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).

Highly Dispersed Pt Nanoparticles Embedded in N-Doped Porous Carbon for Efficient Hydrogen Evolution

A novel and facile strategy is presented to synthesize highly dispersed Pt nanoparticles embedded in N-doped porous carbon (Pt@NPC) via carbonization of Zn-containing metal-organic frameworks and chemical replacement of Zn with Pt. The as-prepared Pt@NPC exhibits superior activity and durability towards hydrogen evolution reaction (HER) in comparison with commercial Pt/C catalyst. The excellent HER performance of Pt@NPC can be ascribed to the combined features of catalyst and support material, including high dispersion and ultrathin particle size of Pt, high surface area and nitrogen doping of carbon support, and the strong interaction between metal and support.