Electrocatalysis for direct alcohol–alkaline fuel cells

Due to the limited supply of fossil fuels and the increased concern for carbon emissions and global warming, Direct alcohol fuel cells (DAFCs) have been identified as promising potential candidates. With advances in alkaline direct alcohol fuel cells, direct ethanol fuel cells (DEFCs) have currently garnered a lot of attention. In this thesis, the temperature effect and the mechanism of Pd electrocatalyst towards alcohol (methanol, ethanol butanol and glycerol) electrooxidation reaction in alkaline media were compared and explored. Pd-based electrocatalysts with high activity and stability performance were designed for ethanol electrooxidation reaction(EOR) in alkaline media and were further characterized using cyclic voltammetry (CV) and chronoamperometry(CA). Moreover, the kinetics of alcohol oxidation reaction on Pd-based electrocatalysts were obtained from the activation energy calculated by Arrhenius plots and compared. For all the alcohol electrooxidation reactions, the catalyst actives and kinetic were facilitated with increasing temperature from 25 to 60 ºC. In comparison of the different alcohols electrooxidation reactions, the positive peak current densities(Jp) at 30 ˚C are following such order: JGlycerol > JButanol > JEthanol > JMethanol while the activation energy(Ea) are following order: EaGlycerol < EaButanol < EaMethanol < EaEthanol. For Ethanol Electrooxidation Reaction(EOR) in alkaline media, the catalytic reactivity of bulk Pd is significant enhanced by being decorated with a second metal(Pb, Ag, AuNPs, Sb). Activation energy(Ea) of X/Pd(X= Pb, Ag, AuNPs, Sb) at an optimal coverage of X is following the order: EaSb(θ=20%)/Pd < EaAg(θ=37%)/Pd < EaAuNPs(30nm) (θ=45%)/Pd < EaPb(θ=29%)/Pd < EaAuNPs(3nm) (θ=16%)/Pd < Eabulk Pd, while Possitivepositive scan peak current density at 30 ºC is following such order: JSb(θ=20%)/Pd > JAuNPs(3nm) (θ=16%)/Pd ≈ JAg(θ=37%)/Pd > JPb(θ=29%)/Pd > JAuNPs(30nm) (θ=45%)/Pd > Jabulk Pd. Among all these catalyst, Sb(θ=20%)/Pd and Ag(θ=37%)/Pd contribute much more than others with the relative lowest Activation energy and highest peak current density.