Enhanced Electrocatalytic CO2 reduction: A Cascade Mechanistic approach enabled by a tandem setup.
V.S.R.K Tandava a, Andrés Alberto García a, Joan Ramón Morante a, Sebastián Murcia López a
a Catalonia Institute for Energy Research (IREC), Sant Adrià de Besos, 08930, Barcelona, Spain.
Materials for Sustainable Development Conference (MATSUS)
Proceedings of MATSUS23 & Sustainable Technology Forum València (STECH23) (MATSUS23)
#e-FuelSyn - Electrocatalysis for the Production of Fuels and Chemicals
València, Spain, 2023 March 6th - 10th
Organizers: Carla Casadevall Serrano and Julio Lloret Fillol
Oral, V.S.R.K Tandava, presentation 359
Publication date: 22nd December 2022

Electrocatalytic CO2 reduction to renewable fuels has drawn increasing attention due to its great potential in addressing the issues of the greenhouse effect, energy crisis, and industrial transformation thus having the utmost importance in attaining a carbon-neutral society. Nevertheless, there are general practical limitations such as poor selectivity for multi-carbon products and most importantly the electrocatalysts suffer from high overpotentials while directly converting the CO2 to C2+ products. To overcome these challenges and enhance the ECO2R, a cascade mechanistic approach is explored as an alternative to the direct conversion of CO2 to C2+ products. A two-step tandem set-up is employed where CO2 is converted to CO in the first step, enabled with a highly efficient Ni single-atom catalyst on activated carbon black, and sequentially CO is converted to multi-carbon products in the second step. The single-atomic catalytic sites yield a nearly 100 % faradaic efficiency towards CO at an average current density of over -40 mA·cm-2. The as-produced product stream is directly supplied as the reactant stream to a second electrolyzer that is equipped with oxide-derived copper supported on carbon black. Initially, it is noticed that the presence of unreacted CO2 in the second cell has an adverse effect and results in poor performance. When the unreacted CO2 is trapped by using an absorption chamber in between these two electrolyzers, a surge in the faradaic efficiency towards ethylene, ethanol, and n-propanol thus accounting for more than 80% total faradaic efficiency at an average current density of over 120-130 mA·cm-2 and the unwanted yet competitive H2 is limited to just 10-12 % faradaic efficiency. The aforementioned approach is found to be highly efficient not only in terms of faradaic efficiency but also energy efficiency. It is evident that multi-step electrolysis yields a highly promising conversion of CO2 to multi-carbon products. On the flip side, direct or indirect routes are also explored to electrocatalytically reduce the carbonated solvent stream placed in between the electrolyzers. The observed results clearly are imperative by enabling a direct cascade approach and exclusive separation of unreacted feed gas aid in attaining higher electro-conversion of CO2 to alternative fuels.

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