January 26, 2015
Conventional fuel cells based on platinum catalysts are too expensive for widespread use. Cheaper systems, however, are significantly less efficient. An international research group including scientists from Jacobs University has now developed a novel catalyst, without platinum and with higher efficiency.
In the fight against climate change, fuel cells are one beacon of hope. They produce electricity from hydrogen and atmospheric oxygen. Instead of exhaust fumes, the only waste product is water. The required hydrogen can be produced sustainably, for example by solar energy.
Unfortunately, there’s a catch: Heavy costs. Power generation with fuel cells is very expensive to date, as precious metals such as platinum are required as catalysts. Now an alternative solution seems to come into reach. Together with an international group of researchers, scientists from Jacobs University in Bremen have built a catalyst for fuel cells that works highly efficient even without platinum or other noble metals.
The innovative combination of two Nobel laureate-materials has now been presented to the public by the research consortium headed by Ulrich Kortz from the Jacobs University, Guangjin Zhang from the Chinese Academy of Sciences in Beijing as well as Naresh Dalal from the Florida State University in Tallahassee. First of all, there is graphene. It comprises a single layer of carbon atoms bonded together in a honeycomb lattice with some exceptional properties. Graphene is stronger than steel, yet flexible, extremely light and nearly transparent. Moreover, it is an excellent conductor of electricity. If a few oxygen atoms are bound to the graphene lattice, it is called graphene oxide (GO). The scientists produced such graphene oxide, which is better manageable and suited for the current project than pure graphene. Onto a layer of graphene oxide they then applied second material, a so-called polyoxometalate (POM), which had been previously synthesized in Bremen by Kortz and his co-worker Ali Haider. This POM took over the role of platinum as a catalyst.
“It has been long known that this polyoxometalate with the abbreviated formula P8W48 does bond to positively charged particles or surfaces in a very stable fashion. This is why we had the idea of using it as a catalyst,” Kortz explains. “We hit the bull’s eye! The efficiency of our catalyst was even higher than that of a standard platinum catalyst. And it was still up and running after a thousand test cycles.”
“This is a very exciting result,” Kortz continues. “Costs are a crucial factor when it comes to fuel cells. Now we have developed a highly efficient system which is significantly cheaper than platinum.”
Li-Kai Yan from Northeast Normal University in Changchun, China, supported the team in additionally describing the system in theoretical terms. Moreover, a selection of electron microscopy images proved that the POM is indeed placed on the surface of the graphene oxide and is responsible for the efficient reaction. “Our project is a prime example of a highly successful international collaboration,” Kortz underlines. It involves scientists from Asia, America, and Europe, and as diverse disciplines as inorganic chemistry, electrochemistry, and theoretical chemistry.
There is a good chance that the newly developed catalyst will influence the design of future fuel cells. “Ideally, we end up with an industrial use,” says Kortz. “Firstly, we need to find the right industrial partners. Fuel cells are an important topic – today and in the future. For sure, the prospects for such an efficient and at the same time cost-efficient system are manifold.”
Rongji Liu, Guangjin Zhang, Hongbin Cao, Suojiang Zhang, Yongbing Xie, Ali Haider, Ulrich Kortz, Banghao Chen, Naresh S. Dalal, Yongsheng Zhao, Linjie Zhi, Cai-Xia Wu, Li-Kai Yan, Zhongmin Su and Bineta Keita:
Enhanced proton and electron reservoir abilities of polyoxometalate grafted on graphene for high-performance hydrogen evolution.
Energy & Environmental Science 2016, 9, 1012-1023.[Read Online]
Prof. Dr. Ulrich Kortz | Department of Life Sciences and Chemistry
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