Tuning Ni-Centered Active Phases with Copper and Cobalt for Ethanol Electrooxidation Reaction

Nickel-based bimetallic oxides were synthesized as noble metal free anode catalysts for ethanol electrooxidation. The effects of Cu and Co incorporation into the Ni-centered oxide phase were comparatively examined. Catalysts with different Ni/Cu and Ni/Co compositions were prepared by co-precipitation and evaluated in alkaline ethanol medium to clarify the secondary metal influences phase evolution, bonding features, surface morphology, textural properties, catalytic activity, stability, and interfacial charge-transfer behavior. Among all compositions, Ni90Cu10 exhibited the best electrochemical performance, reaching 3.04 mA cm-2 at about 0.75 V and retaining 1.5 mA cm-2 after 1000 s, whereas bare Ni delivered about 0.8 mA cm-2. Structural findings indicated that Cu was incorporated into the NiO lattice to form a Ni1-xCuxO type solid solution, while the NiCo series showed a stronger tendency toward the formation of NiCo2O4/Co3O4-type spinel domains. The superior response of the NiCu series was also associated with more favorable charge-transfer behavior, whereas the NiCo catalysts exhibited less efficient interfacial kinetics. These results indicate that limited Cu addition strengthens the Ni-centered active phase for ethanol oxidation, while increasing Co content promotes spinel-rich structures that are less favorable for ethanol electrooxidation.