Interfacial Engineering of Porous Pd/M (M = Au, Cu, Mn) Sponge-like Nanocrystals with a Clean Surface for Enhanced Alkaline Electrochemical Oxidation of Ethanol

Abstract

The interfacial engineering of Pd-based alloys (i.e., PdM with distinct morphologies, compositions, and strain defects) is an efficient way for enhanced catalytic activity; however, it remains a grand challenge to fabricate such alloys in aqueous solutions without heating, organic solvents, and multiple reaction steps. Herein, we present a simple, aqueous-phase, one-step, and ultrafast approach for the interfacial engineering of surfactant-free porous PdM (M = Cu, Au, and Mn) nanocrystals with well-controlled spongy-like morphology and compositions. The electronic interaction in PdM nanocrystals and their effect on the alkaline electrochemical ethanol oxidation reaction (EOR) are investigated using XRD, XPS, and electrochemical tests. Notably, integrating M metals into Pd atoms results in upshifting the d-band center of Pd and subsequently modulating the EOR activity and stability substantially. The EOR mass activity (10.78 A/mg Pd (6.93 A/ mg PdCu )) of PdCu was 1.83, 3.09, 4.51, and 53.90 times higher than those of AuPd (5.90 A/mg Pd (3.27 A/mg AuPd )), PdMn (3.48 A/mg Pd (3.19 A/mg PdMn )), Pd (2.39 A/mg Pd ), and Pd/C (0.20 A/mg Pd ), respectively, besides substantial durability after 1000 cycles. This is due to the porous two-dimensional morphology, a low synergetic effect, higher interfacial interaction, and greater active surface area of PdCu, besides a high Cu content with more oxophilicity that facilitates activation/dissociation of H 2 O to generate − OH species needed for quick EOR electrocatalysis. The electrochemical impedance spectroscopy (EIS) reveals better electrolyte/electrode interfacial interaction and lower charge transfer resistance on PdCu. The EOR activity of PdCu porous sponge-like nanocrystals was superior to all previously reported Pd-based alloys for electrochemical EOR. This study indicates that binary Pd-based catalysts with less synergetic effect are preferred for boosting the EOR activity, which could help in manipulating the surface properties of Pd-based alloys to optimize EOR performance.

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.…”