Abstract
Proton exchange membrane fuel cells (PEMFCs) are an attractive green technology for energy generation. The poor stability and performances under working conditions of the current electrolytes are their major drawbacks. Metal-Organic Frameworks (MOFs) have recently emerged as an alternative to overcome these issues. Here, we propose a robust Zr-phosphonate MOF (UPG-1) bearing labile protons able to act a priori as an efficient electrolyte in PEMFCs. Further, in an attempt to further enhance the stability and conductivity of UPG-1, a proton carrier (the amino acid Lysine, Lys) was successfully encapsulated within its porosity. The behaviors of both solids as an electrolyte were investigated by a complete experimental (impedance spectroscopy, water sorption) and computational approach (MonteCarlo, water sorption). Compared with the pristine UPG-1, the newly prepared Lys@UPG-1 composite showed similar proton conductivity but a higher stability, which allows a better cyclability. This improved cyclability is mainly related to the different hydrophobic-hydrophilic balance of the Lys@UPG-1 and UPG-1 and the steric protection of the reactive sites of the MOF by the Lys.
Highlights
Several innovative technologies have been discovered and used for the green production of energy avoiding pollutant emissions to atmosphere and, environmental damages
Relevant advances have been achieved toward the development of proton-exchange membrane fuel cells (PEMFCs) components, the majority of the efforts faces the challenge of developing efficient and durable electrolyte materials, responsible for the conduction of protons from the anode to the cathode [5,6,7,8,9]
UPG-1 was synthesized according to a◦ previously reported procedure [36], by reacting Zr4+ with with H6 ttbmp under soft conditions (80 C for 48 h; see experimental section for further details)
Summary
Several innovative technologies have been discovered and used for the green production of energy avoiding pollutant emissions to atmosphere and, environmental damages (e.g., global warming, water and air contamination, among others). Fuel cells (FCs), in particular proton-exchange membrane fuel cells (PEMFCs), have attracted a great worldwide scientific interest due to the possibility to generate electrical power by using carbon-free fuels (e.g., H2 ) [1,2,3]. Nowadays, those devices are the most promising clean energy systems for electric vehicles (in terms of specific energy are 5 times higher than rechargeable batteries) due to their capacity to make engines work, while consuming the environmentally friendly hydrogen and producing only water as sub-product [4]. The main problem that the current electrolytes present is the necessity of a complex active humidification process associated with degradation and, loss of efficiency [10].
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