Hydrogen Production from Formic Acid over Au Catalysts Supported on Carbon: Comparison with Au Catalysts Supported on SiO2 and Al2O3

Abstract

Characteristics and catalytic activity in hydrogen production from formic acid of Au catalysts supported on porous N-free (Au/C) and N-doped carbon (Au/N-C) have been compared with those of Au/SiO2 and Au/Al2O3 catalysts. Among the catalysts examined, the Au/N-C catalyst showed the highest Au mass-based catalytic activity. The following trend was found at 448 K: Au/N-C > Au/SiO2 > Au/Al2O3, Au/C. The trend for the selectivity in hydrogen production was different: Au/C (99.5%) > Au/Al2O3 (98.0%) > Au/N-C (96.3%) > Au/SiO2 (83.0%). According to XPS data the Au was present in metallic state in all catalysts after the reaction. TEM analysis revealed that the use of the N-C support allowed obtaining highly dispersed Au nanoparticles with a mean size of about 2 nm, which was close to those for the Au catalysts on the oxide supports. However, it was by a factor of 5 smaller than that for the Au/C catalyst. The difference in dispersion could explain the difference in the catalytic activity for the carbon-based catalysts. Additionally, the high activity of the Au/N-C catalyst could be related to the presence of pyridinic type nitrogen on the N-doped carbon surface, which activates the formic acid molecule forming pyridinium formate species further interacting with Au. This was confirmed by density functional theory (DFT) calculations. The results of this study may assist the development of novel Au catalysts for different catalytic reactions.

Hydrogen Production from Formic Acid Attained by Bimetallic Heterogeneous PdAg Catalytic Systems

“…In this sense, there is an increasing number of publications reporting on the investigation of catalytic systems able to catalyse the reaction while exploring the features of either support or metal active phase. Special mention should be made of those breakthroughs achieved Xu et al [29][30][31][32][33][34], and Bulushev et al [47][48][49][50][51][52][53][54][55][56][57].Most of the heterogeneous catalysts used are based on metal nanoparticles immobilised on supports of diverse nature (i.e. carbon materials, MOF, zeolites, resins, etc.)…”

Progress in Catalytic Hydrogen Production from Formic Acid over Supported Metal Complexes

“…Deprotonation of formic acid can be provided also by traditional oxide supports having basic sites [43] and by introduction of alkali metals promoters to supported metal catalysts [44][45][46]. Deprotonation provided by pyridinic N sites of N-doped carbon support was also reported for the catalysts with single metal atoms [47,48]. In this case, it reminds the effect of basic amine additives.…”

C, N Co-Decorated Alumina-Supported Au Nanoparticles: Enhanced Catalytic Performance for Selective Hydrogenation of Acetylene

“…1. All samples showed a typical type IV isothermal adsorption-desorption curve (the isotherm had a clear H 1 hysteresis curve at partial pressure (P/P 0 ) from 0.5 to 1.0), which can be attributed to capillary condensation and evaporation in the internal mesoporous structure [31,32]. The pore diameter distribution curves were almost the same for these samples as shown in Fig.…”

“…A number of support materials, including so-called active supports (such as CeO 2 [23,24] and TiO 2 [25,26]), and inert supports (such as SiO 2 [27,28], Al 2 O 3 [29,30]) were widely applied and studied in Au catalysis. Among them, Al 2 O 3 was most widely used to support Au catalysts for acetylene hydrogenation, but the acetylene conversion was unsatisfactory [31]. Therefore, we once utilized the modified impregnation-calcination strategy to prepare a series of Au/ MgO x -Al 2 O 3 catalysts, where the MgO x was used to modify the crystal structures of the catalysts to improve acetylene conversion [32].…”