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Updated: Mar 16, 2026

Preparation and Reactivity of a Triphosphenium Bromide Salt: A Convenient and Stable Source of PhosphorusI
Published on: November 22, 2016
A New Alkali-Stable Phosphonium Cation Based on Fundamental Understanding of Degradation Mechanisms
Bingzi Zhang1, Robert B Kaspar1, Shuang Gu2
1Department of Chemical and Biomolecular Engineering, University of Delaware, Newark, DE, 19716, USA.
Abstract:
Highly alkali-stable cationic groups are a critical component of hydroxide exchange membranes (HEMs). To search for such cations, we studied the degradation kinetics and mechanisms of a series of quaternary phosphonium (QP) cations. Benzyl tris(2,4,6-trimethoxyphenyl)phosphonium [BTPP-(2,4,6-MeO)] was determined to have higher alkaline stability than the benchmark cation, benzyl trimethylammonium (BTMA). A multi-step methoxy-triggered degradation mechanism for BTPP-(2,4,6-MeO) was proposed and verified. By replacing methoxy substituents with methyl groups, a superior QP cation, methyl tris(2,4,6-trimethylphenyl)phosphonium [MTPP-(2,4,6-Me)] was developed. MTPP-(2,4,6-Me) is one of the most stable cations reported to date, with <20 % degradation after 5000 h at 80 °C in a 1 m KOD in CD3 OD/D2 O (5:1 v/v) solution.
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