"Carbon-based materials are the most versatile materials used in the field of energy storage and conversion," said Dr Dongjiang Yang of Qingdao University in China. “Given the renewability of seaweed, we chose seaweed extract as a precursor and template to synthesize hierarchical porous carbon materials."
While Yang was at Griffith University in Australia, he worked with colleagues at Qingdao University and at Los Alamos National Laboratory in the US to make porous carbon nanofibres from seaweed extract. Binding metal ions such as cobalt to the alginate molecules resulted in chelated nanofibres with an "egg-box" structure, with the alginate units enveloping the metal ions.
Tests show the seaweed-derived material has a large reversible capacity of 625 mAh/g, more than the 372 mAh/g of traditional graphite anodes for lithium-ion batteries. This could help double the range of electric cars if the cathode material is of equal quality.
The egg-box fibres also performed as well as commercial platinum-based catalysts used in fuel-cell technologies and with much better long-term stability. They also showed high capacitance as a superconductor material at 197 Farads per gram, which could be applied in zinc-air batteries and supercapacitors.
Building on the same egg-box structure, the researchers say they have suppressed defects in seaweed-based, lithium-ion battery cathodes that can block the movement of lithium ions and hinder battery performance. And recently, they have developed an approach using red algae-derived carrageenan and iron to make a porous sulfur-doped carbon aerogel with an ultra-high surface area. The structure could be a good candidate to use in lithium-sulfur batteries and supercapacitors.
More work is needed to commercialize the seaweed-based materials, says Yang. While over 20,000 tons of alginate precursor are extracted from seaweed per year for industrial use, much more will be required to scale up production.
The team are presenting the work at the 253rd National Meeting & Exposition of the American Chemical Society (ACS). www.acs.org