Sulfur-Doped Hierarchically Porous Open Cellular Polymer/Acid Complex Electrolyte Membranes for Efficient Water-Free Proton Transport

Abstract

Fuel cells are cleaner alternatives of sustainable green energy sources. Their proton exchange membranes continue to be a key component; however, there are several challenges associated with their application. To overcome these challenges, we designed and fabricated open cellular anhydrous polybenzimidazole (PBI) electrolyte nanohybrid membranes with high proton conductivity and long-term stability by facile non-solvent-induced phase separation. When the membranes were heated to 300 °C, the Friedel−Crafts reaction between the electron-rich phenyl ring and carboxylic acid groups covalently cross-linked the PBI chains. A hierarchical porous structure was effectively tailored from fingerlike cavities to the sponge pores simply by tuning the S-doped−reduced graphene oxide (S-RGO) concentration. The direct incorporation of S-RGO into the micropore channels of membrane yielded exceptional phosphoric acid (H 3 PO 4 ) doping level of 1158.1% and high proton conductivity of 0.23 S cm −1 at 160 °C and 0% humidity, thereby showing a synergistic effect by proton transfer bridge, continuous proton transport channels, and H 3 PO 4 reservoirs. Furthermore, the current density at 0.6 V and maximum power density of the S-RGO-reinforced PBI (S-PBI) nanohybrid membranes were increased to 716 mA cm −2 and 850 mW cm −2 , respectively. The interconnected spongelike porous S-PBI nanohybrid membranes with significantly reduced mass transfer resistances exhibited excellent performance in high-temperature water-free hydrogen fuel cells.

Rational design of microporous polybenzimidazole framework for efficient proton exchange membrane fuel cells

“…Proton-conducting porous polymer membranes have attracted tremendous attention as a novel type of potential electrolyte owing to their high internal surface area, intrinsic microporosity and tunable functionality. [20][21][22][23][24][25][26] The presence of pores in these membranes pushes the electrolyte uptake, thereby facilitating proton transportation. Hence, to promote effective proton transport, the creation of porous materials with interconnecting pores consisting of a tailored pore volume and size may be a suitable approach.…”

Reinforced Hydroxylated Boron Nitride on Porous Sulfonated Poly(ether sulfone) with Excellent Electrolyte Properties for H2/O2 Fuel Cells

“…The weight retention of PSPES-HBN composite membranes is higher (88.2 ± 4.41, 95.7 ± 4.78, and 93.9 ± 4.66%), and all the fracture time is above 16 h with the increase in HBN contents from 2 to 5 wt % due to its dense porous nature and its impregnation by HBN. 24,79 These made the physical cross-linking network structure of the PSPES membrane through strong interaction between the PSPES and HBN at the SO 3 H−OH interface, which probably caused the polymer chain to be less attacked by radical species and enhanced the oxidative stability. 15 To analyze the porous nature of the PSPES membranes, the porosity test was performed using n-butanol as an adsorbing source, as displayed in Figure 6c.…”

“…However, the reinforcement of HBN into the PSPES membrane exhibits higher weight retention due to strong interfacial interplay between HBN and PSPES that preserves the polymer functional groups. The weight retention of PSPES-HBN composite membranes is higher (88.2 ± 4.41, 95.7 ± 4.78, and 93.9 ± 4.66%), and all the fracture time is above 16 h with the increase in HBN contents from 2 to 5 wt % due to its dense porous nature and its impregnation by HBN. , These made the physical cross-linking network structure of the PSPES membrane through strong interaction between the PSPES and HBN at the SO 3 H–OH interface, which probably caused the polymer chain to be less attacked by radical species and enhanced the oxidative stability …”

“…The porous structure possesses interconnected microstructures that act as the proton transporting channels from one polymer domain to another and afford the continuous proton migration along with the polymer matrix. This porous structure is a promising practical approach for constructing PEM with the tunable porosity and well-interconnected nanostructure; however, the drawback of thermo-mechanical properties is still the primary concern in the porous polymer. − …”

Polymer Concentration and Liquid—Liquid Demixing Time Correlation with Porous Structure of Low Dielectric Polyimide in Diffusion-Driven Phase Separation

“…Non-solvent induced phase separation (NIPS) has been commonly applied to prepare a variety of polymeric materials with specific porous morphologies, such as finger- or sponge-like pores [ 16 ]. NIPS involves three components (polymer, solvent, and nonsolvent), and the process is induced by interactions between a polymer and a solvent of interest [ 17 ].…”