In-situ synthesis of Co-NC/MoS2 derived from ZIF-67 for enhancing the selectivity of electrochemical nitrogen reduction

Electrochemical N2 fixation is a promising method for ammonia synthesis, but competitive hydrogen evolution reaction (HER) results in low faraday efficiency. Thus, simple modification methods to improve the selectivity of catalyst to NRR in aqueous solution are highly requirement. Here, an effective strategy of adding HER attractant (MoS2) is proposed to greatly boost the NRR activity of Co-NC derived from ZIF-67. Therefore, Co-NC/MoS2 composite is prepared. Composites has excellent NRR electrocatalytic ability, with the NH3 yield of 54.66 mu g center dot h-1 center dot mg-1 cat and the Faradaic efficiency of 34.49 % in water medium at ambient conditions. After compounding MoS2, density functional theory calculation verifies that the adsorption sites of H+ and N2 are separated, with H+ tending to adsorb on the S sites, while N2 adsorbing on the metal Co site. Meanwhile, the hybridization of MoS2 and Co-NC can improve the NRR efficiency by optimizing the electron transfer from Co-NC to MoS2. Zn-N2 battery is further successfully assembled, and the battery can discharge stably for 12 h at a discharge current of 0.05 mA center dot cm-2, which the NH3 yield rate can reach 40.23 mu g center dot h-1 center dot mg-1 cat. (c) 2023 Elsevier B.V. All rights reserved.

Automated summary

Electrochemical N2 fixation shows promise for ammonia synthesis, but the competitive hydrogen evolution reaction (HER) reduces its efficiency. Therefore, simple modification methods are needed to improve the catalyst's selectivity for NRR in aqueous solutions. In this study, the addition of the HER attractant (MoS2) was proposed to significantly enhance the NRR activity of Co-NC derived from ZIF-67, resulting in the preparation of a Co-NC/MoS2 composite. This composite exhibited excellent NRR electrocatalytic ability, with a NH3 yield of 54.66 μg·h-1·mg-1 cat and a Faradaic efficiency of 34.49% in water medium at ambient conditions.