How to Make Hydrogen Gas Using Sulfur Dioxide and Electricity
This patent describes a special kind of electrolysis cell that uses sulfur dioxide gas at one electrode to help produce hydrogen gas more efficiently.
Original patent title: “Electrolysis cell comprising sulfur dioxide-depolarized anode and method of using the same in hydrogen generation”
This patent describes a special kind of electrolysis cell that uses sulfur dioxide gas at one electrode to help produce hydrogen gas more efficiently. Owned by Giner Electrochemical Systems with 33 claims and 9 forward citations, and it is expected to expire in 2028.
Coverage
What does this patent actually cover?
The patent describes an electrolysis cell designed to generate molecular hydrogen (H2) by oxidizing sulfur dioxide (SO2). The cell includes a frame (claimclaimA numbered sentence at the end of a patent that legally defines what the inventor owns. The most important section.Read more → 1a) and a separator, such as a proton exchange membrane (PEM) (claim 3), which divides the cell into chambers. An anode, which is a fluid diffusion electrode (claim 1c, claim 4), is placed away from the separator's anodic side, creating a first chamber filled with an electrolytic solution, such as aqueous sulfuric acid (claim 6). A cathode is connected to the separator's cathodic side (claim 1e). In operation, gaseous sulfur dioxide is fed to the anode, where it reacts, while hydrogen gas is produced at the cathode. This process uses sulfur dioxide to reduce the overall energy required for hydrogen production compared to just splitting water.
The gap
What does this patent NOT cover?
- Electrolysis cells that generate hydrogen without oxidizing sulfur dioxide at the anode.
- Systems where the anode is not a fluid diffusion electrode (e.g., a solid metal plate electrode not designed for gas or liquid reactants).
- Hydrogen generation methods that do not use an ionically-conductive separator, such as a proton exchange membrane.
- Electrolysis cells where the anode and cathode do not define specific chambers for sulfur dioxide, electrolyte, and hydrogen.
- Methods of hydrogen production that rely solely on water splitting without a depolarizing agent.
These exclusions are unique to PatentBrief — derived from the actual claim language, not patent-office boilerplate.
Key facts
What made this novel
The clever part is using sulfur dioxide as a reactant at the anode to "depolarize" the cell. Instead of needing a high voltage to split water at both electrodes, the sulfur dioxide reacts more easily, reducing the total energy input required to generate hydrogen. This makes the overall process more energy-efficient.
The Patent Drawing
Schematic visualization of the patent's claim structure. Hand-drawn diagrams in progress for each landmark patent.
Where you've seen this
Real-world examples
Industrial hydrogen production facilities
Chemical plants using sulfur dioxide byproducts
Advanced electrolysis systems for energy storage
Why it matters
The bigger picture
Generating hydrogen efficiently is important because hydrogen is a clean fuel and a key industrial chemical. Traditional water electrolysis uses a lot of electricity. This patent describes a method that uses sulfur dioxide as a "depolarizer" at the anode, meaning it reacts instead of water, potentially lowering the electrical energy needed to produce hydrogen. This approach could make hydrogen production more economical, especially if sulfur dioxide is available as a byproduct from other industrial processes.
Filed
August 1, 2008
Market context
Who's building on this
Companies in this space
Giner Electrochemical Systems LLC, the assigneeassigneeThe entity that owns the patent — usually the inventor's employer or a company.Read more →, continues to be active in advanced electrochemical systems, including hydrogen generation and fuel cells. Other companies in the industrial gas and chemical sectors, such as Linde and Air Products, are also investing in various methods of hydrogen production, including those that aim for higher efficiency or utilize industrial byproducts. Research institutions and startups focused on green hydrogen technologies also explore similar electrochemical pathways.
Market impact
This patent contributes to the ongoing effort to find more energy-efficient and cost-effective ways to produce hydrogen. By reducing the electrical energy input, SO2-depolarized electrolysis could lower the operational costs of hydrogen production, potentially making it more competitive with hydrogen derived from fossil fuels. While not creating an entirely new market, it offers a technological improvement within the existing industrial hydrogen market and for emerging clean energy applications, particularly where sulfur dioxide is readily available as a waste product.
Claim 1 — Plain English
What this patent covers
The patent describes an electrolysis cell designed to generate molecular hydrogen (H2) by oxidizing sulfur dioxide (SO2). The cell includes a frame (claim 1a) and a separator, such as a proton exchange membrane (PEM) (claim 3), which divides the cell into chambers. An anode, which is a fluid diffusion electrode (claim 1c, claim 4), is placed away from the separator's anodic side, creating a first chamber filled with an electrolytic solution, such as aqueous sulfuric acid (claim 6). A cathode is connected to the separator's cathodic side (claim 1e). In operation, gaseous sulfur dioxide is fed to the anode, where it reacts, while hydrogen gas is produced at the cathode. This process uses sulfur dioxide to reduce the overall energy required for hydrogen production compared to just splitting water.
The clever bit
The clever part is using sulfur dioxide as a reactant at the anode to "depolarize" the cell. Instead of needing a high voltage to split water at both electrodes, the sulfur dioxide reacts more easily, reducing the total energy input required to generate hydrogen. This makes the overall process more energy-efficient.
What it does not cover
- Electrolysis cells that generate hydrogen without oxidizing sulfur dioxide at the anode.
- Systems where the anode is not a fluid diffusion electrode (e.g., a solid metal plate electrode not designed for gas or liquid reactants).
- Hydrogen generation methods that do not use an ionically-conductive separator, such as a proton exchange membrane.
- Electrolysis cells where the anode and cathode do not define specific chambers for sulfur dioxide, electrolyte, and hydrogen.
- Methods of hydrogen production that rely solely on water splitting without a depolarizing agent.
Patent timeline
Application submitted to the patent office
Patent enters public domain
PatentBrief Score
Impact Score
Moderate
Citation count
20/40
Early citations
Claim breadth
20/20
Very broad protection
Recency
0/20
Older than 20 years
Assignee scale
0/20
Independent or smaller assigneeassigneeThe entity that owns the patent — usually the inventor's employer or a company.Read more →
PatentBrief Impact Score — based on citation count, claim breadth, recency, and assignee scale. Not a legal assessment.
Heuristic Value Estimate
What this patent might be worth
$92K – $295K
Midpoint $184K · 1.9 yr remaining · industry ×2.4
Heuristic only — blends forward/backward citation counts, claim scope, time remaining, litigation history, and CPC-derived industry baseline. Real valuations need a professional appraisal.
Claim text not yet imported for this patent
The original legal language
Original claims
33 claims as filed with the patent office.
Concepts involved
Citations
Patent lineage
Cite this patent
Stone, S. G., & Gestaut, L. J. How to Make Hydrogen Gas Using Sulfur Dioxide and Electricity (U.S. Patent No. 20,090,045,073). U.S. Patent and Trademark Office. https://patentbrief.org/patent/us/20090045073/electrolysis-cell-comprising-sulfur-dioxide-depolarized-anode-and-method-of-usin
Auto-generated from the patent record. Double-check author order and the issue date against the official USPTO document before submitting.
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Common Questions
Frequently Asked Questions
What does How to Make Hydrogen Gas Using Sulfur Dioxide and Electricity cover?
This patent describes a special kind of electrolysis cell that uses sulfur dioxide gas at one electrode to help produce hydrogen gas more efficiently.
Who owns patent US 20090045073?
This patent is owned by Giner Electrochemical Systems.
When does this patent expire?
This patent is expected to expire on August 1, 2028, when the invention enters the public domain.
What is patent US 20090045073 cited by?
This patent has been cited by 9 later patents that build on its ideas.
What problem does this patent solve?
Generating hydrogen efficiently is important because hydrogen is a clean fuel and a key industrial chemical. Traditional water electrolysis uses a lot of electricity. This patent describes a method that uses sulfur dioxide as a "depolarizer" at the anode, meaning it reacts instead of water, potentially lowering the electrical energy needed to produce hydrogen. This approach could make hydrogen production more economical, especially if sulfur dioxide is available as a byproduct from other industrial processes.
What does this patent NOT cover?
Electrolysis cells that generate hydrogen without oxidizing sulfur dioxide at the anode.
Patent monitoring