Preparation of a Molybdenum Sulfide/Nitride Composite as an Electrochemical CO 2 Reduction Catalyst

ABSTRACT Molybdenum disulfide (MoS 2 ) possesses multiple adsorption sites and is therefore an attractive catalytic material for electrochemical carbon dioxide (CO 2 ) reduction because of the possibility of breaking the scaling relationship that limits the catalytic activity and product selectivity. Doping with hetero elements, such as nitrogen, is a promising strategy to enhance the catalytic activity of MoS 2 ; however, previous works have been limited to small doping amounts (<6 atom%). In the present work, a solid‐state reaction was used to prepare a composite catalytic material comprised of MoS 2 and molybdenum nitride (Mo 2 N) with a high nitrogen content. Elemental analysis demonstrated that a solid‐state reaction between MoS 2 and lithium nitride successfully synthesized a MoS 2 ‐Mo 2 N composite with 14 atom% nitrogen. Notably, the composite exhibited higher Faradaic efficiency and partial current density for HCOOH production from CO 2 in a non‐ionic aqueous medium in comparison to pristine MoS 2 and Mo 2 N. The results of density functional theory calculations indicated that the CO 2 reduction reaction to HCOOH is more favorable than the hydrogen evolution reaction on the MoS 2 –Mo 2 N composite surface at a sufficient applied potential to drive either reaction. The findings presented here provide valuable insights into the design and synthesis of electrocatalysts for CO 2 reduction in aqueous electrolytes.