The scanning electron micrograph of copper/copper oxide, which are electrodeposited onto carbon fibre substrates with applied voltages close to hydrogen evolution. These deposited species are formed into shape of Fern-leaves, which show fascinating perspective. Foto: Amir Masoud Pourrahimi
Research work at the Royal Institute of technology (KTH) and IVL Swedish Environmental Research Institute has enabled the development of a new type of carbon fibre-based electrodes. The electrodes make it possible to efficiently extract hydrogen from sewage waters with high ammonium contents. At the same time the wastewater is purified from ammonium nitrogen, which means a further environmental advantage.
– Using ammonium containing wastewater for making hydrogen requires less energy than electro oxidation of water. This means environmental benefits as compared to electro oxidation of water, says Kåre Tjus, environmental technology specialist at IVL.
The novel electrodes that effectively convert ammonium in wastewater into hydrogen were made in a collaboration between IVL, conducting mostly applied research, and KTH providing fundamental research as valuable input in the project.
– We initiated the work by identifying a simple and inexpensive holder of carbon fibres for a bimetallic catalyst that could convert the ammonia into hydrogen gas. The carbon fibers were firstly coated with copper which is cheap for electroplating tests, then coated with platinum as the main catalyst, which is an expensive metal. In this process we were able to identify that copper mixed with ultralow platinum content provided similar catalysis performance as the pure platinum, says Amir Masoud Pourrahimi who performed the work during his post-doc time at KTH.
Previous experience at KTH using nanotechnology to modify surfaces allowed the preparation of large and effective catalytic surfaces at minimal amount of precious metal in very thin layers of metals.
– In laboratory scale the performance of our copper platina electrodes are on the same level as platinum alone, which provides significant cost benefits. Bimetallic electrodes have previously been made with metals such as iridium, ruthenium, rhodium, in combination with platinum but with added cost due to their more expensive nature, says Richard Olsson, associate professor at KTH.
– Combining innovation both in nanoscale and in pilot scale is demanding and findings developed in this project look promising. The long-term goal is large-scale use, says Anders Björk, project manager at IVL.
The project now proceeds with tests in Syvab’s wastewater treatment plant, Himmerfjärdsverket. This will be the next level of verification of the concept.
– I think we have come a long way in this short time, developed new electrodes, designed and manufactured a pilot. It will be exciting to see what the pilot tests are showing, says Jan Bergsten, from the company Polyproject, participating in the project.
Read more about the work that has recently been published in the journal Sustainable Energy and Fuels under the title "Making ultralow Platinum content bimetallic catalyst on carbon fibres for electro-oxidation of ammonia in wastewater".
The work has been carried out within the project "Innovation for wastewater treatment with a lower environmental impact", funded by Sweden's innovation agency Vinnova. The partners in this project are IVL, KTH, Syvab and the environmental engineering companies Polyprojects, Mercatus.