Stabilizing an ultrathin MoS₂ layer during electrocatalytic hydrogen evolution with a crystalline SnO₂ underlayer

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• Amorphous molybdenum disulfide (MoS₂) is a promising catalyst for hydrogen evolution reactions (HER).
• While its performance and stability are known, adhesion and electrode integration challenges persist.
• Systematic studies on MoS₂ adhesion in electrochemical contexts are limited.

Purpose of the Study:

• To investigate the role of a tin dioxide (SnO₂) underlayer in improving the adhesion and electrocatalytic performance of amorphous MoS₂.
• To optimize electrode fabrication using atomic layer deposition (ALD) on macroporous anodic alumina (AAO) templates.
• To understand the influence of SnO₂ crystallinity on MoS₂ layer continuity and electrode stability.

Main Methods:

• Fabrication of a composite electrode: AAO template, SnO₂ underlayer, and amorphous MoS₂ via ALD.
• Material characterization using spectroscopic ellipsometry, X-ray photoelectron spectroscopy, grazing incidence X-ray diffractometry, scanning electron microscopy, and energy dispersive X-ray spectroscopy.
• Electrocatalytic performance evaluation via voltammetry, chronoamperometry, and electrochemical impedance spectroscopy.

Main Results:

• Annealing the SnO₂ layer before MoS₂ deposition significantly improved electrocatalytic water reduction.
• Optimized electrodes achieved 10 mA cm^-2 at 0.22 V overpotential with a catalyst loading of 0.16 mg cm^-2.
• Electrode stability was critically dependent on SnO₂ crystallinity, with crystalline SnO₂ maintaining MoS₂ continuity.

Conclusions:

• The AAO/SnO₂/MoS₂ electrode architecture effectively addresses MoS₂ adhesion and integration challenges.
• Optimized SnO₂ underlayers enhance both the performance and stability of amorphous MoS₂ electrocatalysts.
• Controlling SnO₂ crystallinity is key to maintaining MoS₂ layer integrity and achieving robust electrocatalytic water reduction.