Interfacial Electronic Interactions within the Pd-CeO₂/Carbon Onions Define the Efficient Electrocatalytic Ethanol Oxidation Reaction in Alkaline Electrolytes

Abstract

Porous Pd-based electrocatalysts are promising materials for alkaline direct ethanol fuel cells (ADEFCs) and ethanol sensors in the development of renewable energy and point-of-contact ethanol sensor test kits for drunk drivers. However, experimental and theoretical investigations of the interfacial interaction among Pd nanocrystals on supports (i.e., carbon black (CB), onion-like carbon (OLC), and CeO 2 /OLC) toward ADEFC and ethanol sensors are not yet reported. This is based on the preparation of Pd-CeO 2 /OLC nanocrystals by the sol−gel and impregnation methods. Evidently, the porous Pd-CeO 2 /OLC significantly increased membranefree micro-3D-printed ADEFC performance with a high peak power density (P max = 27.15 mW cm −2 ) that is 1.38-and 7.58-times those of Pd/OLC (19.72 mW cm −2 ) and Pd/CB (3.59 mW cm −2 ), besides its excellent stability for 48 h. This is due to the excellent interfacial interaction among Pd, CeO 2 , and OLC, evidenced by density functional theory (DFT) simulations that showed a modulated Pd d-band center and facile active oxygenated species formation by the CeO 2 needed for ethanol fuel cells. Similarly, Pd-CeO 2 /OLC gives excellent sensitivity (0.00024 mA mM −1 ) and limit of detection (LoD = 8.7 mM) for ethanol sensing and satisfactory recoveries (89−108%) in commercial alcoholic beverages (i.e., human serum, Amstel beer, and Nederberg Wine). This study shows the excellent possibility of utilizing Pd-CeO 2 /OLC for future applications in fuel cells and alcohol sensors.

Lattice-Expanded PdAg Spatial Nanodendrites as Catalysts for the Ethanol Oxidation Reaction

“…Optimizing the utilization of palladium atoms is at the forefront of current research endeavors . Several methods have been developed to precisely control the morphology, scale, structure, and composition of palladium (Pd)-based nanocatalysts to enhance their catalytic performance. − Several studies have shown that adding a second or third metallic element (M 1 and M 2 ) to palladium-based binary (PdM) or ternary (PdM 1 M 2 ) alloys significantly increases the reaction rates of oxygen reduction reactions (ORR) and alcohol oxidation reactions (AOR). , For instance, a series of porous palladium- and platinum-based alloys were synthesized and exhibited exceptional electrocatalytic properties. − Highly efficient electrode catalysts with ultra-low Pt loadings were obtained by depositing Pt on three-dimensional hydroxylated Ti 3 C 2 T x MXene nanonet or porous carbon substrates. − Alloying processes refine the catalyst’s morphology and electronic configuration, thereby elevating its catalytic efficiency and resistance to poisoning during ethanol oxidation reactions. , The optimized morphology typically contains numerous nanopores and a large specific surface area. Such enhancement can substantially augment ion transport within the nanostructures, thereby offering an abundance of active sites on lattice planes for the catalysis of ethanol oxidation. , Furthermore, the optimized electronic structure enhances KOH/C 2 H 5 OH adsorption and electron transfer during the reaction process, resulting in an improved recovery rate.…”