Available approaches for reusing carbon from captured carbon dioxide emissions involve a reduction step that requires high temperatures and pressures. High pressures are essential, as at low pressures the gas doesn’t stay dissolved in water long enough to be useful. A new route designed at the U.S. Department of Energy’s Idaho National Laboratory provides industrially relevant carbon dioxide-to-syngas conversion rates without stringent process requirements.

Specialized liquid materials — switchable polarity solvents (SPS) — render CO₂ more soluble and allow the The electrolysis setup that could allow efficient production of syngas from captured carbon. Source: Idaho National Laboratorycarbon capture medium to be directly introduced into a cell for electrochemical conversion to syngas. The SPS shift polarity when exposed to a chemical agent, a property enabling control of what molecules will dissolve in the solvent.

In an electrochemical cell, water oxidation occurs on the anode side, releasing oxygen and hydrogen ions that migrate through a membrane to the cathode. The hydrogen ions then react with bicarbonate, the form in which CO₂ is captured in the SPS, allowing its release for electrochemical reduction and formation of syngas. After the release of CO₂, the SPS switches polarity back to a water-insoluble form, permitting recovery and reuse of the carbon capture media.

When syngas can be produced from captured CO₂ at significant current densities, it boosts the process chances for coal-fired power plant emission control and other industrial applications. Unlike other methods based on high temperatures and high pressures, the SPS-based process showed optimal results at 25 degrees Celsius and 40 psi.