Insights into the performance and degradation of polybenzimidazole/muscovite composite membranes in high–temperature proton exchange membrane fuel cells

Advances in ionogels for proton-exchange membranes

To ensure the long-term performance of proton-exchange membrane fuel cells (PEMFCs), proton-exchange membranes (PEMs) have stringent requirements at high temperatures and humidities, as they may lose proton carriers. This issue poses a serious challenge to maintaining their proton conductivity and mechanical performance throughout their service life. Ionogels are ionic liquids (ILs) hybridized with another component (such as organic, inorganic, or organic-inorganic hybrid skeleton). This design is used to maintain the desirable properties of ILs (negligible vapor pressure, thermal stability, and non-flammability), as well as a high ionic conductivity and wide electrochemical stability window with low outflow. Ionogels have opened new routes for designing solid-electrolyte membranes, especially PEMs. This paper reviews recent research progress of ionogels in proton-exchange membranes, focusing on their electrochemical properties and proton transport mechanisms.

Grafting of Amine End-Functionalized Side-Chain Polybenzimidazole Acid-Base Membrane with Enhanced Phosphoric Acid Retention Ability for High-Temperature Proton Exchange Membrane Fuel Cells

A high phosphoric acid uptake and retention capacity are crucial for the high performance and stable operation of phosphoric acid/polybenzimidazole (PA/PBI)-based high-temperature proton exchange membranes. In this work, amine end-functionalized side-chain grafted PBI (AGPBI) with different grafting degrees are synthesized to enhance both the phosphoric acid uptake and the acid retention ability of the accordingly formed membranes. The optimized acid-base membrane exhibits a PA uptake of 374.4% and an anhydrous proton conductivity of 0.067 S cm-1 at 160 °C, with the remaining proton conductivity percentages of 91.0% after a 100 h stability test. The accordingly fabricated membrane electrode assembly deliver peak power densities of 0.407 and 0.638 W cm-2 under backpressure of 0 and 200 kPa, which are significantly higher than 0.305 and 0.477 W cm-2 for the phosphoric acid-doped unmodified PBI membrane under the same conditions.

Water Electrolysis toward Elevated Temperature: Advances, Challenges and Frontiers

Since severe global warming and related climate issues have been caused by the extensive utilization of fossil fuels, the vigorous development of renewable resources is needed, and transformation into stable chemical energy is required to overcome the detriment of their fluctuations as energy sources. As an environmentally friendly and efficient energy carrier, hydrogen can be employed in various industries and produced directly by renewable energy (called green hydrogen). Nevertheless, large-scale green hydrogen production by water electrolysis is prohibited by its uncompetitive cost caused by a high specific energy demand and electricity expenses, which can be overcome by enhancing the corresponding thermodynamics and kinetics at elevated working temperatures. In the present review, the effects of temperature variation are primarily introduced from the perspective of electrolysis cells. Following an increasing order of working temperature, multidimensional evaluations considering materials and structures, performance, degradation mechanisms and mitigation strategies as well as electrolysis in stacks and systems are presented based on elevated temperature alkaline electrolysis cells and polymer electrolyte membrane electrolysis cells (ET-AECs and ET-PEMECs), elevated temperature ionic conductors (ET-ICs), protonic ceramic electrolysis cells (PCECs) and solid oxide electrolysis cells (SOECs).

A Bibliometric Study on Trends in Proton Exchange Membrane Fuel Cell Research during 1990-2022

Proton exchange membrane fuel cell (PEMFC) with high density and safe reliability has been extensively studied in the world. With the circumstance of extensive PEMFC research, in this study we carried out a bibliometric analysis to understand the technological development. The information of 17,769 related publications from 1990 to 2022 was retrieved from the Web of Science Core Collection for bibliometric analysis based on the VOSviewer tool. The results show that the International Journal of Hydrogen Energy dominates among all of the source journals. The closest collaboration is between China and the USA, and publications from both of those account for 53.9% of the total. In terms of institutions, the Chinese Academy of Sciences has prolific publications, in which representative groups, such as Shao Zhigang's, have achieved many outputs in this field. The theme of PEMFC research can be divided into three aspects: "materials", "design" and "mechanisms". This study demonstrated overall mapping knowledge domain and systematic analysis, and contributed to making a guide for researchers on the progress and trends of PEMFC.

Real-Time Monitoring of the Temperature, Flow, and Pressure Inside High-Temperature Proton Exchange Membrane Fuel Cells

The proton exchange membrane fuel cell (PEMFC) system is a highly efficient and environmentally friendly energy conversion technology. However, the local temperature, flow, and pressure inhomogeneity within the fuel cell during the electrochemical reaction process may lead to depletion of PEMFC material and uneven fuel distribution, thus affecting the performance and service life of high-temperature PEMFCs. In this study, micromachining technology is used to develop a three-in-one flexible micro-sensor that is resistant to a high-temperature electrochemical environment (120~200 °C). Appropriate materials and process parameters are used to protect the micro-sensor from failure or damage under long-term testing, and to conduct a real-time micro-monitor of the local temperature, flow, and pressure distribution inside high-temperature PEMFCs.