Sulphonated polyhedral oligomeric silsesquioxane/sulphonated poly ether ether ketone nanocomposite membranes for microbial fuel cell: Insights to the miniatures involved

In this study we demonstrate Sulphonated Polyhedral oligomeric silsesquioxane (S-POSS) incorporated Sulphonated Poly Ether Ether Ketone (SPEEK) as an effective cation exchange membrane (CEM) for improving performance and sustainability in a fabricated tubular Microbial Fuel Cell (MFC). The organic-inorganic caged frame of S-POSS enables several ion conducting channels thereby resulting in better proton conductivity and water uptake in addition to hydroxide ions native in POSS. Among the membranes, SPEEK+ 5 wt% S-POSS exhibits a highest maximum performance of 162 ± 1.4 mW m^-2 with the highest IEC of 1.8 ± 0.05 meq g^-1. Microbial community analysis reveals the predominance of several bacterial strains contributing to wide range of mechanisms. Three phyla including Betaproteobacteria, Gammaproteobacteria and Firmicutes showed maximum predominance. In addition to a novel nanocomposite membrane, the present research introduces perceptions of two metabolic mechanisms of the microbial community available which opens pathway for future insights on how other miniatures involve in electron transfer mechanisms.

Synthesis and characterization of a novel crosslinkable side-chain sulfonated poly(arylene ether sulfone) copolymer proton exchange membranes

A series of novel crosslinkable side-chain sulfonated poly(arylene ether sulfone) copolymers (S-SPAES(x/y)) was prepared from 4,4′-biphenol, 4,4′-difluorodiphenyl sulfone, and a new difluoro aromatic monomer 1-(2,6-difluorophenyl)-2-(3,5-dimethoxyphenyl)-1,2-ethanedione (DFDMED) via co-polycondensation, demethylation, and further nucleophilic substitution of 1,4-butane sultone. Meanwhile, quinoxaline-based crosslinked copolymers (CS-SPAES(x/y)) were obtained via cyclo-condensation between S-SPAES(x/y) and 3,3′-diaminobenzidine. Both the crosslinkable and crosslinked copolymer membranes exhibit good mechanical properties and high anisotropic membrane swelling. Crosslinkable S-SPAES(1/2) with an ion exchange capacity (IEC) of 2.01 mequiv. g⁻¹ displays a relatively high proton conductivity of 180 mS cm⁻¹ and acceptable single-cell performance, which is attributed to its good microphase separation resulting from the side-chain sulfonated copolymer structures. Compared with S-SPAES(1/1) (IEC of 1.68 mequiv. g⁻¹), crosslinked CS-SPAES(1/2) with a comparable IEC exhibits a larger conductivity of 157 mS cm⁻¹, and significantly higher oxidative stability and lower membrane swelling, suggesting a distinct performance improvement due to the quinoxaline-based crosslinking.

A series of novel crosslinkable and crosslinked side-chain SPAES has been prepared. The S-SPAES(1/2) has high proton conductivity and acceptable single-cell performance.

Micro-block versus random quaternized poly(arylene ether sulfones) with highly dense quaternization units for anion exchange membranes

A systematic study was carried out to investigate the effect of different distributions of conducting groups in segments for poly(arylene ether sulfone)s.

A Selenone-Functionalized Polyhedral Oligomeric Silsesquioxane for Selective Detection and Adsorption of Hg2+ ions in Aqueous Solutions

Developing novel functional polyhedral oligomeric silsesquioxane (POSS) for various applications is highly desirable. Herein we present the first example of a novel selenone-functionalized POSS (POSS-Se) by treating an imidazolium-containing POSS with selenium powder under mild condition. The structure of POSS-Se was characterized by FT-IR, ¹H NMR, ¹³C NMR, ²⁹Si NMR, and elemental analysis. Acid treatment of POSS-Se results in a hydrophilic red-orange colored solid, which is highly sensitive and selective for the detection of Hg²⁺ ions in aqueous solutions by visually observing the color change to pale yellow, and to white. Interestingly, POSS-Se has no activity on this detection. This finding is due to the Se-Se formation by acid-treatment and subsequent coordination-induced cleavage upon the addition of Hg²⁺ ions. The detection behavior can be precisely monitored by a "turn-on" fluorescence phenomenon with the limit of detection (LOD) of 8.48 ppb, comparable to or higher than many reported Hg²⁺ sensors. Moreover, POSS-Se demonstrates a selective and efficient adsorption of Hg²⁺ ions with a maximum capacity of 952 mg g^-1. The value is higher than most reported adsorbents for Hg²⁺ ions, typically thiol and/or thioether functional materials, indicating its promise as an efficient adsorbent for the selective removal of Hg²⁺ ions from industrial wastewater. This work may open up new horizons for the exploration of selenium-containing functional POSS.

A novel sPEEK nanocomposite membrane with well-controlled sPOSS aggregation in tunable nanochannels for fast proton conduction

To greatly increase the proton conductivity of a sPEEK nanocomposite membrane without water swelling problems, sulfonated PEEK (sPEEK) nanocomposite membranes were prepared by regulating the nanocomposite concentration of sulfonated POSS (sPOSS). Incorporation of sPOSS into sPEEK afforded a 39% increase in proton conductivity at 80 °C/100% RH and a 70% increase in cell performance at 1.5 wt% sPOSS concentration. In particular, water swelling problems were not observed even with the attained proton conductivity, as with Nafion. The water swelling of the pristine sPEEK membrane was 18.8%; it increased to 24.4% at 5.0 wt% of sPOSS loading, which was 11.1% lower than that of Nafion. The high modulus of sPOSS and the good distribution of sPOSS also enhanced the tensile strength by 40.5% and the strain by 65.8% compared with the pristine sPEEK membrane. At more than 1.5 wt% sPOSS concentration, the conductivity and power output of the nanocomposite membranes decreased despite the increased IEC, which is highly related to aggregation of sPOSS nanoparticles in the proton conducting nanochannels and changes in the nanochannel size. The sizes of the nanochannels were measured by SAXS, and it was found that expansion of the nanochannels was enhanced at 1.5 wt% by the best distribution of sPOSS and absorption of water. The increased IEC, expanded nanochannels and distribution of sPOSS without aggregation promoted proton conduction through the nanochannels.