Using a polymer film that protects photovoltaic cells, researchers at Rice University produce solar hydrogen directly in water.
The new low-cost hydrogen production system is inspired by artificial leaves.
Rice University researchers have designed an efficient and inexpensive device for producing solar hydrogen. And for that, they resorted to the last bet of the photovoltaic industry: perovskite, artificial oxides whose crystalline structure imitates that of the natural mineral.
The researchers bonded a layer of perovskite with catalytic electrodes based on cobalt phosphide (CoP), in a single module. Once in the water and illuminated, the module generates electricity from the cells and current flows to the electrodes. Here, the electrolysis of water molecules takes place, producing hydrogen and oxygen. In general, the whole reaction, from sunlight to hydrogen, has a 6.7% efficiency.
The module is therefore a self-sufficient fuel producer which, according to researchers, has the advantage of being easy to produce.
The concept is basically similar to that of an artificial leaf. What we have is a built-in module that turns sunlight into electricity, which in turn triggers an electrochemical reaction. In this way, it uses water and sunlight to make chemical fuels.
Perovskite solar cells have achieved over 25% efficiency, but the materials are expensive and tend to be “stressed” by moisture and heat. For this reason, researchers replaced more expensive components, such as platinum, with alternative materials, such as carbon.
However, according to the researchers, the key component is not perovskite, but the polymer that encapsulates it (a thin film of Surlyn), protecting the modulus and allowing it to submerge for long periods of time. The molded film allows light to reach the solar cell while protecting it and acting as an insulator between the cells and the catalytic electrodes.
With a smart system design, you can potentially create a self-contained circuit. Even in the absence of sunlight, the energy stored as chemical fuel can be used. You can put hydrogen and oxygen products in separate tanks and incorporate another module to convert these fuels into electricity.
The research was published in ACS Nano.
More information: news.rice.edu