Electrolysis is a promising method for producing carbon-free hydrogen from nuclear and renewable resources. The process of separating hydrogen and oxygen from water through the use of electricity is called electrolysis. An electrolyzer is a device in which this reaction takes place. Electrolyzes can be as small as an appliance and be used for small-scale distributed hydrogen production or as large as central production facilities that could be linked directly to renewable or other forms of electricity production that do not emit greenhouse gases.
Electrolyzers, like fuel cells, have an electrolyte that separates the anode and cathode. Due primarily to the variety of electrolyte material and ionic species it conducts, various electrolyzers perform different functions. Polymer Electrolyte Membrane Electrolyzers are a solid specialty plastic material that serves as the electrolyte in a polymer electrolyte membrane (PEM) electrolyzer.
Oxygen and positively charged hydrogen ions (protons) are produced when water undergoes an anodic reaction. The hydrogen ions selectively cross the PEM to the cathode while the electrons move through an external circuit.
Hydrogen gas is produced when electrons from the external circuit and hydrogen ions combine at the cathode. Cathode Reaction: 2H2O + O2 + 4H+ + 4e. Alkaline electrolyzers work by transporting hydroxide ions (OH-) through the electrolyte from the cathode to the anode, generating hydrogen on the cathode side. 4H+ + 4e- 2H2. For a considerable amount of time, commercially available electrolyzers have utilized a liquid alkaline solution of sodium or potassium hydroxide as the electrolyte. On a laboratory scale, newer methods that use solid alkaline exchange membranes (AEM) as the electrolyte are promising.
Utilizing a solid ceramic material as the electrolyte, solid oxide electrolyzers generate hydrogen in a slightly distinct manner by selectively conducting negatively charged oxygen ions (O2-) at elevated temperatures. Hydrogen gas and negatively charged oxygen ions are produced when steam and electrons from the external circuit combine at the cathode.
After passing through the solid ceramic membrane, the oxygen ions react at the anode to produce oxygen gas and electrons for the external circuit.
Unlike PEM electrolyzers, which operate at 70°–90°C and commercial alkaline electrolyzers, which typically operate at less than 100°C, solid oxide electrolyzers must operate at temperatures that are high enough for the solid oxide membranes to function properly. Proton-conducting ceramic electrolyte-based advanced solid oxide electrolyzers at the laboratory scale have the potential to operate at temperatures between 500°C and 600°C.The solid oxide electrolyzers are able to effectively reduce the amount of electrical energy required to produce hydrogen from water by making better use of the heat that is available at these high temperatures from a variety of sources, including nuclear energy.
Why is this pathway being thought of?
The objective of lowering the price of clean hydrogen by eighty percent to one dollar per kilogram in a decade ("1 1 1") calls for electrolysis to take the lead in the production of hydrogen. Depending on the electricity used, hydrogen produced by electrolysis may produce zero emissions of greenhouse gases. When determining the advantages and economic viability of hydrogen production through electrolysis, it is necessary to take into account the cost and efficiency of the electricity that is required, as well as the emissions that are produced when electricity is generated.
Due to the emissions of greenhouse gases and the need for fuel due to the low efficiency of the electricity generation process, the current power grid is not ideal for providing the electricity required for electrolysis in many parts of the world. For renewable (wind, solar, hydro, and geothermal) and nuclear energy options, electrolysis-based hydrogen production is being investigated. These hydrogen creation pathways bring about practically zero ozone harming substance and models contamination outflows; However, in order to compete with more established carbon-based routes like natural gas reforming, the cost of production needs to be significantly reduced.
Potential for synergy with power generation from renewable energy sources. Hydrogen production through electrolysis may present opportunities for synergy with some renewable energy technologies' dynamic and intermittent power generation. For instance, despite the fact that the price of wind power has continued to fall, wind power's inherent variability prevents it from being used effectively. At a wind farm, hydrogen fuel and electric power generation could be combined, allowing production to be shifted in accordance with resource availability, system operational requirements, and market factors. Additionally, rather than reducing the amount of electricity produced by wind farms, it is possible to use this excess electricity to produce hydrogen through electrolysis during times of excess production.
It is essential to note that the majority of electricity generated by today's grid is generated using energy-intensive and greenhouse gas-emitting technologies, making it unsuitable for electrolysis. It is possible to overcome these limitations for hydrogen production through electrolysis by generating electricity using renewable or nuclear energy technologies, either independently of the grid or as a growing part of the grid mix.
The development of more effective fossil-fuel-based electricity production with carbon capture, utilization, and storage as well as efforts to reduce the price of electricity generated by renewable sources continue. For instance, worldwide, the production of electricity derived from wind is expanding at a rapid rate.
Improved understanding of the performance, cost, and durability trade-offs of electrolyzer systems under predicted future dynamic operating modes using CO2-free electricity is the focus of research aimed at meeting the production cost for green hydrogen at a scalable level so as to commercialize the use of a suitable source of energy in all industries.
Lowering the electrolyzer unit's and the system's balance's initial investment costs can play a major role in this along with improving the efficiency of the use of energy for converting electricity to hydrogen in a variety of different operating conditions. Finally, developing mitigation strategies to extend the operational life of electrolyzer cells and stacks and gaining a better understanding of their degradation processes will smoothen the entire production process for green hydrogen.
