Branched poly(terphenyl trifluoroacetophenone piperidone) membranes with dual-proton conductor assist for enhancing fuel cell performance operation in high-temperature

Abstract

Achieving an optimal balance between phosphoric acid (PA) uptake and membrane dimensional stability remains a critical challenge for the electrochemical performance and long-term durability of PA-doped membranes in high-temperature proton exchange membrane fuel cells (HT-PEMFCs). Herein, dual proton conductor HT-PEMs were prepared by PA immersion of diethylenetriamine penta-(methylene phosphonic acid) (DETPMP) doped branched poly(triphenyl trifluoroacetophenone piperidone) composite membranes. The unique benzimidazole-functionalized side-chains, combined with the branched rigid twisted polymer backbone, create a robust hydrogen bonding network that facilitates efficient proton transport. By tailoring the polymer structure, the optimized dual-proton conductor membrane, b-PTTP-BIm-DP₂₀, achieves a lower PA uptake (<130 %), while exhibiting outstanding proton conductivity (168.5 mS cm⁻¹), excellent dimensional stability, and sufficient PA retention. The PA-doped b-PTTP-BIm-DP₂₀ based HT-PEMFCs delivers a remarkable peak power density of 835.1 mW cm⁻² (200 °C) under backpressure-free and non-humidified. Additionally, the PA-doped b-PTTP-BIm-DP₂₀ membrane demonstrates exceptional durability, with a voltage decay rate of only 0.556 mV h⁻¹ at 160 °C over 100 h of continuous operation. This work highlights the potential of branched polymer designs incorporating dual-proton conductors to achieve a synergistic balance between membrane dimensional stability and electrochemical performance, offering valuable insights for the development of advanced HT-PEMFC membranes.