Investigation on the enhanced catalytic activity of a Ni-promoted Pd/C catalyst for formic acid dehydrogenation: effects of preparation methods and Ni/Pd ratios

Abstract

In this present work, we studied the effects of preparation methods and Ni/Pd ratios on the catalytic activity of a Ni-promoted Pd/C catalyst for the formic acid dehydrogenation (FAD) reaction. Two catalysts prepared by co-impregnation and sequential impregnation methods showed completely different Pd states and catalytic activities. As the sequentially impregnated catalyst showed better activity than the coimpregnated catalyst, the sequentially impregnated catalyst was investigated further to optimize the ratio of Ni/Pd. The highest catalytic activity for the FAD reaction was obtained over the seq-impregnated catalyst having a 1 : 1.3 molar ratio of Pd : Ni. The results of X-ray diffraction (XRD) and transmission electron microscopy (TEM) showed that small particle size is one factor improving the catalytic activity, while those of X-ray photoelectron spectroscopy (XPS) and X-ray adsorption near edge structure (XANES) indicate that the electronic modification of Pd to a positively charged ion is another factor. Thus, it can be concluded that the enhanced catalytic activity of the Ni-promoted Pd/C catalyst is attributed to the role of pre-impregnated Ni in facilitating the activity of Pd by constraining the particle growth and withdrawing an electron from Pd. Fig. 1 Schematic diagram of preparation processes of (a) coimpregnated and (b) seq-impregnated catalysts.Fig. 2 (a) Volumes of produced gas over the 0.05 g of various Pd-Ni bimetallic catalysts during the reaction of 10 mL formic acid (1 M) at 60 C and (b) their initial rates after stabilization (from 3 to 4 min) depending on the molar ratio of Ni/Pd (x).This journal is Fig. 8 (a) Catalytic activity test (10 mL 1 M formic acid at 60 C) over recycled Pd 1 /NiO 1.3 /C (seq) and its (b) TEM images and (c) particle size distribution with average particle size.This journal is

New Approaches Toward the Hydrogen Production From Formic Acid Dehydrogenation Over Pd-Based Heterogeneous Catalysts

“…In light of these results, it was concluded that the improvement of the catalytic ability could not be only attributed to the nitrogen content, since the Pd electronic state as well as the basicity and the pore texture of the support material should be considered. This is because those factors can influence the interaction with formic acid or reaction intermediates, which in turn is one of the most important aspects involved in the formic acid dehydrogenation reaction (Kim et al, 2018).…”

Development of the Applications of Palladium on Charcoal in Organic Synthesis

“…Palladium is the most frequently used metal in catalysis, and heterogeneous palladium catalysts are most commonly used as efficient catalysts. They have indeed been largely applied to redox reactions including oxidation and hydrogenation, alkenylation, C−H bond functionalization, asymmetric synthesis and carbon‐carbon coupling reactions . In addition, they are of interest in the synthesis of natural products (such as γ‐lactams and γ‐lactones) and often employed in total syntheses .…”

In-situ Quantification of Nanoparticles Oxidation: A Fixed Energy X-ray Absorption Approach

“…Although a relevant aliquot of the Pd(II) species investigated by FEXRAV is probably Pd(OH) 4 2− (due to the dissolution process already mentioned) the preparation of a reliable standard solution is impossible in the sense that it could affect the reproducibility of the measurements. Still, PdO and Pd(OH) 4 2− share the same coordination geometry, number and distances and the same ligand species, showing the same features in the respective XAS spectra [47][48][49][50][51][52]. All this considered PdO should be considered the best standard for the XANES of Pd(OH) 4 2− .…”

“…We first acquired the reference spectra of pure Pd and pure PdO samples, to look for the proper energy to investigate palladium oxidation with FEXRAV. The choice of Pd and PdO as a standard is robust as the XANES spectrum of the electrochemically stressed palladium can be successfully fitted using these two chemical species [21,47]. Although a relevant aliquot of the Pd(II) species investigated by FEXRAV is probably Pd(OH) 4 2− (due to the dissolution process already mentioned) the preparation of a reliable standard solution is impossible in the sense that it could affect the reproducibility of the measurements.…”

“…Experiments were performed using the electrochemical cell described in the result and discussion section. In order to coordinate the application of the required electrochemical conditions together with XAS data acquisition, cyclic voltammetries were recorded with a PAR 263 potentiostat that was interfaced with SPEC, exploiting a well-established setup at ESRF [47,48]. A standard Ag/AgCl KCl Sat.…”