Electrolysis Improvement Could Lead to Hydrogen’s Use as a Storage Medium
Hydrogen could be one step closer to becoming a viable storage medium for excess renewable energy as Duke University researchers reportedly enhance the efficiency and affordability of electrolysis.
Passing a current through water to break it into gaseous hydrogen and oxygen—electrolysis—could be a way to store excess energy produced by wind and solar systems. This is because the hydrogen can be stored and used as fuel later on when the sun has died down and the winds have calmed. Unfortunately, without a way to store excess energy affordably, billions of watts of renewable energy continue to be wasted each year.
At Duke University, Ben Wiley and his team have recently tested three new materials that they believe could be used as a porous, flow-through electrode to improve the efficiency of electrolysis. The team initially set out with the goal of increasing the surface area of the electrode for reactions while simultaneously avoiding trapping hydrogen gas bubbles.
Their research was published on May 25 and describes an alkaline water electrolysis process that uses a microfibrous flow-through electrode.
Flow-Through Electrodes
The team fabricated three kinds of the flow-through electrode, each consisting of a 4mm square of sponge-like material 1mm in thickness—the first was made of nickel foam, the second was a type of ‘felt’ made from nickel microfibres, and the third was a ‘felt’ made out of nickel-copper nanowires.
By pulsing current through these electrodes in cycles of five minutes on, five minutes off, the research team found that the nickel-copper nanowire felt initially produced hydrogen more efficiently because of its larger surface area.
Within 30 seconds, however, its efficiency plunged due to the presence of bubbles that got clogged in the material. In contrast, the nickel foam electrode was found to be the best at allowing bubbles to escape but its smaller surface area means that it was less productive.
The nickel 'felt' material as seen under an electron microscope. Image credited to Duke University
The ‘felt’ made of nickel microfibres was found to produce more hydrogen than both of the other materials despite it having a 25 percent smaller surface area for the reaction. Over the course of a 100-hour test, the microfiber ‘felt’ produced hydrogen at a density of 25,000 milliamps per square centimeter. At this rate, it is around 50 times more productive than the conventional alkaline electrolyzers that are currently used in water electrolysis, according to the researchers.
Improving the Hydrogen Production Rate
At the moment, the cheapest way to make hydrogen at industrial quantities is by breaking methane apart with hot steam. This is an energy-intensive process that is also terrible for the environment, creating between 9 and 12 tonnes of carbon dioxide for every ton of hydrogen produced.
Ben Wiley said that commercial producers of water electrolyzers may be able to make improvements in the structure of their electrodes based on his team’s research. If the hydrogen production rate can be increased, the cost of producing hydrogen via water splitting could go down to levels low enough to make it an affordable and viable renewable energy storage solution.
At the moment, Wiley is working with a group of students in Duke’s Bass Connections initiative, exploring whether flow-through electrolysis could be scaled up to make hydrogen from India’s abundance of solar power.
