Carbon Allotropes Accelerate Hydrogenation via Spillover Mechanism

Abstract

Solid-phase hydrogenation kinetics can be substantially increased by utilizing hydrogen spillover phenomenon. Carbonaceous allotropes are considered as promising spillover agents (SOAs) for improved hydrogen transport rate. We studied the effect of carbon-based SOA properties on irreversible hydrogenation. We divided the reaction into two major stages, near-and far-field hydrogenation (with respect to a catalyst), and determined their rate-limiting steps. The hydrogenation kinetics was analyzed for hydrogen originating from either catalyst on activated carbon or catalyst-decorated carbon nanotubes. The far-field hydrogenation is investigated for three types of loaded nanocarbons: 1D (nanotubes), 2D (graphene), and 3D (activated carbon). We found that the kinetics acceleration is strongly correlated with the nanocarbon dimension, 1D > 2D > 3D, and could reach almost 2 orders of magnitude. These findings are useful for the study of reversible hydrogen storage applications. Article pubs.acs.org/JPCC

Influence of graphene oxide supports on solution-phase catalysis of thiolate-protected palladium nanoparticles in water

“…39–41 The UV-vis spectrum of PdNP/GO hybrids shown in Fig S3 (a) was consistent with the spectra of other palladium nanoparticles with similar core sizes, which showed no absorption or plasmon bands with only an exponential decay with increasing wavelength from 300 nm to 800 nm. 19 IR spectrum of PdNP/GO shown in Fig S3 (b) showed a C=O stretch at 1725 cm −1 , sp 3 C-H stretch at 2938 – 2878 cm −1 and a broad O-H stretch at 3300 – 2800 cm −1 , corresponding to the IR characteristics of ω-carboxylate-1-hexanethiolate ligands and GO.…”

“…The increase in the kinetics of substrate delivery by the spill-over, that has been observed by others for catalysts on graphene substrates, was absent for the colloidal PdNP/GO catalysis. 40,41 For PdNP catalysts, most DMAD was hydrogenated to maleic ester, the semi-hydrogenated product in a cis-form (>99% selectivity), in less than 3 h reaction time. However, the initial rate of reaction using PdNP/GO catalysts was slightly slower despite that the reaction resulted in the products with similar selectivity (shown in Table S2, which summarizes the turn-over-frequency (TOF) for semi- and full-hydrogenation products in the hydrogenation of DMAD).…”

n-Hexane Isomerisation: Exploit Hydrogen Spillover to Reduce Catalyst Costs

“…In line with this argument, Pevzner et al [19] found the addition of carbon nanotubes (CNT) to a Pd/C catalyst benefiting the hydrogenation reaction even when the reactants and catalyst were contacted in the solid phase. The same group observed the hydrogenation rate decreased as CNT > graphene > activated carbon, and mentioned that on CNT hydrogen spillover is faster [20]. This result is supported by an observation that the curvature of carbon materials has a pronounced effect on mobility of H atoms [17].…”

Glycerol Hydrogenolysis to 1,3‐Propanediol on Tungstate/Zirconia‐Supported Platinum: Hydrogen Spillover Facilitated by Pt(1 1 1) Formation

“…This concept was developed fully and gained application in the field of hydrogen storage. Pevzner et al . studied solid‐phase hydrogenation kinetics on different carbonaceous allotrope spillover agents and found a dimensionality effect of the support on the hydrogen transport rate.…”