Since the development of alkaline anion exchange membranes (AAEMs), Direct Ethanol Fuel Cell (DEFC) has gained significant research interest as an alternative to high-cost Direct Methanol Fuel Cell (DMFC) based on proton exchange membranes (PEMs). There are several advantages to utilization of ethanol fuel compared to methanol fuel, including: 1) existing infrastructures for ethanol production from various biomasses, liquid fuel storage, and transportation, 2) high specific energy density, and 3) decreased chemical toxicity. Furthermore, alkaline DEFCs have several advantages over PEM DMFCs, including: 1) improved kinetics of anodic ethanol oxidation reactions (EOR) and cathodic oxygen reduction reactions (ORR) in alkaline media; and 2) a wide range of catalyst materials in addition to Pt are stable in alkaline media and can be chosen as the catalysts for either EOR or ORR. Consequently, ADEFCs that do not require expensive Pt catalysts become feasible.

However, the poor kinetics of ethanol oxidation reaction (EOR) and the need to break C-C bonds to complete oxidation of ethanol to CO₂ have been major challenges for the development of DEFCs. Precious metals such as Pt and Pd are commonly used as primary catalysts for EOR in ADEFCs. In order to increase catalyst performance, Pt and Pd are usually combined with other transition metals, such as Ru, Sn, Pb, Au, Ni, Ag, Cu or Bi, as alloys, deposits, or ad-atoms. In our previous work, the electrocatalytic activity of Pd_xRu_y/C catalysts for the EOR was demonstrated to be much better than that of Pd/C in ADEFCs. The transition metal Ru in Ru_xPd_y was thought to enhance ethanol oxidation with the assistance of hydroxyl groups on the catalyst surface formed at lower potentials. However the oxidation of ethanol in alkaline media is very complex and involves many types of intermediates, such as C₁ species (most likely CO_ad and CH_x,ad), OH_ad, CH₃CO_ad and other forms of acetaldehyde in alkaline media. The roles of Ru in Pd_xRu_y/C and durability of PdRu/C catalysts for ethanol oxidation have not been elucidated and require further investigation.

In our recent work, we conducted comprehensive studies of EOR on several Pt-based and Pd-based catalysts by not only using half-cell testing, such as cyclic voltammetry (CV) and chronoamperometry (CA), but also fuel cell testing under various test conditions. An accelerated test was established to evaluate the stability of anode catalysts. In situ FTIR experiments were carried out to determine EOR intermediate and final products on these various catalyst systems. These comprehensive studies provide novel insights regarding the roles of second transition metal (Ru, Pb or Cu) in Pd or Pt catalyst for EOR in alkaline media, unveil the causes of the performance degradation of fuel cells with traditional catalysts, and indicate that catalysts with good initial performances are not essential for being appropriate for ADEFC applications.