Interchangeable Biomass Fuels for Paper-Based Microfluidic Fuel Cells: Finding Their Power Density Limits.

Area of Science:

• Electrochemistry
• Materials Science
• Renewable Energy

Background:

• Paper batteries are emerging as low-cost, disposable power sources for portable analytical systems.
• Achieving high energy density while maintaining low cost is a key challenge for paper batteries.
• Biomass-derived fuels offer a sustainable alternative for powering such devices.

Purpose of the Study:

• To develop and characterize a paper-based microfluidic fuel cell (PμFC) utilizing biomass-derived fuels for high power generation.
• To investigate the performance of PμFCs with different fuels (methanol, ethanol, ethylene glycol, glycerol) in a mixed-media configuration.
• To establish a benchmark for paper battery power output using alcohol-based fuels.

Main Methods:

• Engineered a PμFC with a Pt/C carbon paper anode and a metal-free carbon paper cathode.
• Utilized a mixed-media configuration with alkaline electro-oxidation of fuels and acidic reduction of Na2S2O8.
• Chemically mapped the colaminar channel and analyzed flow rates using video recordings to understand reactant residence time and system stability.

Main Results:

• The PμFC system demonstrated stable colaminar flow within 150-200 seconds, correlating with stable open circuit voltage.
• Power densities ranged from approximately 2.2-3.9 mW cm⁻² with various biomass-derived fuels.
• An unprecedented PμFC fueled by ethylene glycol achieved a benchmark power density of 6.76 mW cm⁻², the highest reported for alcohol-fueled paper batteries.

Conclusions:

• The developed PμFCs offer a sustainable and adaptable power solution for portable devices, capable of utilizing various biomass-derived fuels.
• The mixed-media configuration allows independent optimization of half-cell reactions, enhancing overall performance.
• Ethylene glycol emerges as a highly effective fuel, setting a new standard for power output in paper-based energy systems.