Activating triple-phase boundary via building oxygen-electrolyte interfaces to construct high-performance pH-disparate direct liquid fuel cells

The uniform pH reaction environment of both acid proton-exchange membrane and alkaline anion-exchange membrane direct liquid fuel cells (DLFCs) substantially lowers the cell performance. Herein we propose a high-performance pH-disparate DLFC (ΔpH-DLFC), which can harvest the neutralization energy to maximize the thermodynamic voltage of DLFCs. Benefiting from the construction of oxygen-electrolyte interfaces, the triple-phase boundary density of cathode is significantly increased. The ΔpH-DLFCs yield peak power densities of 279, 341 and 610 mW cm⁻² when methanol, ethanol and sodium formate are fed into the anode respectively. The stable operation of direct formate fuel cell at 200 mA cm⁻² for 24 h further confirms the feasibility of the ΔpH-DLFCs. Moreover, the flexibility of the ΔpH-DLFC in oxidants and catalysts was also investigated. The experimental result indicates that the air-based pH-disparate direct formate fuel cell with non-platinum catalyst obtains a peak power density of 140 mW cm⁻² at 80 °C, suggesting the great potential for practical application.