Probing the Origin of Photocatalytic Effects in Photothermochemical Dry Reforming of Methane on a Pt/CeO<sub>2</sub> Catalyst
Zichen Du, Fuping Pan, Erik Sarnello, Xuhui Feng, Yang Gang, Tao Li, Ying Li
Abstract
Solar-driven photothermochemical dry reforming of methane (PTC-DRM) that integrates thermocatalysis and photocatalysis in one catalyst system is an emerging approach that has demonstrated higher efficiency than thermocatalytic DRM. However, how photocatalysis contributes to the PTC-DRM process at high temperatures remains elusive. Herein, we systematically investigated the photocatalytic effects in PTC-DRM using a photoactive CeO2-supported Pt catalyst (Pt/CeO2). The Pt/CeO2 catalyst showed significant photocatalytic contributions in PTC-DRM, producing CO and H2 at rates under light irradiation 2.0 and 2.9 times as much as those obtained in the dark at the same temperature, 650 °C. Wavelength-dependence investigation by applying various long-pass filters reveals that the contributions of photocatalysis are mainly from lights less than 435 nm in wavelength, coincident with the band-gap energy of CeO2, while those longer than 435 nm merely provide heat to drive thermocatalysis. Mechanistic studies from in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and from materials characterization before and after the PTC-DRM reaction suggest that photoirradiation regenerates surface oxygen vacancies, thus boosting CO2 activation and promoting formate and carbonate intermediates conversion to final products. Understanding the photocatalytic effects in PTC-DRM from this work provided insights in designing high-performance catalysts for more efficient solar energy utilization.