For decades, researchers have been dreaming of a device that captures water from the air and hydrogen as a fuel supplies, which is operated exclusively with solar energy. Now, Kevin Sivula and his team from EPFL’s Chemical Engineering department have taken a big step towards making that dream a reality.
Semiconductor coating absorbs water from the air and produces hydrogen.
Their ingenious and simple system combines semiconductor-based technology with novel electrodes that have two important properties: they are both porous to maximize contact with the water in the air and transparent to block solar radiation on the semiconductor coating to maximize. When the device is exposed to sunlight, it absorbs water from the air and produces hydrogen.
These transparent, porous and conductive electrodes enable the conversion of water – in its gaseous state from the air – into hydrogen for fuel. With these state-of-the-art electrodes, you can harness the power of the sun and power your devices with it.
“To achieve a sustainable society, we need ways to store renewable energy in the form of chemicals that can be used as fuels and feedstocks in industry. Solar energy is the most common form of renewable energy, and we are striving to develop economically competitive processes to produce solar fuels.”
says Sivula from the EPFL Laboratory for Molecular Engineering of Optoelectronic Nanomaterials and lead author of the study.
Inspiration comes from a plant leaf
Inspired by the way plants convert sunlight into chemical energy using carbon dioxide from the air, EPFL engineers and Toyota Motor Europe developed transparent gas diffusion electrodes that can act like an artificial leaf. Coated with a light-harvesting semiconductor material, these electrodes can absorb water from the air and sunlight to generate hydrogen gas. The energy from sunlight is then stored in the form of hydrogen bonds, enabling the production of renewable, fossil-free fuels.
This process mimics the Photosynthesis in which a plant absorbs carbon dioxide and water from the environment and converts these molecules into sugars and starches, storing the energy of sunlight in the form of chemical bonds.
Marina Caretti, lead author of the work says:
“Developing our prototype was challenging because transparent gas diffusion electrodes have not been demonstrated before and we had to develop new processes for each step. However, since each step is relatively simple and scalable, I think our approach will open new horizons for a wide range of applications, starting with gas diffusion substrates for solar-powered hydrogen production.”
The researchers are now concentrating on optimizing the system. What is the ideal fiber size? The ideal pore size? The ideal semiconductor and membrane materials? The EU project “Sun-to-X” is looking into these questions, which is intended to advance this technology and develop new ways of converting hydrogen into liquid fuels.
Hydrogen conversion efficiency still low
The scientists admit that the efficiency of their prototype in converting from solar to hydrogen is modest and is currently below the efficiency that can be achieved with liquid-based PEC cells. Based on the materials used, the maximum theoretical solar to hydrogen conversion efficiency with this method at 12%while at Liquid cells an efficiency of up to 19% has been proven. However, the scientists did not formally investigate this conversion efficiency in their demonstration.
But it would be exciting if, for example, solar cells mounted on an airplane could still produce the hydrogen in the air that a hydrogen plane burns. In this way, travel could perhaps even become ecologically justifiable again.
Those: https://www.eurekalert.org/news-releases/975314?