Structure and activity of supported bimetallic NiPd nanoparticles: influence of preparation method on CO₂ reduction

Abstract

Bimetallic Ni−Pd and monometallic reference catalysts were prepared by decomposing organometallic precursors, Ni(cod)2 and Pd2(dba)3, leading to nanoparticles with sizes ranging from 3 to 6 nm. Two different synthesis procedures were followed: i) solution synthesis using capping ligand (hexadecylamine) followed by impregnation of pre‐formed nanoparticles on SiO2, called Sol‐immobilization (SI); and 2) direct precursor decomposition onto SiO2, without stabilizer, called Direct Decomposition (DD). Samples prepared by SI procedure are alloyed bimetallic nanoparticles, whereas samples obtained by DD one show phase segregation. Interestingly, DD samples show better activity for CO2 hydrogenation into CO (reverse water‐gas shift reaction ‐ RWGS) than SI ones. The best compromise between activity for CO2 activation (at lower temperature) and CO selectivity was achieved with Ni DD and NiPd DD catalysts. Moreover, the addition of palladium increased the concentration of surface undercoordinated sites, which chemisorb CO weakly, thus improving activity and selectivity, in opposition to other samples that chemisorb CO strongly, in multibond configuration. In the presence of Pd, different decomposition rates drives the formation of smaller and more active Ni clusters. The knowledge acquired here on the influence of synthesis conditions on the catalytic properties of Ni−Pd catalysts should guide us to better catalysts for CO2 transformations into valuable products.

Steam Reforming of Ethanol Using Ni–Co Catalysts Supported on MgAl2O4: Structural Study and Catalytic Properties at Different Temperatures

“…The strength of adsorption of carbon-containing intermediates also plays an important role. For example, strongly chemisorbed CO is more likely to be hydrogenated to CH 4 than weakly chemisorbed CO, with this strength being able to be tuned on bimetallic nanoparticles, as reported previously for Ni–Pd catalysts …”

“…For example, strongly chemisorbed CO is more likely to be hydrogenated to CH 4 than weakly chemisorbed CO, with this strength being able to be tuned on bimetallic nanoparticles, as reported previously for Ni−Pd catalysts. 38 The addition of Co to Ni catalysts has been studied for many reactions, 39−41 especially methane reforming. 39,42,43 Considering that ethanol is activated much more easily than methane, the equilibrium between the rates of ethanol decomposition and carbon oxidation can become challenging.…”

Zeolitic‐Imidazolate Framework Derived Intermetallic Nickel Zinc Carbide Material as a Selective Catalyst for CO2 to CO Reduction at High Pressure

“…[14,15] Therefore, to obtain a high yield of CO, the formed product should be easily desorbed from the surface of the catalyst to avoid further hydrogenation towards CH 4 . While the literature for atmospheric pressure RWGS is vast, [7,16] including active and selective catalysts based on non-noble metals such as Mo, [17] Cu, [18] and Ni, [19] few examples of RWGS under high-pressure conditions are described, with selectivity to CO in some extent only achieved by using a combination of precious metals (i. e., Pt, Au, and Pd). [16] Prior attempts at employing a Ni-based catalyst in high-pressure RWGS at a temperature range from 550-800 °C evidenced that increasing the pressure to 30 bar dramatically decreases selectivity to CO, wherein the main product was CH 4 at temperatures up to 650 °C.…”

Electrochemical control of the morphology and functional properties of hierarchically structured, dendritic Cu surfaces

“…An example is the patterning of an electrocatalyst layer to minimize reflection, parasitic absorption, and impairing the photovoltage-generating effects of a semiconductor-liquid junction. 10,11 The structure of the material induces heterogeneities in the environment at the electrocatalyst interface that can influence the resulting chemical reactions. For example, the electrode structure affects the diffusion layer and local pH in a nanostructured electrode, influencing the product distribution during electrochemical CO2 reduction.…”

“…Studies have shown that a Cu 2+ ion forms a complex with four monodentate lactate ligands, which prevents the spontaneous formation of copper hydroxide in alkaline conditions. 22 Aqueous solutions of lactate-stabilized Cu 2+ at high pH (9)(10)(11)(12) are used for the electrodeposition of Cu2O in the narrow range of electrode potentials noted by the Pourbaix diagram. [23][24][25][26] The Pourbaix diagram also suggests that metallic copper can be deposited at more negative potentials in the same alkaline conditions.…”