Recent advances in spinel-type electrocatalysts for bifunctional oxygen reduction and oxygen evolution reactions

The demand for efficient and environmentally-benign electrocatalysts that help availably harness the renewable energy resources is growing rapidly. In recent years, increasing insights into the design of water electrolysers, fuel cells, and metal–air batteries emerge in response to the need for developing sustainable energy carriers, in which the oxygen evolution reaction and the oxygen reduction reaction play key roles. However, both reactions suffer from sluggish kinetics that restricts the reactivity. Therefore, it is vital to probe into the structure of the catalysts to exploit high-performance bifunctional oxygen electrocatalysts. Spinel-type catalysts are a class of materials with advantages of versatility, low toxicity, low expense, high abundance, flexible ion arrangement, and multivalence structure. In this review, we afford a basic overview of spinel-type materials and then introduce the relevant theoretical principles for electrocatalytic activity, following that we shed light on the structure–property relationship strategies for spinel-type catalysts including electronic structure, microstructure, phase and composition regulation,and coupling with electrically conductive supports. We elaborate the relationship between structure and property, in order to provide some insights into the design of spinel-type bifunctional oxygen electrocatalysts.

电针对骶上脊髓损伤后神经源性膀胱大鼠尿流动力学及髓内凋亡,神经营养因子双向调控作用的影响

Objective:To observe the effects of electroacupuncture on urodynamics and intramedullary apoptosis related factor B cell lymphoma gene-2(Bcl-2),Bcl-2 related protein X(Bax)and brain-derived neurotrophic factor(BDNF)in neurogenic bladder rats after supersacral spinal cord injury.Methods:A total of 60 female SD rats,SPF grade,were randomly selected,12 rats in the blank group and 12 rats in the sham operation group,and the remaining 36 rats were made models.Of these 36 rats,24 rats meeting the model standard were randomized into the model group and electroacupuncture group,with 12 rats in each group.The neurogenic bladder models after supracacral spinal cord injury were prepared by the Hassan Shaker spinal cord transection method,via combining the previous model study experience.At the end of spinal shock stage,"Dazhui(大椎GV14)""Zhongji(中极CV 3)""Ciliao(次髎BL 32)",and"Sanyinjiao(三阴交SP 6)"were selected for electroacupuncture.Observation on the histomorphological changes of bladder detrusor and spinal cord in rats was conducted by HE staining.The apoptosis rate of spinal cord cells was measured by TUNEL assay.The maximum bladder volume and compliance were measured by urodynamics test.The protein expressions of Bcl-2,Bax,and BDNF in spinal cord tissues were measured by Western blot assay.The expressions of Bcl-2,Bax,and BDNF mRNA were measured by RT-PCR assay.Results:(1)The results of HE staining showed that compared with the blank group and sham operation group,in the model group the bladder epithelial cell structure was destroyed,the detrusor muscle fibers proliferated,and there were severe bleeding changes,the spinal cord tissue was disordered,the structure was destroyed,the cell space was enlarged,and accompanied by a large number of inflammatory cell infiltration and cystic cavity formation.Compared with the model group,in the electroacupuncture group,the intact bladder epithelial cells increased,the detrusor muscle fiber proliferation decreased,the bleeding changes decreased,the complete structural area of spinal cord tissues increased,the cell space decreased,the levels were clearer,and the cystic cavity decreased.(2)The results of TUNEL assay indicated that the TUNEL positive rate of spinal cord cells in the model group was significantly higher than that in the blank group and sham group(both P<0.05).Compared with the model group,the TUNEL positive rate of spinal cord cells in the electroacupuncture group was significantly reduced(P<0.05).(3)The results of urodynamics test suggested that compared with the blank group and sham operation group,the maximum bladder volume and compliance of the model group were significantly reduced(all P<0.05).Compared with the model group,the maximum bladder volume and compliance were significantly increased in the electroacupuncture group(both P<0.05).(4)The results of Western blot assay indicated that,compared with the blank group and sham operation group,in the model group the protein contents of Bcl-2 and BDNF were significantly reduced(all P<0.05),while the protein content of Bax in the model group was significantly increased(both P<0.05).(5)The results of RT-PCR assay indicated that,compared with blank group and sham operation group,in the model group the intramedullary Bcl-2 and BDNF mRNA were significantly reduced(all P<0.05),and Bax mRNA was significantly increased(both P<0.05).Conclusion:Electroacupuncture at"GV14""CV3""BL32",and"SP6"can promote the repair of bladder detrusor,improve the maximum bladder volume and compliance of bladder,promote morphological repair of bladder detrusor,reduce spinal cord cell apoptosis rate,thus to restore the function of bladder.This is maybe related with the electroacupuncture’s two-way regulatory mechanism of increased expression of protein and gene of Bcl-2 and BDNF and decreased expression of protein and gene of Bax in spinal cord tissues.