Zero-Chem: Zerogap bipolar membrane electrolyser for CO2 reduction to chemicals & fuels

Carbon dioxide is a waste molecule that is generated by many industries and processes. Humanity is striving to prevent the production of carbon dioxide by industrial processes but emissions from certain sectors such as steel manufacture, cement production and brewing are difficult to prevent.

But carbon dioxide should not just be thought of as a waste product, it can be converted, essentially chemically recycled, to make the energy rich fuels and products (e.g. jet fuel, plastics, medicines) on which society relies. Electrocatalytic carbon dioxide reduction is one of the most promising ways to convert carbon dioxide to useful products. The generation of storable, high energy density, fuels using only water, waste carbon dioxide and renewable power is particularly attractive as way to addressing seasonal energy storage. Displacement of carbon dioxide derived products for the chemicals and pharmaceuticals industries, a sector which employs more than 150,000 people in the UK and generates more than £25 billion in value, can also play an important role in achieving net-zero by displacing existing virigin fossil derived carbon products.

Impressive lab based results are being achieved for electrocatalytic carbon dioxide reduction at room temperature but the current generation of devices have a fundamental flaw. They use conditions where hydroxide is either generated or already present at the site of carbon dioxide reduction. Hydroxide reacts rapidly with carbon dioxide to form carbonate and bicarbonate, meaning that it is no longer available for conversion. This leads to solids forming and device failure as well as lowering the efficiency of the device. It is estimated that recovering the carbon dioxide adds at least 50% to the energy of cost of conversion. In many cases the energy cost associated with the reaction between hydroxide and carbon dioxide exceeds the energy content of the carbon based fuel or feedstock stored. Rather than being fuel generating devices many carbon dioxide electrolysers are fuel wasting.

Carbonate and bicarbonate are not formed in acids, they are not stable. Instead the carbon dioxide remains available for conversion. But in acids all of the current generation of carbon dioxide reduction electrodes that use precious metals (e.g. gold, silver) do not produce carbon products, instead only hydrogen is made. The dogma of the community is that the catalyst site must not be operated at low pH as the catalysts do not work. The ZeroChem approach is simple - if the
catalyst does not work under the conditions that are required for the process to operate effectively then the catalyst needs to be redesigned. This feasibility study will assess if gas diffusion electrodes can be made which operate in strong acid. We will then demonstrate their use in a novel type of zero-gap bipolar membrane electrolyser to deliver an entirely new approach to carbon dioxide utilisation.