Hierarchical Carbon Nanosheets Research Articles

Open and Hierarchical Carbon Framework with Ultralarge Pore Volume for Efficient Capture of Carbon Dioxide.

Amine-impregnated adsorbents are promising candidates for the selective capture of CO2 from flue gas. The key is to develop suitable supports possessing large pore sizes and very large pore volumes, and the material has to be facilely synthesized from readily available reagents. In this work, hierarchical carbon nanosheet (CNS) featuring large pore width (30-100 nm) and extraordinarily huge pore volume (8.41 cm3/g) was prepared through controlled carbonization of glucose and dicyandiamide. The CNS was physically impregnated with pentaethylenehexamine (PEHA) to act as adsorbents for selective capture of CO2. Owing to the unique porosity of CNS, the amount of amine loading in CNS can be ultrahigh (6 g PEHA/g CNS) in comparison with those of known amine-impregnated adsorbents, and the CO2 capacity in a flow of 15 v/v % of CO2 balanced in N2 was up to 5.0 mmol/g at 75 °C. The synthesized PEHA-CNS composite materials perform well in capturing CO2 under humid condition and display good stability in a test of 10 adsorption-desorption cycles. It is believed that the CNS synthesized in this work has great potential to act as a support material for CO2 adsorption.

High performance sodium ion hybrid supercapacitors based on Na2Ti3O7 nanosheet arrays

Sodium ion hybrid supercapacitors (SICs) have attracted considerable attentions as a result of the highly cost-effective advantages. However, the large radius of Na+ ions imparts the serious capacity fading and poor rate performance. In order to obtain the ideal SICs with appealing electrochemical performance, we utilized porous Na2Ti3O7 nanosheet arrays as anode and hierarchical carbon nanosheets on Al foils as cathode. The assembled SICs can afford a high energy density of 49.0 Wh kg−1 at the power density of 825 W kg−1 in the voltage window of 1.0–4.0 V. Even at the ultrahigh power density of 4000 W kg−1, the SICs still manifested an energy density of 35.6 Wh kg−1. Meanwhile, the SICs demonstrated superior electrochemical performance at a current density of 3.3 A g−1, with a capacity retention of 73.89% going through 2000 cycles. In this regard, it is considered that engineering array architecture is an efficient way for high performance SICs.

Tubular MoO2 organized by 2D assemblies for fast and durable alkali-ion storage

Multifunctional anode materials with high durability and outstanding rate capability are desirable for alkali-ion storage applications, such as lithium ion batteries (LIBs) and sodium ion batteries (SIBs). The present study illustrates a tubular nanoarchitecture composed of ultra-fine MoO2 nanodomains embedded in hierarchical carbon nanosheets by sol-gel processing and post-annealing. The metallic characteristics and small crystallites of MoO2 not only favor ionic/electronic transport, but also shorten the diffusion length. Hierarchical arrangement of nanosheets and tubular architecture offer sufficient electrode/electrolyte contact and excellent strain-accommodation associated with Li/Na-intercalation. Electrochemical measurements show that hierarchical tubular MoO2 enable the rapid, reversible, and durable storage of Li/Na-ions. A capacity retention of 89% and 96% is retained at a high rate of 10Ag−1 over 10 000 cycles for LIBs and SIBs, respectively. The greatly enhanced Li/Na ion storage capacity is attributed to the significant pseudocapacitance contributions up to approximately 80% and 95% at 2mVs−1 for LIBs and SIBs, respectively. These results not only hold prospects for the multifunctional fabrication of durable energy storage devices, but also demonstrate the potential applications of metallic MoO2 for next-generation clean energy strategies.