Conductivity study of Zeolitic Imidazolate Frameworks, Tetrabutylammonium hydroxide doped with Zeolitic Imidazolate Frameworks, and mixed matrix membranes of Polyetherimide/Tetrabutylammonium hydroxide doped with Zeolitic Imidazolate Frameworks for proton conducting applications

Abstract

Currently, proton exchange membrane fuel cells (PEMFC) are the focus of attention in the development of electrochemical devices called fuel cells. These devices, which are capable of transforming chemical energy into electrical energy, have shown high performance in the conversion of energy from fuels such as hydrogen and methanol [1]. The operation of a PEMFC is similar to that of a galvanic cell where the electrons produced travel through an external circuit while the protons are transported through a barrier called a proton exchange membrane (PEM) which, in turn, prevents the passage of electrons and fuel [2]. Today, the most popular materials for PEMs are the perfluorosulphonic materials, among which the most outstanding is Nafion ®. This is because the Nafion exhibits excellent mechanical properties, chemical stability, and high proton conductivity; however, its high cost and low operating temperature for proton transport are factors that influence the search for new proton conductive materials [3,4]. Sulfonation of polymers to produce, for example, sulfonated poly-ether-ether-ketone (SPEEK) seems to be a promising solution for the substitution of perfluorosulphonic materials because it has a proton conduction on the order of 10 −2 S cm −1 (above 80 °C), which is similar to the that of Nafion membranes [5]. However, the degree of sulfonation of

Phosphoric Acid Doped Polybenzimidazole (PBI)/Zeolitic Imidazolate Framework Composite Membranes with Significantly Enhanced Proton Conductivity under Low Humidity Conditions

“…In the case of the PBI@ZIF-mix, the activation energy was 19.6 ± 1.4 kJ·mol −1 . These values are lower than those obtained for the pure PBI membrane (E a = 36 ± 2 kJ·mol −1 ), and similar to those obtained for the ZIFs doped with tetrabutylammonium hydroxide used as fillers in a polyetherimide (PEI) polymeric matrix [ 59 ], those obtained for phosphoric acid doped polybenzimidazole/imidazolium-modified silsesquioxane membranes [ 60 ], and those obtained for the SPEEK composite membranes [ 42 ], but they are higher than those for the Nafion ® -117 membranes (E a = 12 kJ·mol −1 ). Considering that the activation energy for the PBI@ZIF membranes is lower than that for pure PBI membrane, we suggest that the ZIFs clearly favor the conductivity of the membrane at moderate and high temperatures.…”

Recent Progress in the Development of Composite Membranes Based on Polybenzimidazole for High Temperature Proton Exchange Membrane (PEM) Fuel Cell Applications

“…As illustrated in Figure 20 , the number of published research articles on MOF containing materials for fuel cell applications has increased significantly over the past decade, especially in recent years (2016–2019). Over the past decade, a diverse range of MOFs have been used as fillers in the preparation of mixed matrix membranes based on Nafion ® [ 197 , 198 , 199 , 200 , 201 ], SPEEK [ 202 , 203 , 204 , 205 , 206 ], and other polymeric materials [ 207 , 208 , 209 , 210 , 211 ]; however, their use in PBI polymers is still very scarce.…”

Proton Conductivity of Composite Polyelectrolyte Membranes with Metal‐Organic Frameworks for Fuel Cell Applications

“…From the dielectric results, the direct current conductivity (dc‐conductivity) can be expressed in the real and imaginary part taking into account the dielectric permittivity ε* (ω) = ε′ (ω) − jε″ (ω), then is easy obtain that σ′( ω,T ) = ε 0 ωε ″ ( ω,T ) and σ ″ ( ω,T ) = ε 0 ωε ′( ω,T ). In polyelectrolytes materials such as polymers, membranes and electrolytes, the real part of conductivity, σ′, is characterized in some frequency range by a plateau that represents the dc‐conductivity (σ dc ) of the sample . However, the value of the frequency at which the conductivity is obtained is subject to variable criteria.…”

“…Compañ and co‐workers described the fabrication of polyetherimide (PEI) mixed membranes ( Figure ) containing ZIFs doped with tetrabutylammonium hydroxide (TBAH) . Initially, ZIFs (ZIF‐8, ZIF‐67 and a binary mixture of both (ZIF‐MIX)) were added to a solution of TBAH to give the corresponding TBAH‐doped ZIF.…”

“…A) Chemical structures of PEI and TBAH. B) Plot of proton conductivity of PEI composite membranes with different ZIFs at 20 wt% loading …”