Scientists develop solar battery for hydrogen production

Chemical engineers at Lausanne’s École Polytechnique Federale developed a translucent and porous electrode-based solar-powered artificial sheet.

The artificial leaf converts atmospheric water into hydrogen fuel. Semiconductor technology is scalable.

For decades, academics have dreamed of a solar-powered gadget that harvests airborne water and produces hydrogen fuel. EPFL Chemical Engineer Kevin Sivula and his team have advanced that vision.

The team’s innovative yet simple approach combines semiconductor technology with new electrodes that are porous to promote air-water contact and transparent to optimize sunlight’s effect on the semiconductor coating. The device absorbs airborne water and generates hydrogen gas when exposed to sunshine.

This solar-powered system uses transparent, porous, and conductive gaseous diffusion electrodes to transform air-borne water into hydrogen fuel.

EPFL engineers and Toyota Motor Europe used plant photosynthesis to develop fossil-free renewable fuels. Photosynthesis converts carbon dioxide and water from the environment into sugars and starches. Sugar and starch molecular connections store sunlight energy.

Sivula and his team created transparent gas diffusion electrodes that gather water from the air and sunlight to make hydrogen gas. Hydrogen bonds store sunlight. Their foundation is a three-dimensional grid of felted glass fibers, not opaque layers.

Sivula and others have used photoelectrochemical (PEC) cells to make hydrogen fuel from liquid water and sunlight for artificial photosynthesis. PEC cells employ incident light to excite a photosensitive material like a semiconductor in a liquid solution to create a chemical reaction. However, liquid is hard to use to make huge PEC devices.

Sivula developed their gas diffusion electrode to demonstrate that PEC technology could harvest moisture from the air. Gas diffusion electrodes, utilized in electrochemical cells like fuel cells, are opaque and incompatible with solar-powered PEC technology.

Researchers are optimizing the system now. Ideal fiber size? Porosity ideal? Ideal semiconductors and membranes? The EU’s Sun-to-X project is developing this technology and novel techniques to convert hydrogen into liquid fuels.

Clear gas diffusion electrodes

Researchers fuse quartz (silicon oxide) fibers into felt plates at high temperatures to construct transparent gas diffusion electrodes. A translucent thin film of fluorine-doped tin oxide, known for its conductivity, dependability, and scalability, is applied to the wafer.

These first processes create a translucent, porous, and conductive plate for maximal air-water interaction and photon transmission. Another semiconductor film absorbs sunlight and covers the wafer. This second thin layer transmits light but seems opaque due to the porous substrate’s huge surface area. Thus, sunlight on this coated plate produces hydrogen fuel.

The scientists developed a tiny container with a membrane and coated plate to measure the hydrogen gas. The scientists’ transparent gaseous diffusion electrode may produce solar-powered hydrogen gas when exposed to sunlight in humid conditions.

The scientists did not analyze the solar-to-hydrogen conversion efficiency in their demonstration, but they concede that it is modest for this prototype and lower than liquid-based PEC cells. Coated wafers have a theoretical solar-to-hydrogen conversion efficiency of 12%, whereas liquid cells can reach 19%.

Important milestone. No water treatment, acid salts, etc. Probably seizes in sunny, humid conditions. Only oxygen-O2 combo is absent.

This breakthrough is merely weeks old. Research naturally boosts efficiency. Observing. This technology is more practical than power generating.

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