Caiyan Gao,Xuezhen Feng,Lian Yi,Xiaoyong Wu,Renji Zheng,Gaoke Zhang,Yubiao Li
Formaldehyde (FA), as an important chemical raw material, has been widely used in many fields. However, the discharge of a large amount of FA-containing wastewater poses a serious threat to the environment and human health. Recently, the in-situ hydrogen energy release technology of hydrogen-containing stable liquid has been extensively explored due to its safe storage. Exploring a robust method to achieve FA removal and synchronous in-situ hydrogen release from FA containing wastewater is of great significant for environmental protection and energy crisis alleviation. Here, we have innovatively introduced peroxymonosulfate (PMS) activation technology into FA removal and hydrogen production simultaneously. The composite of nitrogen doped carbon coating Co 9 S 8 nanotubes (Co 9 S 8 @N−C) is employed as a proof of concept for FA decomposition and simultaneously hydrogen production based on PMS activation system. As expected, the Co 9 S 8 @N−C/PMS system presents much superior hydrogen production efficiency and satisfactory FA removal rate towards FA wastewater than those of common catalysis, photocatalysis and Fenton reaction in the basic condition in a wide range of FA concentration. The hydrogen yield reaches a value as high as 471 μmol within 60 min, corresponding to a FA degradation rate of 30% with an initial FA concentration of 0.722 mol L −1 . Characterizations and density functional theory (DFT) calculations suggest that the free radical process dominated by superoxide radical (O 2 ⋅ − ) and nonradical process dominated by singlet oxygen ( 1 O 2 ), which are induced by Co 9 S 8 @N−C/PMS system, are responsible for highly efficient hydrogen production via FA degradation. These generated O 2 ⋅ − and 1 O 2 can extract ⋅ H from FA to form ⋅ OOH intermediate, which can further combine with the ⋅ H from water to produce hydrogen. This study provides an applicable technique for environmental purification and new energy development based on FA containing wastewater.
One of the urgent problems in the commercialization of fuel cells is the high cost of electrode materials due to the use of Pt/C as the catalyst for oxygen reduction reaction (ORR). Herein, by taking advantages of the metal-organic frameworks, a novel ORR catalyst of Co@Co 9 S 8 –N/C with composite porous structure is synthesized with a facile coprecipitation-pyrolysis method. Co@Co 9 S 8 –N/C is composed of graphitic carbon skeleton with Co 9 S 8 covered Co nanoparticles (Co@Co 9 S 8 ) and nitrogen atoms doping on, on which Co@Co 9 S 8 and pyridinic N provide catalytic sites for ORR. The N, S doped surrounding graphitic carbon skeleton after pyrolysis and vulcanization processes can protect the electrochemical active sites from deactivation. The fabricated Co@Co 9 S 8 –N/C with abundant catalytic active sites performs excellent ORR activity and stability. Thereafter, the structure of the Co@Co 9 S 8 –N/C is optimized by changing the Zn/Co ratio in the precursor to improve its ORR performance. The results show that with the Zn/Co ratio of 3:2, Co@Co 9 S 8 –N/C gives the best ORR activity relying on its well specific surface area, sufficient and uniform-dispersed catalytic sites. Based on this, the Co@Co 9 S 8 –N/C catalytic alkaline direct glucose fuel cells perform better than the Pt/C catalytic one.
Graphical Better batteries : Co 9 S 8 /N-C hollow spheres were successfully synthesized through synchronous pyrolysis and sulfurization of ZIF-67 (see figure). These structures deliver a distinguished performance when applied as the anode in lithium-ion batteries. Co 9 S 8 is considered a promising candidate as the anode material in lithium-ion batteries (LIBs) because of its remarkable electrical conductivity, high theoretical capacity, and low cost. However, the practical application of Co 9 S 8 is greatly restricted because of its poor cycling stability and rate performance, which result mainly from the large volume expansion and dissolution of the polysulfide intermediates during the charge/discharge process. In this report, Co 9 S 8 embedded in N-rich carbon hollow spheres are successfully designed and synthesized through an in situ pyrolysis and sulfurization process, employing the well-known ZIF-67 as the precursor and ethanethiol as the sulfur source. Co 9 S 8 nanoparticles embedded in the N-rich hollow carbon shell exhibit excellent lithium storage properties at a high charge/discharge rate. A discharge capacity of 784 mAh g −1 is obtained upon battery testing at a current density of 1 C (544 mA g −1 ). Even upon cycling at a current density of 4 C, the as-prepared Co 9 S 8 /N-C can still deliver a discharge capacity of 518 mAh g −1 . The excellent battery performance can be attributed to the hollow structure as well as the N-rich carbon encapsulation. Moreover, this metal–organic framework sulfurization route also shows good generality for the synthesis of other metal sulfide–carbon composites such as ZnS/N-C and Cu 2 S/C.
危险品化学品经营许可证（带存储）