Water Electrolyzer For Hydrogen

Electrolysis is a promising option for carbon-free hydrogen production from renewable and nuclear resources. Electrolysis is the process of using electricity to split water into hydrogen and oxygen. This reaction takes place in a unit called an electrolyzer. Electrolyzers can range in size from small, appliance-size equipment that is well-suited for small-scale distributed hydrogen production to large-scale, central production facilities that could be tied directly to renewable or other non-greenhouse-gas-emitting forms of electricity production.

How Does it Work
Like fuel cells, electrolyzers consist of an anode and a cathode separated by an electrolyte. Different electrolyzers function in different ways, mainly due to the different type of electrolyte material involved and the ionic species it conducts.

Polymer Electrolyte Membrane Electrolyzers
In a polymer electrolyte membrane (PEM) electrolyzer, the electrolyte is a solid specialty plastic material.

Water reacts at the anode to form oxygen and positively charged hydrogen ions (protons).
The electrons flow through an external circuit and the hydrogen ions selectively move across the PEM to the cathode.
At the cathode, hydrogen ions combine with electrons from the external circuit to form hydrogen gas. Anode Reaction: 2H2O → O2 + 4H+ + 4e- Cathode Reaction: 4H+ + 4e- → 2H2

Alkaline Electrolyzers
Alkaline electrolyzers operate via transport of hydroxide ions (OH-) through the electrolyte from the cathode to the anode with hydrogen being generated on the cathode side. Electrolyzers using a liquid alkaline solution of sodium or potassium hydroxide as the electrolyte have been commercially available for many years. Newer approaches using solid alkaline exchange membranes (AEM) as the electrolyte are showing promise on the lab scale.

Solid Oxide Electrolyzers
Solid oxide electrolyzers, which use a solid ceramic material as the electrolyte that selectively conducts negatively charged oxygen ions (O2-) at elevated temperatures, generate hydrogen in a slightly different way.
Steam at the cathode combines with electrons from the external circuit to form hydrogen gas and negatively charged oxygen ions.
The oxygen ions pass through the solid ceramic membrane and react at the anode to form oxygen gas and generate electrons for the external circuit.
Solid oxide electrolyzers must operate at temperatures high enough for the solid oxide membranes to function properly (about 700°–800°C, compared to PEM electrolyzers, which operate at 70°–90°C, and commercial alkaline electrolyzers, which typically operate at less than 100°C). Advanced lab-scale solid oxide electrolyzers based on proton-conducting ceramic electrolytes are showing promise for lowering the operating temperature to 500°–600°C. The solid oxide electrolyzers can effectively use heat available at these elevated temperatures (from various sources, including nuclear energy) to decrease the amount of electrical energy needed to produce hydrogen from water.

Why Is This Pathway Being Considered
Electrolysis is a leading hydrogen production pathway to achieve the Hydrogen Energy Earthshot goal of reducing the cost of clean hydrogen by 80% to $1 per 1 kilogram in 1 decade ("1 1 1"). Hydrogen produced via electrolysis can result in zero greenhouse gas emissions, depending on the source of the electricity used. The source of the required electricity-including its cost and efficiency, as well as emissions resulting from electricity generation-must be considered when evaluating the benefits and economic viability of hydrogen production via electrolysis. In many regions of the country, today's power grid is not ideal for providing the electricity required for electrolysis because of the greenhouse gases released and the amount of fuel required due to the low efficiency of the electricity generation process. Hydrogen production via electrolysis is being pursued for renewable (wind, solar, hydro, geothermal) and nuclear energy options. These hydrogen production pathways result in virtually zero greenhouse gas and criteria pollutant emissions; however, the production cost needs to be decreased significantly to be competitive with more mature carbon-based pathways such as natural gas reforming.

Potential for synergy with renewable energy power generation
Hydrogen production via electrolysis may offer opportunities for synergy with dynamic and intermittent power generation, which is characteristic of some renewable energy technologies. For example, though the cost of wind power has continued to drop, the inherent variability of wind is an impediment to the effective use of wind power. Hydrogen fuel and electric power generation could be integrated at a wind farm, allowing flexibility to shift production to best match resource availability with system operational needs and market factors. Also, in times of excess electricity production from wind farms, instead of curtailing the electricity as is commonly done, it is possible to use this excess electricity to produce hydrogen through electrolysis.

It is important to note...
Today's grid electricity is not the ideal source of electricity for electrolysis because most of the electricity is generated using technologies that result in greenhouse gas emissions and are energy intensive. Electricity generation using renewable or nuclear energy technologies, either separate from the grid, or as a growing portion of the grid mix, is a possible option to overcome these limitations for hydrogen production via electrolysis.

In an electrolysis process, two different ionization processes are taking place at the same time. Both water and electrolyte are competing in this case.

An electrolyte undergoes the same ionization process as water. The same oxidation and reduction would occur in an electrolyte.
Because an anion from the electrolyte competes with the hydroxide ions to give up an electron, and a cation competes with the hydrogen ion to get reduced by accepting the electron, an electrolyte must be chosen with care.

The cation of the electrolyte must have a lower electrode potential than H+. Always remember in any electrolysis the electrode potential of the cation of the electrolyte should be less than the electrode potential of the cation of the substance being electrolyzed and the electrode potential of the anion of the electrolyte should be more than the electrode potential of the anion of the substance being electrolyzed.

The production of green hydrogen using renewable energy sources has sparked enough interest in the electrolysis of water to produce hydrogen. Water electrolysis using renewable energy sources with no CO2 emissions is viewed as a promising method of increasing the rate of hydrogen production. In 2020, approximately 87 million tonnes of hydrogen were produced worldwide for various uses, including oil refining, the production of ammonia (NH3) (via the Haber process) and methanol (CH3OH) (via carbon monoxide [CO] reduction), and as a transportation fuel. The demand for hydrogen is expected to reach 500-680 million MT by 2050. The hydrogen production market was valued at $130 billion from 2020 to 2021 and is expected to grow at a 9.2% annual rate through 2030. But there's a catch: over 95% of current hydrogen production is based on fossil fuels, with very little being "green." Today, hydrogen production consumes 6% of global natural gas and 2% of global coal. Nonetheless, green hydrogen production technologies are gaining popularity. 

Electrolysis is a process that uses electricity to split water into H2 and O2. The flow of electrons through a conductive path, such as a wire, is what electricity is. This path is known as a circuit. The electrons move due to the electrical potential difference between the anode and the cathode. The anode has more electrons and is more unstable due to electron crowding. The electrons want to rearrange themselves in order to eliminate the difference. Electrons repel one another and try to move to a location with fewer electrons. That is a cathode.
Because pure water does not conduct electricity, water splitting is a slow redox reaction.

Chemistry
In the electrolyzer, there is one cathode and one anode connected to a power source. Electrons always flow from anode to cathode no matter what. The cathode is always where reduction occurs therefore electrons need to be there. Oxidation is the loss of electrons and reduction is the gain of electrons.
Briefly, at the negatively charged cathode, a reduction reaction takes place, with electrons (e−) from the cathode being given to hydrogen cations to form hydrogen gas
Cathode (reduction):2 H2O(l) + 2e− -- > H2(g) + 2 OH−(aq)
At the positively charged anode, an oxidation reaction occurs, generating oxygen gas and giving electrons to the anode to complete the circuit
Anode (oxidation): 2 OH−(aq) -- > 1/2 O2(g) + H2O(l) + 2 e−
A combination of these reactions produces:
2 H2O(l) → 2 H2(g) + O2(g)
H2 is produced at the cathode and O2 at the anode.
Electrolysis of water requires a minimum potential difference of 1.23 volts, though at that voltage external heat is required from the environment.

Water electrolysis bipolar cell stacks are composed of many individual electrochemical cells in electrical series. In practice, water electrolysis cell stacks that have just been stopped can retain a significant electrical charge due to residual hydrogen and oxygen remaining within each cell. Left alone, it may take many hours for this residual electrochemical charge to dissipate. System service and maintenance personnel must exercise extreme caution if attempting to service or replace these cell stacks soon after operation. For instance, a metal tool such as a wrench could inadvertently bridge a gap between a cell stack positive current terminal plate and an earth-grounded metal support frame, drawing a large current or an electrical arc with damage and injury as an unwanted result. Personnel not wearing appropriate insulating protective equipment are at risk as well.

Best practice for maintenance and service personnel is to verify that no significant electrical charge remains in the cell stack before removing safety guards and electrical connections from the cell stack. Personnel are advised to perform a cell stack voltage measurement to verify that the cell stack is discharged. In some cases, service personnel may also apply a properly designed service tool composed of a high-current shorting resistor across the discharged cell stack as an additional safeguard. 

Products are sold in all regions of China and exported to countries around the world. They have been sold in more than 20 countries and regions including the United States, Germany, Morocco, Kenya, Saudi Arabia, Vietnam, Algeria, India, Tanzania, and Taiwan. Successfully provided well -known enterprises such as China Aerospace, PetroChina, China Nuclear Group, BYD, Jiuli Specialty, Tony Electronics, Zheng Energy Group and other well -known enterprises. There are many green hydrogen hydrogen hydrogenation stations such as Wulanchabu, Haikou, Hainan, Hainan Haikou, Yunnan Kunming, etc. provide green and hydrogen -making projects.