Enhancing Proton Conduction of Poly(benzimidazole) with Sulfonated Titania Nano Composite Membrane for PEM Fuel Cell Applications

Effect of Sulfonated Inorganic Additives Incorporated Hybrid Composite Polymer Membranes on Enhancing the Performance of Microbial Fuel Cells

Microbial fuel cells (MFCs) provide considerable benefits in the energy and environmental sectors for producing bioenergy during bioremediation. Recently, new hybrid composite membranes with inorganic additives have been considered for MFC application to replace the high cost of commercial membranes and improve the performances of cost-effective polymers, such as MFC membranes. The homogeneous impregnation of inorganic additives in the polymer matrix effectively enhances the physicochemical, thermal, and mechanical stabilities and prevents the crossover of substrate and oxygen through polymer membranes. However, the typical incorporation of inorganic additives in the membrane decreases the proton conductivity and ion exchange capacity. In this critical review, we systematically explained the impact of sulfonated inorganic additives (such as (sulfonated) sSiO₂, sTiO₂, sFe₃O₄, and s-graphene oxide) on different kinds of hybrid polymers (such as PFSA, PVDF, SPEEK, SPAEK, SSEBS, and PBI) membrane for MFC applications. The membrane mechanism and interaction between the polymers and sulfonated inorganic additives are explained. The impact of sulfonated inorganic additives on polymer membranes is highlighted based on the physicochemical, mechanical, and MFC performances. The core understandings in this review can provide vital direction for future development.

Enhancement of the Green H2 Production by Using TiO2 Composite Polybenzimidazole Membranes

This study reports the hydrogen production using TiO₂ based composite polybenzimidazole membranes through the SO₂ depolarized electrolysis that requires lower energy input than the direct water electrolysis. Composite membranes prepared and studied in this work showed very promising results in terms of proton conductivity, chemical stability, and crossover. Thus, a reduction in SO₂ crossover was observed with the increase of the concentration of TiO₂, obtaining reductions as high as 42% with the 3.0 wt% TiO₂-PBI membrane at 120 °C. Higher hydrogen production rates and Faradaic efficiencies were achieved by all the composite membranes, with an optimum for the 1.0 wt% TiO₂-PBI membrane (with this membrane, the production of hydrogen increased a 53% at 110 °C and a 49% at 120 °C as compared with the standard PBI membrane), demonstrated the benefit of the use of composite membranes with respect to the standard one for green hydrogen production.

Synthesis and characterization of phosphonated polybenzimidazole membranes with improved proton conductivity for high-temperature proton exchange membrane applications

The study has synthesized a novel dicarboxylic acid monomer with phosphonate group, 2-((diethoxyphosphoryl)methyl)-[1,1′-biphenyl]-4,4′-dicarboxylic acid (PMDA), and then successfully prepared a series of polybenzimidazole polymers containing methyl-phosphonic acid group and ether group (POPBI-x) via the polycondensation between PMDA, 4,4′-oxybis (benzoic acid) (OBBA) and 3,3′-diaminobenzidine (DAB) in polyphosphoric acid (PPA)/phosphorus pentoxide (P2O5). Meanwhile, the smooth membranes were fabricated via the solution-casting method. Results of TGA, the Fenton’s reagent immersing test, and the tensile test showed that the POPBI-x membranes possessed good thermo-oxidative stability and mechanical properties. Moreover, compared to poly[2,2′-(p-oxydiphenylene)-5,5′-benzimidazole] (OPBI), POPBI-x had a significant enhancement in the phosphoric acid doping level, PA retention ability, and proton conductivity after doped with phosphoric acid (PA) because the methyl-phosphonic acid groups on the backbones enriched the hydrogen bonding interactions between the polymer chain and phosphoric acid. Notably, the POPBI-19 exhibited a high phosphoric acid doping level of approximately 11.3 and excellent proton conductivity of approximately 0.0523 S cm−1 at 180°C under anhydrous conditions.