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Efficient Hydrolytic Hydrogen Evolution from Sodium Borohydride Catalyzed by Polymer Immobilized Ionic Liquid-Stabilized Platinum Nanoparticles

Lookup NU author(s): Dr Simon DohertyORCiD, Dr Julian Knight, Dr Hussam Alharbi, Reece Paterson, Dr Corinne Wills, Dr Casey Dixon, Professor Lidija Siller

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This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).

Abstract

Platinum nanoparticles stabilized by imidazolium-based phosphine-decorated Polymer Immobilized Ionic Liquids (PPh₂-PIIL) catalyze the hydrolytic evolution of hydrogen from sodium borohydride with remarkable efficiency, under mild conditions. The composition of the polymer influences efficiency with the catalyst based on a polyethylene glycol modified imidazolium monomer (PtNP@PPh₂-PEGPIILS) more active than its N-alkylated counterpart (PtNP@PPh₂-N-decylPIILS). The maximum initial TOF of 169 moleH₂.molcat^-1.min^-1 obtained at 30 °C with a catalyst loading of 0.08 mol% is among the highest to be reported for the aqueous phase hydrolysis of sodium borohydride catalyzed by a PtNP-based system. Kinetic studies revealed that the activation energy (E_a) of 23.9 kJ mol^-1 for the hydrolysis of NaBH₄ catalyzed by PtNP@PPh₂-PEGPIILS is significantly lower than that of 35.6 kJ mol^-1 for PtNP@PPh₂-N-decylPIILS. Primary kinetic isotope effects k_H/k_D of 1.8 and 2.1 obtained with PtNP@PPh₂-PEGPIILS and PtNP@PPh₂-N-decylPIILS, respectively, for the hydrolysis with D₂O support a mechanism involving rate determining oxidative addition or s-bond metathesis of the O-H bond. Catalyst stability and reuse studies showed that PtNP@PPh₂-PEGPIILS retained 70% of its activity across five runs; the gradual drop in conversion appears to be due to poisoning of the catalyst by the accumulated metaborate product as well as the increased viscosity of the reaction mixture.

Publication metadata

Author(s): Doherty S, Knight JG, Alharbi HY, Paterson R, Wills C, Dixon C, Siller L, Chamberlain TW, Griffiths A, Collins SM, Wu KJ, Simmonds SD, Bourne RA, Lovelock KRJ, Seymour J

Publication type: Article

Publication status: Published

Journal: ChemCatChem

Year: 2022

Volume: 14

Issue: 4

Print publication date: 18/02/2022

Online publication date: 20/12/2021

Acceptance date: 17/12/2021

Date deposited: 28/01/2022

ISSN (print): 1867-3880

ISSN (electronic): 1867-3899

Publisher: Wiley-VCH

URL: https://doi.org/10.1002/cctc.202101752

DOI: 10.1002/cctc.202101752R1

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