In situ fabrication of defect-rich MoS2-x onto consecutive nanofibers to construct proton exchange membrane with enhanced direct methanol fuel cell performance

Abstract

It remains highly challenging to construct proton exchange membranes (PEMs) with high proton conductivity and low methanol permeability, as both proton and methanol are mainly transported through the hydrophilic region of PEMs. Here, we first designed novel ultrathin two-dimensional molybdenum disulfide nanosheets rich in sulfur vacancy defects anchored onto bacterial cellulose nanofiber surface (BC@MoS_2-x) via a one-step hydrothermal method, which were then embedded in sulfonated poly (ether ether ketone) (SPEEK) matrix to obtain high-performance composite PEMs (SPEEK/BC@MoS_2-x) with a consecutive and orderly arrangement of MoS_2-x. SPEEK/BC@MoS_2-x exhibited a proton conductivity of 0.132 S cm⁻¹ (80 °C, 100 % RH) and methanol permeability of 31.15 × 10^-7 cm² s⁻¹. Such superior performance can be attributed to the interconnected hydrophilic BC@MoS_2-x nanofiber structure, which provides consecutive proton transfer channels to allow easy proton transfer through the hydration channels, as well as a 3D nanofiber network structure to result in more tortuous penetration of methanol. In addition, the robust and continuous nanofiber network of BC@MoS_2-x can support the composite membrane to promote the thermal dimensional stability and mechanical properties. Overall, this study provides a novel method for the preparation of high-performance PEMs for direct methanol fuel cells.