Hydrogen from solar energy can be produced without platinum
Researchers have now succeeded in producing hydrogen gas from electrically conductive plastic, also known as conjugated polymers. Photo: Chalmers University of Technology/Henrik Sandsjö.
In a new study, researchers from Chalmers University of Technology and Uppsala University, among others, present a groundbreaking method for producing hydrogen gas in an efficient and sustainable way. Using sunlight, water and minimal particles of electrically conductive plastic, the researchers have succeeded in producing hydrogen without relying on platinum, one of the world's most expensive and scarce metals.
Hydrogen plays a key role in the global pursuit for renewable energy. Although its use produces only water as a by-product, significant challenges remain before hydrogen can be produced both on a large-scale and in an environmentally friendly way.
A major challenge is the use of the metal platinum as a co-catalyst when sunlight and water are used to produce hydrogen. The Earth’s reserves of platinum are limited, and extraction is associated with risks to both the environment and to human health. Moreover, the production is concentrated in only a few countries, for example South Africa and Russia.
Better performance without platinum
In a new study published in the prestigious journal Advanced Materials, researchers show how hydrogen from solar energy can be produced efficiently without the use of platinum. Jingwen Pan from Jiefang Zhu's research group at the Department of Chemistry – Ångström, Uppsala University, is co-first author of the study.
“During the initial investigation phase, Jingwen examined the performance of the plastic-based photocatalyst developed at Chalmers,” says Jiefang Zhu. When two variants were compared, it was discovered that the one without added platinum was actually better. This unexpected discovery gave us new ideas about how the material actually works and helped us formulate both the innovation and the proposed reaction mechanism in the article.”
Advanced material design
Efforts to overcome the platinum bottleneck have been underway for several years in Professor Ergang Wang's research group at Chalmers.
The key to the new approach lies in advanced materials design of the electrically conductive plastic used in the process. This type of plastic, known as conjugated polymers, absorbs light efficiently, but is typically less compatible with water.
By adjusting the material properties at the molecular level, the researchers made the material much more water compatible.
“We also developed a way to form the plastic into nanoparticles that can enhance the interactions with water and boost the light-to-hydrogen process. The improvement comes from more loosely packed, more hydrophilic polymer chains inside the particles”, says Chalmers researcher Alexandre Holmes, co-first author of the study.
Hydrogen process without added helper chemicals next step
The next major step for Wang’s group will be to make the hydrogen process work using only sunlight and water, without any added helper chemicals.
Currently, they use vitamin C, which acts as a so-called sacrificial antioxidant. By donating electrons, it prevents the reaction from stalling, which in the laboratory can show high hydrogen production rates.
To realise truly sustainable solar hydrogen, Professor Wang explains, the goal is to split water molecules into hydrogen and oxygen simultaneously, with sunlight and water as the only inputs.
“Removing the need for platinum in this system is an important step towards sustainable hydrogen production for society. Now we are starting to explore materials and strategies aimed at achieving overall water splitting without additives. That will need a few more years, but we believe we are on the right track”, says research leader Ergang Wang, professor at the Department of Chemistry and Chemical Engineering at Chalmers.
The research team's findings provide important guidelines for how future solar hydrogen technology can be designed, according to Jiefang Zhu.
"These advances mean that sustainable, metal-free hydrogen production has taken a significant step closer to practical application.
Anneli Björkman
Publication:
- Highly Efficient Platinum-Free Photocatalytic Hydrogen Evolution From Low-cost Conjugated Polymer Nanoparticles, Advanced Materials. Authors: Alexandre Holmes, Jingwen Pan, Li Wang, Leandro Franco, Rafael R. Bicudo, Bo Albinsson, C. Moyses Araujo, Weiguo Zhu, Dongbo Wang, Thuc-Quyen Nguyen, Jiefang Zhu and Ergang Wang.
- At the time of the study, the researchers were active at Chalmers University of Technology, Uppsala University and Karlstad University in Sweden, the University of São Paulo in Brazil, Harbin Institute of Technology and Changzhou University in China, and the University of California in the United States.