Gas-liquid separation mechanism and promotion strategy of the bubble-trap structure in microfluidic fuel cell

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Membraneless microfluidic fuel cell (MMFC) shows promising in portable electronics with the advantages of high efficiency and compact construction. However, the ineffective management of CO2 bubbles in acidic condition still restricts the mass transfer and anodic electrochemical reaction rate. Herein, the internal mechanism of bubble-trap layer (BTL) for eliminating CO2 accumulation in the anode is revealed by finite element analysis, and a novel BTL-based structure, gas-emission anode (GEA), is proposed to fully exploit the ability of gas-liquid separation and further strengthen electrochemical reaction. By comparative analysis and quantitative analysis, the growth rates of maximum power density and current density are 28.97% and 38.17%, respectively, with a CO2 gas removal rate of 60.1% in the GEA, which far exceeds that in the MMFC equipped with the BTL. The maximum power density and current density reach 34.37 mW cm−2 and 172.55 mA cm−2, respectively. Although the air-exposed characteristic of the GEA causes parasitic effect, it has broad development space for the optimization focused on reducing the parasitic current and improving the upper limit of the cell performance. More importantly, the integrated modeling and optimization strategy of the BTL-based structure provides a theoretical basis for further eliminating the bubble effect in experiments.