Advancing paper-based microfluidic ethanol fuel cells with gel-assisted dual electrolytes: A step towards scalable power solutions

Paper-based microfluidic fuel cells are steadily emerging as alternative energy sources due to their simplicity, affordability, and independence from auxiliary equipment. However, some studies have reported low maximum power density and open circuit voltage in alcohol fuel cells, primarily due to mixed potentials caused by simultaneous oxidation and reduction of reactants on the same electrode surface. To address these challenges, a novel gel-assisted dual-electrolyte configuration was developed for paper-based microfluidic ethanol fuel cells. By incorporating an ion-conducting hydrogel between independent cathode and anode, this design achieved a remarkable open circuit voltage of 1.18 V. Systematic optimization revealed that the properties of paper channels, such as pore size and fluid flow rates, are critical factors in enhancing performance. Paper with larger pore sizes facilitated higher fluid flow rates, which, in turn enhanced ion transport, and significantly improved both power density and overall efficiency. By employing a dual-electrolyte system i.e. electro-oxidation of ethanol in an alkaline environment with the reduction of potassium dichromate in an acidic medium, this optimized approach yielded an impressive current density of ∼31 mA cm⁻² with a maximum power density of 4.47 mW cm⁻². Moreover, the cell demonstrated exceptional durability and instant reactivation upon refueling, making it practical for real-world applications. The scalability of these cells was further demonstrated by connecting multiple cells in series, making them capable of powering diverse electronic devices with varying power requirements. This optimization approach thus set a new trajectory for advancing the field towards real-world implementations.