Heavy dependence on fossil fuels has caused an astonishing growth in atmospheric CO2 levels for the past decades. The increase of anthropogenic CO2 emissions accelerates global warming and sea-level rising, which could lead to irreversible environmental damages. Electrochemically converting CO2 to value-added fuels is a promising approach to reduce carbon footprint and store over-generating renewable electricity as chemical energy. Studies have shown the excellent catalytic performance of bulk MoS2 concerning the low overpotential and high product selectivity towards CO for electrochemical CO2 reduction reaction (CO2RR) in ionic liquid-based solutions. However, its performance in different configurations and electrolytes remains unexplored. In this study, two types of MoS2, namely bulk MoS2 and MoS2 film coated on a glassy carbon electrode (GCE), were used. Their CO2RR performance in the KHCO3 aqueous and ionic liquid-based solutions was investigated using electrochemical methods, gas chromatography (GC), and attenuated total reflectance - Fourier transform infrared spectroscopy (ATR-FTIR). Additionally, the photochemical activity of MoS2 was explored using scanning vibrating electrode technique (SVET).

The selected catalysts were characterized before and after the CO2 reduction process using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS). GC measurement results showed that MoS2 film coated on GCE exclusively catalyzed H2 evolution in aqueous solutions. It was also observed that higher activity was achieved on the MoS2 film mixed with glassy carbon powder. Furthermore, the MoS2 film with the changed bandgap structure also performed better in ionic liquid-based aqueous electrolyte. These findings suggest that the catalytic performance of MoS2 film for CO2RR could be enhanced by interspersing materials with high conductivity or modifying the bandgap structure.