Co-catalytic enhancement of H2 production by SiO2 nanoparticles

Stathi, Panagiota; Deligiannakis, Yiannis; Louloudi, Maria

doi:10.1016/j.cattod.2014.07.012

Cited by 18 publications

(47 citation statements)

References 23 publications

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“…Recently, our group demonstrated an alternative to this requirement, showing that-instead of amines-SiO 2 nanoparticles can enhance H 2 production by a Fe/PPh 3 /FA catalyst, in propylene carbonate solvent [54]. This study provided the first evidence that the H 2 -production boosting effect by SiO 2 -particles was linked to the FA deprotonation e.g., enhanced catalytic H 2 production is promoted by the basic sites of SiO 2 particles.…”

Section: Deprotonation Of Fa By Heterogeneous Co-catalytic-particlesmentioning

confidence: 82%

“…While in aqueous media, H + are abundant, in aprotic media i.e., such as propylene carbonate, availability of this proton should be considered with care. So far, the origin of this proton has not been proven is none of the published works, including ours [25,54]. Traces of H 2 O present in the solvent can be invoked, however since these H + participate stoichiometrically for each one HCOOconverted to H 2 , the H 2 O content should be able to provide H + at high concentrations i.e., stoichiometric vs. the HCOOsubstrate.…”

Section: Outline Of the Catalytic Mechanismsmentioning

confidence: 87%

“…In this context, we have experimentally demonstrated that silica nanoparticles can act as co-catalyst to the Fe/PPh3 system [54] (see Figure 6) suppressing the energy barrier of the reaction from 77 kJ/mol to 36 kJ/mol [54]. This effect is attributed to the deprotonation of the FA (FA activation) before insertion in the catalytic cycle via bidentate coordination facilitating hydride formation [54]. This step drives the overall reaction to operate via Cycle-II.…”

Section: Outline Of the Catalytic Mechanismsmentioning

confidence: 96%

“…Despite the methodological limitations of the theoretical analysis, experimental work [48] provides evidence that the energy barriers in Cycle-I and Cycle-II are influenced by the experimental parameters (type of complex, solvent, traces of H 2 O, FA deprotonation, presence of co-catalysts), which might decisively affect the contribution of each cycle to the overall H 2 production rates. In this context, we have experimentally demonstrated that silica nanoparticles can act as co-catalyst to the Fe/PPh 3 system [54] (see Figure 6) suppressing the energy barrier of the reaction from 77 kJ/mol to 36 kJ/mol [54].…”

Section: Outline Of the Catalytic Mechanismsmentioning

confidence: 97%

“…This effect is attributed to the deprotonation of the FA (FA activation) before insertion in the catalytic cycle via bidentate coordination facilitating hydride formation [54]. This step drives the overall reaction to operate via Cycle-II.…”

Section: Outline Of the Catalytic Mechanismsmentioning

confidence: 99%

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From Homogeneous to Heterogenized Molecular Catalysts for H2 Production by Formic Acid Dehydrogenation: Mechanistic Aspects, Role of Additives, and Co-Catalysts

et al. 2020

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H2 production via dehydrogenation of formic acid (HCOOH, FA), sodium formate (HCOONa, SF), or their mixtures, at near-ambient conditions, T < 100 °C, P = 1 bar, is intensively pursued, in the context of the most economically and environmentally eligible technologies. Herein we discuss molecular catalysts (ML), consisting of a metal center (M, e.g., Ru, Ir, Fe, Co) and an appropriate ligand (L), which exemplify highly efficient Turnover Numbers (TONs) and Turnover Frequencies (TOFs) in H2 production from FA/SF. Typically, many of these ML catalysts require the presence of a cofactor that promotes their optimal cycling. Thus, we distinguish the concept of such cofactors in additives vs. co-catalysts: When used at high concentrations, that is stoichiometric amounts vs. the substrate (HCOONa, SF), the cofactors are sacrificial additives. In contrast, co-catalysts are used at much lower concentrations, that is at stoichiometric amount vs. the catalyst. The first part of the present review article discusses the mechanistic key steps and key controversies in the literature, taking into account theoretical modeling data. Then, in the second part, the role of additives and co-catalysts as well as the role of the solvent and the eventual inhibitory role of H2O are discussed in connection to the main mechanistic steps. For completeness, photons used as activators of ML catalysts are also discussed in the context of co-catalysts. In the third part, we discuss examples of promising hybrid nanocatalysts, consisting of a molecular catalyst ML attached on the surface of a nanoparticle. In the same context, we discuss nanoparticulate co-catalysts and hybrid co-catalysts, consisting of catalyst attached on the surface of a nanoparticle, and their role in the performance of molecular catalysts ML.

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Section: Deprotonation Of Fa By Heterogeneous Co-catalytic-particlesmentioning

confidence: 82%

Section: Outline Of the Catalytic Mechanismsmentioning

confidence: 87%