A cost-effective and chemically stable electrode binder for alkaline-acid direct ethylene glycol fuel cells

In preparing direct liquid fuel cell electrodes, an ionomer is necessary, whose functions are not only to bind the discrete catalyst nanoparticles onto the substrate materials to build the porous catalyst layer, but also to construct the triple phase boundaries to provide continuous pathways for reactant delivery. In this work, a cost-effective and chemically stable poly(vinylidene fluoride-co-hexafluoropropylene) electrode binder is adopted and compared with the conventional Nafion and polytetrafluoroethylene in terms of the electrode morphology and the fuel cell performance. It is found that the fuel cell using the poly(vinylidene fluoride-co-hexafluoropropylene)-based electrode exhibits the best performance in terms of an open-circuit voltage of 1.47 V, a maximum current density of 300 mA cm⁻², and a peak power density of 120.0 mW cm⁻². Comparing to the fuel cell performances fabricated with the conventional Nafion and polytetrafluoroethylene as electrode binder, the peak power density achieved by using the new type of electrode binder shows an improvement of 13.7% and 58.1%, respectively. Poly(vinylidene fluoride-co-hexafluoropropylene) shows the lowest cost of $0.18 kW⁻¹, while polytetrafluoroethylene and Nafion possess the higher cost of $0.80 kW⁻¹ and $145.59 kW⁻¹, respectively. The impressive improvement is attributed to the fact that the poly(vinylidene fluoride-co-hexafluoropropylene)-based electrode has a higher electrochemical surface area due to its intrinsic porous property, enhancing the anodic reaction kinetics. It is found that the best cell performance is achieved with 1.0 M EG and 5.0 M KOH in the anolyte and 1.0 M H₂O₂ and 4.0 M H₂SO₄ in the catholyte at 60 °C.