H2 Production: A Shift Towards Electrolysis

Hydrogen production technology, according to the joint EPO-IEA report summarizing patent trends in the hydrogen economy (summarized here), accounts for the largest percentage of patenting activity since 2011 among the three primary stages of the hydrogen value chain (i.e., (i) production, (ii) storage, distribution, and transformation, and (iii) end-use industrial applications). Trends show a shift in hydrogen production from carbon-intensive methods to technologies that do not rely on fossil fuels. The bulk of recent increased patent activity is directed to electrolysis development, while patent activity related to production from biomass and waste has decreased.


Electrolysis is attractive because it’s a low-emission source, meaning that hydrogen produced through electrolysis creates little to no greenhouse gas emissions. It is possible that water electrolyzers are powered by electricity derived from natural gas or fossil fuels, but unlike most other hydrogen production technology, electrolyzers do not produce greenhouse gas emissions and thereby offer the ability to produce hydrogen with net zero carbon emissions.

In this article, we will first briefly explain electrolysis and conventional concepts using electrolysis. Then, we will give an example of a technology that recently emerged from conventional electrolysis-based solutions. We will close with a brief description of alternative technologies for hydrogen production.

State of the Art

Electrolyzers use electricity to split water into hydrogen and oxygen. Specifically, an electrolyzer cell includes an anode and a cathode separated by a polymer electrolyte membrane. Water reacts at the anode to form oxygen and positively charged hydrogen ions. The hydrogen ions selectively move across the membrane to the cathode, where they combine with electrons from an external circuit to form hydrogen gas. A number of cells are assembled into a cell stack that efficiently produces hydrogen and oxygen. A standard electrolyzer stack includes membrane electrode assemblies, current collectors, and separator or bipolar plates.

Electrolyzers also range in size and type. Electrolyzer sizes range from small, appliance-size units to large-scale, central production facilities. Electrolyzer types include polymer electrolyte membrane (PEM) electrolyzers, alkaline electrolyzers, and solid oxide electrolyzers. Conventional electrolyzer stacks have capacities of 5 MW to 100 MW per stack, depending primarily on the membrane technology. 

Emerging Technologies

EvolOh is a California-based startup planning to build the world’s largest hydrogen manufacturing plant in Massachusetts this year to manufacture its anion-exchange membrane (AEM) electrolyzers. The plant will be used for fabrication and assembly of the AEM electrolyzer stacks for producing green hydrogen1. These compact and high-power density electrolyzer stacks should allow for high-speed manufacturing using low-cost materials based on domestic supply chain and no precious metals. With anticipated power ratings of up to 5 MW for a single stack and 50 MW for a single module, EvolOH’s stacks are intended to be designed for large-scale facilities.

As disclosed in EvolOH’s IP, its electrolyzer stack features a bipolar plate assembly including a bipolar plate, a hydrogen seal, a water seal, and a fluid distribution frame. The fluid distribution frame serves multiple purposes within the electrolyzer stack, including containing a cathode flow field, distributing water flow from one water delivery window to a leading edge of the anode flow field, collecting water and oxygen flow from the anode flow field and distributing the flows to oxygen collection windows, and engaging and curing hydrogen seal between the frame and a bipolar plate adjacent to the cathode flow field and a water seal between the frame and a bipolar plate adjacent to the anode flow field.2 In contrast to conventional bipolar plates that include simple flow distribution channels, the bipolar plate assembly of the EvolOH electrolyzer stack is intended to provide for a scalable electrolysis cell that can be utilized in a variety of electrolyzer types.

Also as described in EvolOH’s IP, its electrolyzer stack includes a compression system having a lower wrap and an upper wrap connected at a joint to form a continuous vertical tension boundary around the cell stack and its end units while providing access to opposite lateral ends of the stack.3 Conventional electrolyzer stacks may apply a compressive load on the cell stack using end structural plates drawn together by tie rods and adjustable elements such as screws, nuts, and springs. Unlike the conventional tie rod compression, the compressive system of EvolOH’s electrolyzer stack is intended to maintain adequate compression on the stack over a range of temperatures taking into account thermal expansion and compression.

EvolOH is among many companies focused on the development of electrolyzer technology to scale-up hydrogen to reach a broader market. For example, Air Liquide and Siemens Energy recently teamed up to form a joint venture last year to produce large-scale hydrogen electrolyzers in Europe. Set to open in 2023, they intend to produce a large-scale electrolyzer with an intended capacity of 100 MW that may reduce costs per kW by 33% by 2030. The EPO-IEA study finds that Siemens is one of the leading applicants in electrolyzer patent families since 2011 and that Air Liquide is a top applicant in patent families directed to established hydrogen production technologies as well as hydrogen storage and distribution technologies.

Alternative Hydrogen Production Options

In addition to electrolysis, hydrogen can be produced from other methods such as biomass or waste via gasification or pyrolysis, recovery of by-product hydrogen from chlor-alkali electrolysis, and methane pyrolysis. Hydrogen can be produced from natural gas through methods such as steam reforming, which emits carbon dioxide in the process. Widespread natural gas infrastructure makes hydrogen production from natural gas appealing, and developments in carbon capture, utilization, and storage technology may make this option even more appealing.

In our next post on the EPO-IEA’s report, “Hydrogen Patents for a Clean Energy Future: A Global Trend Analysis of Innovation Along Hydrogen Value Chains,” we will dive into the second technology segment of the hydrogen value chain—hydrogen storage, distribution, and transformation.

By Jason Engel, Ben Fechner, and Clare Frederick


1 Green hydrogen refers to hydrogen produced using renewable electricity, whereas gray hydrogen is generated from natural gas and black/brown hydrogen is generated from fossil fuel electricity.

2 U.S. Publication No. 2023/0002920, paragraph [0018] and Figs. 7A and 7B.

3 Id., at paragraph [0072].

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