Capillary-Driven Separate Gas-Liquid Transport: Alleviating Mass Transport Losses for Efficient Hydrogen Evolution

Area of Science:

• Electrochemistry
• Materials Science
• Catalysis

Background:

• Efficient hydrogen production is vital for sustainable energy. Earth-abundant transition metal electrodes are key for cost-effective hydrogen evolution reaction (HER) catalysis.
• Current HER research often overlooks the impact of gas-liquid transport, focusing solely on catalyst activity, which limits performance.

Purpose of the Study:

• To address mass transport limitations in HER by introducing separate-path gas-liquid transport.
• To develop a novel hierarchical porous electrode for enhanced HER performance.

Main Methods:

• Fabrication of a novel hierarchical porous Ni-doped cobalt phosphide electrode (CoNi-P@Ni).
• Utilized visualization and numerical simulations to analyze gas-liquid transport dynamics.
• Investigated the role of microvalleys and crack structures in facilitating water supply and bubble evolution.

Main Results:

• The CoNi-P@Ni electrode's unique structure separates gas and liquid paths, improving mass transport.
• Cracks act as water supply channels, ensuring continuous electrolyte wetting and reducing hydrogen supersaturation.
• Microvalleys serve as preferential sites for bubble release, enhancing hydrogen transport flux and accelerating bubble growth.

Conclusions:

• The developed hierarchical porous electrode design significantly enhances HER performance by optimizing gas-liquid countercurrent transport.
• Optimized Ni doping in CoNi-P@Ni electrodes led to superior HER activity, with an overpotential of 51 mV at 10 mA cm⁻².
• This study presents a promising strategy for designing high-performance electrocatalysts by considering integrated mass transport and catalytic activity.