this application is to provide a device and method for measuring the surface potential of catalysts with microsecond-level time resolution. By inputting the potential signal into an oscilloscope and reading the potential at nanosecond-scale time intervals, the limitation of electrochemical workstations as detectors on the sampling time interval is overcome, verifying that the fastest response of the testing device to the surface potential signal is 10 microseconds. Furthermore, by using a signal generator to control a field-effect transistor, the circuit can be switched on and off, and the zero-point of time can be determined. This invention is suitable for measuring the surface potential of conductors or semiconductor materials.

[0005] According to one aspect of this application, a testing apparatus for measuring the surface potential of a catalyst is provided;

[0006] The testing device includes: a circuit control unit, a surface potential testing unit, a signal acquisition unit, and a signal output unit;

[0007] The circuit control unit is connected to the surface potential testing unit and controls the on / off state of the surface potential testing unit;

[0008] The surface potential testing unit is connected to the signal output unit;

[0009] The signal acquisition unit is connected to the circuit control unit and the signal output unit, respectively.

[0010] Optionally, the circuit control unit includes a signal generator;

[0011] The surface potential testing unit includes an electrochemical workstation, a reference electrode, a field-effect transistor, and a working electrode that is in contact with the catalyst to be tested. The electrochemical workstation is connected to the reference electrode and the source of the field-effect transistor, respectively. The drain of the field-effect transistor is connected to the working electrode. The field-effect transistor is used to control the current on and off of the working electrode.

[0012] The signal acquisition unit includes an oscilloscope;

[0013] The signal output unit includes a differential amplifier;

[0014] The differential amplifier includes an input terminal I for connection to the catalyst under test and an input terminal II for connection to the reference electrode;

[0015] The signal output terminal of the differential amplifier is connected to the oscilloscope;

[0016] The signal output terminal of the signal generator is connected to the gate of the field-effect transistor and the oscilloscope, respectively. The signal generator applies a bias voltage to the field-effect transistor through the gate to control the on / off state between the source and drain, thereby indirectly controlling the on / off state of the working electrode applied to the back potential of the catalyst under test.

[0017] The impedance of the differential amplifier is ≥10. 12 ohm.

[0018] Optionally, the surface potential testing unit further includes a sample cell and a counter electrode; the working electrode, the reference electrode, and the counter electrode are placed in the sample cell; the counter electrode is connected to the electrochemical workstation.

[0019] The electrochemical workstation applies a potential to the back of the catalyst under test via the working electrode (WE); the potential of the reference electrode (RE) serves as the zero point of the potential reference; and the counter electrode (CE) is used to form a circuit with the working electrode when measuring in solution.

[0020] Optionally, the input terminal I of the differential amplifier is electrically connected to a probe used to test the surface potential of the catalyst under test.

[0021] A differential amplifier can read the potential difference between its two input terminals. It has two input terminals: one connected to a probe and the other to a reference electrode. Reading the potential difference between the probe and the reference electrode is equivalent to reading the potential difference between the surface potential of the catalyst under test and the reference electrode. It also has two output terminals: one connected to the signal port of the auxiliary signal channel of an electrochemical workstation, and the other connected to an oscilloscope via a BNC interface.

[0022] According to another aspect of this application, a surface potential measurement method is provided. An electrochemical workstation applies a constant potential difference to a three-electrode system in a sample cell. The on / off state of the surface potential testing unit circuit is controlled by a signal generator. The potential of the reference electrode is input to a differential amplifier. The potential of the catalyst to be tested is input to the differential amplifier through a probe. The differential amplifier outputs the potential difference between the reference electrode and the catalyst to be tested. The change of the surface potential of the catalyst to be tested over time during the on / off state of the surface potential testing unit circuit is output via an oscilloscope.

[0023] The sample cell contains a horizontally placed catalyst to be tested, which may include a semiconductor single-crystal wafer, a metal sheet, a metal sheet with powder particles deposited on its surface, a semiconductor single-crystal wafer with powder particles deposited on its surface, or a hard substrate, etc. The working electrode is electrically connected to the lower surface of the catalyst to be tested, and the tip of the probe is in contact with the upper surface of the catalyst to be tested. The potential of the probe is equal to the surface potential of the catalyst to be tested.

[0024] The method uses the aforementioned testing apparatus.

[0025] Optionally, the method specifically includes the following steps:

[0026] (1) The electrochemical workstation applies a constant potential difference to the working electrode and the reference electrode in the three-electrode system, the signal generator is turned off, and the source and drain are disconnected.

[0027] (2) Turn on the signal generator, connect the source and drain, and input the trigger signal from the signal generator to the oscilloscope as the timing zero point;

[0028] (3) Turn off the signal generator and disconnect the source and drain;

[0029] (4) Read the change law of potential difference detected by differential amplifier over time during steps (1) to (3) from the oscilloscope.

[0030] Optionally, the output of the change in the surface potential of the catalyst under test over time has a time resolution on the order of microseconds.

[0031] According to another aspect of this application, an application for surface potential measurement is provided, wherein the testing apparatus and the method described herein are used to measure the surface potential of conductors and semiconductor materials. Laser pulses can be used simultaneously to study changes in the surface potential of the catalyst under illumination.

[0032] This invention can apply electrical pulses or light pulses to the catalyst under test to study the changes in surface potential over time in photo / photoelectric / electrocatalytic systems and provide information on catalytic reaction kinetics.

[0033] The beneficial effects that this application can produce include:

[0034] This application enables the reading of catalyst surface potential at nanosecond time intervals by inputting the catalyst surface potential signal into an oscilloscope, overcoming the limitation of electrochemical workstations as detectors regarding sampling time intervals. Furthermore, by using a signal generator to control a field-effect transistor, the on / off state of the circuit can be achieved, thus determining the zero-point of time. It is applicable to the measurement of localized surface potential of conductors or semiconductor materials under in-situ conditions. Attached Figure Description

[0035] Figure 1 This is a diagram of a device for testing the change in potential difference across a resistor in air.

[0036] Figure 2 This is a data graph showing the potential signal of a differential amplifier read using an electrochemical workstation. Figure 2 In diagram A, the potential difference across the resistor changes over time at the instant the electrical signal is applied. Figure 2 In the figure, B represents the change in the potential difference across the resistor over time at the instant the electrical signal is removed.

[0037] Figure 3 This is a data graph showing the readings of the differential amplifier's potential signal using an oscilloscope. Figure 3 In the diagram, A represents the rising edge data from the signal generator. Figure 3 B represents the falling edge data from the signal generator. Figure 3 In the figure, C represents the change in potential difference across the resistor over time at the instant the electrical signal is applied. Figure 3 In the figure, D represents the change in potential difference across the resistor over time at the instant the electrical signal is removed.

[0038] Figure 4 This is a diagram of the apparatus used to test the surface potential change of a gold electrode catalyst in situ in a 0.1 mol / L potassium chloride solution.

[0039] Figure 5 This is a data graph showing the readings of the differential amplifier's potential signal using an oscilloscope. Figure 5 In diagram A, the change in surface potential of the gold sheet over time at the instant the electrical signal is applied. Figure 5In Figure B, the change in surface potential of the catalyst gold sheet over time is shown at the instant the electrical signal is removed.

[0040] in:

[0041] 1-Electrochemical workstation; 2-Field-effect transistor; 3-Signal generator; 4-Oscilloscope; 5-Differential amplifier; 6-Sample to be tested (resistance wire); 7-Working electrode; 8-Counter electrode; 9-Reference electrode; 10-Gold probe; 11-Sample cell; 12-Catalyst to be tested (gold sheet). Detailed Implementation

[0042] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.

[0043] Unless otherwise specified, the raw materials and catalysts used in the embodiments of this application were all purchased commercially. The electrochemical workstation was purchased from Shanghai Chenhua Instrument Co., Ltd., and the field-effect transistor (STF8NM50N), signal generator (victory), differential amplifier (impedance of 1T ohm, Shanghai Chenhua Instrument Co., Ltd.), oscilloscope (Tektronix 5 series mixed signal), gold working electrode, gold probe (tip diameter 100um), graphite counter electrode, silver wire reference electrode, sample cell, and resistance wire (1kΩ) were also included.

[0044] Example 1

[0045] Test circuit response time: using Figure 1 The apparatus shown uses a resistance wire to conduct tests in air.

[0046] (1) Device connection

[0047] One end of the sample to be tested (resistance wire) 6 is connected to the working electrode 7, and the other end is simultaneously connected to the reference electrode 9 (counter electrode 8). The reference electrode 9 (counter electrode 8) is connected to the electrochemical workstation 1. The working electrode of the electrochemical workstation 1 is connected to the source of the field-effect transistor 2, passes through the inside, comes out from the drain, and is then connected to the other end of the working electrode 7.

[0048] The two input terminals of the differential amplifier 5 are connected to the reference electrode 9 (counter electrode 8) and the working electrode 7, respectively, and the two output terminals are connected to the oscilloscope 4 and the electrochemical workstation 1, respectively. The electrochemical workstation 1 is connected to the power supply terminal of the differential amplifier 5, and the differential amplifier 5 is powered by the electrochemical workstation 1.

[0049] The oscilloscope 4 is connected to the signal generator 3, and the other end of the signal generator 3 is connected to the gate of the field-effect transistor 2.

[0050] (2) Test

[0051] Turn on the electrochemical workstation 1, select the timing current (it) mode, and apply a potential difference of 0.5V between the working electrode 7 and the reference electrode 9 (counter electrode 8). Since the source and drain are open-circuited at this time, no current flows, and the sample under test (resistance wire) 6 does not sense the potential difference applied by the electrochemical workstation. The differential amplifier 5 reads the change in potential difference across the resistor and generates two signals. One signal is input to the electrochemical workstation 1, and the other is input to the oscilloscope 4, which are then processed by… Figure 2 Figure A in the middle and Figure 3 The data in graph C indicates that the reading is 0V at this time.

[0052] Turn on signal generator 3. Apply voltage to the gate of field-effect transistor 2 through signal generator 3, switching the source and drain to a conducting state. Input a trigger signal to oscilloscope 4 (e.g., Figure 3 As shown in Figure A), this serves as the zero point for timing. At this time, the working electrode 7 changes from an open circuit to a closed circuit, and the 0.5V potential difference applied by the electrochemical workstation 1 is sensed across the resistor. After the differential amplifier 5 reads the change in potential difference, it is input to the electrochemical workstation 1 and the oscilloscope 4.

[0053] Data from electrochemical workstation 1 ( Figure 2 As can be seen from Figure A, due to its limited sampling interval (when using the auxiliary potential measurement function, the sampling interval is required to be no less than 5 milliseconds), it can only read potential changes on the order of milliseconds, has low time resolution, and cannot determine the zero point of timing, which is not conducive to dynamic analysis.

[0054] As for the oscilloscope 4, it can read data on the order of nanoseconds, has high time resolution, and can accurately determine its timing zero point through a trigger signal. For example... Figure 3 As shown in Figure C, the time required for the potential difference across the resistor wire to jump from 0V to a stable 0.5V is approximately 10 microseconds, indicating that the circuit's response time to potential changes is approximately 10 microseconds, and signal changes greater than 10 microseconds can be accurately read.

[0055] Similarly, when signal generator 3 is turned off, signal generator 3 no longer applies voltage to the gate of field-effect transistor 2. At this time, there is an open circuit between the source and drain, no current flows, and the potential difference across the resistance wire decays to 0V. Figure 2 Figure B and Figure 3 The D-plots represent the potential decay values ​​read from electrochemical workstation 1 and oscilloscope 4, respectively.

[0056] from Figure 2 Figure B in the middle and Figure 3 As shown in Figure D, electrochemical workstation 1 cannot determine the zero point of timing and cannot read data in the microsecond range. Oscilloscope 4 shows that the time it takes for its potential to decay to zero is approximately 10 microseconds.

[0057] Example 2

[0058] The test measures the change in surface potential of the catalyst under solution conditions. The apparatus connection is as follows: Figure 4 As shown.

[0059] (1) Device connection

[0060] The catalyst to be tested (gold sheet) 12, counter electrode 8, reference electrode 9, and working electrode 7 are placed in the sample cell 11, and a 0.1 mol / L potassium chloride solution is added to the cell.

[0061] Graphite serves as the counter electrode 8, forming a current loop with the working electrode 7; silver wire serves as the reference electrode 9, acting as a reference point for potential measurement.

[0062] The back of the catalyst (gold sheet) 12 to be tested is connected to the working electrode 7. Specifically, the working electrode of the electrochemical workstation 1 is connected to the source of the field-effect transistor 2, and then from the drain through the inside to the back of the catalyst (gold sheet) 12 to be tested, which means that the potential value of the back of the catalyst (gold sheet) 12 to be tested is directly controlled.

[0063] The gold probe 10 directly contacts the surface of the catalyst (gold sheet) 12 to be tested. The two input terminals of the differential amplifier 5 are connected to the reference electrode 9 and the probe 10, respectively, to measure the potential value of the probe 10 relative to the reference electrode 9. The output terminal is connected to the oscilloscope 4. The electrochemical workstation 1 is connected to the power supply terminal of the differential amplifier 5, and the electrochemical workstation 1 supplies power to the differential amplifier 5.

[0064] Signal generator 3 is connected to the gate of oscilloscope 4 and field-effect transistor 2, respectively.

[0065] (2) Potential measurement

[0066] Turn on the electrochemical workstation 1 and select the chronoamperometry (IT) mode. Using the reference electrode 9 (silver wire) as the potential reference point, apply a constant potential of 0.5V to the working electrode 7 (the back of the catalyst (gold sheet) 12 under test). Since there is no current flowing between the source and drain at this time, the back of the catalyst (gold sheet) 12 under test cannot sense the constant potential applied by the electrochemical workstation 1. The value measured by the differential amplifier 5 can be read from the oscilloscope 4. The potential of the gold probe 10 relative to the reference electrode 9 is 0V. Figure 5 The data in Figure A is shown in the figure.

[0067] Signal generator 3 is turned on, and a voltage is applied to the gate of field-effect transistor 2 through signal generator 3, causing the source and drain to switch to a conducting state. A trigger signal is input to oscilloscope 4 as a timing zero point. At this time, the working electrode switches from an open circuit to a closed circuit, and a constant potential of 0.5V (relative to reference electrode 9) is sensed on the back of the catalyst (gold sheet) 12. The potential value detected by differential amplifier 5 is then read from oscilloscope 4. At this time, the potential of gold probe 10 relative to reference electrode 9 is 0.5V. Figure 5 As shown in Figure A.

[0068] Since the gold probe 10 is in direct contact with the surface of the catalyst (gold sheet) 12 under test, the potential value of the gold probe 10 is the surface potential value of the catalyst (gold sheet) 12 under test. That is, by applying a potential step signal to the back of the catalyst under test, the change in its surface potential can be detected by the gold probe 10.

[0069] When signal generator 3 is turned off, signal generator 3 no longer applies voltage to the gate of field-effect transistor 2. At this time, there is an open circuit between the source and drain, and no current flows. Electrochemical workstation 1 no longer applies potential to the back of the catalyst (gold sheet) 12 to be tested.

[0070] Read the differential amplifier values ​​from the oscilloscope, such as... Figure 5 As shown in Figure B, unlike the instantaneous potential decay phenomenon of the catalyst (resistance wire) 6 in Example 1, the potential of the gold probe (relative to the reference electrode 9) decays slowly over a microsecond timescale, indicating that the surface potential of the catalyst (gold sheet) 12 changes slowly. This experiment provides microsecond-scale time-resolved potential data for studying the discharge mechanism of metals in solution.

[0071] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A testing device for measuring the surface potential of a catalyst, characterized in that, The testing device includes: a circuit control unit, a surface potential testing unit, a signal acquisition unit, and a signal output unit; The circuit control unit is connected to the surface potential testing unit and controls the on / off state of the surface potential testing unit circuit; the circuit control unit includes a signal generator, which is used to control the on / off state of the circuit and output a trigger signal to an oscilloscope to determine the zero point of time; The surface potential testing unit is connected to the signal output unit; the surface potential testing unit includes a field-effect transistor, whose gate is connected to a signal generator, its source is connected to an electrochemical workstation, and its drain is connected to a working electrode. The signal acquisition unit includes an oscilloscope for acquiring signals with a time resolution on the order of microseconds; the signal acquisition unit is connected to the circuit control unit and the signal output unit respectively.

2. The testing apparatus according to claim 1, characterized in that, The circuit control unit includes a signal generator; The surface potential testing unit includes an electrochemical workstation, a reference electrode, a field-effect transistor, and a working electrode that is in contact with the catalyst to be tested. The electrochemical workstation is connected to the reference electrode and the source of the field-effect transistor, respectively, and the drain of the field-effect transistor is connected to the working electrode. The signal acquisition unit includes an oscilloscope; The signal output unit includes a differential amplifier; The differential amplifier includes an input terminal I for connection to the catalyst under test and an input terminal II for connection to the reference electrode; The signal output terminal of the differential amplifier is connected to the oscilloscope; The signal output terminal of the signal generator is connected to the gate of the field-effect transistor and an oscilloscope, respectively.

3. The testing apparatus according to claim 2, characterized in that, The impedance of the differential amplifier is ≥10. 12 ohm.

4. The testing apparatus according to claim 2, characterized in that, The surface potential testing unit also includes a sample cell and a counter electrode; The working electrode, the reference electrode, and the counter electrode are placed in the sample cell; the counter electrode is connected to the electrochemical workstation.

5. The testing apparatus according to claim 2, characterized in that, The input terminal I of the differential amplifier is electrically connected to a probe used to test the surface potential of the catalyst under test.

6. A method for measuring the surface potential of a catalyst, characterized in that, The method uses the testing apparatus according to any one of claims 1 to 5; The electrochemical workstation applies a constant potential difference to the three-electrode system in the sample cell. The on / off state of the surface potential testing unit circuit is controlled by the switch of the signal generator. The potential of the reference electrode is input to the differential amplifier. The potential of the catalyst to be tested is input to the differential amplifier through the probe. The differential amplifier outputs the potential difference between the reference electrode and the catalyst to be tested. The change of the surface potential of the catalyst to be tested over time during the on / off state of the surface potential testing unit circuit is output by the oscilloscope. The sample cell contains a horizontally placed catalyst to be tested, the upper surface of which is in contact with the probe and the lower surface of which is electrically connected to the working electrode. The catalyst to be tested is selected from one of the following: semiconductor single crystal wafer, metal sheet, metal sheet with powder coating on surface, and semiconductor single crystal wafer with powder coating on surface.

7. The measurement method according to claim 6, characterized in that, The method further includes the following steps: (1) The electrochemical workstation applies a constant potential difference to the working electrode and the reference electrode in the three-electrode system, the signal generator is turned off, and the source and drain are disconnected; (2) Turn on the signal generator, and conduct between the source and drain. The trigger signal is input from the signal generator to the oscilloscope as the timing zero point. (3) Turn off the signal generator and disconnect the source and drain; (4) Read the change law of potential difference detected by differential amplifier over time during steps (1) to (3) from the oscilloscope.

8. The measurement method according to claim 6, characterized in that, The output shows the change in the surface potential of the catalyst under test over time with a time resolution on the order of microseconds.

9. An application of surface potential measurement, characterized in that, The testing apparatus according to any one of claims 1 to 5 and the measurement method according to any one of claims 6 to 8 are used for measuring the surface potential of conductors and semiconductor materials.

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