Solar-powered leaf helps combat climate change

Researchers supported by the EU-funded Sun-To-X project have developed an artificial leaf that can harvest water and then convert it into hydrogen fuel. According to a news item posted on ‘chemeurope.com’, this “semiconductor-based technology is scalable and easy to prepare.” The research is described in the journal ‘Advanced Materials’.

“To realize a sustainable society, we need ways to store renewable energy as chemicals that can be used as fuels and feedstocks in industry,” remarks study senior author Prof. Kevin Sivula of Sun-To-X project partner Swiss Federal Institute of Technology Lausanne (EPFL), Switzerland, in the ‘chemeurope.com’ news item. “Solar energy is the most abundant form of renewable energy, and we are striving to develop economically-competitive ways to produce solar fuels.”

This invention brings researchers much closer to their long-standing goal of creating an entirely solar-powered device that can harvest water from the air and produce hydrogen fuel. Together with his team, Prof. Sivula created a system that combines semiconductor-based technology with novel electrodes. Breaking away from traditional electrode layers that are opaque to sunlight, the electrode substrate is a 3D mesh of felted glass fibres. The gas diffusion electrodes are therefore porous, allowing them to maximise contact with water in the air. They are also transparent, which maximises the semiconductor coating’s exposure to sunlight. So when the device is exposed to sunlight, it draws water from the air and produces hydrogen gas.In their research, EPFL’s chemical engineers, working together with the Sun-To-X project coordinator Toyota Motor Europe, Belgium, were inspired by a plant’s ability to convert sunlight into chemical energy using CO2 drawn from the air. They coated the electrodes with a light-harvesting semiconductor material so that they could harvest water from the air and sunlight to produce hydrogen gas just like an artificial leaf. The sunlight’s energy is stored in the form of hydrogen bonds, according to the news item.

Scientists had previously shown that we can use photoelectrochemical (PEC) technology to generate hydrogen fuel from liquid water and sunlight. However, making large-area PEC devices that use liquid is difficult. The novel electrodes are the result of adapting PEC to harvest humidity from air instead.

“Developing our prototype device was challenging since transparent gas-diffusion electrodes have not been previously demonstrated, and we had to develop new procedures for each step,” reports EPFL engineer Dr Marina Caretti. “However, since each step is relatively simple and scalable, I think that our approach will open new horizons for a wide range of applications starting from gas diffusion substrates for solar-driven hydrogen production.”

The Sun-To-X (Solar Energy for Carbon-Free Liquid Fuel) team is now focusing on optimising their system to help further the energy-efficient synthesis of alternative liquid fuels for use in transport and energy storage. These results are expected to help build a sustainable future and mitigate climate change.

For more information, please see:

Sun-To-X project website