The integration of electrochemical reduction of CO2 with renewable energy sources offers an attractive approach for utilising carbon chemical feed stocks. Previous attempt to electro-reduce CO2 have shown some limitations in energy efficiency, scalability, product selectivity, and production rate (refers to the current efficiency during the electrochemical process). The electrochemical conversion of CO2 can lead to value-added chemicals and fuels, such as carbon monoxide, formic acid/formate, ethylene, ethanol, methane, and methanol. Yet, the conversion into formic acid/formate stands out as one of the few economically viable products due to its high product value per electron. In addition, the process has the possibility to be integrated with biological systems for further conversion of the formate to more highly valuable products.
In this new approach, researchers at the National Renewable Energy Laboratory (NREL) have designed a scalable cell architecture utilising a gas diffusion electrode (GDE) and a carbon supported SnO2 electrocatalyst to enable up to 90% faraday efficiency for CO2 reduction to formate at 500 mA/cm2. A bipolar membrane (BPM) was used to prevent the product crossover and to enable the use of non-precious metal electrocatalysts for the oxygen evolution reaction (OER) in an alkaline environment. With such configuration, the researchers have achieved efficient production rates, selectivity and a cell design capable to be scalable, which enable a pathway toward square-meter-scale testing of electrochemical conversions.
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Some additional references:
Jouny et al. General Techno-Economic Analysis of CO2 Electrolysis Systems. Ind. Eng. Chem. Res. (2018) 57(6), 2165-2177 https://pubs.acs.org/doi/10.1021/acs.iecr.7b03514
Valentini et al. Formic acid, a biomass-derived source of energy and hydrogen for biomass upgrading. Energy Environ. Sci. (2019) 12, 2646-2664 https://pubs.rsc.org/en/content/articlelanding/2019/ee/c9ee01747j#!divAbstract
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