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.

An exploratory experiment using temperature drop curve features to identify activity information of duck eggs at mid-incubation.

To address the problem that duck egg mortality is not easily detected at mid-incubation, this paper explored a method to detect mid-incubation egg activity information based on temperature drop curve (TDC) features. In this paper, we used a thermal infrared camera to obtain continuous thermal images of death fertilized duck eggs (DFDE) on the 16th day of incubation and alive fertilized duck eggs (AFDE) hatched for 16-19 days in a 20 °C environment. By observing the temperature drop curve of egg surface, we extracted and visualized five features that could reflect the activity information of duck eggs. And we used K-Nearest Neighbor (KNN), Naive Bayesian (NB) and Support Vector Machine (SVM) to establish the activity information detection models for different incubation days. The results showed that KNN could better distinguish the activity of eggs at the 16th and the 17th day of incubation, with F1-score of 85.43% and 85.98%, respectively. The SVM showed better results at the 18th and the 19th day of incubation, with F1-score of 90.57% and 96.3%, respectively. The experimental results demonstrated that the activity detection method based on the temperature drop curve features in this paper could efficiently and nondestructively detect the activity information of mid-incubation duck eggs, which provided a technical foundation for detecting the activity information of duck eggs at mid-incubation.

Evolution of the network structure and voltage loss of anode electrode with the polymeric dispersion in PEM water electrolyzer.

Exploring the intrinsic relationship between the network structure and the performance of catalyst layer (CL) by rational design its structure is of paramount importance for proton exchange membrane (PEM) electrolyzers. This study reveals the relative effect of polymeric dispersion evolution on oxygen evolution reaction (OER) performance and cell voltage loss and linked to CL network structure. The results show that although the dispersed particle size of the ionomer and ink increases with increasing the solubility parameter (δ) difference between the mixed solvent and the ionomer, MeOH-cat (ink from MeOH aqueous solution) has the largest ionomer and ink particle size resulting in the poorest stability, but has comparable OER overpotential to that of IPA-cat (249 mV@10 mA cm-2), which has the smallest dispersed size. While at 100 mA cm-2, the overpotential of the ink rises as the particle size increases, suggesting that the electrode structure becomes more influential as the current density increases. Quantitatively analyzed the electrolyzers' voltage losses and determined that the CL from MeOH-cat has the lowest kinetic overpotential. However, its performance is the worst because of the insufficient network structure of CL, resulting in an output of 1.96 V at 1.5 A cm-2. Comparatively, the CL from IPA-cat has the highest kinetic overpotential yet can achieve the greatest performance of 1.76 V at 2 A cm-2 due to its homogeneous network structure and optimal mass transport. Furthermore, the performance variation becomes more pronounced as current density rises. Hence, this study highlights the significant impact of CL structure on electrolyzer's performance. To improve performance in PEM water electrolysis technology, especially for large work current density, it is crucial to enhance the CL's network structure.

Construction of catalyst layer network structure for proton exchange membrane fuel cell derived from polymeric dispersion.

A rational design of the structure of catalyst layer (CL) is required for proton exchange membrane fuel cells to attain outstanding performance and excellent stability. It is crucial to have a profound comprehension of the correlations existing between the properties (catalyst ink), network structures of CL and proton exchange membrane fuel cells' performance for the rational design of the structure of CL. This study deeply investigates the effects of a series of alcohol solvents on the properties and network structure of CL. The results demonstrate that the CL aggregates in higher ε solution show smaller particle sizes, and the sulfonic acid groups (∼SO3H) tend to extend more outward due to the strong dissociation. A more continuous and homogeneous ionomer distribution around Pt/C aggregates is observed in the CL, which improves the electrochemically active surface area (ECSA) and performance of the electrode. But, the electrode has a poor performance at high current density regions due to the mass transfer resistance. Based on this, a two-step solvent control strategy is proposed to maintain uniform ionomer and aggerates distribution and optimize the mass transfer for CL. The performance of the cell improves from 0.555 V to 0.615 V at 2000 mA·cm-2.

Modification of sulfonated poly(arylene ether nitrile) proton exchange membranes by poly(ethylene-co-vinyl alcohol).

The modification of the physicochemical properties of sulfonated poly(arylene ether nitrile) (SPAEN) proton exchange membranes was demonstrated by poly(ethylene-co-vinyl alcohol) (EVOH) doping (named SPAEN-x%). By controlling the temperature during membrane preparation, the side reactions of the sulfonic acid groups to form sulfonic acid esters were effectively prevented, greatly reducing the proton conductivity of the membranes. Due to the flexible chain of EVOH, SPAEN-8% showed a relatively high elongation of 30.2%, which enhanced the aromatic polymers' flexibility. The SPAEN-2% membrane exhibited proton conductivity of 166, 55, and 9.6 mS cm-1 at 95%, 70%, and 50% relative humidity, respectively, higher than those of the other SPAEN-x% membranes and even comparable to that of Nafion 212. The water uptake, morphological study, and through-plane proton conductivity of the membranes were studied and discussed. The results suggest that EVOH doping can be used as an effective strategy to improve SPAEN-based proton exchange membranes' performance.

Recent Advances Regarding Precious Metal-Based Electrocatalysts for Acidic Water Splitting.

Electrochemical water splitting has wide applicability in preparing high-density green energy. The Proton exchange membrane (PEM) water electrolysis system is a promising technique for the generation of hydrogen due to its high electrolytic efficiency, safety and reliability, compactness, and quick response to renewable energy sources. However, the instability of catalysts for electrochemical water splitting under operating conditions limits their practical applications. Until now, only precious metal-based materials have met the requirements for rigorous long-term stability and high catalytic activity under acid conditions. In this review, the recent progress made in this regard is presented and analyzed to clarify the role of precious metals in the promotion of the electrolytic decomposition of water. Reducing precious metal loading, enhancing catalytic activity, and improving catalytic lifetime are crucial directions for developing a new generation of PEM water electrolysis catalysts. A summary of the synthesis of high-performance catalysts based on precious metals and an analysis of the factors affecting catalytic performance were derived from a recent investigation. Finally, we present the remaining challenges and future perspectives as guidelines for practical use.