Efficient and Water-Resistant Methane Combustion via Photoassisted Thermal Catalysis over Hierarchical Hollow NiCo-Mixed Oxides with Asymmetric Oxygen Vacancies

Efficient catalytic combustion is crucial for CH4 abatement, but its practical implementation is hindered by the trade-off between the combustion temperature and water poisoning of catalysts. Herein, hierarchical porous NiCo-mixed oxides with abundant phase interfaces and oxygen vacancies (OV) were prepared by calcinating a hollow NiCo-LDH precursor. Synergy of heterointerface and asymmetric OV in NiCoOx and NiCoOx-OV boosted the activation and mobility of surface lattice oxygen and adsorbed oxygen, significantly enhancing the thermal catalytic activity of methane oxidation. Photoassisted thermal catalysis under full-spectrum irradiation further reduced the T90 and apparent activation energy of methane oxidation to 337 °C and 56.1 kJ·mol–1 under dry conditions. This enhancement is ascribed to the generation of photoinduced charges (hot electrons and holes), which directly participate in the generation of oxygen species and methane activation. More importantly, the photothermal catalysis in the presence of 10 vol % water vapor exhibited intriguing oxidation activity with its T90 of 392 °C, outperforming most recently reported catalysts for wet methane combustion. It could be attributed to photoinduced dissociation of adsorbed water to surface hydroxyl radicals, substantially improving the water resistance of catalysts. A boosting mechanism of methane oxidation and water resistance via photothermal synergy was proposed based on the results of in situ ESR, CH4-TPSR, and in situ DRIFTS. This work provides innovative guidance and potential utility for practical methane abatement in high-humidity environments.