Stability In Alkaline Environment Research Articles

Organic-inorganic hybrid interfaces with π-d electron coupling for preventing metal and sulfur leaching toward enhanced oxygen evolution reaction

Transition metal sulfides (TMSs) catalysts with high catalytic oxygen evolution reaction (OER) activity have been extensively studied, especially Fe and Co-based sulfides. Fe and Co active sites with a strong synergistic effect, which can adjust the electron density distribution and effectively improve the electrocatalytic OER activity. However, TMSs has poor stability in alkaline environment caused by metal ions and sulfur elements are facilitated to dissolve. In this work, TMSs was modified by polyaniline (PANI) to inhibit the precipitation of iron, cobalt, and sulfur elements and enhance its stability under alkaline conditions. Moreover, π-d structure can also be formed by the coating of polyaniline, which can further adjust its own electronic structure on the basis of stabilizing the TMSs structure, so as to improve the electrochemical performance, rendering them to stably operate at harsh environment for more than 90 h. These findings offer new guidance for improving the electrocatalytic stability of TMSs.

Vacancy-Enhanced Sb-N4 Sites for the Oxygen Reduction Reaction and Zn-Air Battery.

With the advantages of a Fenton-inactive characteristic and unique p electrons that can hybridize with O2 molecules, p-block metal-based single-atom catalysts (SACs) for the oxygen reduction reaction (ORR) have tremendous potential. Nevertheless, their undesirable intrinsic activity caused by the closed d10 electronic configuration remains a major challenge. Herein, an Sb-based SAC featuring carbon vacancy-enhanced Sb-N4 active centers, corroborated by the results of high-angle annular dark-field scanning transmission electron microscopy and X-ray absorption fine structure, has been developed for an incredibly effective ORR. The obtained SbSA-N-C demonstrates a positive half-wave potential of 0.905 V and excellent structural stability in alkaline environments. Density functional theory calculations reveal that the carbon vacancies weaken the adsorption between Sb atoms and the OH* intermediate, thus promoting the ORR performance. Practically, the SbSA-N-C-based Zn-air batteries achieve impressive outcomes, such as a high power density of 181 mW cm-2, showing great potential in real-world applications.

Interfacial engineering of cobalt phosphide heterostructures confined in N,P-doped carbon for efficient bifunctional electrocatalysis in Zn–air batteries

The current focus of research lies in the advancement of electrocatalysts based on phosphides, which exhibit exceptional features and robust stability in alkaline environments.

Ultra-efficient electrooxidation of ethylene glycol enable by Pd-loaded Fe-doped Nb2O5 with abundant oxygen vacancies

Niobium pentoxide (Nb2O5) has emerged as a highly promising electrocatalyst for ethylene glycol oxidation reaction (EGOR) due to its eco-friendly nature and its ability to maintain structural stability in alkaline environments. However, its inherent electronic structure has posed a significant barrier to further enhancing of EGOR activity. In this study, we successfully synthesized Pd-based electrocatalysts by incorporating Fe-doped Nb2O5 with abundant oxygen vacancies (Pd/FNO-2.5), which effectively promoted ethylene glycol oxidation. The results showed that the introduction of Fe doping not only altered the electronic structure of Nb2O5, leading to the generation of oxygen vacancies, but also decreased the d-band center of Pd, thereby reducing thermodynamic energy barrier of the rate-determining step by approximately 0.58 eV. Impressively, the Pd/FNO-2.5 catalyst demonstrated remarkable electrocatalytic performance exhibiting a relatively low initial potential (−0.11 V) and high mass activity (0.380 A mg−1Pd). Furthermore, even after undergoing 100 consecutive recycling experiments, the Pd/FNO-2.5 catalyst still retained 81.10 % of its current density. This study demonstrates that doping-induced oxygen vacancy engineering is a promising approach for developing efficient EGOR electrocatalysts for direct ethylene glycol fuel cells, which is associating with the efficient and sustainable development of fuel cell and the carbon neutrality efforts.

Preparation and properties of rubber nanocomposites based on natural rubber/ ethylene propylene diene monomer reinforced with nanosilica, carbon black and barium sulfate

In this work, rubber nanocomposites based on natural rubber/ethylene propylene diene monomer (NR/EPDM) blends and reinforced with nanosilica (NS) in combination with carbon black (CB) and barium sulfate (BS) were prepared by melt blending method in a Brabender internal mixer. The appropriate contents of NS and CB for reinforcing the rubber nanocomposites based on NR/EPDM are 10 and 30 phr (parts per hundred rubber), respectively. The NR/EPDM nanocomposites material reinforced with 10 phr NS and 30 phr CB has the best mechanical properties that with the enhancement of tensile strength over 117% and 40 % compared to that of the NR/EPDM nanocomposite material unreinforced and reinforced with only 10 phr NS, respectively. The appropriate content of BS for replacement of CB in the NR/EPDM blend is 6 phr. The rubber nanocomposite based on NR/EPDM (60/40) blend reinforced with 10 phr NS, 24 phr CB and 6 phr BS has a tight structure, high mechanical properties, and especially, high alkali resistance and heat resistance, abrasion resistance and low endogenous heat due to rotation and friction. This material may be used to manufacture technical rubber products that require heat resistance and stability in alkaline environments, such as conveyor belts used in the cement industry.

Enhanced thermostability of formate dehydrogenase via semi-rational design

An NAD+-dependent formate dehydrogenase from Lodderomyces elongisporus (LeFDH) was expressed in Escherichia coli and then purified by nickel affinity chromatography. The analysis of enzymatic properties showed that the specific activity of LeFDH was much high (16.26 U·mg–1), while the thermal stability may be insufficient for industrial application. To further enhance the thermal stability by semi-rational design, sequences alignment, homologous modeling and molecular dynamic simulations were conducted. As a result, seven non-conserved amino acid residues far from the active center were selected for site-directed mutagenesis. Several mutants as well as a binary mutant displayed improved thermal stability and unreduced specific activity. Then temperature and pH stability, kinetic parameters and specific activity, and structural characteristics of wild-type and mutant LeFDH were compared and evaluated. The variant K21P/K22R exhibited an increased half-life by 211% at 60 °C and a 4.5 °C higher Tm than those of wild type, and good stability in alkaline environment. This binary mutant enhances the operational stability of LeFDH in the catalytic reaction and thus improves its potential for application in coenzyme regenerations.

Ionic liquid-derived FeCo alloys encapsulated in nitrogen-doped carbon framework as advanced bifunctional catalysts for rechargeable Zn-air batteries

Developing bifunctional ORR&OER electrocatalysts with high activity and stability is challenging for practical application of rechargeable Zinc air batteries. Herein, an ionic liquid strategy is proposed for construction of FeCo alloys encapsulated in nitrogen-doped carbon as bifunctional electrocatalyst for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). By taking advantages of the unique properties such as solvent effect and low volatility, ionic liquid serves as solvent to disperse metal ions in the precursor preparation and nitrogen-containing carbon source during pyrolysis. The FeCo alloy nanoparticles encapsulated in the N-doped carbon matrix show a homogeneous distribution with average sizes of 50–100 nm. Such a core-shell structure endows the catalyst with both high ORR and OER activity and robust stability in alkaline environments. Especially, the half-wave potential (E 1/2 ) for ORR is 0.86 V and the overpotential (E over ) for OER to reach the 10 mA·cm −2 current density is only 280 mV. Furthermore, the obtained bifunctional electrocatalyst also displays high efficiency and great durability when applied in the rechargeable Zn-air battery. The specific capacity and energy density at the discharge current density of 10 mA·cm −2 reach up to 741.5 mAh·g −1 and 830.1 Wh kg −1 , respectively. It’s envisioned that this ultra-facile method would be applicable to synthesize highly efficient catalysts for other energy conversion systems. • The FeCo@NC electrocatalyst is prepared through a facile two-step method by employing the ionic liquid ([EMIM][DCA]). • The FeCo@NC electrocatalyst exhibits excellent ORR and OER activity and stability in alkaline environments. • The FeCo@NC based Zn-air battery displays high efficiency and good reversibility.

Aerobic oxidation of 5-[(formyloxy)methyl]furfural to 2,5-furandicarboxylic acid over MoCuOx catalyst

Generally, 5-hydroxymethylfurfural (HMF) is used as feedstock to produce 2,5-furandicarboxylic acid (FDCA). Whereas, its poor stability in alkaline environment results in low yield of FDCA. By contrast, 5-[(formyloxy)methyl]furfural (FMF), a novel platform compound derived from HMF, with higher thermal and alkaline stability than HMF, is more promising to replace HMF as substrate for the production of FDCA. In this study, FMF was successfully converted into FDCA over MoCuOx by using NaClO as oxidant, undergoing 2,5-diformylfuran (DFF) and 5-hydroxymethylfuran-2-carboxylic acid (HMFCA) as intermediates. Under optimization condition (30 min, 40 °C), 100% yield of FDCA was obtained. Furthermore, it was also demonstrated that the yield of FDCA up to 90% was gained in 5 wt % FMF concentration. Higher oxygen species mobility and lattice oxygen ratio endowed MoCuOx excellent catalytic activity. The synergy of Mo and Cu species in MoCuOx ensured an efficient conversion of HMF to FDCA through synergistic redox couple of Mo6+/Mo5+ and Cu2+/Cu+.

Carbon nanotube boosting electrocatalytic oxygen evolution of NiFe-polyphenol coordination catalyst through donor-acceptor modulation

Herein, we reported a facile strategy to prepare bimetal-polyphenol complexes coating on carbon nanotube (CNT) as a highly efficient OER catalyst. Tannic acid was used as an organic ligand to simultaneously coordinate with Ni and Fe ions and at the same time wrapped the surface of CNT. The obtained Ni3Fe/TA@CNT catalyst showed superior catalytic activity with a low overpotential of 287 mV to reach the current density of 10 mA cm−2 under a small Tafel slope of 70.24 mV dec-1 and exhibited persistent stability in alkaline environment. Experimental results and density functional theory (DFT) calculations revealed that the electron transfer from CNT to Ni3Fe/TA on the heterointerface modified the local electronic environment of the catalyst at atomic level and decreased the binding energies of adsorbed species, thus greatly accelerating the OER kinetic process and enhancing electrocatalytic activity.

Improved hole extraction and durability of BiVO4 photoanode for solar water splitting under extreme pH condition

The artificial photosynthesis system relies on the semiconductors that are chemically stable and can efficiently capture solar energy. However, material stability and water splitting efficiency are often poor under the harsh conditions because of thermodynamic and kinetic challenges that hamper its practical use in large-scale integrated devices. Here, we integrate BiVO4 photoanode into a metal–insulator-semiconductor (MIS) device to provide high stability. In addition, graphene is employed as hole extraction layer between catalyst and insulator layer to provide high-density states at the interface of the insulator to efficiently improve hole tunneling efficiency in BiVO4 MIS photoanode without reducing the light absorption. With graphene hole extraction layer, the photocurrent of BiVO4 photoanode can be increased nearly 1.5 times. More importantly, BiVO4 MIS photoanode exhibits high stability in alkaline environments (pH = 13).

Significantly enhanced activity of ZIF-67-supported nickel phosphate for electrocatalytic glucose oxidation

Nickel-based nanoparticles have been widely used in detection of glucose due to its multiple oxidation states and high stability in alkaline environment. In this work, amorphous nickel phosphate was supported by Co-based zeolitic imidazolate framework (ZIF-67) through ion exchange to prepare Ni3(PO4)2@ZIF-67 composites as the electrode material. In comparison to glassy carbon electrode (GCE), Ni3(PO4)2/GCE and ZIF-67/GCE, the Ni3(PO4)2@ZIF-67/GCE showed significantly enhanced performances in electrocatalytic oxidation of glucose. The great improvement on glucose oxidation current could be ascribed to the unique structure of Ni3(PO4)2@ZIF-67, the mutual promotion between Ni(III)/Ni(II) and Co(IV)/Co(III) interfacial redox reactions and increased surface areas. Under optimum conditions, as-prepared Ni3(PO4)2@ZIF-67/GCE showed an ultra-high sensitivity of 2783 μA mM−1 cm−2 with a wide linear ranged from 1.0 μM to 4.0 mM, and a low limit detection of 0.7 μM at a signal-to-noise ratio of 3. Moreover, Ni3(PO4)2@ZIF-67/GCE were successfully applied to detect glucose of human serum with good recoveries (92–109%), which indicated that Ni3(PO4)2@ZIF-67 can found application in the clinical detection.

2D carbide nanomeshes and their assembling into 3D microflowers for efficient water splitting

Herein, we have developed a facile process of synthesizing N and O surface-terminated 2D molybdenum carbide nanomeshes (Mo2CTx NMs) and assembling them into 3D microflowers (Mo2CTx MFs) by one-step pyrolysis of Mo/Zn bimetallic imidazolate frameworks. When used as an oxygen evolution reaction (OER) catalyst, the Mo2CTx NMs thus derived exhibit outstanding catalytic activity with an overpotential of 180 mV at the current density of 10 mA cm−2. This enables Mo2CTx NMs to become one of the best OER electrocatalysts ever reported, with the desired stability in alkaline environment which is a major challenge for most of the non-oxide/hydroxide based electrocatalyts. Additionally, the Mo2CTx MFs can catalyze the hydrogen evolution reaction (HER) and act as bifunctional electrocatalysts for overall water splitting which can attain a current density of 10 mA cm−2 at 1.7 V. Mo LIII-edge X-ray near-edge absorption studies combined with theoretical calculations imply that surface-terminated oxygen is crucial in activating the outstanding OER performance, whereas the top Mo atomic sites on the surface contribute to excellent HER performance.

Construction of Hierarchically Structured CuO@CoP Anode for Efficient Oxygen Evolution Reaction

The water oxidation that occurred at the anode is related to various renewable energy systems, and the electrode structure and morphology play a significant impact in its catalytic performance. In this work, we report a handy electrodeposition technique to incorporate CoP on a three-dimensional (3D) CuO microflower to construct a hierarchically structured anode (denoted as CuO-FR@CoP) for efficient oxygen evolution reaction. Resulting from the large quantity electroactive sites provided by the hierarchically interconnected 3D configuration and the intense electronic interactions between CuO core and CoP shell, the anode shows superior activity and stability in alkaline environment with a low Tafel slope (56 mV dec–1); the overpotentials are only 290 and 330 mV respectively to drive the 50 and 300 mA cm–2 current densities. The bulk electrolysis shows that the CuO-FR@CoP material is capable of maintaining a stable current density of 56 mA cm–2 for at least 30 h, giving rise to a high Faraday efficiency of ...

Core-shell structured CsxWO3@ZnO with excellent stability and high performance on near-infrared shielding

Cesium-doped tungsten bronze CsxWO3 (CWO) is a promising candidate for near-infrared (NIR) shielding materials on windows of buildings and automobiles. However, the NIR shielding ability of CWO easily deteriorates in hot humid and alkaline environments, which hinders further applications of CWO. In this paper, we firstly reported a novel core-shell structure of CWO@ZnO, which exhibited high NIR shielding performance with excellent stability. In hot humid environment, CWO@ZnO nanoparticles kept their outstanding NIR shielding ability after 150 days while uncoated CWO nanoparticles showed an evident deterioration in just 1day. Moreover, the CWO@ZnO core-shell structure also exhibits excellent stability in alkaline environment. The good protection of the uniform, continuous and compact ZnO shells played an important role on enhancing the stabilities of CWO nanoparticles. This study provides a novel route for promoting the practical applications of CWO NIR shielding materials.

Ag, Co/graphene interactions and its effect on electrocatalytic oxygen reduction in alkaline media

Silver nanoparticles supported on cobalt and nitrogen embedded reduced graphene oxide, Ag/Co-NGr, are synthesized by one-step hydrothermal route with remarkable catalytic activity for oxygen reduction reaction (ORR). As-synthesized electrocatalyst exhibits half-wave potential (0.82 V) comparable to commercial Pt/C (0.85 V), specific activity (0.45 mA cm−2) better than commercial Pt/C (0.35 mA cm−2) along with superior stability in alkaline environment (≈95% activity retention after 5000s compared to 80% for Pt/C). Moreover, Ag/Co-NGr is highly tolerant to methanol poisoning during ORR and delivers an excellent specific capacity of 789 mAh.g−1Zn with energy density of 947 Wh. kg−1 at a current density of 20 mA cm−2 in a Zn-air battery. For the first time, it is proven that particle size refinement and electronic perturbation of Ag nanoparticles take place due to metal-support interactions between Ag and Co/NGr. d-band center of Ag in Ag/Co-NGr upshifts toward the Fermi level with respect to the Ag/NGr as a result of charge transfer between Ag and Co/NGr. The superior catalytic activity and excellent stability of Ag/Co-NGr is attributed to the structural and electronic modification of Ag nanoparticles by Co and N elements on graphene.

Azide-assisted crosslinked quaternized polysulfone with reduced graphene oxide for highly stable anion exchange membranes

As an important component for anion exchange membrane fuel cells (AEMFCs), anion exchange membranes (AEMs) should possess good mechanical strength and relatively high stability in alkaline environment. Besides, fuel permeation as a serious issue which may lead to the potential decrease and catalyst poisoning could also affect the application for AEMs. Herein, we prepared a series of crosslinked composite membranes which using reduced graphene (rGO) as both inorganic nanofillers and crosslinkers. During a simple thermal crosslinking at 160°C, a covalently cross-linked structure was formed between side chains with azide groups and rGO with alkenyl groups without sacrificing ionic groups. Properties such as water uptake (WU) and swelling ratio were significantly decreased after crosslinking, which caused the decline of ion conductivity for the membranes. However, it was found that when only a small amount of rGO (less than 0.5wt%) was incorporated into QPSU to induced crosslinking, the methanol permeability of membranes obviously decreased by two orders of magnitude, and the mechanical strength and thermal stability of the composite membranes were enhanced. Moreover, the crosslinked membrane maintained stable in Fenton's reagent and exhibited high alkaline resistance in 1M of KOH at 60°C for more than 500h. Therefore, the crosslinked membranes with rGO demonstrate great potential as anion exchange membrane for fuel cell.

On the Design of a Comb-Shaped, Poly(phenylene oxide)-Based Anodic Binder for Anion-Exchange Membrane Direct Methanol Fuel Cell (AEM-DMFC)

Anion-exchange ionomers are used in wide range of applications such as water treatment (desalination, purification, decontamination), chromatography and fuel cells. They consist of polymer chains functionalized with cationic groups to carry anionic molecules and can therefore be used as membrane and catalyst binder in anion-exchange membrane fuel cells (AEMFCs). In the last years there were many improvements related to alkaline stability and ion conductivity of anion-exchange membranes making these fuel cells more feasible. Anion-exchange membrane direct methanol fuel cells (AEM-DMFCs) are a subcategory of AEMFCs and convert the chemical energy of methanol into electric current by oxidizing methanol and reducing oxygen on the anode and cathode, respectively. Advantages of the alkaline over the acidic environment are enhanced methanol oxidation kinetics, lower overpotentials for oxygen reduction reaction, usage of cheaper catalysts than platinum, no need of highly alloyed steels due to less corrosive medium and possible usage of alcohol tolerant oxygen reduction reaction catalysts. It was recently demonstrated that AEM-DMFCs free from platinum reach power densities of up to 0.1 W cm-2 [1,2] making them an interesting alternative as power source for mobile and back-up power applications. In AEM-DMFCs, an ionomeric binder is needed to fix the carbon supported catalyst onto the liquid/gas diffusion layer. The catalyst layer consisting of the ionomer and the catalyst is supposed to build a three-phase boundary (TPB). The TPB facilitates the simultaneous transport of hydroxide ions, electrons and reactants/products. Research groups working on AEM-DMFCs currently rely on highly stable polytetra-fluoroethylene (PTFE) as binder as it is forming a microporously structured catalyst layer. On the downside, PTFE is non-anion conductive polymer. Hence, AEM-DMFCs with PTFE as binder need KOH added to the anodic fuel as electrolytic supplement to reach high current densities. As most anion-exchange membranes are not stable in highly alkaline media at elevated temperatures the addition of KOH to the fuel is considered to be problematic leading to the failure of the cell. Besides this, the addition of KOH is not consumer friendly and could therefore lead to problems in commercialization of the AEM-DMFCs. Thus, it is favorable to eliminate KOH as a fuel supplement. To reach this, ionomeric binders have to be designed for the needs of the AEM-DMFC especially on the anode compartment as the liquid methanolic fuel and the methanol oxidation reaction demand special properties from the ionomeric binder: Anionic conductivity, low swelling in water/methanol, high stability in alkaline environment and formation of a microporous catalyst layer structure. We herein present the synthesis, characterization and implementation in single cells of a comb-shaped anion-conductive ionomer with poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) as backbone polymer for the use as anodic binder in AEM-DMFCs. To synthesize the ionomer, PPO was brominated to further functionalize it. The comb-shaped ionomer resulted from a subsequent reaction of linking (2-methylimidazole, 2MIm), side chain (octafluoro-1,4-diiodobutane, DIFB) and quaternization (1,2,4,5-tetramethylimidazole, TMIm) agents. Successful synthesis was confirmed by 1H-NMR-spectroscopy. In Figure 1 the alkaline stability of comb-like PPO-2MIm-DIFB-TMIm is compared with a non-comb-shaped ionomer (PPO-TMIm). It is observed that the alkaline stability is greatly enhanced especially at high temperatures when the cationic group is not directly linked to the PPO backbone. Besides this, the comb-shaped ionomer shows several other advantageous properties over PPO-TMIm like lower swelling ratios while having similar water/methanol uptakes, higher thermal stability and higher ionic conductivity. Further investigations were done by implementing the ionomer as anodic binder in membrane electrode assemblies and conducting CO stripping and performance experiments on single cell level. Resulting UI and power curves (Fig. 2) showed a significant performance gain for the single cells with the comb-shaped ionomer used as binder. Fig. 1 (A) Loss of ionic conductivity of PPO-TMIm (black) and PPO-2MIm-DIFB-TMIm membranes (red) immersed in 3M KOH solution for 10 days at room temperature (straight lines), 60 °C (dashed lines) and 80 °C (dotted lines). (B) UI and power density curves of single cells fed with 4M CH3OH and O2 as anodic and cathodic fuels in dependency of the ionomer content in the anodic catalyst layers. Anodes consisted of various amounts of comb-like ionomer or PTFE and 2 mgPt cm-2 Pt/C. Cathodes consisted of 2 mgPt cm-2 Pt/C and 12.5wt% PTFE binder. Membrane: Tokuyama A201.

N-Functionalised Polyketone Ion Exchange Membranes for Aemfcs

Anion-exchange membrane fuel cells (AEMFCs) provide significant advantages over their proton-exchange membrane counterparts. In the alkaline environment, the oxygen reduction reaction (ORR) is more facile, there is diminished fuel crossover, and a greater flexibility regarding fuel and catalyst choice. The membrane at the heart of AEMFCs not only facilitates the ion exchange but also separates the fuel feedstocks and acts as a support for the membrane-electrode assembly (MEA). However, to date there are still no membrane materials that satisfy all the needs (long-term stability in alkaline environment, high ionic conductivity, low swelling and good structural integrity) for use in AEMFCs and this remains one of the larger obstacles for further AEMFC development. The amination and subsequent quarternisation of polyketone leads to a new family of ionomers containing N-substituted pyrrole moieties. The degree of amination can be controlled by manipulating reaction conditions, allowing the composition and resulting structural properties of the polymer to be tuned. Membrane fabrication results in thermally stable (TD > 250 oC), structurally robust polymer electrolytes that exhibit ionic conductivity ( > 10-3 S cm-1). These new solid-state ion conducting materials have the potential to be used in a variety of applications including AEMFCs. Here we present an in-depth study focusing on the structure-property relationships of this new polypyrrole/polyketone polymer. A variety of analytical techniques are used to probe the thermal and structural properties of the polymers, these include high-resolution thermogravimetric analysis, modulated differential scanning calorimetry, dynamic mechanical analysis, vibrational, NMR and UV-Vis spectroscopies. In addition, broadband electrical spectroscopy is used to gauge the interplay between the structural properties and electrical response. Figure 1

Wittig reaction constructed an alkaline stable anion exchange membrane

Pendant type anion exchange membranes are currently believed to the state of the art membrane due to enhanced stability. Yet, challenge lies in the limited strategy to construct such structure. Herein, pendant type anion exchange membranes with flexible quaternary ammonium groups attached to poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) backbone via length-tunable spacers were successfully prepared by mild and one-pot Wittig reaction. The as-prepared membranes show restricted water swelling, high hydroxide conductivity and low methanol permeability at low ion exchange capacity due to spacer induced microphase separation. Among them, QPPO-SC6 exhibits highest hydroxide conductivity (from 37.6 mS/cm at 20°C to 99.5mS/cm at 80°C) and good chemical stability in alkaline environment at 80°C. The mechanical and thermal properties of these membranes were also investigated. Results prove that our strategy in preparing anion exchange membranes with flexible spacers has great application potential in anion exchange membrane fuel cells.

Alkali doped poly (2,5-benzimidazole) membrane for alkaline water electrolysis: Characterization and performance

The properties and performance of linear and cross-linked KOH doped ABPBI membranes as electrolyte/separator for zero gap alkaline water electrolysis cells are evaluated and compared with a commercial Zirfon® diaphragm. Stability in alkaline environment, swelling, thermal properties, water sorption, KOH uptake and conductivity of linear (L-ABPBI) and cross-linked (C-ABPBI) membranes doped with different concentrations of KOH are analyzed. Linear membranes show stability up to 3.0 mol·dm−3 KOH doping, while cross-linked membranes are stable up to 4.2 mol·dm−3 KOH doping. Both kinds of membranes exhibit good thermal stability and reasonable specific ionic conductivity at 22 °C in the range between 7 and 25 mS·cm−1, being slightly higher the conductivity of C-ABPBI membranes than that of L-ABPBI ones. In short-term electrolysis tests both L-ABPBI and C-ABPBI membranes show better performance than Zirfon diaphragm in the range from 50 to 70 °C. A current density of 335 mA·cm−2 at a cell voltage of 2.0 V is attained with C-ABPBI membranes doped in 3 mol·dm−3 KOH at 70 °C, a performance comparable with that of commercial units operating at temperatures ca. 80 °C and 30 wt% KOH (6.7 mol·dm−3) as electrolyte.