Low-pH electrolyser has greater efficiency

08 June 2021 | Muriel Cozier

‘…This electrolyser enables the creation of high-value products such as ethylene.’

An engineering researcher from the University of Sydney, Australia, in collaboration with a team at the University of Toronto, Canada, has developed an electrochemical system that converts larger amounts of CO2 into useful building blocks for every day materials.

The team’s electrolyser operates in strongly acidic conditions. This development reduces undesired reactions and enhances overall efficiency. Running the electrolyser under low pH conditions prevents the formation of carbonate. Systems operating in neutral or alkaline conditions see much of the CO2 wasted as it is converted to carbonate.

However, while the low pH prevented the formation of carbonate, it did lead to hydrogen ions in the acidic solution forming hydrogen gas. This left few electrons available to combine with the CO2. The team overcame this problem by increasing the electrical current, flooding the reactor with electrons, and adding positively charged ions, in the form of potassium, to the reaction. Adding the potassium created an electric field near the solid catalyst, making it easier for the CO2 to be absorbed by the surface.

The researchers said that these two changes made a ‘big difference.’ Previous systems typically used less than 15 percent of the available CO2, losing the rest to carbonate. The new system uses about 77 percent of available CO2, with more than 50 percent being converted to multi-carbon products.

The researchers say that that there are still hurdles to overcome before their system can be scaled up to an industrial level. These hurdles include the stability of the catalyst when its size is increased, and the need for even further energy savings.

Dr Fengwang Li, from the University of Sydney’s School of Chemical and Biomolecular Engineering said: ‘Our research differs to previous approaches. Instead of choosing between an efficient use of electricity or an efficient use of carbon, we do both. This electrolyser enables the creation of high-value products such as ethylene.’


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