A highly efficient 2D siloxene coated Ni foam catalyst for methane dry reforming and an effective approach to recycle the spent catalyst for energy storage applications

Abstract

The dry reforming of methane (DRM) using CO₂ for the production of syngas (H₂ and CO) has received increasing attention for reducing global CO₂ emissions. The main drawback of DRM reactions is the limited reusability of the spent catalyst due to carbon deposition on its surface. Thus, designing an appropriate catalytic system is adequate to achieve increased syngas production with low carbon deposition, and developing smart strategies to reuse the carbon deposited spent catalyst is highly desirable. In this work, two dimensional siloxene sheet (silicon analog of graphene oxide) coated nickel foam is examined as a novel catalyst for the DRM reaction. The siloxene/Ni foam catalyst demonstrated superior catalytic performance in terms of conversion efficiencies (for CH₄ and CO₂) and syngas production (H₂ and CO) with a high H₂/CO ratio of 1.5. Further, the carbon deposited siloxene/Ni spent catalyst recovered after the DRM reaction was effectively re-utilized as electrodes for a symmetric supercapacitor (SSC) using an organic electrolyte. The fabricated SSC (using the spent catalyst as electrodes) delivered a high device capacitance (24.65 F g⁻¹), high energy density (30.81 Wh kg⁻¹), and high-power density (15 625 W kg⁻¹) with a long cycle life. Considering that the estimated carbon cost for developing a supercapacitor electrode is about $15 per kilogram, our strategy to effectively reutilize the recovered carbon deposited spent catalyst for energy storage applications might be a promising and economical approach for utilization of the spent catalyst.