Novel phosphoric acid (PA)-poly(ether ketone sulfone) with flexible benzotriazole side chains for high-temperature proton exchange membranes

Strategies for Mitigating Phosphoric Acid Leaching in High-Temperature Proton Exchange Membrane Fuel Cells

High-temperature proton exchange membrane fuel cells (HT-PEMFCs) have become one of the important development directions of PEMFCs because of their outstanding features, including fast reaction kinetics, high tolerance against impurities in fuel, and easy heat and water management. The proton exchange membrane (PEM), as the core component of HT-PEMFCs, plays the most critical role in the performance of fuel cells. Phosphoric acid (PA)-doped membranes have showed satisfied proton conductivity at high-temperature and anhydrous conditions, and significant advancements have been achieved in the design and development of HT-PEMFCs based on PA-doped membranes. However, the persistent issue of HT-PEMFCs caused by PA leaching remains a challenge that cannot be ignored. This paper provides a concise overview of the proton conduction mechanism in HT-PEMs and the underlying causes of PA leaching in HT-PEMFCs and highlights the strategies aimed at mitigating PA leaching, such as designing crosslinked structures, incorporation of hygroscopic nanoparticles, improving the alkalinity of polymers, covalently linking acidic groups, preparation of multilayer membranes, constructing microporous structures, and formation of micro-phase separation. This review will offer a guidance for further research and development of HT-PEMFCs with high performance and longevity.

Effect of Covalent Organic Frameworks Containing Different Groups on Properties of Sulfonated Poly(ether ether ketone) Matrix Proton Exchange Membranes

The rich -SO₃H groups enable sulfonated poly (ether ether ketone) (SPEEK) to possess excellent proton conductivities in proton exchange membrane (PEM), but cause excessive water absorption, resulting in the decline of dimensional stability. It is a challenge to resolve the conflict between conductivity and stability. Owing to its unique structural designability, covalent organic frameworks (COFs) have been used to regulate the performances of PEMs. The authors propose the use of COFs with acidic and basic groups for meeting the requirements of proton conductivity and dimensional stability. Herein, COFs containing different groups (sulfoacid, pyridine, and both) were uniformly dispersed into the SPEEK matrix by in situ synthesis, and the effects on the properties of SPEEK matrix PEMs were revealed. The sulfoacid group significantly improves proton conductivities. At 60 °C, under 95% RH, the conductivity of the SPEEK/TpPa-SO₃H-20 composite membrane was 443.6 mS·cm^-1, which was 3.3 times that of the pristine SPEEK membrane. The pyridine group reduced the swelling ratio at 50 °C from 220.7% to 2.4%, indicating an enhancement in dimensional stability. Combining the benefits of sulfoacid and pyridine groups, SPEEK/TpPa-(SO₃H-Py) composite membrane has a conductivity of 360.3 mS·cm^-1 at 60 °C and 95% RH, which is 1.86 times that of SPEEK, and its swelling ratio is 11.8%, about 1/20 of that of SPEEK membrane. The method of in situ combination and regulation of groups open up a way for the development of SPEEK/COFs composite PEMs.

Correlation Analysis of TSB Level and Globus Pallidus-Related Metabolite Indexes of Proton Magnetic Resonance Spectroscopy in the Newborn with Neonatal Jaundice

Objective

To investigate the correlation between serum total serum bilirubin (TSB) levels and globus pallidus-related metabolic indexes of proton magnetic resonance spectroscopy (1H-MRS) in the newborn with neonatal jaundice.

Methods

50 children with neonatal jaundice admitted to our hospital from January 2019 to January 2021 were recruited and assigned to a mild condition group (TSB < 221 μmol/L, n = 16), a moderate condition group (221 μmol/L ≤ TSB < 3 42 μmol/L, n = 18), and a severe condition group (342 μmol/L ≤ TSB < 428 μmol/L, n = 16) based on peak TSB. The differences in globus pallidus-related metabolic indexes of 1H-MRS between the groups were compared and their correlation with TSB levels was analyzed.

Results

The three groups had comparable N-acetylaspartic acid (NAA)/creatine (Cr), choline (Cho)/Cr, lactic acid (Lac)/Cr, and ml/Cr levels (P > 0.05), while there were statistical differences in glutamine (Glx)/Cr levels (P < 0.05). The severe condition group showed the highest levels of neuron-specific enolase (NSE), creatine kinase-MB (CK-MB), and troponin (cTnl), followed by the moderate group, and then the mild group (P < 0.05). The TSB level is positively correlated with the 1H-MRS metabolic index Glx/Cr.

Conclusions

The serum TSB level is correlated with the 1H-MRS metabolic index Glx/Cr in the newborn with neonatal jaundice, and the levels of TSB and Glx/Cr provide a reference for the diagnosis of bilirubin encephalopathy.

Impact of N-Substituent and pKa of Azole Rings on Fuel Cell Performance and Phosphoric Acid Loss

The influence of N-substituent and pK_a of azole rings has been investigated for the performance of high-temperature polymer electrolyte membrane fuel cells (HT-PEMFCs). Imidazole, benzimidazole, and triazole groups were functionalized on the side chains of poly(phenylene oxide), respectively. Each azole group is categorized by their N-substituent into two types: unsubstituted and methyl-substituted azoles. The membranes with methyl-substituted azoles showed higher phosphoric acid (PA) doping levels with an average increase of 20% compared to those with unsubstituted azoles in the full-doped states. However, unsubstituted azoles more effectively improved the proton conductivity and the membrane with unsubstituted imidazole (IMPPO-H) showed a high anhydrous proton conductivity of 153 mS/cm at 150 °C. In contrast, the membranes with methyl-substituted azoles showed a higher PA retention with an average increase of 81% compared to those with unsubstituted azoles. The higher PA retention of methyl-substituted azoles also led to the higher fuel cell performance with the maximum increase of 95% in the power density. It was also revealed that higher pK_a of azoles enhanced the PA retention and the fuel cell performance. Based on the experimental results of PA retention and density functional theory calculations, the PA loss mechanism was also proposed.