Unravelling the trifunctional electrochemical properties of WSe2 nanosheets for self-powered hydrogen production

Two dimensional materials have received increasing recognition for their utility in electrochemical energy storage and conversion devices, as well as for self-powered systems. In this work, we are reporting the tri-functional electrochemical properties (such as energy-storage, hydrogen evolution reaction (HER) and oxygen evolution reaction (OER)) of WSe2 nanosheets (prepared by a solvothermal method) towards the development of a self-powered system for uninterrupted hydrogen (H2) production. First, we have examined the energy storage properties of the WSe2 nanosheets in the form of flexible solid-state supercapacitor (FSSC) that shows the presence of ion-intercalation pseudocapacitance in the WSe2 nanosheets. The fabricated WSe2 FSSC possess a high device capacitance, energy density, and power density with 119% capacitance retention over 5,000 cycles. Second, we explored the electrocatalytic properties of WSe2 nanosheets that indicated they possess effective HER and OER properties with low overpotential (115 mV for HER and 312 mV for OER), respectively. Finally, a proof-of-concept self-powered system comprising a solar cell, WSe2 FSSC, and lab-scale WSe2 electrolyzer (with a low overpotential of 1.604 V at 10 mA cm-2) was demonstrated to overcome the power fluctuation issues for effective and uninterrupted H2 production.