This work explores the incorporation of a carbon‑supported zinc oxide-sulfide composite (ZnO–ZnS/C) into alcohol‑fueled paper‑based microfluidic fuel cells (paper‑based µFCs) to develop more efficient, sustainable, and low‑cost portable energy systems. The ZnO–ZnS/C materials were synthesized from banana peel–derived carbon (BC) and zinc sulfate using zinc salt: BC weight ratios of 1:2 (BCZ1), 1:1 (BCZ2), and 2:1 (BCZ3). FTIR analysis confirmed the presence of lignocellulosic components after the carbonization process. The specific surface areas were 232 m2/g, 239 m2/g, and 141 m2/g for BCZ1, BCZ2, and BCZ3, respectively. BCZ1 and BCZ2 exhibited more developed porous structures than BCZ3, likely due to a higher degree of activation and fewer pore‑blocking effects. SEM analysis revealed irregular and porous morphologies for all BCZ samples, with well‑dispersed zinc species. Raman spectroscopy confirmed the presence of characteristic D and G bands at ~ 1350 and ~ 1580 cm⁻¹, indicative of partially graphitized carbon with moderate structural disorder. The ID/IG ratios (0.95–0.97) suggest similar graphitization degrees among the samples, with BCZ3 exhibiting slightly fewer defects. This balanced structure, combining good electrical conductivity with a suitable number of defect sites, is favorable for electrochemical applications, such as microfluidic fuel cell anodes, as demonstrated in this study. Paper‑based µFCs were evaluated using ethanol (0.1–1.5 M), tequila, and antioquian aguardiente as fuels. The highest power densities were obtained using BCZ2 as the anode, with antioquian aguardiente (0.21422 mW cm− 2) and tequila (0.22436 mW cm− 2), highlighting the potential of these materials for powering portable sensing devices under real‑sample conditions.
Mediavilla et al. (Tue,) studied this question.