Selective Gas-Permeable Anode Flow Field for CO₂ Removal in Direct Formic Acid Fuel Cells

Background

Liquid fuel cells, particularly direct formic acid fuel cells (DFAFCs), harness the electro-oxidation of formic acid at the anode to generate electrical power through a proton exchange membrane architecture. These systems promise higher energy densities and faster refueling compared to conventional batteries, making them attractive for portable electronics, remote sensors, and auxiliary power units. Continuous operation without frequent recharging or bulky battery packs can extend device runtime and reduce environmental impact. The liquid fuel format simplifies storage and handling relative to gaseous hydrogen while providing the potential for near-zero emissions when CO₂ byproduct is efficiently managed, addressing the growing demand for compact, high-performance power sources.

Conventional anode flow field designs rely on single-channel serpentine patterns where liquid formic acid and gaseous CO₂ coexist, leading to two-phase flow challenges. CO₂ bubbles can accumulate, obstructing reactive sites and disrupting fuel distribution, while liquid flooding can impede mass transport and lower catalyst utilization. The intertwined gas-liquid streams reduce overall current density and create localized hot spots that degrade membrane performance over time. Moreover, inefficient CO₂ extraction often necessitates complex purge loops and reduces fuel utilization efficiency, limiting cell scalability and operational stability under high loading or variable power demands.

Technology

This advanced anode flow field architecture for direct formic acid fuel cells features two distinct flow fields—a gaseous channel and a liquid channel—separated by a semi-permeable, hydrophobic and electrically conductive separator. The design channels liquid formic acid and water through one side while directing CO₂ gas through the other, enabling direct diffusive transport of CO₂ across the separator to the gaseous flow field. The separator, fabricated from hydrophobic carbon-based or superhydrophobic materials, prevents liquid crossover, minimizes electron transfer distances, and enhances overall cell performance. Integration of side feed and exit ports outside the active area further streamlines fuel delivery and gas venting.

Unlike conventional serpentine anode plates that suffer from two-phase flow inefficiencies, this technology achieves perpendicular CO₂ removal at the catalyst interface, maintaining efficient reactant access and gas evacuation. By shortening electron pathways and leveraging superhydrophobic separators with high CO₂ permeability, it supports higher acid concentrations, nearly complete fuel conversion without secondary loops, and “dead-end” operation. Its scalable footprint (≥5 cm²) and stackable architecture deliver superior power density, continuous operation, and compact form factors ideal for portable electronics, drones, and auxiliary power units, outpacing traditional battery solutions.

Benefits

• Efficient CO₂ removal directly at the catalyst layer via selectively gas-permeable separator
• Enhanced fuel cell performance through minimized electron transfer path
• Increased power density and reduced device size by supporting higher liquid fuel concentrations
• Nearly 100% fuel conversion without the need for a recycling loop
• Improved mass transport and fuel utilization, including support for dead-end operation
• Scalability and compatibility with stack-level integration for high-voltage applications
• Broad applicability as a compact power source for portable devices

Applications

• Portable electronics power source
• Long-endurance drone power system
• Remote sensor power supply
• Handheld power tool battery replacement
• Vehicle auxiliary power unit

Additional info

An advanced anode plate for direct formic acid fuel cells features dual, mating liquid and gaseous flow fields separated by an electrically conductive, hydrophobic semi-permeable separator. CO₂ diffuses perpendicularly from the catalyst layer through the separator into the gas channel, minimizing two-phase flow issues. The separator’s super-hydrophobic, carbon-based structure prevents liquid crossover while shortening electron pathways, boosting fuel conversion, power density, and enabling compact, dead-end operation for portable power applications.