“We wanted to produce carbon-based materials via a really ‘green’ pathway,” he said. “Given the renewability of seaweed, we chose seaweed extract as a precursor and template to synthesise hierarchical porous carbon materials.”
While Yang was at Griffith University in Australia, he worked with colleagues at Qingdao University (where he now works) and at Los Alamos National Laboratory to make porous carbon nanofibres from seaweed extract.
Binding metal ions, such as cobalt, copper, iron and nickel, to the alginate molecules resulted in nanofibers with an egg-box structure (see diagram) with alginate units enveloping the metal ions – this architecture is key to the material’s stability and controllable synthesis, said Yang.
Testing, showed that versions of the material had a reversible capacity of 625mAh/g, which it compares with 372mAh/g for traditional Li-ion cell graphite anodes, according to the Americal Chemical Society.
Egg-box fibres also performed as well as commercial platinum-based catalysts used in fuel-cells, but with better long-term stability, and exhibited 197F/g in supercapacitors.
Building on the 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 sulphur-doped carbon aerogel as a candidate for lithium-sulphur batteries and supercapacitors.
The team will present the work at the 253rd National Meeting & Exposition of the American Chemical Society (ACS).