Development of Co₀.₈₅Se/MoSe₂ Composite: an Efficient Electrocatalyst for Alkaline HER

Banerjee, Koustav (2022) Development of Co₀.₈₅Se/MoSe₂ Composite: an Efficient Electrocatalyst for Alkaline HER. Masters thesis, Indian Institute of Science Education and Research Kolkata.

Text (MS dissertation of Koustav Banerjee (17MS031)) 17MS031_Thesis_file.pdf - Submitted Version Restricted to Repository staff only Download (3MB)

Abstract

Alkaline Hydrogen evolution reaction (HER) is a challenging process because of the extra energy barrier of dissociation of the HOH bond in the Volmer step. There is still finding of a suitable catalyst for HER in alkaline medium with low overpotential, better kinetics and stability. Here, we report Co₀.₈₅Se/MoSe₂ composite material, developed by an easier and facile one-step hydrothermal synthetic route, which shows agglomerated nanograins like morphology. This composite material needed 71 mV overpotential to reach benchmark current density of 10 mA/cm² for HER in alkaline conditions. Its Tafel slope is 70.6 mV/dec, which is better than its individual components. This composite has higher ECSA (electrochemically active surface area) and prolonged stability of 25 h in1 M KOH electrolyte. From the Tafel slope, it can be inferred that the catalyst follows Volmer- Heyrovsky mechanism for HER. Improved activity of Co₀.₈₅Se/MoSe₂ can be explained by the synergistic effect of Co₀.₈₅Se and MoSe₂, where Co₀.₈₅Se helps to dissociate the HOH bond (Volmer step) and MoSe2 helps in the Heyrovsky step. For OER, CoSe₂ shows the lowest overpotential (341 mV) to reach 10 mA/cm² current density. So, overall, water splitting can be done by using Co₀.₈₅Se/MoSe₂ at the cathode and CoSe₂ at the anode.

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