CO2 conversion plays a vital role in addressing climate change by cutting greenhouse gas emissions and promoting a circular carbon economy. Rather than releasing carbon dioxide into the atmosphere, carbon dioxide recycling technologies allows transformation of the captured CO2 into valuable end-products such as fuels and building block molecules. In this context, energy-efficient and electrified CO2 conversion offers a promising pathway for carbon-neutral chemical production, as CO2 captured from the air can be valorized by using fully renewable electricity. This approach not only reduces reliance on fossil fuels as an energy source but also enables the use of CO2 as a sustainable carbon feedstock, offering a renewable alternative for material synthesis.

In this work, we present a novel device capable of generating tunable micro-plasma modes (arc, pulsed, pulsed arc) on a chip, enabling efficient, low-power and scalable CO2 valorization. In the first part of the thesis, we show a simple and scalable clean room fabrication method for producing compact micro-plasma devices for electrified CO2 valorization and investigate the impact of device geometry on the CO2 splitting. Detailed micro-plasma image processing reveals that the micro-plasma pulse formation exhibits a random nature, which significantly influences reaction kinetics. As a result, the effects of random micro-plasma pulse formation on overall CO2 splitting kinetics are decoupled by developing single-site devices, where the minimized electrode length ensures that pulses are confined to a single spot. Extensive experimental kinetic studies conducted on these single-site devices reveal that CO2 splitting proceeds via a vibrational excitation mechanism, achieving a maximum energy efficiency of 29%. In addition, these studies introduce pulsed arc as a novel way of enhancing CO2 conversion with negligible loses in the efficiency, where we show that sequentially combining pulsed and arc plasma triples the CO2 conversion with only a 14.5 % decrease in the energy efficiency. We demonstrate that the peak energy efficiency of 29% is maintained across a broad CO2 conversion range (from 0.2% to 21%) for plasma powers less than 1 W -at least an order magnitude lower power than the systems with similar performance.

Lastly, we demonstrate the versatility of our devices through dry reforming methane and CO2 hydrogenation reactions. Dry reforming of methane results reveal that it is possible achieve 33% energy efficiency with a syngas ratio close to 1, which is desirable for the synthesis of oxygenated chemicals. Catalytic CO2 hydrogenation results reveal that deposition copper catalyst inside the discharge gap significantly increases CO2 hydrogenation selectivity towards methanol, demonstrating that it is possible to incorporate catalysts with the micro-plasma devices, where the integration of robust and easily fabricated catalysts underscores the potential of our devices have for a wide range of chemical processes.