Transition metal oxy/hydroxides functionalized flexible halloysite nanotubes for hydrogen evolution reaction

Area of Science:

• Materials Science
• Electrochemistry
• Nanotechnology

Background:

• Hierarchical halloysite nanotubes (HNT) possess unique surface chemistry with positive Al-OH and negative Si-O-Si groups.
• The abundant hydroxyl groups on HNT provide exceptional cation/anion exchange capacity, crucial for enhancing electrocatalytic activity.
• Surface functionalization of HNT is a promising strategy to develop efficient electrocatalysts.

Purpose of the Study:

• To synthesize and evaluate Ni, Co, and Cu metal oxy/hydroxides functionalized HNT as electrocatalysts for the hydrogen evolution reaction (HER).
• To investigate the electrocatalytic performance and stability of these novel materials in alkaline media.
• To explore the potential of HNT as a support material for next-generation HER catalysts.

Main Methods:

• Facile hydrothermal synthesis of metal oxy/hydroxides (Ni, Co, Cu) functionalized HNT.
• Electrocatalytic characterization of synthesized materials for HER, including overpotential, Tafel slope, and exchange current density measurements.
• Electrolyzer testing using anion exchange membranes with RuO2||Co(OH)2@HNT for long-term stability assessment.

Main Results:

• Cobalt hydroxide functionalized HNT (Co(OH)2@HNT) on carbon cloth exhibited an ultra-low overpotential of 65 mV at 10 mA cm⁻² and a Tafel slope of 181 mV dec⁻¹.
• Co(OH)2@HNT demonstrated a high exchange current density of 3.98 mA cm⁻² in 1 M KOH, attributed to strong electrostatic affinity.
• Electrolyzers utilizing RuO2||Co(OH)2@HNT showed remarkable stability, operating for over 50 hours at 10 mA cm⁻² without degradation.

Conclusions:

• Surface-functionalized HNT, particularly Co(OH)2@HNT, significantly enhances electrocatalytic activity for the hydrogen evolution reaction in alkaline electrolytes.
• The synthesized Co(OH)2@HNT catalyst exhibits superior performance and robustness compared to many existing transition metal-based electrocatalysts.
• Hierarchical halloysite nanotubes represent a highly promising and cost-effective alternative to benchmark platinum catalysts for efficient hydrogen production.