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

Abstract

Paper batteries are self-pumping emerging tools for powering portable analytical systems. These disposable energy converters must be low-cost and must achieve enough energy to power electronic devices. The challenge is reaching high energy while keeping the low cost. Here, for the first time, we report a paper-based microfluidic fuel cell (PμFC) equipped with Pt/C on a carbon paper (CP) anode and a metal-free CP cathode fed by biomass-derived fuels to deliver high power. The cells were engineered in a mixed-media configuration, where methanol, ethanol, ethylene glycol, or glycerol is electro-oxidized in an alkaline medium, while Na 2 S 2 O 8 is reduced in an acidic medium. This strategy allows for optimizing each half-cell reaction independently. The colaminar channel of the cellulose paper was chemically investigated by mapping the composition, which reveals a majority of elements from the catholyte and anolyte on each respective side and a mixture of both at the interface, assuring the existing colaminar system. Moreover, the colaminar flow was studied by investigating the flow rate by considering recorded videos for the first time. All PμFCs show 150−200 s to build a stable colaminar flow, which matches the time to reach a stable open circuit voltage. The flow rate is similar for different concentrations of methanol and ethanol, but it decreases with the increase in ethylene glycol and glycerol concentrations, suggesting a longer residence time for the reactants. The cells perform differently for the different concentrations, and their limiting power densities are composed of a balance among anode poisoning, residence time, and viscosity of the liquids. The sustainable PμFCs can be interchangeably fed by the four biomass-derived fuels to deliver ∼2.2−3.9 mW cm −2 . This allows choosing the proper fuel due to their availability. The unprecedented PμFC fed by ethylene glycol delivered 6.76 mW cm −2 , which is the benchmark output power for a paper battery fed by alcohol.

Enhanced Power Generation Using a Dual-Surface-Modified Hematite Photoanode in a Direct Glyphosate Photo Fuel Cell

“…We used commercial 5 nm Pt/C nanoparticles dispersed on CP as a dark cathode. Images of the Pt/C/CP may be found elsewhere . Regarding the photoanodes, Figure displays the XRD analysis, confirming the formation of the α-Fe 2 O 3 phase (JCPDS card no.…”

“…Images of the Pt/C/CP may be found elsewhere. 37 Regarding the photoanodes, Figure 3 displays the XRD analysis, confirming the formation of the α-Fe 2 O 3 phase (JCPDS card no. 33-0664, rhombohedral system, space group R3̅ c), with no detected phases due to Hf or FeNi addition.…”

“…Lima et al showed that even metal-free CP may reduce persulfate in an alkaline medium. 37 However, the onset potential (E onset ) for persulfate reduction on CP is too high, making it unfeasible to couple this cathodic reaction to Gly electro-oxidation. Moreover, the Pt/C/CP cathode increases current density from the persulfate reduction reaction from approximately −4 to −48 mA cm −2 at 0.6 V RHE .…”

“…After the addition of persulfate, the current density increased considerably. Lima et al showed that even metal-free CP may reduce persulfate in an alkaline medium . However, the onset potential ( E onset ) for persulfate reduction on CP is too high, making it unfeasible to couple this cathodic reaction to Gly electro-oxidation.…”