Synergistic Enhancement of Ethanol Oxidation on Pd/Ce ₂ Ti ₂ O ₇ –TiO ₂ via Multiorbital (p–d–f) Interactions

Ethanol oxidation reaction (EOR) is a key component of direct ethanol fuel cells (DEFCs). However, due to its slow kinetics, EOR remains a significant challenge, leading to an increasing search for low-cost, efficient, and stable catalysts. Herein, palladium (Pd) nanostructured catalysts supported on titanium dioxide (Pd/TiO₂) and cerium titanate (Pd/Ce₂Ti₂O₇-TiO₂) were prepared for EOR. The Pd/Ce₂Ti₂O₇-TiO₂ catalyst exhibits superior electroactivity toward the EOR, demonstrating a high mass activity of 2.70 and 2.63-fold relative to Pd/TiO₂ and Pd/C, respectively. The enhanced behavior was attributed to the bifunctional mechanism, improved electron transport, and downshifted d-band center (ε_d). Density functional theory (DFT) calculations show a higher density of states for Pd/Ce₂Ti₂O₇-TiO₂,suggesting higher EOR kinetics than the Pd and Pd/TiO₂, due to its multiorbital (p-d-f) hybridization. The accelerated durability test (ADT) reveals that the Pd/Ce₂Ti₂O₇-TiO₂ catalyst exhibits satisfactory durability, showing an electrochemically active surface area (ECSA) loss of 18.8% compared with the Pd/C catalyst (33.3% loss) after 1000 cycles. Furthermore, the Pd/Ce₂Ti₂O₇-TiO₂ catalyst exhibited a low detection limit of 12.0 μM toward the nonenzymatic amperometric detection of ethanol. Thus, this study demonstrates the promising use of Ce₂Ti₂O₇-TiO₂ as a support for Pd-based catalysts for EOR in DEFCs and a nonenzymatic amperometric sensor.