Periodic trend of transition metals in the activity of 2D/2D MoS2/g-C3N4 nanohybrids in the HER and OER

Abstract

This work presents a novel method for preparing nanohybrids by adding previously synthesized graphitic carbon nitride g-C₃N₄ nanosheets to an aqueous solution of ammonium thiomolybdate (NH₄)₂MoS₄ which was synthesized in ammonia solution to form MoS₂/g-C₃N₄ (2D/2D) interlayered nanostructured hybrid material. This approach increases the activity of MoS₂ since its electronic structure, featuring “d” orbitals, allows the generation of active sites at the Mo edges for H⁺, OH⁻, ⁻OOH, and O⁻² adsorption, thus making it a highly efficient catalyst in chemical and electrochemical reactions. The interaction of g-C₃N₄ nanosheets with the MoS₂ was determined by NMR and XPS, leading to a disorder in the MoS₂ crystalline structure as shown from XRD, and therefore increasing the number of unsaturated sites S-Mo-S and 1T-MoS₂ phase formation, as shown in Raman spectra. Additionally, incorporating transition metals such as Ni, Co, and Fe opens a new promising scenario to evaluate their electrochemical effect in the nanohybrid that enhances the availability of active sites during the HER and OER. In this context, NiMoSCN electrocatalyst is the most effective for HER whereas CoMoSCN is for OER. At the current rate of 10 mA/cm², the overpotential of CoMoSCN decreases by up to 50 % with respect to the MoSCN.