System and method for increasing hydrogen production in an electrolytic cell

Abstract

The present invention relates to a polymer electrolyte membrane (PEM) or an alkaline electrolytic cell having a compact structure for generating high-purity hydrogen, and an apparatus and a method for enhancing the hydrogen generation efficiency of these apparatuses.

Description

Technical Field

[0001] The present invention relates to a polymer electrolyte membrane (PEM) or an alkaline electrolytic cell having a compact structure for generating high-purity hydrogen, and an apparatus and a method for enhancing the hydrogen generation efficiency of these apparatuses.

Background Art

[0002] Hydrogen production can be achieved from fossil fuels, solar energy, biomass, natural gas, and electrolysis of water. Among these methods, the method by electrolysis of water is the cleanest and simplest method. Electrolysis of water is performed by applying a direct current (DC) potential via an external circuit to an anode electrode and a cathode electrode immersed in an electrolyte to separate water into hydrogen ions and oxygen ions. The electrolysis method of water is divided into two types: alkaline water electrolysis and PEM water electrolysis at low temperature.

Summary of the Invention

Problems to be Solved by the Invention

[0003] In the prior art, the generation of hydrogen and oxygen was performed in the cell at a constant voltage. During electrolysis, oxygen bubbles formed by the reaction at the anode adhere to the electrode surface. This corrodes the electrode and reduces the active surface area in contact with the interface between the electrode and the electrolyte. As a result, the electrode consumes more energy and the cell efficiency is reduced.

[0004] The paper "Pulsed water electrolysis: A review" by Rocha et al. discloses possible reasons for the increase in efficiency, including an increase in the concentration of reactants on the electrode surface, improvement in bubble separation from the electrode, and deterioration of the electric double layer.

[0005] In the prior art, no operation can reduce the impact voltage to 0 volts. In the present invention, the fact that the voltage value drops to 0 volts stops the generation of hydrogen and provides time for the bubbles to separate from the electrode surface. This reduces the corrosion effect of oxygen on the anode side.

Means for Solving the Problems

[0006] The solution provided by the present invention is a system developed to prevent electrode corrosion, reduce the problem that the electrode consumes more energy due to the decrease in the active surface area in contact with the interface between the electrode and the electrolyte, resulting in a decrease in cell efficiency, and generate more hydrogen per unit power value over a long period of time.

[0007] There is a prior art electrolysis system to which a pulsed voltage is applied, but the method of hydrogen generation by applying a pulsed voltage to a PEM or an alkaline electrolytic cell is not included in the prior art.

[0008] In the food industry and medical and biomedical applications in the health-related fields, space research, especially the defense industry, the energy industry and the automotive industry, the use of hydrogen or oxygen obtained by applying a square wave signal obtained by PWM to a PEM or an alkaline electrolytic cell is very important.

Effects of the Invention

[0009] According to the present invention, the overvoltage caused by gas accumulation in the cell is reduced by the pulsed voltage, and the hydrogen generation ability per unit power value is improved.

[0010] PWM is known as a method of controlling the levels of logic 1 and logic 0 by switching a DC potential at a predetermined time point. One of the greatest advantages of the PWM method is that the average power of the constant voltage applied to the load is divided into multiple parts. In this case, instead of applying a DC potential to a PEM or an alkaline electrolytic cell, the oxygen bubbles formed on the anode side of the pulsed voltage application reduce the energy required for hydrogen generation during electrolysis while adhering to the electrode surface.

[0011] The voltage pulses applied to the PEM or alkaline electrolytic cell reduce the concentration loss by increasing the cell's energy consumption and mass transfer. However, the O2 gas formed during the decomposition of H2O separates from the electrode surface during the dead time, thereby improving the cell efficiency.

Brief Description of the Drawings

[0012]

Figure 1

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Figure 5

Embodiments for Carrying Out the Invention

[0013] The device of the present invention includes a square-wave oscillator integrated circuit (1) used to control the MOSFET transmission state or cut-off state, a potentiometer (2, 3) used when adjusting the duty cycle value of the square-wave signal (the duty cycle means the ratio of the total time (Period) during which the system is operating), a MOSFET drive integrated circuit (4) for enhancing the performance of the MOSFET transmission state and cut-off state, a resistor-1 (5) for enabling stable operation of the MOSFET, a resistor-2 (6) for transmitting the square-wave signal to the MOSFET door pin, a MOSFET (7) functioning as an electronic switching element used to supply the square-wave signal to the PEM electrolytic cell, and a PEM or alkaline electrolytic cell (8) used for hydrogen generation. An adjustable DC power supply (9) is preferably used to operate the square-wave oscillator integrated circuit and the MOSFET drive integrated circuit of +15V. Another DC power supply (10) of preferably +2V or +2.5V is connected to the electrodes of the electrolytic cell. An oscilloscope (11) is used to monitor and control the changes in the duty cycle value, frequency value, and amplitude value from the parameters of the square-wave signal applied to the PEM electrolytic cell.

[0014] The pulsed voltage of the PEM electrolytic cell and the procedure of the hydrogen generation method are as follows.

[0015] Electronic circuit board Pulse width modulation is performed using a MOSFET, which is an electronic switching element for the DC potential applied to a PEM or an alkaline electrolytic cell. The control of the transmitting state and the cut-off state of the MOSFET is preferably performed using a square wave oscillator integrated circuit (1) of the TL type, and even more preferably the TL494 integrated circuit. The square wave signal at the output pin of the TL494 integrated circuit is amplified by using a MOSFET drive integrated circuit (4), preferably the TC4420, so as to be transmitted to the MOSFET, and is applied to the gate pin of the MOSFET. The anode electrode of the PEM or the alkaline electrolytic cell depends on the DC potential at the drain pin of the MOSFET. The MOSFET acts as a short circuit when the MOSFET is in the transmitting zone and no voltage is generated at the electrode, while it acts as an open switch when the MOSFET is in the cut-off zone and the voltage at the drain terminal is generated at the electrode. Therefore, pulse width modulation is executed, and a pulsed potential is obtained in the PEM or the alkaline electrolytic cell. The amplitude value of the pulsed potential is determined by the amplitude value of the DC potential used, but the frequency and the duty cycle can be adjusted by the potentiometer used in the square wave oscillator. Therefore, the amount of hydrogen generated and the energy consumed by the PEM or the alkaline electrolytic cell are controlled.

[0016] Control card algorithm The control of the desired hydrogen production amount and the energy consumed by the PEM or the alkaline electrolytic cell is achieved by changing the value of the potentiometer in the square wave oscillator or by changing the voltage supplied by the adjustable DC power supply used to determine the amplitude of the square wave. The optimum values of the frequency and the duty cycle are determined so as to achieve the desired hydrogen production amount value. The duty cycle and the amplitude value are used to determine the amount of energy by which the cell expands, and the frequency value is used to determine the frequency of the signal applied to the PEM or the alkaline electrolytic cell.

[0017] Figure 1 shows the application of the square wave signal obtained by PWM to the PEM or the electrodes of the alkaline electrolytic cell. The square wave oscillator integrated circuit (1) controls the transmission state and the cut-off state of the MOSFET (7). Since the output current of this integrated circuit is insufficient to change the state of the MOSFET, it is amplified by the MOSFET drive integrated circuit (4). The anode (+) electrode of the PEM or the alkaline electrolytic cell is connected to the drain pin of the MOSFET. The cathode (-) electrode is grounded, and the PEM electrolytic cell circuit is complete.

[0018] Figure 2 shows the control algorithm of the frequency and duty cycle of the square wave signal for the optimal hydrogen production amount and the energy consumption value. As initial values, the preparation of the electrolyte, the application of an adjustable DC potential to the circuit for operating the TL494 square wave oscillator integrated circuit (1), and the application of an adjustable DC power supply (7) to the drain terminal of the MOSFET to determine the amplitude value of the square wave signal to be applied to the PEM or the alkaline electrolytic cell are performed. After adjusting the initial values, a square wave signal is obtained at the electrodes of the PEM electrolytic cell. Hydrogen production is observed with the start of electrolysis. The performance of the PEM or the alkaline electrolytic cell can be compared with the amount of hydrogen generated at different duty cycle values, frequency values, and amplitude values. For the comparison of the amount of hydrogen, the duty cycle of the square wave signal is maintained at a constant value between 0% and 100%. The frequency of the signal is selected at a value between 0 Hz and 1 MHz. The amplitude value from the adjustable DC power supply to the cell operating voltage is set, and the amount of hydrogen generated value is recorded. The same process is continued by changing the duty cycle value, frequency value, and amplitude value of the square wave signal. The inventors draw conclusions by comparing the recorded amounts of hydrogen.

[0019] In the prior art, no operation reduces the impact voltage to 0 volts. In the present invention, the fact that the voltage value drops to 0 volts stops the production of hydrogen and gives time for the bubbles to separate from the electrode surface. Thereby, the corrosion effect of oxygen on the anode side is reduced.

[0020] The method applied to electrolysis implemented in the system targeted by the present invention will be described below. · As a result of ion transport in the electrolytic cell where an electrochemical reaction occurs, hydrogen is generated. The current applied between the anode electrode and the cathode electrode attracts opposite charges. · H+ ions are transported to the electrodes by the ion-conductive electrolyte. At the cathode, hydrogen gas is generated as electrons pass through the external circuit. This situation also occurs similarly in PEM and alkaline electrolytic cells. · The electronic control board controls the current applied to the electrolytic cell and is connected to the anode current collector. This system switches the positive (+) pole of the resource. The cathode current collector of the cell is directly connected to the ground (GND).

Industrial Applicability

[0021] Hydrogen is a widely spread energy carrier because it has a high weight density. Today, hydrogen production methods are still not widely used due to their high cost. However, research is being conducted to reduce the production cost and improve the performance of hydrogen production systems. The amount of hydrogen generated in the present invention is shown in FIGS. 4 and 5, where the same amount of hydrogen is generated with lower energy requirements compared to the prior art. Therefore, while the hydrogen production cost is reduced according to the consumed energy, the hydrogen production performance of the system is improved. As a result, an increase in the utilization of hydrogen energy in fields such as the defense industry, space, automotive industry, and portable and stationary large-scale systems is expected.

Explanation of Signs

[0022] 1 Square wave oscillator integrated circuit 2 Potentiometer - 1 3 Potentiometer - 2 4 MOSFET drive integrated circuit 5 Resistor - 1 6 Resistor - 2 7 MOSFET 8 Electrolytic cell 9 Adjustable DC power supply (for integrated circuit) 10 Adjustable DC power supply (for electrolytic cell) 11 Oscilloscope

Claims

1. A control circuit for an electrolytic cell, comprising an electrolytic cell (8), a MOSFET (7) acting as an electronic switching element for supplying a square wave signal to the electrolytic cell (8), a square wave oscillator integrated circuit (1) for controlling the MOSFET transmission state or cut-off state, a potentiometer (2, 3) for adjusting the duty cycle value of the square wave signal, a MOSFET drive integrated circuit (4) for enhancing the performance of the MOSFET transmission state and cut-off state, a resistor-1 (5) enabling stable operation of the MOSFET (7), a resistor-2 (6) for transmitting the square wave signal to the door pin of the MOSFET (7), an adjustable DC power supply (9) for operating the square wave oscillator integrated circuit (1) and the MOSFET drive integrated circuit (4), an adjustable DC power supply (10) connected to the electrodes of the electrolytic cell, an oscilloscope (11) for monitoring the duty cycle value, frequency value, and amplitude value of the square wave signal applied to the electrolytic cell, The control circuit is provided.

2. The control circuit according to claim 1, characterized in that the electrolytic cell is a polymer electrolyte membrane (PEM) electrolytic cell.

3. The control circuit according to claim 1, characterized in that the electrolytic cell is an alkaline electrolytic cell.

4. The control circuit according to claim 1, characterized in that the DC power supply (9) used for the operation of the integrated circuit (4) is +15V.

5. The control circuit according to claim 1, characterized in that the adjustable DC power supply (10) connected to the electrodes of the electrolytic cell is +2Vf.

6. The control circuit according to claim 1, characterized in that the square wave oscillator integrated circuit (1) is of the TL type.

7. The control circuit according to claim 6, characterized in that the square wave oscillator integrated circuit (1) is TL494.

8. An electrolytic cell, characterized by comprising the control circuit according to claim 1.

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