Synergistic effect of nitrogen and oxygen dopants in 3D hierarchical porous carbon cathodes for ultra-fast zinc ion hybrid supercapacitors.

Zinc-ion hybrid supercapacitor is one of the most promising electrochemical energy storage devices for the applications needing both high energy densities and power densities. Nitrogen doping is an effective way to enhance the capacitive performance of porous carbon cathodes in zinc-ion hybrid supercapacitor. However, accurate evidence is yet needed to demonstrate how nitrogen dopants influence the charge storage of Zn2+ and H+ cations. Herein, we prepared 3D interconnected hierarchical porous carbon nanosheets by a one-step explosion method. The effect of nitrogen dopants on pseudocapacitance was analyzed by the electrochemical behaviors of as-prepared porous carbon samples with similar morphology and pore structure but different nitrogen and oxygen doping levels. Ex-situ XPS and DFT calculation demonstrate that nitrogen dopants promote the pseudocapacitive reactions by lowering the energy barrier for the change of oxidation states of carbonyl moieties. Owing to the improved pseudocapacitance by nitrogen/oxygen dopants and fast diffusion of Zn2+ ions in 3D interconnected hierarchical porous carbon matrix, the as-constructed ZIHCs show both high gravimetric capacitance (301 F g-1 at 0.1 A g-1) and excellent rate capability (a capacitance retention of 30% at 200 A g-1).

Can CO2 and Steam React in the Absence of Electrolysis at High Temperatures?

The fundamental question of whether CO2 can react with steam at high temperatures in the absence of electrolysis or high pressures is answered. These two gases are commonly co-present as industrial wastes. Herein, a simple experiment by flowing CO2 and steam through a CaCl2 matrix at 500-1000 °C and atmospheric pressure was designed. Comprehensive characterizations and density functional theory calculations were conducted. Meanwhile, this study aims to recover HCl from CaCl2 via a low-emission oxy-pyrohydrolysis process. As confirmed, CO2 and steam interact strongly on the CaCl2 surface, leading to an explicit formation of CaCO3 /CaO and a nearly complete release of HCl. This is mainly contributed to a halved energy required for the splitting of H2 O, resulting from the formation of a bicarbonate-like structure to replace Cl- out of CaCl2 , an otherwise industrial waste, whilst an important dopant for carbon capture, utilization and storage, and medium for electrochemical synthesis.

Rapid synthesis of ultrathin, defect-free ZIF-8 membranes via chemical vapour modification of a polymeric support.

Ultrathin ZIF-8 membranes with a thickness of around 200 nm were prepared by chemical vapour modification of surface chemistry and nanopores of an asymmetric bromomethylated poly(2,6-dimethyl-1,4-phenylene oxide) (BPPO) substrate. The resulting ZIF-8 membranes exhibited exceptional H2 permeance as high as 2.05 × 10(-6) mol m(-2) s(-1) Pa(-1) with high H2/N2 and H2/CO2 selectivities (9.7 and 12.8, respectively).