Porous coordination polymer-based composite membranes for high-temperature polymer exchange membrane fuel cells

Proton exchange membrane fuel cells (PEMFCs), promising energy-transforming devices, can directly convert the chemical energy of fuels to electricity with high efficiency (40%–60%) and low emissions. Commercial PEMFCs operating below 80°C have many challenges, such as complex water management, low electrode kinetics, and catalyst toxicity. High-temperature PEMFCs (HT-PEMFCs) with higher operating temperatures (120°C–250°C) can address these issues and have much potential as next-generation PEMFCs. Proton exchange membranes (PEMs) are the heart of PEMFCs for promoting proton transfer. Traditional PEMs, such as Nafion membranes, cannot meet the operating requirements (e.g., a conductivity of 0.1 S cm−1 at 120°C, the US Department of Energy 2020 target). To meet this criterion, one promising approach to boost the insufficient proton conductivity of existing PEMs is to incorporate functional fillers into the proton-conductive membranes as the nanocomposite polymer electrolyte membranes. Porous coordination polymer (PCP)-based composite membranes have great potential as proton exchange electrolytes for high-temperature PEMFC applications. This review summarizes the materials and engineering strategies for designing PCP-based high-temperature proton exchange composite membranes and discusses the remaining challenges as well as future research areas. Proton exchange membrane fuel cells (PEMFCs), promising energy-transforming devices, can directly convert the chemical energy of fuels to electricity with high efficiency (40%–60%) and low emissions. Commercial PEMFCs operating below 80°C have many challenges, such as complex water management, low electrode kinetics, and catalyst toxicity. High-temperature PEMFCs (HT-PEMFCs) with higher operating temperatures (120°C–250°C) can address these issues and have much potential as next-generation PEMFCs. Proton exchange membranes (PEMs) are the heart of PEMFCs for promoting proton transfer. Traditional PEMs, such as Nafion membranes, cannot meet the operating requirements (e.g., a conductivity of 0.1 S cm−1 at 120°C, the US Department of Energy 2020 target). To meet this criterion, one promising approach to boost the insufficient proton conductivity of existing PEMs is to incorporate functional fillers into the proton-conductive membranes as the nanocomposite polymer electrolyte membranes. Porous coordination polymer (PCP)-based composite membranes have great potential as proton exchange electrolytes for high-temperature PEMFC applications. This review summarizes the materials and engineering strategies for designing PCP-based high-temperature proton exchange composite membranes and discusses the remaining challenges as well as future research areas.