The O ₂-assisted Al/CO ₂ electrochemical cell: A system for CO ₂ capture/conversion and electric power generation

Abstract

A new approach for converting CO ₂ to valuable C2 products while producing significant amounts of electrical energy.

Abstract

Economical and efficient carbon capture, utilization, and sequestration technologies are a requirement for successful implementation of global action plans to reduce carbon emissions and to mitigate climate change. These technologies are also essential for longer-term use of fossil fuels while reducing the associated carbon footprint. We demonstrate an O ₂-assisted Al/CO ₂ electrochemical cell as a new approach to sequester CO ₂ emissions and, at the same time, to generate substantial amounts of electrical energy. We report on the fundamental principles that guide operations of these cells using multiple intrusive electrochemical and physical analytical methods, including chronopotentiometry, cyclic voltammetry, direct analysis in real-time mass spectrometry, energy-dispersive x-ray spectroscopy, x-ray photoelectron spectroscopy, and coupled thermogravimetric analysis–Fourier transform infrared spectroscopy. On this basis, we demonstrate that an electrochemical cell that uses metallic aluminum as anode and a carbon dioxide/oxygen gas mixture as the active material in the cathode provides a path toward electrochemical generation of a valuable (C ₂) species and electrical energy. Specifically, we show that the cell first reduces O ₂ at the cathode to form superoxide intermediates. Chemical reaction of the superoxide with CO ₂ sequesters the CO ₂ in the form of aluminum oxalate, Al ₂(C ₂O ₄) ₃, as the dominant product. On the basis of an analysis of the overall CO ₂ footprint, which considers emissions associated with the production of the aluminum anode and the CO ₂ captured/abated by the Al/CO ₂-O ₂ electrochemical cell, we conclude that the proposed process offers an important strategy for net reduction of CO ₂ emissions.