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

By inducing CO-pulsed discharges within microchannel bubbles and regulating thus-forming plasma microbubbles, we observe high-performance, catalyst-free coformation of hydrogen peroxide (HO) and oxalate directly from CO and water. With isotope-labeled CO as the feedstock, peaks of HOO and HO observed by ex situ surface-enhanced Raman spectra indicate that single-atom oxygen (O) from CO dissociations and HO-derived OH radicals both contribute to HO formation. The global plasma chemistry modeling suggests that high-density, energy-intense electron supply enables high-density CO (aq) and HCO (aq) formation and their subsequent coupling to produce oxalate. The enhanced solvation of CO, facilitated by the efficient transport of CO 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 into valuable HO and oxalic acid platform chemicals, thus leveraging renewable energy resources.