Calcium-intercalated molybdenum disulfide as electrocatalyst for carbon dioxide reduction

Abstract

In recent years, carbon dioxide and other greenhouse gases have been emitted on a large scale, leading to global warming, rising of sea levels, and causing many ecological problems. The use of fossil fuels is the chief source of large-scale emissions of CO2, but the reliability and economy of fossil fuels make it difficult for other energy sources to replace it in a short time. Reducing CO2 into other useful products like CO and CH4 is a potential solution. The electrochemical methods stand out in the field of CO2 reduction due to its mild and controllable conditions and the utilization of renewable source of energy. Design of efficient catalysts are essential for the electrochemical reduction of CO2. Transition metal dichalcogenides, such as MoS2 with high selectivity, low overpotential, and tunable structure is a potential candidate for catalysts. However, its performance still need to improve. The aim of this thesis us to develop a catalyst for CO2RR. As the intercalation of ions increases the conductivity of MoS2, the intercalation process of Ca2+ ions into MoS2 was studied. Furthermore, how the newly engineered material performs in the CO2RR was investigated.

In this study, two types of MoS2, namely pristine MoS2 and MoS2 intercalated with Ca2+ ions were used. The Linear sweep voltammetry (LSV), Electrochemical Impedance Spectroscopy (EIS) and Chronoamperometry (CA) were used to examine the electrochemical performance. Their CO2 reduction reaction performance in the KHCO3 aqueous solutions was investigated by gas chromatography (GC), high pressure liquid chromatography (HPLC), and Nuclear Magnetic Resonance spectroscopy (NMR). The catalysts were characterized before and after the intercalation process using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray Diffraction (XRD), and X-ray photoelectron spectroscopy (XPS).