Cu2CCl2 MXene nanosheets developed by molten salt-shielded synthesis as a bifunctional electrocatalyst for hydrogen and oxygen evolution reactions

Abstract

The molten salt-assisted synthesis offers a new facile and safe pathway for directly synthesizing two-dimensional (2D) carbide MXenes, eliminating conventional acid-etching synthesis. Ternary copper-aluminum carbides (Cu2AlC) represent a member of a new class of precursor MAX phases ideal for developing a new family of Cu-based MXenes (e.g., Cu2C). We successfully synthesize Cu2CCl2 MXene 2D nanomaterials in an open-air atmosphere using a molten salt-shielded synthesis (MS3) method. The method uses a Lewis-acid salt (CuCl2) as an etchant and a low-melting-point eutectic salt mixture as the reaction medium to prevent oxidation of the MXene structure at high temperatures. The Cu2AlC and Cu2CCl2 MXene materials exhibit bifunctional electrochemical performances for both oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in acidic 0.5 M H2SO4 media through water splitting reactions. When tested as an HER electrocatalyst, Cu2CCl2 MXene shows a small overpotential of ≈48 mV and a Tafel slope of ≈85 mV dec−1 (an overpotential of ≈39 mV and a Tafel slope of ≈78 mV dec−1 for OER) rivaling other MXene-based electrocatalysts reported so far. Our findings suggest that Cu2CCl2 MXene holds promise as a potential heterogeneous electrocatalyst for renewable oxygen and hydrogen production applications.

Keywords

• Cu2AlC MAX phase
• Cu2CCl2 MXene
• Molten salt-shielded synthesis
• Bifunctional electrochemical
• Hydrogen evolution reaction
• Oxygen evolution reaction