Green Syngas Production by Microwave-Assisted Dry Reforming of Methane on Doped Ceria Catalysts

Syngas (H-2 + CO) is the key to a future circular economy, but decarbonizing its production is challenging. Here, we electrify the dry reforming of methane (DRM) via selective coupling of microwave (MW) radiation to metal-free doped ceria catalysts. Reactivity studies on cerium-zirconium mixed oxides and comprehensive characterization reveal that the reduced Ce3+ centers with adjacent oxygen vacancies (Ce3+-V-O) are catalytically active and responsible for absorbing the MW energy. We introduce bulk bed spatial temperature measurements to compare MW to furnace heating. The selective deposition at MW energy to the reactive sites leads to excellent performance, unattainable by conventional electrical furnace heating. Step-change experiments, isotopic labeling, and spectroscopic insights elucidate a Mars-van-Krevelen (MvK)-type DRM turnover in concert with a MW-absorbing cycle that relies on the oxidation state of the catalyst. The reaction is periodically excited and quenched at the reactive centers without elevating the bulk measured temperature. These new insights may guide the design of catalysts and process intensification for carbon-free syngas production.