Ultrathin Two-Dimensional Polyoxometalate-Based Metal-Organic Framework Nanosheets for Efficient Electrocatalytic...

Area of Science:

• Materials Science
• Electrochemistry
• Nanotechnology

Background:

• Designing 2D polyoxometalate-based metal-organic framework (POMOF) nanosheets as self-supporting electrodes for catalysis is challenging.
• Developing efficient electrocatalysts for the hydrogen evolution reaction (HER) is crucial for clean energy technologies.

Purpose of the Study:

• To demonstrate the first POMOF nanopillar arrays composed of 2D nanosheets as a self-supported electrode.
• To investigate the electrocatalytic performance of these novel POMOF electrodes for the HER in acidic media.

Main Methods:

• Synthesized 2D [Co2(TIB)2(PMo12O40)]·Cl·4H2O (CoMo-POMOF) crystalline materials using Co-α-Keggin polymolybdate units and 1,3,5-tris(1-imidazoly)benzene (TIB) ligands.
• Fabricated CoMo-POMOF nanopillar arrays on nickel foam via a CoO nanorod template-assisted strategy.
• Evaluated electrocatalytic activity using electrochemical techniques and employed density-functional theory (DFT) for mechanistic insights.

Main Results:

• The CoMo-POMOF nanopillar arrays exhibited superior HER electrocatalytic performance with a low overpotential of 137 mV and a Tafel slope of 59 mV dec⁻¹ at 10 mA cm⁻².
• Performance is comparable to state-of-the-art POMOF-based electrocatalysts.
• DFT calculations revealed that exposed bridging oxygen active sites (Oa) optimize H* adsorption, enhancing intrinsic HER activity (ΔG_H* = -0.11 eV).

Conclusions:

• Successfully fabricated 2D CoMo-POMOF nanosheet arrays on conductive substrates as self-supporting electrodes.
• The developed POMOF electrodes demonstrate high efficiency and stability for the hydrogen evolution reaction in acidic conditions.
• This work provides a promising strategy for designing advanced POMOF-based electrocatalysts for energy conversion applications.