Formation of Pt-Based Alloy Nanoparticles Assisted by Molybdenum Hexacarbonyl

Abstract

We report on an optimized, scalable solution-phase synthetic procedure for the fabrication of fine-tuned monodisperse nanostructures (Pt(NiCo), PtNi and PtCo). The influence of different solute metal precursors and surfactants on the morphological evolution of homogeneous alloy nanoparticles (NPs) has been investigated. Molybdenum hexacarbonyl (Mo(CO)6) was used as the reductant. We demonstrate that this solution-based strategy results in uniform-sized NPs, the morphology of which can be manipulated by appropriate selection of surfactants and solute metal precursors. Co-surfactants (oleylamine, OAm, and hexadecylamine, HDA) enabled the development of a variety of high-index faceted NP morphologies with varying degrees of curvatures while pure OAm selectively produced octahedral NP morphologies. This Mo(CO)6-based synthetic protocol offers new avenues for the fabrication of multi-structured alloy NPs as high-performance electrocatalysts.

Catalytic Properties of Molybdenum-Modified Platinum Nanoalloys toward Hydrogen Evolution, Oxygen Reduction Reaction, and Methanol Oxidation

“…Pt(NiCo)-Mo, PtNi-Mo, and PtCo-Mo NPs were prepared using our synthetic procedure described elsewhere. 35 Electrochemical measurements show that these Pt-solute-Mo nanoalloys, immobilized on a carbon black support material, display enhanced electrocatalytic performances in the HER, ORR, and MOR and are ultra-durable in terms of CO ads poisoning tolerance in an acidic electrolyte when compared with a commercially available Pt/C electrocatalyst. Stability measurements showed that the initially outstanding catalytic activities degraded in the ORR and MOR as a function of extended electrochemical cycling to 8k cycles.…”

“…Alloy NP structures of Pt(NiCo)-Mo, PtNi-Mo, and PtCo-Mo were solution-derived by co-reducing precursors platinum acetylacetonate (Pt(acac) 2 , 97%), nickel(II) acetate tetrahydrate (Ni(Ac) 2 , 95%), and/or cobalt(II) acetate tetrahydrate (Co(Ac) 2 , ≥99%) with molybdenum hexacarbonyl (Mo(CO) 6 , 98%) in the presence of amine surfactants oleylamine (OAm, 70%) and hexadecylamine (HDA, 90%) in a high boiling point solvent benzyl ether (BE, 98%) at 240 °C for 60 min. 35 In a typical synthesis, metal precursor sources (Pt(acac) 2 (0.08 g, 0.2 mmol) + Ni(Ac) 2 (0.048 g, 0.2 mmol)), (Pt(acac) 2 (0.08 g, 0.2 mmol) + Co(Ac) 2 (0.048 g, 0.2 mmol)), or (Pt(acac) 2 (0.08 g, 0.2 mmol) + Ni(Ac) 2 (0.024 g, 0.1 mmol) + Co(Ac) 2 (0.024 g, 0.1 mmol)) were dissolved in binary surfactants OAm (20 mL) and HDA (4.4 g) using BE (25 mL) as the high boiling point solvent. The resulting metal salt−surfactant−solvent reaction mixture was heated to 150 °C for 5−10 min under vigorous magnetic stirring in a roundbottom flask.…”

“…All of the chemicals were purchased from Sigma-Aldrich and used as received without any further purification. Alloy NP structures of Pt­(NiCo)-Mo, PtNi-Mo, and PtCo-Mo were solution-derived by co-reducing precursors platinum acetylacetonate (Pt­(acac) 2 , 97%), nickel­(II) acetate tetrahydrate (Ni­(Ac) 2 , 95%), and/or cobalt­(II) acetate tetrahydrate (Co­(Ac) 2 , ≥99%) with molybdenum hexacarbonyl (Mo­(CO) 6 , 98%) in the presence of amine surfactants oleylamine (OAm, 70%) and hexadecylamine (HDA, 90%) in a high boiling point solvent benzyl ether (BE, 98%) at 240 °C for 60 min …”

“…The Pt(NiCo)-Mo, PtNi-Mo, and PtCo-Mo nanoalloys were solution-derived according to our previously reported synthetic approach. 35 Briefly, the alloy NPs were synthesized in a homogeneous organic growth mixture of platinum acetylacetonate (Pt(acac) 2 ), molybdenum hexacarbonyl (Mo(CO) 6 ), nickel(II) acetate tetrahydrate (Ni(Ac) 2 ), and/or cobalt(II) acetate tetrahydrate (Co(Ac) 2 ), using amine binary surfactants (oleylamine (OA) and hexadecylamine (HDA)) and a high boiling point solvent, benzyl ether (BE), at 240 °C for 60 min. Transmission electron microscopy bright field (TEM-BF) images showed nanoparticle (NP) populations with good monodispersity and well-defined geometries (Figure S1a−c).…”

Manipulating morphology and composition in colloidal heterometallic nanopods and nanodendrites

“…16 These external factors can include capping agents and mixtures thereof that selectively cap specific facets, [33][34][35][36] or temperature and precursor concentration that encourage growth in the kinetic regime. 20,37 Two theories have been developed to explain branching; atomic deposition 38 and oriented attachment. 39 In the first, atoms continuously add to high energy NP facets, with branching seen when the deposition rate exceeds that of the subsequent migration of these adatoms to lower energy facets.…”