Gas Diffusion Layer for Proton Exchange Membrane Fuel Cells: A Review.

Proton exchange membrane fuel cells (PEMFCs) are an attractive type of fuel cell that have received successful commercialization, benefitted from its unique advantages (including an all solid-state structure, a low operating temperature and low environmental impact). In general, the structure of PEMFCs can be regarded as a sequential stacking of functional layers, among which the gas diffusion layer (GDL) plays an important role in connecting bipolar plates and catalyst layers both physically and electrically, offering a route for gas diffusion and drainage and providing mechanical support to the membrane electrode assemblies. The GDL commonly contains two layers; one is a thick and rigid macroporous substrate (MPS) and the other is a thin microporous layer (MPL), both with special functions. This work provides a brief review on the GDL to explain its structure and functions, summarize recent progress and outline future perspectives.

(La1-x Mx )2 (Nb0.45 Yb0.55 )2 O7-δ (M=Ca, Sr, Ba) Ionic Conductors Promoted by Foreign/Domestic Dual Acceptor-Doping Strategies.

In this work, a class of ionic conductor (La1-x Mx )2 (Nb0.45 Yb0.55 )2 O7-δ (M=Ca, Sr, and Ba) with a cubic pyrochlore structure was reported. Two strategies were adopted to increase the concentration of oxygen vacancies favoring the hydration reaction to introduce protons. One was increasing the cation ratio between Yb and Nb over unity, the other was doping divalent alkaline earth elements to replace trivalent La. Proton conduction was evidenced by confirming the proton incorporation and H/D isotope effect in electrical conductivity. Doping Ca, Sr, and Ba further promoted the proton conduction. The results of crystal structure refinement indicated that the extrinsically introduced oxygen vacancies by the two strategies were accommodated in the tetrahedra (48 f) containing two La and two Yb/Nb cations, while the tetrahedra containing four La cations (8a) were fully occupied by oxide ions. A discussion was thereby performed, leading to the suggestion that not all the tetrahedra in the cubic pyrochlore structure of (La1-x Mx )2 (Nb0.45 Yb0.55 )2 O7-δ helped in incorporating and conducting protons, and only the oxygen vacancies surrounded by four Y cations (48 f site) or two La and two Y cations (8b site) were hydratable. It is thereby suggested that to enhance the proton conduction in pyrochlore oxides, an effective strategy might be tuning the ability of hydration or protonation of the tetrahedra to increase the proton concentration and expand the route for proton conduction.

[Effectiveness of repairing the deep layer of deltoid ligament by suture anchor repair method in treatment of mixed medial injury associated with ankle fractures].

OBJECTIVE: To explore the necessity of repairing the deep layer of deltoid ligament in the treatment of mixed medial injury associated with ankle fractures. METHODS: Between January 2016 and December 2018, 12 patients with mixed medial injury associated with ankle fractures were treated with the fixation of the lateral malleolus by bone plates, the fixation of the anterior colliculus of medial malleolus by cannulated screws, and the repair of the deltoid ligament by suture anchors. There were 8 males and 4 females, with an average age of 42 years (range, 18-56 years). According to the Lauge-Hansen classification criteria, there were 11 cases of supination-external rotation type and 1 case of pronation-external rotation type. According to the Weber classification criteria, all cases were type B. The time from injury to operation was 3-6 days, with an average of 4.7 days. In each patient, X-ray films of anteroposterior and lateral views and mortise view of ankle were taken postoperatively. The motion range of ankle joints was observed. The function of the ankle and the outcome of the treatment were evaluated according to the American Orthopaedic Foot and Ankle Society (AOFAS) scoring system, Olerud-Molander scoring system, and the visual analogue scale (VAS) score. RESULTS: All cases were followed up 12-42 months (mean, 28 months). The 12 patients returned to their pre-injury jobs. Five patients with sports injury completely recovered to their pre-injury motor function. No patient experienced persistent medial ankle pain or ankle instability. At last follow-up, the ankle range of motion in dorsiflexion was 9°-25° (mean, 17.96°), which was 0°-11° (mean, 4.02°) less than that in normal side; the range of motion in plantar flexion was 38°-50° (mean, 43.90°), which was 0°-7° (mean, 2.53°) less than that in normal side. The AOFAS score was 88-100 (mean, 96.7); the Olerud-Molander score was 90-100 (mean, 96.5); the VAS score was 0-3 (mean, 1.1). CONCLUSION: It is necessary to repair the deep layer of deltoid ligament in the mixed medial injuries associated with ankle fracture, which include anterior colliculus fracture and deep deltoid ligament injury. A better outcome can be achieved by employing the suture anchor repair method.