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

MoSe 2 nanosheets with defective microstructure were designed and investigated as anode materials for superior Na-ion storage and hydrogen evolution in alkaline media, displaying long cycling stability at high rate and excellent electrocatalytic activity. • Remarkable rate capability and excellent cycling performance could be achieved. • Isolated crystallinities of defect-rich MoSe 2 shortened charge transport path. • Defect-rich microstructures facilitated ionic contact and transfer. • Enriched edge sites promoted the hydrogen evolution reaction in alkali solution. The development of MoSe 2 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 MoSe 2 platelets with defective edge-sites (denoted as defect-rich, DR-MoSe 2) have been synthesized with a nonstoichiometric ratio of precursors. The resulting DR-MoSe 2 consists of highly defective ultrasmall MoSe 2 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-MoSe 2 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. [ABSTRACT FROM AUTHOR]