A paper‐based self‐pumping microfluidic fuel cell stack with a novel vertical structure

Abstract

Summary Microfluidic fuel cell (MFC) stacking is a prerequisite to enhance its power output for practical applications. However, most MFC stacks reported in the present literature require external pumps to maintain the co‐laminar flow and complex fluidic management networks for homogeneous flow and reactant distributions. To address these issues, a novel paper‐based self‐pumping MFC stack with potassium formate as the fuel and hydrogen peroxide as the oxidant is proposed in this study. The capillary action is employed to achieve passive liquid flow. A vertical stack structure with the unit cells piled one above another compactly is adopted to reduce the volumetric costs. The experimental results show that the maximum power outputs of the two‐cell and three‐cell stack prototypes are 4.01 and 7.26 mW cm−2, outperforming the MFC unit by 5.81 and 10.52 times, respectively. The superior performance is attributed to its distinct vertical stacking structure, which brings the enhanced capillary flows in the paper wicks and reduced ohmic losses in comparison with the unit cell. Further, effects of the filter paper and reactant concentrations on the stack performance were examined, and mass transfer of the fuel and/or oxidant to the electrode/electrolyte interface was identified as the main limiting factor. A loose microstructure of the paper wick was found beneficial in enhancing the mass transfer. The potential applications of the MFC stack in a variety of portable electronics are broad.

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

“…Most of the PμFCs fed by biomass-derived alcohols reported here are also higher than those reported in the literature, even considering other fuels and oxidants. 16 Under our knowledge, the systems that deliver higher power density than reported here are fed by other liquids, such as formic acid, 17 potassium formate in stacks, 18 zinc and vanadium, 34 and others detailed by Tanveer et al 16 Moreover, the PμFC reported here may benefit further from an improved design, such as folding, 35 adding patterns to change the flow mechanism, 23 changing the size of electrodes, and flow configuration. 16 Figure 6 reveals the limits in terms of the peak power density of the biomass-fed PμFC with different concentrations of alcohols.…”

“…The PμFC was designed in a simple and well-known architecture, aiming to investigate the use of biomass-derived fuels as the sole variable. A similar design can be found elsewhere, 18 and the mechanism of fluid transport throughout the paper is based on the capillarity of the cellulose paper, without intricate sets of hydrophilic/hydrophobic patterns. 23 The polarization curves were collected by linear voltammetry from the OCV to 0.001 V at 0.01 V s −1 .…”

“…In addition, capillarity is an intrinsic feature of the paper, making it extremely reproducible. , Tanveer et al schematically reviewed the historical development and state-of-the-art PμFCs . The use of paper to pump the flow gathers advantages such as low-cost, lightweightedness, flexibility, biodegradability, portability, scalability, and reproducibility. , Thus, building PμFCs fed by biomass-derived fuels seems to be a good strategy to aggregate value to these clean and renewable alcohols.…”

“…16 The use of paper to pump the flow gathers advantages such as low-cost, lightweightedness, flexibility, biodegradability, portability, scalability, and reproducibility. 16,18 Thus, building PμFCs fed by biomass-derived fuels seems to be a good strategy to aggregate value to these clean and renewable alcohols.…”

A plant-like battery: a biodegradable power source ecodesigned for precision agriculture

“…A common strategy used in the literature to increase the output voltage of paper power sources is cell stacking; different studies have reported stacking designs and their effects on the cell output. [59][60][61][62][63] In this work, however, a voltage boost converter (VBC) integrated circuit was used to amplify the operating voltage up to 3.1 V (see additional details in ESI †). We favoured this option because the commercial Flower Caret sensing unit is not an eco-friendly sensing unit; namely, it is made of conventional electronic components (e.g., printed circuit board, integrated circuits, etc.).…”