Solution-Phase Synthesis of PdH_0.706 Nanocubes with Enhanced Stability and Activity toward Formic Acid Oxidation

Abstract

Palladium is one of the few metals capable of forming hydrides, with the catalytic properties being dependent on the elemental composition and spatial distribution of H atoms in the lattice. Herein, we report a facile method for the complete transformation of Pd nanocubes into a stable phase made of PdH0.706 by treating them with aqueous hydrazine at a concentration as low as 9.2 mM. Using formic acid oxidation (FAO) as a model reaction, we systematically investigated the structure–catalytic property relationship of the resultant nanocubes with different degrees of hydride formation. The current density at 0.4 V was enhanced by four times when the nanocubes were completely converted from Pd to PdH0.706. On the basis of a set of slab models with PdH(100) overlayers on Pd(100), we conducted density functional theory calculations to demonstrate that the degree of hybrid formation could influence both the activity and selectivity toward FAO by modulating the relative stability of formate (HCOO) and carboxyl (COOH) intermediates. This work provides a viable strategy for augmenting the performance of Pd-based catalysts toward various reactions without altering the loading of this scarce metal.

Interstitial B-Doping in Pt Lattice to Upgrade Oxygen Electroreduction Performance

“…Recently, there have been a surge of interest in the design of light elements (including B, H, P, and N) interstitially doped with platinum-group-metal (PGM) electrocatalysts. − Unlike the traditional bimetallic alloys, where the secondary atoms replace the PGM primary host atoms by substitution, a light nonmetal or metalloid element of an appropriate concentration tends to be an interstitial dopant in the PGM primary metal lattice instead of substitutional dopants by occupying the largest available interstitial sites. Interstitial dopants are relatively stable, and in the case of partial leaching, interstitial alloys largely maintain the lattice structure of primary PGMs, in contrast to substitutional alloys. , Besides, the strong hybridization of s–p orbitals of an interstitial-dopant and d orbitals of a PGM may regulate the electronic structure of surface active sites and thus result in the activity and/or durability of the designed catalyst .…”

Efficient shape transformation of palladium nanocrystals by biphasic oxidative etching and regrowth

“…Both results agree well with our expectations of hydrogen doping into the Pd lattice. 10,33–36 The nanocrystals after 2 h of reaction (with NaNO 2 ) show a (111) peak with a d spacing of 2.295 Å, which is in between the d spacing values of Pd (2.246 Å) and PdH 0.706 (2.320 Å). Therefore, the composition of the nanocrystals can be estimated to be PdH 0.47 , according to Vegard's law.…”

Ethanol‐Induced Hydrogen Insertion in Ultrafine IrPdH Boosts pH‐Universal Hydrogen Evolution

“…[17] However, Pd is exceptionally inapplicable for HER compared to Pt (more than 30 times lower than Pt) owing to the strong Pd-H bonding and difficult H desorption, thus leading to an inferior HER performance. [18] Alloy with light elements to form the interstitial Pd-H, [19,20] Pd-C, [21] Pd-O, [22,23] Pd-B, [24,25] Pd-P, [26,27] Pd-S [28] and Pd-N [29] compounds have been proved to be a powerful strategy to optimize the electrocatalytic performance. [30,31] The doping light elements can reform the performance of conventional Pd-based catalysts in the following ways [32] : i) The light elements (e.g., H, C, and B) can evenly infiltrate into the metal lattice in consequence of their smaller atomic size resulting in the lattice expansion of Pd; ii) There would occur a significant electron transfer between doping light atoms and adjacent Pd atoms on the basis of the different electronegativities; iii) The orbital hybrid mode in Pd-nonmetal alloys is s, p-d orbital hybridization between light elements and Pd atoms, distinct from the d-d orbital hybridization in conventional Pd-based catalysts, which can change the charge distribution of Pd atoms and ameliorate the adsorption free energy of catalytic sites.…”

“…It is even more challenging that the fabrication methods of Pd hydrides are relatively scarce, which usually are the direct exposure of Pd-based nanocrystals to hydrogen atmosphere under certain conditions. The commonly used molecules as H sources contains H 2 gas, [38] DMF, [39] NaBH 4 , [40] N 2 H 4 , [20] HCHO, [41] and amine molecules (e. g. oleylamine [42] and n-butylamine [43] ). However, the hydrogenation mechanism of Pd-based hydrides was usually not sufficiently detailed, and few alcohol molecules have been reported to generate hydrogen to form Pd-based hydrides yet.…”