Removing CO2 from power plant exhaust

Some power plants use materials called sorbents to remove carbon dioxide (CO₂) from their exhaust so it can be sequestered from the environment. But separating the CO₂ from the sorbent requires high temperatures and produces CO₂ gas that must be put into long-term storage—a prospect that raises safety and security concerns. In a proof-of-concept study, MIT researchers have demonstrated a battery-like system that uses the same CO₂-capturing sorbent in a specially designed electrolyte that drives electrochemical reactions with three benefits: They separate the CO₂ from the sorbent; they promote the discharge of electricity from the battery; and they incorporate the CO₂ into a solid that can serve as electrode material or be safely discarded. Their system—made of lithium and carbon electrodes plus the special electrolyte—achieves discharge voltages similar to those of other lithium-gas batteries under development. The researchers are now working to understand and optimize their lithium-based system and to see whether less-expensive, earth-abundant metals might work as well.