System and Method for Increasing Hydrogen Production in Electrolyzers

This application is the national phase entry of International Application No. PCT/TR2023/050497, filed on May 31, 2023, which is based upon and claims priority to Turkish Patent Application No. 2022/015892, filed on Oct. 19, 2022, the entire contents of which are incorporated herein by reference.

The invention relates to Polymer Electrolyte Membrane (PEM) or alkali electrolyzers with a compact structure that produces high-purity hydrogen and a device and method for increasing the hydrogen production efficiency of these devices.

Hydrogen production can be realized from fossil fuels, solar energy, biomass, natural gas, and electrolysis of water. Among these methods, the method of electrolysis of water is the cleanest and simplest method. The electrolysis of the water takes place by separating the water into hydrogen and oxygen ions by applying direct current (DC) potential to the anode and cathode electrodes immersed in the electrolyte through the external circuit. The method of electrolysis of water is divided into two: alkaline water electrolysis at low temperature and PEM water electrolysis. In the prior art, hydrogen and oxygen production was performed in the cell with constant voltage. During electrolysis, oxygen gas bubbles formed in the reaction at the anode are attached to the electrode surface. This causes both corrosion of the electrodes and reduction of the active surface area in contact with the electrode and electrolyte interface, causing the electrodes to consume more energy and decrease cell efficiency.

The article “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 of bubble separation from the electrode, and degradation of the electrical double layer.

In the prior art, no operation reduces the impact voltage to 0 volts. In the invention, the fact that the voltage value decreases to 0 volts stops the production of hydrogen and allows time for the gas bubbles to separate from the electrode surface. This reduces the corrosive effects of oxygen on the anode side.

An electrolyzer control circuit includes:

The solution provided by the invention is a system developed both to prevent corrosion of the electrodes and to reduce the problems of decreasing the active surface area in contact with the electrode and electrolyte interface, causing the electrodes to consume more energy and decreasing the cell efficiency, and to produce more hydrogen with long life and unit power value.

Although there are electrolysis systems in the prior art where pulse voltage is applied, the method of hydrogen production by applying a pulse voltage to PEM or alkaline electrolyzers is not included in the state of the art.

The use of hydrogen or oxygen, which will be obtained by applying the square wave signal obtained by PWM to PEM or alkali electrolyzers, in medical and biomedical applications in the food industry and health, from space research, especially in the defense industry, to the energy and automotive industry, is of great importance.

With this invention, the overvoltage caused by gas accumulations in the cell is reduced with the pulse voltage, and the hydrogen production potential at the unit power value is increased. PWM is known as the method of controlling logic 1 and logic 0 levels by switching the DC potential at certain times. One of the biggest advantages of the PWM method is that the average power of the constant voltage applied to the load is divided into parts. In this context, instead of applying DC potential to PEM or alkaline electrolysis cells, oxygen gas bubbles formed on the anode side of pulse voltage application reduced the energy required for hydrogen production during electrolysis with the duration of adhesion to the electrode surface.

Voltage pulses applied to PEM or alkaline electrolyzers decreased concentration losses by increasing the cell's energy consumption and mass transfer. However, it was ensured that the Ogases formed during the decomposition of HO were separated from the electrode surface in the dead time zone and cell efficiency was increased.

The device of the invention includes a square wave oscillator integration () used to control mosfet transmission or cutting states, a Potentiometer (,) to be used in adjusting the duty cycle value of the square wave signal (duty cycle means the ratio of the period when the system is active to the total time (Period)), a mosfet driver integration () to increase the performance of the mosfet transmission and cutting states, a Resistance-1 () to ensure the stable operation of the mosfet, a Resistance-2 () to ensure that the square wave signal is transmitted to the mosfet door pin, a mosfet () to act as an electronic switching element used to provide a square wave signal to the PEM electrolyzer, and a PEM or alkali electrolysis cell () used for hydrogen production. The adjustable direct current power supply () is preferably used for operating the +15V, square wave oscillator integration, and mosfet drive integration. The other direct current power source (), preferably +2V or +2.5V, is connected to the electrodes of the electrolyzer. Oscilloscope () is used to monitor and control the change of duty cycle, frequency, and amplitude values from the parameters of the square wave signal applied to the PEM electrolyzer.

The steps followed for the pulsed voltage and hydrogen production method in the PEM Electrolyzer are as follows.

Pulse width modulation is performed using mosfet, an electronic switching element of the direct current potential applied to PEM or alkaline electrolyzers. The control of the transmission and cutting states of the mosfet is carried out with a square wave oscillator integration (), preferably TL-type, even more preferably TL494 integrated circuit. The square wave signal at the output pin of the TL494 integrated circuit is applied to the gate pin of the mosfet by amplifying a mosfet driver integration circuit (), preferably with TC4420 so that it can transmit the mosfet. The anode electrode of the PEM or alkaline electrolyzer depends on the direct current potential located in the drain pin of the mosfet. The mosfet acts as a short-circuit when it is in the transmission zone and no voltage is generated on the electrodes; it acts as an open switch when it is in the cutting zone and the voltage at the drain end is generated on the electrodes. Thus, pulse width modulation is carried out and the pulse potential is obtained on the PEM or alkali electrolyzer. While the amplitude value of the pulse potential is determined by the amplitude value of the direct current potential used, the frequency and duty cycle can be adjusted with the potentiometers used in the square wave oscillator. Thus, the amount of hydrogen produced, and the energy spent by the PEM or alkaline electrolyzer are controlled.

The desired amount of hydrogen production and control of the energy expended by the PEM or alkaline electrolyzer is accomplished by changing the values of the potentiometers in the square wave oscillator or by changing the voltage provided by the adjustable direct current power supply used to determine the amplitude of the square wave. The optimum value of the frequency and duty cycle is determined to achieve the desired hydrogen production amount values. The duty cycle and the amplitude value are used to determine the amount of energy the cell expands, while the frequency value is used to determine the frequency of the signal to be applied to the PEM or alkaline electrolyzer.

shows the application of the square wave signal obtained by the PWM to the electrodes of the PEM or alkaline electrolyzer. The square wave oscillator integration () controls the transmission and cutting states of the mosfet (). The output current of this integration is amplified by the mosfet drive integration () as it is not sufficient to change the state of the mosfet. The anode (+) electrode of the PEM or alkali electrolyzer is connected to the drain pin of the mosfet. The cathode (−) electrode has been grounded and the PEM electrolyzer circuit has been completed.shows the control algorithm of the frequency and duty cycle of the square wave signal for the optimum amount of hydrogen production and the energy value spent. Preparation of the electrolyte as initial values, application of the adjustable direct current potential to the circuit in order for the TL494 square wave oscillator integration () to operate, and application of the adjustable direct current power supply () to the drain end of the mosfet to determine the amplitude value of the square wave signal to be applied to the PEM or alkali electrolyzer are performed. After adjusting the initial values, a square wave signal is obtained at the electrodes of the PEM electrolyzer. Hydrogen production is observed with the start of electrolysis. The performance of the PEM or alkaline electrolyzer can be compared with the amount of hydrogen produced at a different duty cycle, frequency, and amplitude values. For 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 is set from the adjustable direct current power source to the cell operating voltage and the hydrogen amount values produced are recorded. The same process continues with changing the duty cycle, frequency, and amplitude value of the square wave signal. We conclude by comparing the recorded hydrogen amounts.

In the prior art, no operation reduces the impact voltage to 0 volts. In the invention, the fact that the voltage value decreases to 0 volts stops the production of hydrogen and allows time for the gas bubbles to separate from the electrode surface. This reduces the corrosive effects of oxygen on the anode side.

The method applied for the electrolysis to be performed with the system subject to the invention is described below.

Hydrogen has become quite popular as it is an energy carrier with a high gravimetric density. Today, hydrogen production methods are still not a widely used method due to their high cost. However, research is being conducted to reduce production costs and to improve the performance of hydrogen production systems. The amount of hydrogen produced in the present invention is shown in, where the same amount of hydrogen is produced as the lower energy requirement compared to the previous art. Thus, the cost of hydrogen production is reduced depending on the energy consumed, while the hydrogen production performance of the system is increased. As a result, the use of hydrogen energy is expected to increase in areas such as the defense industry, space, automotive industry, and portable and fixed large-scale systems.