Designed synthesis of a hierarchical MoSe2@WSe2 hybrid nanostructure as a bifunctional electrocatalyst for total water-splitting

Abstract

Layered metal dichalcogenides (LMDs) and their heterostructures with different morphologies are next generation materials for sensing, electronics, optoelectronics, topological insulators and devices, and catalytic applications. In recent years, LMDs with more exposed electrochemically active sites have been explored as cost-effective alternatives for the water-splitting reaction. However, morphology engineering and heterostructure synthesis of LMDs through low-cost and high-yield methods are still challenging. Herein, we present a simple and facile wet-chemical method to synthesize few-layered MoSe₂ and WSe₂ nanoflowers with a large number of exposed edges. Temperature-controlled reactions reveal the faster synthesis of MoSe₂ as compared to WSe₂. Exploiting the faster kinetics of the synthesis of MoSe₂, we have synthesized a hierarchical heterostructure of MoSe₂@WSe₂ through a one-step synthesis method. The as-synthesized nanostructures were used for the water-splitting reaction that involves the hydrogen evolution reaction (HER) at the cathode and the oxygen evolution reaction (OER) at the anode. The hierarchical nanostructure exhibits better electrocatalytic activity among the as-synthesized nanostructures. The hierarchical nanostructure requires an overpotential of 231 mV (HER) and 300 mV (OER) to achieve a current density of 10 mA cm⁻². This study opens the door for wet-chemical synthesis of hierarchical heterostructures based on LMDs with enhanced properties.