Solar-Driven Photothermocatalytic Dry Reforming of Methane for Syngas Production

Carbon dioxide (CO₂) reforming or dry reforming of methane (CH₄) to produce syngas, hydrogen (H₂) and carbon monoxide (CO), is a promising low-carbon energy technology that converts two greenhouse gases (CO₂ and CH₄) into valuable chemicals and fuels. Recently, solar-driven dry reforming of methane (DRM) has attracted increasing attention as it further lowers the carbon footprint by using renewable energy as the input. Most of studies in this area focus on solar thermochemical DRM, i.e. using sunlight merely as the thermal energy source. In this chapter, an innovative photothermocatalytic DRM (PTC-DRM) approach is introduced, which integrates photocatalysis and thermocatalysis to maximize the solar energy efficiency through the design of a unique catalyst that can promote the synergies between photo- and thermo-catalysis. Platinum (Pt) loaded on cerium oxide (CeO₂) support is one example of such catalysts. This chapter presents recent advancements in Pt/CeO₂-based catalysts and their effectiveness and stability in the PTC-DRM process powered by concentrated sunlight. First, the contribution of photocatalysis in the PTC-DRM process on a Pt/CeO₂ catalyst is confirmed and the PTC-DRM mechanisms unraveled. Secondly, the effects of dopants such as silicon (Si) in the CeO₂ support on the PTC-DRM performance are discussed, which is mainly due to the generation of surface oxygen vacancies and increased light absorption. Thirdly, a new materials innovation is introduced, i.e. the incorporation of Zn promoter and atomic layer deposition (ALD) enabled ultrathin MgO coating on Pt/CeO₂, which significantly enhances the efficiency and stability of PTC-DRM. Lastly, this chapter presents an approach of engineering surface acidity of the support by mixing Al₂O₃ with CeO₂, and the resultant Pt/Al₂O₃-CeO₂ catalyst achieves a near unity H₂/CO ratio in the produced syngas. The studies discussed in this chapter provide valuable insights on the importance of materials innovations to the advancement of sustainable energy technologies, in particular, solar energy harvesting and low-carbon fuels production.