摘要: Zn-air batteries (ZABs) featuring high safety, low-cost, high specific capacity and environmentally friendliness have attracted much attention and emerged as a hot topic in energy storage devices. However, the sluggish kinetics of the oxygen evolution/reduction reactions (OER/ORR) at the air electrode and the non-negligible dendritic growth at the anode have hindered their large scale applications. Carbon materials with low-cost, good electrical conductivity, chemical stability and bifunctional OER/ORR activities have been widely studied for ZABs in the past few years. This review begins with a discussion of the basic working principle of ZABs, followed by an introduction of various carbon materials which focuses on their roles and superior properties in the applications of ZABs. This review also discusses the essential roles of multi-dimensional carbon materials as major components of ZABs, i.e., air electrodes, zinc anodes and separators, in improving the performance of ZABs. Finally, prospects for the future use of carbon materials to improve ZAB performance are explored.
摘要: Carbon materials for the room-temperature selective oxidation of H2S have attracted growing attention in recent years. The recent development of carbon-based desulfurization catalysts is reviewed, including activated carbon modified by alkalis, porous carbon doped with nitrogen or modified with functional groups, and carbon composites with other species such as alkaline metal oxides. The oxidation mechanisms for H2S on the various catalysts are discussed, and the important function of carbon in desulfurization are emphasized, including its large specific area, porous structure and adjustable surface chemistry. In addition to the catalytic oxidation of H2S, the extended use of the spent catalysts, sulfur/carbon composites, as sulfur cathode materials for high-performance lithium-sulfur batteries, is discussed as a way to add extra value to the sulfur-containing pollutants. Finally, the outlook for using carbon-based materials for room-temperature desulfurization and the key challenges to its large-scale use are explored.
摘要: The synthesis of porous carbon nanosheets without acid treatment for high-performance supercapacitors (SCs) is difficult. We report the construction of N/S co-doped porous carbon nanosheets (NS-PCNs) from coal tar pitch (CTP), using Na2S2O3·5H2O as the sulfur source and K2CO3 as an activator, under flowing ammonia at high temperature. NS-IPCN800 prepared at 800 °C is composed of two-dimensional (2D) nanosheets with abundant pores and an interconnected 3D carbon skeleton. The abundant microspores increase the number of active sites for electrolyte ion adsorption and small mesopores act as channels for fast ion transmission. The 3D carbon skeleton provides paths for electron conduction. Heteroatom doping provides an additional pseudocapacitance for the NS-IPCN electrodes. As a result the NS-IPCN800 electrode has a high capacitance of 302 F g−1 at 0.05 A g−1 in a 6 mol L−1 of KOH electrolyte, and has a high energy density of 9.71 Wh kg−1 at a power density of 25.98 W kg−1. It also has excellent cycling stability with a capacitance retention of over 94.2% after 10 000 charge-discharge cycles. This work suggests an environmentally friendly way to produce NS-IPCNs from CTP for use as high-performance SC electrode materials.
摘要: Activated carbon fibers (ACFs) have high adsorption capacities and can be used in the treatment of benzene, while electrospun nanofibers are expected to be used as a filtration material. In this work, two hybrids of electrospun nanofibers and ACF cloth were prepared by electrospinning polyvinyl alcohol and polyacrylonitrile nanofibers into a phenolic resin-based ACF cloth. The filtration performance of the two hybrids was evaluated. Results indicate that there is a positive correlation between the filtration efficiency and the amount of electrospun nanofibers in the hybrid. The filtration efficiency increases with increasing air velocity, which is attributed to a piezoelectric effect introduced by the electrospun nanofibers. The hybrids have a good adsorption capacity for benzene, which suggests that the materials are promising for treating air pollution.
摘要: Lithium–sulfur (Li–S) batteries suffer from fast capacity fade and an inferior rate performance due to the shuttling of polysulfides (LiPSs) and slow redox kinetics. To solve these issues, a three-dimensional (3D) CNT/Ti3C2Tx aerogel was prepared, with Ti3C2Tx as the active matrix and CNTs as the conductive pillars, and used as a LiPS immobilizer and promoter to modify a commercial Li–S battery separator. The unique design of highly porous 3D aerogel results in the exposure of more Ti3C2Tx active sites by preventing the restacking of their sheets, which not only provides abundant charge transport paths, but also strengthens the adsorption and catalytic conversion of LiPSs. The incorporation of CNTs forms a highly conductive network to connect the adjacent Ti3C2Tx sheets, thereby improving the conductivity and robustness of the 3D aerogel. As a result, a Li–S cell using the CNT/ Ti3C2Tx aerogel-modified separator has a high rate capacity of 1 043.2 mAh g−1 up to 2 C and an excellent cycling life of over 800 cycles at 0.5 C with a low capacity decay rate of 0.07% per cycle.
摘要: Developing highly selective, economical and stable catalysts for the electrochemical conversion of CO2 into value-added carbon products to mitigate both CO2 emission and the energy crisis is challenging. We report an efficient and robust electrocatalyst for the CO2 reduction reaction (CO2RR) by embedding CoN4 active sites in a graphene matrix. These highly dispersed CoN4 sites show an extraordinary CO2RR activity, with a high CO Faradaic efficiency of nearly 95% at −0.76 V (vs. RHE) and remarkable durability. The corresponding overpotential is 0.65 V. Our finding could pave the way for the design at the atomic scale of highly efficient electrocatalysts for the CO2RR.
摘要: Fabricating electrically conductive porous electrode for supercapacitors from abundant raw materials remains a significant challenge in the field of energy storage. 3D porous carbon with high surface areas was synthesized by high-temperature carbonization and activation of lignin from cornstalks. When used as electrode materials in supercapacitors they showed a specific capacitance of 280 F g−1 and an area-specific capacitance of 1.3 F cm−2 at a current density of 0.5 A g−1. An assembled symmetric supercapacitor showed a high energy density of 7.7 Wh kg−1 at power density of 5 200 W kg−1. It is demonstrated here that the use of lignin waste to fabricate electrode materials is feasible, affording lignin new value-added utilization.
摘要: The highly efficient synthesis of nitrogen-doped carbons with different pore structures is reported using shrimp shell as the carbon and nitrogen source, and its CaCO3 component as the hard template and activator. The CaCO3 content of shrimp shells can be easily changed by changing the leaching time to remove it. CaCO3 acts as the activator and template to tailor the pore sizes of the carbons. CO2 from the decomposition of CaCO3 also plays an activating role. Their specific surface areas, pore volumes, ratios of micropore volume to total pore volume can be adjusted in the ranges 117.6-1 137 m2 g−1, 0.14-0.64 cm3 g−1, and 0-73.4%, respectively. When used as the electrodes of a supercapacitor, the porous carbon obtained with a leaching time of 92 min has a high capacitance of 328 F g−1 at 0.05 A g−1 in a 6 mol L−1 KOH electrolyte and 619.2 F g−1 at 0.05 A g−1 in a 1 mol L−1 H2SO4 electrolyte. Its corresponding energy density at a power density of 1 470.9 W kg−1 is 26.0 Wh kg−1. This study provides a low cost method for fabricating porous carbons from biomass with a high added value.
摘要: It is known that the electrochemical determination of phenacetin, a widely used analgesic, is challenging because of the interference of the electroactive intermediate, acetaminophen. Phenacetin was proven to be electroactive in 1980s, but its electrochemical determination has not been widely reported. This determination on an electrochemically reduced graphene oxide (ERGO) electrode was investigated and compared with several nitrogen-doped graphene samples. Results indicate that ERGO has a higher current response and lower oxidation potential than nitrogen-doped graphene. An ERGO electrode as a phenacetin sensor has a detection limit of 0.91 μmol L−1. The redox mechanism of phenacetin is inferred by electrochemical experiments, and the reactions under different pH values are proposed. Acetaminophen is considered to be the main intermediate and that does not interfere with the determination of phenacetin. But phenacetin obviously interferes with the response of acetaminophen, suggesting that the simultaneous detection of phenacetin and acetaminophen is not possible. Species such as Cu2+, Al3+, methanol, ethylene glycol, glucose, and ascorbic acid do not interfere with the determination of phenacetin.
摘要: Phosphorus-doped carbon materials are one of the novel carbon catalysts for the hydrogen evolution reaction (HER) that have attracted considerable attention in recent years. However, the role of C―P species played in the HER activity is still not clear. Phosphorus-doped carbon nanotubes were prepared by chemical vapor deposition and annealed at 900, 1000 and 1200 °C to remove all or part of the phosporus, resulting in four samples with different amounts of substitutional-, pyridine- and pyrrole-like P species. The correlations between the HER activity and the contents of the three species were investigated. Results showed that the content of substitutional P decreased with annealing temperature and none was retained at 1200 °C. The HER activity increased with annealing temperature and the sample annealed at 1200 °C had the highest HER activity in an acid medium with an overpotential of 0.266 V at a current density of 10 mA cm−2. Density functional theory calculations showed that the pentagon- and nine-membered ring defects formed by the elimination of substitutional P mainly contributed to the HER activity.