Floating solar fuels rig created for seawater electrolysis

  • The scientist have found a way to convert electricity from solar photovoltaics into storable hydrogen fuel.
  • Hydrogen is a clean fuel that is currently used to propel rockets in NASA’s space program and is widely expected to play an important role in a sustainable energy future.
  • The vast majority of today’s hydrogen is produced from natural gas through a process called steam methane reforming that simultaneously releases CO2, but water electrolysis using electricity from solar PV offers a promising route to produce H2without any associated CO2The team has now developed  photovoltaic-powered electrolysis device that can operate as a stand-alone platform that floats on open water.
  • Their floating PV-electrolyzer can be thought of as a “solar fuels rig” that bears some resemblance to deep-sea oil rigs, except that it would produce hydrogen fuel from sunlight and water instead of extracting petroleum from beneath the sea floor.
  • Their key innovation is the method by which they separate the H2and O2gasses produced by water electrolysis.
  • State-of-the-art electrolyzers use expensive membranes to maintain separation of these two gases.
  • Their prototype  is the first demonstration of a practical membraneless floating PV-electrolyzer system, and could inspire large-scale ‘solar fuels rigs’ that could generate large quantities of H2fuel from abundant sunlight and seawater without taking up any space on land or competing with fresh water for agricultural uses.
  • These solar fuels generators are essentially artificial photosynthesis systems, doing the same thing that plants do with photosynthesis, so their device may open up all kinds of opportunities to generate clean, renewable energy. Crucial to the operation of Esposito’s PV-electrolyzer is a novel electrode configuration comprising mesh flow-through electrodes that are coated with a catalyst only on one side.
  • These asymmetric electrodes promote the evolution of gaseous H2and O2products on only the outer surfaces of the electrodes where the catalysts have been deposited.
  • When the growing H2and O2bubbles become large enough, their buoyancy causes them to detach from the electrode surfaces and float upwards into separate overhead collection chambers.
  • They have used the Columbia Clean Room to deposit platinum electrocatalyst onto the mesh electrodes and the 3D-printers in the Columbia Makerspace to make many of the reactor components.
  • They also used a high-speed video camera to monitor transport of H2and O2bubbles between electrodes, a process known as “crossover.”
  • Crossover between electrodes is undesirable because it decreases product purity, leading to safety concerns and the need for downstream separation units that make the process more expensive.
  • The team is refining their design for more efficient operation in real seawater, which poses additional challenges compared to the more ideal aqueous electrolytes used in their laboratory studies.
  • They also plan to develop modular designs that they can use to build larger, scaled-up systems.
  • Their challenge is to find scalable and economical technologies that convert sunlight into a useful form of energy that can also be stored for times when the sun is not shining.

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