Synergistic effects of CNF-TiO2 composites and process parameters on DMFC performance enhancement

BACKGROUND

Direct methanol fuel cells (DMFCs) face challenges from methanol crossover and performance degradation caused by inefficient microporous layer (MPL) designs, where conventional carbon-based MPLs show limitations in surface coverage uniformity, catalyst utilization efficiency, and pore structure balance. To address these issues, this study developed an optimized MPL using carbon nanofiber-titanium dioxide (CNF-TiO₂) composites through parametric optimization of the fabrication process. Key variables included MPL loading density, CNF:TiO₂ mass ratio, Nafion binder concentration, and methanol feed concentration, which were analyzed via screening experiments and Response Surface Methodology (RSM) using a Central Composite Design (CCD). The optimization targeted three response metrics: power density (R1), open-circuit voltage (R2), and peak current density (R3).

RESULTS

The results demonstrated that the modified CNF-TiO₂ microporous layer (MPL) exhibited a synergistic effect when optimized with the selected parameters. Initial screening experiments examined MPL loading, CNF-to-TiO₂ ratio, Nafion® content, and methanol concentration, revealing that the composition ratio, Nafion® content, and methanol concentration had significant impacts on the cell's performance responses. These key parameters were further explored using Response Surface Methodology (RSM). The optimized MPL exhibited improved surface coverage and promoted pore development, resulting in 1.22% microporosity and 34.31% mesoporosity. As a result, the composite MPL enhanced peak power density by 55%, reaching 70.43 mW cm⁻². Analysis of variance (ANOVA) confirmed that the improvements in power density, open-circuit voltage, and optimal current density were statistically significant, highlighting the effectiveness of the composite MPL design and process optimization in enhancing DMFC performance.

CONCLUSION

These findings highlight the essential need to integrate nanocomposite engineering with parametric optimization to achieve coverage uniformity, catalyst utilization efficiency, and pore structure balance. The research presents a verified methodology for multi-objective optimization in DMFCs, enhancing scalable, high-performance fuel cell systems for sustainable energy applications. © 2025 Society of Chemical Industry (SCI).