Microwave-Induced Self-Activation of LaNiO ₃ -Derived Catalysts for Susceptor-Free Dry Reforming of Methane

Dry reforming of methane (DRM) requires high heat input, and identifying microwave-responsive catalysts that do not rely on external susceptors remains challenging. Here, we show that LaNiO3-derived catalysts enable susceptor-free microwave-assisted DRM and exhibit faster activation and higher CH4 and CO2 conversions than conventional external heating at an apparent bed temperature of 600 °C. Time-resolved XRD, XAFS, and H2-TPR analyses indicate that microwave irradiation accelerates the reduction of LaNiO3 via a transient La2NiO4 intermediate, followed by formation of Ni/La2O3. In situ dielectric measurements show a sharp increase in dielectric loss during the initial reaction stage, consistent with enhanced microwave coupling during catalyst activation. Under microwave irradiation, whisker-like carbon species are also formed and are suggested to contribute to sustained microwave absorption at later reaction stages, based on the temporal correlation between carbon accumulation and the recovery of dielectric loss. Microwave power-control experiments further suggest that maintaining a moderately reduced state containing La2NiO4 improves heating behavior while sustaining catalytic performance. These results support a structure−dielectric−activity relationship in microwave-assisted DRM and provide guidance for designing susceptor-free catalysts for electrified reforming.