Catalyst-Free Carbon Dioxide Conversion in Water Facilitated by Pulse Discharges.

By inducing CO 2 -pulsed discharges within microchannel bubbles and regulating thus-forming plasma microbubbles, we observe high-performance, catalyst-free coformation of hydrogen peroxide (H 2 O 2 ) and oxalate directly from CO 2 and water. With isotope-labeled C 18 O 2 as the feedstock, peaks of H 2 18 O 16 O and H 2 16 O 2 observed by ex situ surface-enhanced Raman spectra indicate that single-atom oxygen (O) from CO 2 dissociations and H 2 O-derived OH radicals both contribute to H 2 O 2 formation. The global plasma chemistry modeling suggests that high-density, energy-intense electron supply enables high-density CO 2 - (aq) and HCO 2 - (aq) formation and their subsequent coupling to produce oxalate. The enhanced solvation of CO 2 , facilitated by the efficient transport of C x O y ionic species and CO, is demonstrated as a crucial benefit of spark discharges interacting with water at the bubble interface. We expect this plasma microbubble approach to provide a novel power-to-chemical avenue to convert CO 2 into valuable H 2 O 2 and oxalic acid platform chemicals, thus leveraging renewable energy resources.