MoSe2 nanoplatelets with enriched active edge sites for superior sodium-ion storage and enhanced alkaline hydrogen evolution activity

Abstract The development of MoSe2 with largely exposed active sites have recently been studied as promising high-performance active materials for sodium ion batteries (SIBs) and hydrogen evolution reactions (HER) due to their excellent energy storage and conversion capabilities. In the present study, nanostructured MoSe2 platelets with defective edge-sites (denoted as defect-rich, DR-MoSe2) have been synthesized with a nonstoichiometric ratio of precursors. The resulting DR-MoSe2 consists of highly defective ultrasmall MoSe2 nanoplatelets, showing ample pore distribution and highly exposed active edge sites. When testified as SIBs anodes, it reveals enhanced sodium-ion storage capacity and improved rate capability based on a pseudocapacitive charge storage mechanism. Density functional theory (DFT) calculations disclosed that sodium-ions trend to adsorb on the edge sites with a high binding energy and then diffuse along the basal planes with a low transport energy barrier. A hybrid sodium-ion capacitor based on DR-MoSe2 anode has further displayed a maximum energy density of 89 Wh kg−1 at a power output of 5436 W kg−1. In addition, the Tafel slope of 68 mV dec−1 for HER is also achieved in 1 M KOH. This work shed lights on design of two-dimensional materials through edge defect engineering for high-performance energy storage and catalysis.