Search

Hollow-structured conducting polymers such as polypyrrole microspheres (PPy MSs) and polypyrrole microtubes (PPy MTs) have attracted ever-growing interests as pseudocapacitive materials for supercapacitors. However, the poor cyclic stability heavily impedes their practical applications. Herein, the rational design of hollow core-shell polypyrrole@poly(1,5-diaminoanthraquinone) composites is reported to enhance the capacitance performance of PPy microspheres and microtubes. Both PPy@PDAAQ microspheres and microtubes showed much higher specific capacitance, rate capability and cycling stability than the corresponding PPy cores. Owing to the higher aspect ratio, the PPy@PDAAQ MTs exhibited better electrochemical performance than the PPy@PDAAQ MSs, possessing specific capacitance of 533 F g−1 at the current density 1 A g−1, rate capability of 57.0% even at a high current density of 10 A g−1 and cycling stability of 107.4% after 10,000 cycles. This strategy is expected to offer valuable inspiration for the development of electrode materials with high performance.

Herein, a series of non-precious metal catalysts, nitrogen, phosphorus co-doped porous carbon (NP-PC) materials are successfully fabricated via a facile pyrolysis and activation strategy employing low-cost precursors. Among all prepared catalysts, the optimized NP-PC-0.5 (with 0.5 wt% FeCl3) possesses comparable catalytic activity to that of state-of-the-art commercial Pt/C (C-Pt/C) catalyst. Noticeably, it exhibits significantly superior methanol crossover resistance and better stability than C-Pt/C. The synergetic effect between nitrogen and phosphorus, together with nanoporous structure endow NP-PC-0.5 with practical significance of applicability, rendering it as a promising candidate of Pt-based electrocatalysts in fuel cells. This preparation approach is facile and scalable for fabricating non-precious metal electrocatalysts.

Heteroatoms doped nano-porous carbon materials possess well-designed porosity and also exhibit extremely advantages over high-performance electrodes for supercapacitors (SCs). Herein, we fabricate hierarchically porous boron-doped carbon material (B-HPC) with high specific surface area by a facile synthesis strategy using boric acid as B doping agent, NaCl as retrievable template and ZnCl2 as activation agent. The B doping significantly enhance surface hydrophilicity/wettability and improve capacitance thereby via efficient electrolyte ion penetration and interactions with the surface of carbon electrode. As a result, B-HPC exhibits high specific capacitance (379.9 F/g at 1 A/g) and excellent cycling performance (96.3% capacitance retention over 10 000 cycles). Furthermore, the symmetric SC based on B-HPC can reach up to a high voltage window (1.8 V) and achieve excellent energy density of 25.9 Wh/kg at 447.2 W/kg using 1 M Na2SO4 as electrolyte. B-HPC electrode is demonstrated to possess excellent capacitive behaviors and supposed as a promising material for application in SCs and other energy storage systems.

Aqueous electrolytes can provide high capacitance owing to their high ionic conductivity. In the present work, the aqueous electrolyte was optimized for the polyaniline (PANI)-based electrode, with a flexible PANI coated polylactic acid/multi-walled carbon nanotubes (PLA/MWCNTs) composite film as a model electrode. The electrochemical performance of the PLA/MWCNTs composite film electrode was investigated in the most used acidic and neutral electrolytes, H2SO4 and Na2SO4. As a result, the optimized aqueous electrolyte for the PANI-based electrodes in supercapacitor was achieved as 1.1 mol L−1 H2SO4/0.1 mol L−1 Na2SO4 mixed electrolyte (1.1–0.1), in which the specific capacitance was enhanced by 17.28% in comparison with the commonly used acidic electrolyte (1.0 mol L−1 H2SO4). The analysis of the electrode and electrolytes after electrochemical cycles demonstrated that the addition of the neutral electrolyte Na2SO4 could efficiently inhibit the acid-induced hydrolysis of PANI, improving the specific capacitance and cycling stability. The finding is expected to promote the development of the advanced aqueous polyaniline-based supercapacitors.