(114b) Non-Aqueous CO2 Reduction for Economical Multicarbon Products from CO2

Electrochemical CO₂ reduction (CO₂R) offers a promising pathway to convert captured carbon dioxide into valuable chemical feedstocks. While aqueous electrolyzers have been prioritized for their low cell voltages, they suffer from low selectivity and high costs for producing valuable C₂₊ products. Here we present a techno-economic assessment focused on CO₂R to oxalic acid, a 2-electron C₂ product formed only in aprotic non-aqueous electrolytes. Extending our prior work on aqueous CO₂R,^1,2 we discuss the impacts of electrolyzer and electrolyte design on the process design and cost of non-aqueous CO₂R. We extract performance parameters from the largest collection of literature data on aprotic non-aqueous CO₂R to inform the techno-economic base case. Beyond the current baseline, we present sensitivity analyses towards electrolyzer, process, and market variables, as well as Monte Carlo assessments of future technical progress in non-aqueous CO₂R.

We show that oxalic acid can be produced at $2.87/kg in a small-scale process with minimal technology developments beyond the current state-of-the-art. Commercial-scale CO₂R to oxalic acid could reach $1.56/kg with minimal technology improvement, approaching the market price of $0.7 – 2.5/kg. Although liquid-liquid separation adds capital cost, oxalic acid is a more economical product than ethylene on a levelized basis. Its cost competitiveness is driven by its market value and 2-electron reaction pathway. We also present a recommended pathway towards economical CO₂R to oxalic acid. Key priorities for achieving cost targets include increased current density, extended cell lifetimes, and optimized flow cell configurations. Additionally, lowering cell resistance by enhancing electrolyte conductivity or reducing catholyte chamber width is crucial. This assessment highlights the immense potential of non-aqueous CO₂R, which has been largely overlooked compared to aqueous CO₂R.

1. Da Cunha, S. C. & Resasco, J. Nat. Commun. 14, 5513 (2023).
2. Da Cunha, S. C. & Resasco, J. ACS Energy Lett. 9, 5550–5561 (2024).