Carbon-Neutralized Direct Methanol Fuel Cell Using Bifunctional (Methanol Oxidation/CO₂Reduction) Electrodes

In this study, a carbon-neutralized direct methanol fuel cell (DMFC) using two bifunctional electrodes, Pd-Ag and Pt-Zn, has been designed. This system has two modes, which are fuel-cell mode and spontaneous CO₂ reduction mode. In the operation of fuel-cell mode, the methanol has been oxidized into CO₂ on the Pd-Ag electrode and generates electricity. In the next step of the operation, CO₂, which is the product of fuel-cell mode, has been spontaneously reduced to CO on Pd-Ag, and electricity has been obtained. In contrast, the Pt in the Pt-Zn electrode catalyzes the oxygen reduction reaction in the fuel-cell mode, and the Zn in Pt-Zn is oxidized sacrificially in the CO₂ reduction mode. During operation in the fuel-cell mode, a power density of 12.11 mW/cm2 has been obtained with the production of CO₂. On the other hand, the power density out of the CO₂ reduction mode has been 11.76 mW/cm2. In each mode, the faradaic efficiencies of CO₂ and CO have been 98.81% and 89.11%, respectively.