Artificial leaf produces hydrogen from air

EPFL scientists have developed a solar-powered artificial leaf capable of extracting water from the air and converting it into hydrogen. The system is based on newly developed electrodes that have two important key characteristics: they are porous, to maximize contact with water in the air; and transparent, to maximize sunlight exposure of the semiconductor coating. When the device is simply exposed to sunlight, it takes water from the air and produces hydrogen gas.

The EPFL engineers took inspiration from photosynthesis: the way plants manage to convert sunlight into chemical energy. The sunlight’s energy is stored in the form of chemical bonds inside of the sugars and starches. The EPFL researchers designed a similar process using specially developed transparent gas diffusion electrodes. When coated with a light harvesting semiconductor material, the system indeed acts like an artificial leaf, whit the difference that it’s harvesting water from the air and sunlight to produce hydrogen gas. The sunlight’s energy is stored in the form of hydrogen bonds. Previous research had shown that it is possible to achieve artificial photosyn- thesis with so-called photoelectrochemical (PEC) cells that work with an aqueous solution. But for practical purposes, this process has drawbacks; for instance, it is complicated to make large-area PEC systems. The researchers at EPFL wanted to show that the PEC technology could be adapted to extract water from the air instead, which led to the development of their new gas diffusion electrode. It had also been shown that electrochemical cells (fuel cells) work with gases instead of liquids, but the gas diffusion electrodes used previously are opaque and not compatible with PEC solar energy technology. Now, the researchers are focusing their efforts into optimizing the system.

Credits: epfl.ch>

The results are published on 4 January 2023 in Advanced Materials. The article ‘Transparent Porous Conductive Substrates for Gas-Phase Photoelectrochemical Hydrogen Production‘ is online>