Atomistic Insights into H₂O₂ Direct Synthesis of Ni–Pt Nanoparticle Catalysts under Water Solvents by Reactive Molecular Dynamics Simulations

Abstract

In computational catalysis, density-functional theory (DFT) calculations are usually utilized, although they suffer from high computational costs. Thus, it would be challenging to explicitly predict the catalytic properties of nanoparticles (NPs) at the nanoscale under solvents. Using molecular dynamics (MD) simulations with a reactive force field (ReaxFF), we investigated the catalytic performance of Ni–Pt NPs for the direct synthesis of hydrogen peroxide (H2O2), in which water solvents were explicitly considered along with the effects of the sizes (1.5, 2.0, 3.0, and 3.5 nm) and compositions (Ni90Pt10, Ni80Pt20, and Ni50Pt50) of the NPs. Among the Ni–Pt NPs, 3.0 nm NPs show the highest activity and selectivity for the direct synthesis of H2O2, revealing that the catalytic performance is not well correlated with the surface areas of NPs. The superior catalytic performance results from the high H2 dissociation and low O2 dissociation properties, which are correlated with the numbers of NiNiPt-fcc and NiNi-bridge sites on the surface of Ni–Pt NPs, respectively. The ReaxFF-MD simulations propose the optimum composition (Ni80Pt20) of 3.0 nm Ni–Pt NPs, which is also explained by the numbers of NiNiPt-fcc and NiNi-bridge sites. Furthermore, from the ReaxFF-MD simulations, the direct synthesis of H2O2 for the Ni–Pt NPs can be achieved not only with the Langmuir–Hinshelwood mechanism, which has been conventionally considered, but also with the water-induced mechanism, which is unlikely to occur on pure Pd and Pd-based alloy catalysts; these results are supported by DFT calculations. These results reveal that the ReaxFF-MD method provides significant information for predicting the catalytic properties of NPs, which could be difficult to provide with DFT calculations; thus, it can be a useful framework for the design of nanocatalysts through complementation with a DFT method.

Enhancing catalytic performance of AuPd catalysts towards the direct synthesis of H2O2 through incorporation of base metals

“…Interestingly, the addition of several base metals; Ni, (107 mol H 2 O 2 kg cat −1 h −1 ) Zn, (100 mol H 2 O 2 kg cat −1 h −1 ) and Cu (94 mol H 2 O 2 kg cat −1 h −1 ) was also observed to improve catalytic activity considerably, achieving H 2 O 2 synthesis rates far greater than the bimetallic 1% AuPd (1.00) /TiO 2 catalyst, and comparable to that offered by 1% AuPd (0.975) Pt (0.025) /TiO 2 analogue. While the incorporation of Ni 17,18,46 and Zn 21,22 into supported precious metal catalysts has previously been reported to result in an improvement in catalytic performance towards H 2 O 2 production, the addition of Cu, either into AuPd 47 or Pd-only 48 catalysts has been found to inhibit catalyst activity towards H 2 O 2 synthesis. With DFT studies by Joshi et al indicating that the formation of the intermediate hydroperoxy (OOH*) species and in turn H 2 O 2 , to be thermodynamically unfavourable over Cu-containing supported catalysts.…”

Insight into the Competitive and Synergistic Effects during Coal/NH3 Cofiring via Reactive Molecular Dynamics Simulations

“…The maturity of reactive force field molecular dynamics (ReaxFF MD) makes it possible to study chemical reactions in large systems. ReaxFF MD has been widely used in pyrolysis, − combustion, − and other processes involving complex chemical reactions. − Castro-Marcano et al established the Illinois No. 6 coal char model and applied ReaxFF MD for combustion simulations.…”

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

“…The ReaxFF parameters retrained by Gai et al,38 denoted as ReaxFF Pt/C/H/O, are adopted here without any modifications. The Pt/C/H/O parameters have been successfully used in modeling complex catalytic systems with Pt, such as methane catalytic oxidation with the Pt/graphene-based catalysts39 and direct synthesis of hydrogen peroxide (H 2 O 2 ) with Ni-Pt catalysts 40. 2.2.…”