Multi-functionalized carbon aerogels derived from chitosan.

Carbon aerogels are prepared by a thermal treating-freeze drying approach from chitosan, with glycine hydrochloride ionic liquid (IL) acting as solvent and nitrogen source. Different post-treatments such as ball milling and high temperature carbonization are employed to functionalize the obtained carbon aerogels with tuned properties, making it promising candidates as fluorescence material (NACs-Q), electrode material (FDC-800) and catalyst support (NACPd-C). NACs-Q is water-soluble quantum dot with average particle sizes of 3.8 nm, presenting excitation-/emission-independent and pH-sensitive properties, which could be used as sensor for testing acetone vapor or an "on-off-on" sensor for detections of Fe3+ and vitamin C in fruits. FDC-800 exhibits fluffy lamellar structure with developed micro-mesopores and nitrogen-containing groups on their surfaces, which is beneficial for building flexible solid-state supercapacitor with excellent performance, delivering a capacitance of 208F/g at 0.5 A/g, and achieving an energy density of 7.2 W h/kg at a power density of 50 W/kg. Moreover, NACPd-C can be used as catalyst for phenol hydrogenation, and phenol conversion of 100% with cyclohexanone selectivity of 98.3% is achieved, due to the synergetic effects of the Pd active-site, the N-containing groups, and the Lewis acid sites on the support.

Highly selective hydrogenation of phenol to cyclohexanone over a Pd-loaded N-doped carbon catalyst derived from chitosan.

A highly stable Pd-loaded N-doped carbon catalyst (ACNpd) for phenol hydrogenation was prepared from chitosan by hydrothermal carbonization. ACNpd does not require a reduction step before catalytic use due to the Pd in the as-prepared catalyst mainly exists in the form of Pd0 (80%). The carbon support involves N-containing groups such as pyridinic nitrogen and pyrrolic nitrogen, which could provide basic sites to adsorb phenol effectively. The as-fabricated ACNpd shows high catalytic performance with turnover frequency (TOF) of 29.34 h-1. Accordingly, a phenol conversion of 100% and a cyclohexanone selectivity of 99.1% are achieved in 5 h at 100 °C and 1 MPa H2. This outstanding performance is attributed to the synergetic effects of the Pd particles, the N-functional groups, and the Lewis acid sites on the support. The carbon support presents intrinsic Lewis acid sites due to its electrophilicity, and Pd doping further increases the strength of such acid sites as it causes electron-deficient structural features. Moreover, the Lewis acid sites inhibit the over-hydrogenation from cyclohexanone to cyclohexanol. This study provides new insights into the application of functional biomass-based carbon materials as catalyst supports.

Sandwich construction of chitosan/reduced graphene oxide composite as additive-free electrode material for high-performance supercapacitors.

The sandwich construction of chitosan (CS)/reduced graphene oxide (rGO) composite was synthesized through microwave-assisted hydrothermal method without further carbonization or activation process (CRG). CS homogeneous attached between the rGO slice sheet and improve the dispersion of CRG effectively, which can increase its specific surface area with hierarchical porous structure. Dehydration condensation occurred between CS and rGO, forming NHCO groups that can promote the wettability and conductivity of the composites. CRG exhibited improved degree of order and reduced graphitization defect, N-5 and OI groups were the dominant nitrogen and oxygen-containing groups. When used as additive-free electrode, CRG exhibited a high specific capacitance of 274 F g-1 at the current density of 0.5 A g-1 with good rate performance in a three-electrode system using 1 M H2SO4 electrolyte. Solid-state supercapacitor device was assembled with CRG electrode and lignin hydrogel electrolytes, high gravimetric energy densities of 8.4 Wh kg-1 at the power density of 50 W kg-1 was achieved.