Enhanced Fuel Decomposition in the Presence of Colloidal Functionalized Graphene Sheet-Supported Platinum Nanoparticles

Abstract

Experiments and simulations were used to demonstrate that decorating functionalized graphene sheets (FGSs) with platinum nanoparticles (Pt@FGS) stabilized these particles. Addition of these particles to liquid hydrocarbon fuels was observed to significantly affect decomposition under supercritical conditions at a pressure of 4.75 MPa and temperatures from 753 to 803 K. The suspension of only 50 ppmw Pt@FGS in the fuel (equivalent to adding 10 ppmw Pt) enhanced fuel conversion rates (by up to 24%) with a major effect on specific product yields. The production of lowmolecular-weight species increased in the pyrolysis products (with the hydrogen yield increasing by a factor of 12.5). ReaxFF molecular dynamics (MD) simulations supported a mechanism in which synergy between Pt and FGS catalyzed dehydrogenation during n-C 12 H 26 pyrolysis. The highest conversion rates and greatest yields of hydrogen and low-molecular-weight species were observed for fuels containing Pt@FGS particles rather than those containing either FGSs or Pt-clusters alone. Analysis of the platinum decorated FGSs post reaction indicated no deterioration of the composite particles.

Reactive Molecular Dynamics Simulations of the Depolymerization of Polyethylene Using Graphene-Oxide-Supported Platinum Nanoparticles

“…The fraction of hydrogen molecules is evaluated as the fraction of hydrogen atoms in hydrogen molecules among all hydrogen atoms in the simulation. We find that as T increases, more H 2 gas is generated, as expected because the Pt NP attracts and removes hydrogen from the hydrocarbons during the catalytic dehydrogenation process, and the adsorbed hydrogen atoms “roam” on the Pt surface, forming hydrogen molecules, and subsequently desorb from the Pt surface . Furthermore, we find that simulations with graphene oxide yield more H 2 than those without graphene oxide.…”

“…Polyethylene with a Pt NP, but without graphene oxide (green curve), shows a similar conversion rate compared to the case of PE with the Pt NP alone. This result is in contrast to the catalytic fuel decomposition using graphene-supported Pt NPs, where graphene oxide enhances the reaction rate. The difference might be due to the higher molecular mass and density of hydrocarbons used in our simulations.…”

“…Our simulations are performed within the canonical ensemble ( NVT ) with T ranging from 1900 to 2400 K and density 0.63 g/cm 3 excluding Pt. Although these temperatures are significantly higher than those used in experiments, it is a common practice in computational studies to use higher temperatures to allow for reactions to occur in accessible computational time scale on the order of a few nanoseconds − and still provides insight into the catalytic reactions from a molecular level. Previous work , have shown that despite higher temperatures used in simulations, the estimated activation energy from simulations is similar to that from experiments and the results we shall show support this trend.…”

“…Moreover, our study more focuses on contrasting the relative performance of polyethylene with and without platinum nanoparticles rather than the absolute degree of depolymerization at various temperatures. Previously, this reactive force field has been successfully used to simulate the catalytic reaction of combustion, , fuel decomposition, and pyrolysis, , with accuracy comparable to that from the electronic structure method. For more details on this force field, Senftle et al reviewed the recent development and application of ReaxFF.…”

Decomposition Mechanism of Isoprenoid Hydrocarbon p-Menthane in the Presence of Pt@FGS Nanoparticles: A ReaxFF-MD Study

“…The simulation results revealed that the JP-10 decompositions initiated by either H or OH on the FGS reacted at a relatively lower energy barrier, compared to the unimolecular decompositions or reactions with O 2 , which then greatly promoted JP-10 initiation. More recent ReaxFF-MD studies of Hyung et al supported the catalytic mechanisms in which synergy between Pt-cluster and FGS was found to catalyze n -C 12 H 26 and MCH (methylcyclohexane) decomposition. , The simulation results indicated that the synergy of Pt-cluster and FGS effectually enhanced the initial dehydrogenation, which further formed the n -C 12 H 25 /C 7 H 13 radical.…”