# Anisotropically Wettable Porous Transport Layers for Gas Management in Water Electrolyzers

## TL;DR

This paper introduces a new porous transport layer with anisotropic wettability to improve gas and liquid transport in water electrolyzers, enhancing efficiency and scalability.

## Contribution

The novel anisotropically wettable porous transport layer design enables directional transport and efficient gas removal in water electrolysis.

## Key findings

- Anisotropic wettability in PTLs improves AEMWE efficiency by removing gas bubbles and enhancing electrolyte transport.
- The method is scalable to large-area AEMWEs and works with conventional PTL types.
- In situ visualization shows dual-phase wetting suppresses gas accumulation and enables stable, bubble-free electrolysis.

## Abstract

Conventional studies on water electrolysis have primarily focused on designing novel electrocatalysts and membranes, with intrinsic properties closely linked to the immediate performance of water electrolyzers. However, less attention is directed toward porous transport layers (PTLs), which are essential for sustaining efficient, long‐term, high‐current operation by enabling effective mass transport. Here, a novel PTL with anisotropic wettability (AW‐PTL) is introduced to enhance the efficiency of anion exchange membrane water electrolyzers (AEMWEs). By hydrophobically modifying the upper half of hydrophilic Ni foam with polytetrafluoroethylene using a simple spray‐coating method, anisotropic wettability is achieved, enabling the directional transport of liquid electrolytes and gaseous products. This design significantly improves AEMWE efficiency by facilitating the removal of gas bubbles, which typically block catalyst active sites and hinder electrolyte supply. The method is universally applicable across conventional PTL types and demonstrates scalability to large‐area (up to 225 cm2) and short‐stack AEMWEs. This work advances the practical application of water electrolysis, providing an adaptable solution for other water electrolyzer types using existing catalysts and membranes.

Synergistic wetting, achieved by integrating hydrophilic and hydrophobic domains, enhances mass transport in porous transport layers. In situ visualization reveals that dual‐phase wetting suppresses gas accumulation and promotes continuous bubble release, enabling stable, bubble‐free electrolysis within membrane electrode assemblies. This simple yet powerful strategy overcomes transport limitations and advances porous transport layer design for efficient gas/liquid diffusion.