Ultra‐High‐Efficiency On‐Chip CO ₂ Conversion by Nanosecond Self‐Pulsing Micro‐Plasma Devices

ABSTRACT Conversion of CO ₂ into carbon‐neutral fuels and chemicals remains a central challenge in sustainable chemistry and energy sectors, as conventional catalytic processes are critically limited by the thermodynamic equilibrium and low overall energy efficiency. Here, a micro‐plasma chip for CO ₂ ‐to‐CO conversion is introduced that achieves ultra‐high energy efficiency and breaks the thermodynamic equilibrium limitation under ambient conditions. These micro‐plasma devices (MPDs) with sub‐10‐µm discharge gaps self‐generate nanosecond pulses directly from a DC bias without external pulsed‐power sources and drive discharges through field emission at substantially lower voltages than conventional plasma systems, together yielding an ultra‐high energy efficiency. An experimentally validated theoretical framework elucidates the device's working principle and is used for performance improvement. The resulting optimized, scaled‐up MPD array constructed for benchmark comparison demonstrates 30% single‐pass CO ₂ conversion and 50% overall energy efficiency without any catalyst, which is unprecedented among all previously reported micro‐plasma systems. Remarkably, its performance exceeds that of many conventional large‐scale plasma systems, while consuming orders of magnitude less power. Integration of localized on‐chip reactive species generation by MPDs with catalytic, synthetic, or electrochemical processes could spur the development of new CO ₂ reduction pathways.