A direct ethylene glycol fuel cell stack as air-independent power sources for underwater and outer space applications

A passive direct ethylene glycol fuel cell stack is developed and tested, in which each single cell consists of an alkaline Pd-based anode, an acid Au-based cathode, and a cation exchange membrane. Experimentally, at the optimal reactant-feeding concentrations of 5.0 M EG and 9.0 M KOH as anolyte and 4.0 M H₂O₂ and 1.0 M H₂SO₄ as catholyte, this passive stack yields an open-circuit voltage of 3.0 V, a maximum current of 860 mA, and a peak power of 1178 mW at room temperature, which exhibits a two-time higher peak power density (24.5 mW cm⁻²) than a passive stack using the same type of fuel but the air as oxidant (12 mW cm⁻²). The impressive improvement can be ascribed to the faster hydrogen peroxide reduction reaction due to its two-electron transfer process rather than a four-electron process. In addition, the effects of feeding concentrations of reactants in both anolyte and catholyte on the stack performance are studied. Finally, the present passive stack is applied to power an electric fan for around 3 h under the mimetic underwater circumstance, demonstrating that this passive stack is a promising power source for airtight situations, such as underwater and outer space.