Sustainable valorization of biodiesel-derived glycerin using CeO₂-Ni nanofiber anodes for high-performance direct...

In this work, CeO₂-Ni nanoparticles were successfully integrated into electrospun carbon nanofibers (CNFs) via calcination under inert atmosphere to develop a low-cost, high-performance anode material for direct glycerin fuel cells (DGFCs). By tuning the CeO₂ content, a series of nanofiber electrodes were prepared and systematically evaluated. The optimized sample containing 5 wt% cerium acetate exhibited the most favorable electrochemical behavior, achieving a maximum current density of 85 mA cm^-2 (in CV), a low Tafel slope of 30.5 mV dec^-1, and excellent electrochemical stability. High-resolution XPS confirmed the coexistence of Ce⁺³/Ce⁺⁴ and Ni⁺²/Ni⁺³/Ni⁰ species, indicating synergistic redox activity and oxygen vacancy generation, which contribute to improved glycerin electrooxidation. When applied in a membrane-less DGFC configuration using a Pt/C cathode, the optimized CeO₂-Ni CNFs anode delivered a peak current density of 6.3 × 10³ mA m^-2 at a glycerin concentration of 0.3 M, while the maximum power density reached 508 mW m^-2 at higher glycerin concentration, placing this system among the most competitive non-precious metal-based DGFC anodes reported to date. Furthermore, Design Expert® statistical modeling revealed strong predictive correlations between CeO₂ content, glycerin concentration, and performance metrics (OCP, current, and power densities), with an OCP model F-value of 14.7 and p < 0.0001. This study introduces a scalable and effective strategy for the electrochemical valorization of biodiesel-derived glycerin, offering significant advancements in waste-to-energy conversion through nanostructured redox-active anode design.