Sun, sea and electrochemistry

Posted on 13 December 2017

Researchers from the Department of Chemistry have found a new way of safely trapping the greenhouse gas, carbon dioxide, as a solid mineral, dawsonite.

PhD student Katie Lamb – from seawater to an electrochemical carbon capture cell

The process, developed by Professor Michael North and Dr Alison Parkin, uses scrap metal, sea water and electricity from solar panels, and is highly scalable. Some 850 million tonnes of carbon dioxide per year could be captured using nothing more than the dream summer holiday combination of sun and sea, along with some scrap metal and electricity.

The scientific breakthrough came from realising that using graphite, the material used in pencils, to line an aluminium reactor, enabled low energy mineralisation of carbon dioxide. Filling the reactor with Whitby sea water and passing electricity through the graphite caused carbon dioxide to be selectively transferred from a gas mixture above the liquid into the sea water via a process called supercapacitance. Normally high energy gas-pressurisation or the use of highly caustic agents would be required to drive this process. The reaction between the electricity and the aluminium then turns the dissolved carbon dioxide into the mineral dawsonite, a natural component of the Earth’s crust.

The aluminium required in the electrode can be derived from waste sources such as those found in cooking foil, pie trays or KitKat foil wrappers. Alternatively, aluminium can be replaced by iron, allowing the system to use two of the most abundant metals in the Earth’s crust. There are tens of millions of tonnes of waste aluminium that are not recycled each year, and hundreds of millions of tonnes of waste iron is available. Unlike other carbon dioxide treatment systems that require hydrogen as an expensive input reagent, this approach completes its electrical circuit by actually producing hydrogen gas – a valuable fuel commodity.

The researchers are now working to maximise the energy efficiency of the process and allow the hydrogen by-product to be collected and utilised, before seeking to build toward full-scale production.

This work is published as a paper with VIP status in ChemSusChem.