Ethanol Electrooxidation Catalyzed by Tungsten Core@Palladium Shell Nanoparticles

Hydrogen-bonded linear chain assemblies of palladium(II)-selenoether complexes: solid state aggregates as templates for nano-structural Pd17Se15 leading to efficient electrocatalytic activity

A analogous series of 2-(3,5-dimethylpyrazol-1-yl)phenyl substituted selenoether complexes of palladium [PdCl2(RSeC6H4dmpz)]; (R = CH2COOH (1), CH2CH2COOH (2), and CH2CH2OH (3); dmpz = dimethylpyrazole) were ably synthesized in a facile manner and exhaustively characterized. Insight into molecular structures of these complexes was keenly probed through single crystal X-ray diffraction (XRD) analysis, unfolding the structural scaffolds and laying into molecular aggregation, availed through hydrogen bonding interactions borne out of tethered protic groups. The complexes were converted to capping free palladium selenide (Pd17Se15) nanoparticles through pyrolysis and evaluated for their electrocatalytic efficacy towards the hydrogen evolution reaction (HER), the oxygen evolution reaction (OER) and methanol oxidation reaction (MOR) in alkaline medium. In an alkaline medium, PSNP1 (Pd17Se15) obtained from the hydrogen bonded aggregate of complex PdCl2L1 (1) produced good HER activity. PSNP1 had a little decrease in current density after 300 continuous cycles, which proves that the catalyst presents high stability in the recycling process. For the electrocatalytic oxidation of CH3OH, the electrocatalytic rate constant (k) obtained was 0.3 × 103 cm3 mol-1 s-1.

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

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/mgPd (6.93 A/mgPdCu)) of PdCu was 1.83, 3.09, 4.51, and 53.90 times higher than those of AuPd (5.90 A/mgPd (3.27 A/mgAuPd)), PdMn (3.48 A/mgPd (3.19 A/mgPdMn)), Pd (2.39 A/mgPd), and Pd/C (0.20 A/mgPd), 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 H2O 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.

C2 Alcohol Oxidation Boosted by Trimetallic PtPbBi Hexagonal Nanoplates

The exploration of ternary Pt-based catalysts represents a new trend for the application of electrocatalysts in fuel cells. In the present study, intermetallic PtPbBi hexagonal nanoplates (HNPs) with a hexagonal close-packed structure have been successfully synthesized via a facile solvothermal synthesis approach. The optimized PtPbBi HNPs exhibited excellent mass activity in the ethanol oxidation reaction (8870 mA mg^-1_Pt) in an alkaline ethanol solution, which is 12.7 times higher than that of JM Pt/C. Meanwhile, the mass activity of PtPbBi HNPs in an ethylene glycol solution (10,225 mA mg^-1_Pt) is 1.85 times higher than that of JM Pt/C. In particular, its catalytic activity is better than that of most reported Pt-based catalysts. In addition, the optimized PtPbBi HNPs also show a better operational durability than commercial Pt/C. For the ethylene glycol oxidation reaction, a mass activity of 42.7% was retained even after a chronoamperometric test for 3600 s, which is rare among the reported Pt-based catalysts. By combining X-ray photoelectron spectroscopy and electrochemical characterization, we reveal the electron transfer between Pt, Pb, and Bi; this would lead to weakened CO adsorption and enhanced OH adsorption, thereby promoting the removal of toxic intermediates and ensuring that PtPbBi HNP samples have high activity and excellent stability. This work can inspire the design and synthesis of Pt-based nanocatalysts.