Observation of Ni Species on Alumina in Photothermal Dry Reforming of Methane by Operando X-ray Absorption Spectroscopy

Abstract

Photothermal dry reforming of methane (PT-DRM) is an effective catalytic approach for CO₂ utilization into valuable synthesis gas (mixture of CO and H₂) using solar energy for the catalyst heating. Nickel is one of the most active catalytic components for thermal DRM reactions, and various Ni-based catalysts have been developed for PT-DRM. The oxidation state of Ni is considered to change depending on the reaction conditions such as gas atmosphere and temperature; however, the changes in the oxidation state in the rapid heating and cooling conditions induced by light irradiation have not been studied so far. In the present study, we investigated the chemical state and structure of nickel species in a Ni/Al₂O₃ catalyst during PT-DRM under visible and near-infrared light by operando X-ray absorption spectroscopy (XAS). We found that the spectral shape changed in response to the light on/off, and the origin was discussed based on the extracted information by analyzing the XANES and EXAFS spectra.