By using materials that are much cheaper than other high performance competitors, this could be an important step towards producing clean and affordable hydrogen.

The high energy density of hydrogen offers interesting advantages that could make the difference in the sectors of electric aviation and eVTOL, as well as in renewable energies, where it is a light and transportable means. , if not particularly efficient, to store energy. Clean which is not necessarily generated where and when it is needed.

It is also being promoted as a way of exporting green energy, and Japan and Korea in particular are investing strongly in the idea of ​​a hydrogen energy economy that powers everything from vehicles to homes, and passing. by industry.

In order for this to happen on a commercial scale, it is imperative that the production of clean and green hydrogen becomes more economical, because at the present time, the simplest and cheapest ways to get a full tank of hydrogen are complex.

Thus, green and renewable production methods are the most important for researchers and industry, and a new breakthrough by scientists from the Australian National University (ANU) could make a significant contribution.

It’s a Hydrogen Solar Energy (STH) Photoelectrochemical Cell (PEC), a cell that captures solar energy and water and produces hydrogen directly instead of powering an external electrolysis system. In this case, you put a perovskite photovoltaic cell in tandem with a photoelectrode, and it works better than any similar device ever built, using relatively cheap semiconductors.

The voltage generated by a semiconductor material in sunlight is proportional to its bandwidth. Silicon, the most popular photovoltaic material on the market, can only produce one-third of the voltage needed to directly split water. If we use a semiconductor with a bandgap twice that of silicon, it can provide enough voltage, but there is a trade-off. The larger the band gap, the lower the ability of a semiconductor to pick up sunlight. To break this compromise, we use two semiconductors with smaller bands in tandem that not only effectively capture sunlight, but together produce the voltage needed to spontaneously generate hydrogen.

Dr Siva Karuturi, PhD, Principal Investigator, ANU College of Engineering and Computer Science.

A key metric here is the efficiency of solar on hydrogen, and the ultimate goal, as defined by the US Department of Energy almost ten years ago, is 25%, with a target of 20 % for the year 2020.

And while the cells designed so far reached 19%, they used prohibitively expensive semiconductor materials. Nothing that could be called affordable has succeeded in breaking the 10% barrier until this design, which laboratory simulations under controlled conditions have set at a impressive efficiency of 17.6% thanks to a silicon / titanium / platinum photoelectrode.

The team says their results suggest “immense opportunities” for further optimization. The design can be made more efficient by refining the designs of the individual components, and it can be made even less expensive by substituting more abundant materials for the catalytic metals.

The ultimate goal is to bring the production of truly clean and renewable hydrogen back to prices of around $ 2 per kg, where it can compete directly with dirty hydrogen and, indeed, fossil fuels.

Significant cost reductions could be achieved by using the solar-hydrogen approach, as it avoids the need for additional electricity and the necessary grid infrastructure when hydrogen is produced instead using an electrolyser. . And by avoiding having to convert solar energy from direct current to alternating current and vice versa, in addition to avoiding energy transmission losses, the direct conversion of solar energy to hydrogen can achieve greater overall efficiency for the whole process.

Dr Karuturi

More information: onlinelibrary.wiley.com