The conventional process for CO2 conversion requires high energy and expensive catalysts, and shows poor product selectivity. In this study, we address these challenges by investigating an environmentally friendly method for CO production through the variable frequency microwave-driven CO2 Boudouard reaction over biochar. We hypothesized that tuning the microwave frequency to align with the dielectric properties of biochar, and thereby induce a resonance effect, could significantly enhance reaction efficiency. Experiments were conducted to explore the effect of microwave frequency on CO2 conversion efficiency in the variable frequency microwave reactor operating within a frequency range of 2430-6000 MHz. Results reveal a significant resonance effect at 4225 MHz resulting in an outstanding CO2 conversion of 96.3%, in sharp contrast to the complete absence of conversion observed at the conventional 2450 MHz. The resonance frequency not only facilitated exceptional conversion but also remarkably improved energy efficiency, yielding a productivity of 1427.5 mu mol/kJ of CO. This represents a remarkable 474-fold increase compared to electrical heating. Furthermore, continuous microwave irradiation at this optimized frequency demonstrated remarkable stability and induced substantial enhancements in the pore structure and surface area of biochar. This innovative approach provides promising insights into sustainable and efficient CO production processes.
